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Umeno, Marc M., and Michael E. Goldberg. "Spatial Processing in the Monkey Frontal Eye Field. II. Memory Responses." Journal of Neurophysiology 86, no. 5 (November 1, 2001): 2344–52. http://dx.doi.org/10.1152/jn.2001.86.5.2344.
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Monkeys and humans can easily make accurate saccades to stimuli that appear and disappear before an intervening saccade to a different location. We used the flashed-stimulus task to study the memory processes that enable this behavior, and we found two different kinds of memory responses under these conditions. In the short-term spatial memory response, the monkey fixated, a stimulus appeared for 50 ms outside the neuron's receptive field, and from 200 to 1,000 ms later the monkey made a saccade that brought the receptive field onto the spatial location of the vanished stimulus. Twenty-eight of 48 visuomovement cells and 21/32 visual cells responded significantly under these circumstances even though they did not discharge when the monkey made the same saccade without the stimulus present or when the stimulus appeared and the monkey did not make a saccade that brought its spatial location into the receptive field. Response latencies ranged from 48 ms before the beginning of the saccade (predictive responses) to 272 ms after the beginning of the saccade. After the monkey made a series of 16 saccades that brought a stimulus into the receptive field, 21 neurons demonstrated a longer term, intertrial memory response: they discharged even on trials in which no stimulus appeared at all. This intertrial memory response was usually much weaker than the within-trial memory response, and it often lasted for over 20 trials. We suggest that the frontal eye field maintains a spatially accurate representation of the visual world that is not dependent on constant or continuous visual stimulation, and can last for several minutes.
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Fuster, Joaquín M. "More than working memory rides on long-term memory." Behavioral and Brain Sciences 26, no. 6 (December 2003): 737. http://dx.doi.org/10.1017/s0140525x03300160.
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Single-unit data from the cortex of monkeys performing working-memory tasks support the main point of the target article. Those data, however, also indicate that the activation of long-term memory is essential to the processing of all cognitive functions. The activation of cortical long-term memory networks is a key neural mechanism in attention (working memory is a form thereof), perception, memory acquisition and retrieval, intelligence, and language.
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Wright, A., H. Santiago, S. Sands, D. Kendrick, and R. Cook. "Memory processing of serial lists by pigeons, monkeys, and people." Science 229, no. 4710 (July 19, 1985): 287–89. http://dx.doi.org/10.1126/science.9304205.
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Rapp, Peter R., Mary T. Kansky, and Jeffrey A. Roberts. "Impaired spatial information processing in aged monkeys with preserved recognition memory." NeuroReport 8, no. 8 (May 1997): 1923–28. http://dx.doi.org/10.1097/00001756-199705260-00026.
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Friedman, Harriet R., Janice D. Janas, and Patricia S. Goldman-Rakic. "Enhancement of Metabolic Activity in the Diencephalon of Monkeys Performing Working Memory Task: A 2-Deoxyglucose Study in Behaving Rhesus Monkeys." Journal of Cognitive Neuroscience 2, no. 1 (January 1990): 18–31. http://dx.doi.org/10.1162/jocn.1990.2.1.18.
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The 2-deoxyglucose (2-DG) method was used to study the effect of working memory processing on local cerebral glucose utilization (LCGU) in the diencephalon of the rhesus monkey. Monkeys were given [14C]2-DG while performing either one of three tasks that engaged working memory (WORK group) or one of two control tasks (CONT group) that used associative or non associative processes. The tasks of the WORK group—spatial delayed response, spatial delayed alternation, and delayed object alternation—are alike in that the information guiding a correct response changes from trial to trial and only the accurate record of the preceding response (or cue) is relevant for each successive trial. The CONT group, in contrast, performed on either a visual pattern discrimination test, in which the correct stimulus–response association was invariant across all trials and all test sessions, or on a sensorimotor task in which there was no explicit memory requirement. LCGU was examined in five diencephalic regions: the mammillary bodies, the anteroventral and anteromedial thalamus, and the parvocellular and magnocellular components of the mediodorsal thalamic nucleus. Comparisons across the two groups showed that mean LCGU in the anterior and mediodorsal thalamic nuclei was significantly elevated (by 12–16%) in the WORK group relative to the CONT group. Mean LCGU in the mammillary bodies also was higher in the WORK group than in the CONT group, but this difference was not significant. The present findings suggest that the anterior and mediodorsal thalamic nuclei represent diecephalic components of a neural network processing working memory. Together with our previous report on the enhancement of metabolic activity in the hippocampus and dentate gyrus, these results show that working memory has a wide-ranging influence on cerebral metabolism and emphasize the cooperative, rather than dissociable, roles of the hippocampus and medial thalamus in this function.
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Gulya, Michelle, Carolyn Rovee-Collier, Lissa Galluccio, and Amy Wilk. "Memory Processing of a Serial List by Young Infants." Psychological Science 9, no. 4 (July 1998): 303–7. http://dx.doi.org/10.1111/1467-9280.00060.
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Serial list learning is thought to be beyond the capabilities of infants before the end of their 1st year. In separate experiments with 3- and 6-month-olds, we studied infants' memory for a serial list using a modified serial probe recognition procedure that was originally developed for monkeys and a precuing procedure that was previously used with human adults. Infants were trained with a three-item list. One day later, they were precued with one list member and tested for recognition of another. When the precue specified valid order information, infants of both ages recognized the test item; when the precue specified invalid order information, infants of neither age did. These findings reveal that even very young infants can learn and remember the order of items on a serial list.
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Parker, Amanda, Edward Wilding, and Colin Akerman. "The von Restorff Effect in Visual Object Recognition Memory in Humans and Monkeys: The Role of Frontal/Perirhinal Interaction." Journal of Cognitive Neuroscience 10, no. 6 (November 1998): 691–703. http://dx.doi.org/10.1162/089892998563103.
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This study reports the development of a new, modified delayed matching to sample (DMS) visual recognition memory task that controls the relative novelty of test stimuli and can be used in human and nonhuman primates. We report findings from normal humans and unoperated monkeys, as well as three groups of operated monkeys. In the study phase of this modified paradigm, subjects studied lists of two-dimensional visual object stimuli. In the test phase each studied object was presented again, now paired with a new stimulus (a foil), and the subject had to choose the studied item. In some lists one study item (the novel or isolate item) and its associated foil differed from the others (the homogenous items) along one stimulus dimension (color). The critical experimental measure was the comparison of the visual object recognition error rates for isolate and homogenous test items. This task was initially administered to human subjects and unoperated monkeys. Error rates for both groups were reliably lower for isolate than for homogenous stimuli in the same list position (the von Restorff effect). The task was then administered to three groups of monkeys who had selective brain lesions. Monkeys with bilateral lesions of the amygdala and fornix, two structures that have been proposed to play a role in novelty and memory encoding, were similar to normal monkeys in their performance on this task. Two further groups— with disconnection lesions of the perirhinal cortex and either the prefrontal cortex or the magnocellular mediodorsal thalamus—showed no evidence of a von Restorff effect. These findings are not consistent with previous proposals that the hippocampus and amygdala constitute a general novelty processing network. Instead, the results support an interaction between the perirhinal and frontal cortices in the processing of certain kinds of novel information that support visual object recognition memory.
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Wright, Anthony A., Jacquelyne J. Rivera, Jeffrey S. Katz, and Jocelyne Bachevalier. "Abstract-concept learning and list-memory processing by capuchin and rhesus monkeys." Journal of Experimental Psychology: Animal Behavior Processes 29, no. 3 (2003): 184–98. http://dx.doi.org/10.1037/0097-7403.29.3.184.
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Bongard, Sylvia, and Andreas Nieder. "Basic mathematical rules are encoded by primate prefrontal cortex neurons." Proceedings of the National Academy of Sciences 107, no. 5 (January 19, 2010): 2277–82. http://dx.doi.org/10.1073/pnas.0909180107.
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Mathematics is based on highly abstract principles, or rules, of how to structure, process, and evaluate numerical information. If and how mathematical rules can be represented by single neurons, however, has remained elusive. We therefore recorded the activity of individual prefrontal cortex (PFC) neurons in rhesus monkeys required to switch flexibly between “greater than” and “less than” rules. The monkeys performed this task with different numerical quantities and generalized to set sizes that had not been presented previously, indicating that they had learned an abstract mathematical principle. The most prevalent activity recorded from randomly selected PFC neurons reflected the mathematical rules; purely sensory- and memory-related activity was almost absent. These data show that single PFC neurons have the capacity to represent flexible operations on most abstract numerical quantities. Our findings support PFC network models implementing specific “rule-coding” units that control the flow of information between segregated input, memory, and output layers. We speculate that these neuronal circuits in the monkey lateral PFC could readily have been adopted in the course of primate evolution for syntactic processing of numbers in formalized mathematical systems.
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Ringo, J. L. "Brevity of processing in a mnemonic task." Journal of Neurophysiology 73, no. 4 (April 1, 1995): 1712–15. http://dx.doi.org/10.1152/jn.1995.73.4.1712.
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1. A burst of from one to four current pulses of 0.2 ms at 100 Hz was administered bilaterally to medial temporal lobe areas while monkeys worked in a delayed matching-to-sample visual memory task. The brief electrical stimulation was used as a probe to determine when, around the 20 or 50 ms sample presentation, the disruption was most severe. 2. Stimulation within about 200 ms of the sample image onset severely perturbed the animals' ability subsequently to recognize that image. Identical stimulation at other times did not. 3. Thus, the processing during encoding, that is accessible to the implanted medial temporal lobe electrodes, appears to occur only in a brief interval associated with receipt of the sensory input.
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Colombo, Michael, Tom Fernandez, Katsuki Nakamura, and Charles G. Gross. "Functional Differentiation Along the Anterior-Posterior Axis of the Hippocampus in Monkeys." Journal of Neurophysiology 80, no. 2 (August 1, 1998): 1002–5. http://dx.doi.org/10.1152/jn.1998.80.2.1002.
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Colombo, Michael, Tom Fernandez, Katsuki Nakamura, and Charles G. Gross. Functional differentiation along the anterior-posterior axis of the hippocampus in monkeys. J. Neurophysiol. 80: 1002–1005, 1998. We tested whether the primate hippocampus was functionally heterogenous along its anterior-posterior axis. Two monkeys were trained on both a spatial and nonspatial memory task and the incidence of spatial and nonspatial delay activity in the anterior, middle, and posterior hippocampus was noted. Spatial delay activity (activity in the delay period after the sample stimulus on the spatial memory task) was more common in the posterior than the anterior hippocampus, whereas nonspatial delay activity (activity in the delay period after the sample stimulus on the nonspatial memory task) was evenly distributed throughout the hippocampus. Furthermore, delay neurons in the anterior hippocampus exhibited scalloping delay activity, whereas those in the middle and posterior hippocampus did not. These findings suggest that the hippocampus is functionally heterogeneous and that the posterior regions may be more important for processing spatial information, whereas the anterior regions may be more important for directing or coding movements to points in space.
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Nichols, Shaun, and Claudia Uller. "Explicit factuality and comparative evidence." Behavioral and Brain Sciences 22, no. 5 (October 1999): 776–77. http://dx.doi.org/10.1017/s0140525x99462181.
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We argue that Dienes & Perner's (D&P's) proposal needs to specify independent criteria when a subject explicitly represents factuality. This task is complicated by the fact that people typically “tacitly” believe that each of their beliefs is a fact. This problem does not arise for comparative evidence on monkeys, for they presumably lack the capacity to represent factuality explicitly. D&P suggest that explicit visual processing and declarative memory depend on explicit representations of factuality, whereas the analogous implicit processes do not require such representations. Many of the implicit/explicit findings are also found in monkeys, however, and D&P's account needs to explain this striking parallel.
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Cowell, Rosemary A., Timothy J. Bussey, and Lisa M. Saksida. "Functional Dissociations within the Ventral Object Processing Pathway: Cognitive Modules or a Hierarchical Continuum?" Journal of Cognitive Neuroscience 22, no. 11 (November 2010): 2460–79. http://dx.doi.org/10.1162/jocn.2009.21373.
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We examined the organization and function of the ventral object processing pathway. The prevailing theoretical approach in this field holds that the ventral object processing stream has a modular organization, in which visual perception is carried out in posterior regions and visual memory is carried out, independently, in the anterior temporal lobe. In contrast, recent work has argued against this modular framework, favoring instead a continuous, hierarchical account of cognitive processing in these regions. We join the latter group and illustrate our view with simulations from a computational model that extends the perceptual-mnemonic feature-conjunction model of visual discrimination proposed by Bussey and Saksida [Bussey, T. J., & Saksida, L. M. The organization of visual object representations: A connectionist model of effects of lesions in perirhinal cortex. European Journal of Neuroscience, 15, 355–364, 2002]. We use the extended model to revisit early data from Iwai and Mishkin [Iwai, E., & Mishkin, M. Two visual foci in the temporal lobe of monkeys. In N. Yoshii & N. Buchwald (Eds.), Neurophysiological basis of learning and behavior (pp. 1–11). Japan: Osaka University Press, 1968]; this seminal study was interpreted as evidence for the modularity of visual perception and visual memory. The model accounts for a double dissociation in monkeys' visual discrimination performance following lesions to different regions of the ventral visual stream. This double dissociation is frequently cited as evidence for separate systems for perception and memory. However, the model provides a parsimonious, mechanistic, single-system account of the double dissociation data. We propose that the effects of lesions in ventral visual stream on visual discrimination are due to compromised representations within a hierarchical representational continuum rather than impairment in a specific type of learning, memory, or perception. We argue that consideration of the nature of stimulus representations and their processing in cortex is a more fruitful approach than attempting to map cognition onto functional modules.
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Ng, Chi-Wing, Bethany Plakke, and Amy Poremba. "Neural correlates of auditory recognition memory in the primate dorsal temporal pole." Journal of Neurophysiology 111, no. 3 (February 1, 2014): 455–69. http://dx.doi.org/10.1152/jn.00401.2012.
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Temporal pole (TP) cortex is associated with higher-order sensory perception and/or recognition memory, as human patients with damage in this region show impaired performance during some tasks requiring recognition memory ( Olson et al. 2007 ). The underlying mechanisms of TP processing are largely based on examination of the visual nervous system in humans and monkeys, while little is known about neuronal activity patterns in the auditory portion of this region, dorsal TP (dTP; Poremba et al. 2003 ). The present study examines single-unit activity of dTP in rhesus monkeys performing a delayed matching-to-sample task utilizing auditory stimuli, wherein two sounds are determined to be the same or different. Neurons of dTP encode several task-relevant events during the delayed matching-to-sample task, and encoding of auditory cues in this region is associated with accurate recognition performance. Population activity in dTP shows a match suppression mechanism to identical, repeated sound stimuli similar to that observed in the visual object identification pathway located ventral to dTP ( Desimone 1996 ; Nakamura and Kubota 1996 ). However, in contrast to sustained visual delay-related activity in nearby analogous regions, auditory delay-related activity in dTP is transient and limited. Neurons in dTP respond selectively to different sound stimuli and often change their sound response preferences between experimental contexts. Current findings suggest a significant role for dTP in auditory recognition memory similar in many respects to the visual nervous system, while delay memory firing patterns are not prominent, which may relate to monkeys' shorter forgetting thresholds for auditory vs. visual objects.
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Truppa, Valentina, Diego A. De Simone, and Carlo De Lillo. "Short-term memory effects on visual global/local processing in tufted capuchin monkeys (Sapajus spp.)." Journal of Comparative Psychology 130, no. 2 (May 2016): 162–73. http://dx.doi.org/10.1037/com0000018.
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Davachi, Lila, and Patricia S. Goldman-Rakic. "Primate Rhinal Cortex Participates in Both Visual Recognition and Working Memory Tasks: Functional Mapping With 2-DG." Journal of Neurophysiology 85, no. 6 (June 1, 2001): 2590–601. http://dx.doi.org/10.1152/jn.2001.85.6.2590.
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The rhinal cortex in the medial temporal lobe has been implicated in object recognition memory tasks and indeed is considered to be the critical node in a visual memory network. Previous studies using the 2-deoxyglucose method have shown that thalamic and hippocampal structures thought to be involved in visual recognition memory are also engaged by spatial and object working memory tasks in the nonhuman primate. Networks engaged in memory processing can be recognized by analysis of patterns of activation accompanying performance of specifically designed tasks. In the present study, we compared metabolic activation of the entorhinal and perirhinal cortex during the performance of three working memory tasks [delayed response (DR), delayed alternation (DA), and delayed object alternation (DOA)] to that induced by a standard recognition memory task [delayed match-to-sample (DMS)] and a sensorimotor control task in rhesus monkeys. A region-of-interest analysis revealed elevated local cerebral glucose utilization in the perirhinal cortex in animals performing the DA, DOA, and DMS tasks, and animals performing the DMS task were distinct in showing a strong focus of activation in the lateral perirhinal cortex. No significant differences were evident between groups performing memory and control tasks in the entorhinal cortex. These findings suggest that the perirhinal cortex may play a much broader role in memory processing than has been previously thought, encompassing explicit working memory as well as recognition memory.
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Brady, Ryan J., and Robert R. Hampton. "Post-encoding control of working memory enhances processing of relevant information in rhesus monkeys (Macaca mulatta)." Cognition 175 (June 2018): 26–35. http://dx.doi.org/10.1016/j.cognition.2018.02.012.
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Buckley, Mark J. "The Role of the Perirhinal Cortex and Hippocampus in Learning, Memory, and Perception." Quarterly Journal of Experimental Psychology Section B 58, no. 3-4b (July 2005): 246–68. http://dx.doi.org/10.1080/02724990444000186.
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One traditional and long-held view of medial temporal lobe (MTL) function is that it contains a system of structures that are exclusively involved in memory, and that the extent of memory loss following MTL damage is simply related to the amount of MTL damage sustained. Indeed, human patients with extensive MTL damage are typically profoundly amnesic whereas patients with less extensive brain lesions centred upon the hippocampus typically exhibit only moderately severe anterograde amnesia. Accordingly, the latter observations have elevated the hippocampus to a particularly prominent position within the purported MTL memory system. This article reviews recent lesion studies in macaque monkeys in which the behavioural effects of more highly circumscribed lesions (than those observed to occur in human patients with MTL lesions) to different subregions of the MTL have been examined. These studies have reported new findings that contradict this concept of a MTL memory system. First, the MTL is not exclusively involved in mnemonic processes; some MTL structures, most notably the perirhinal cortex, also contribute to perception. Second, there are some forms of memory, including recognition memory, that are not always affected by selective hippocampal lesions. Third, the data support the idea that regional functional specializations exist within the MTL. For example, the macaque perirhinal cortex appears to be specialized for processing object identity whereas the hippocampus may be specialized for processing spatial and temporal relationships.
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Li, Chiang-Shan Ray, Pietro Mazzoni, and Richard A. Andersen. "Effect of Reversible Inactivation of Macaque Lateral Intraparietal Area on Visual and Memory Saccades." Journal of Neurophysiology 81, no. 4 (April 1, 1999): 1827–38. http://dx.doi.org/10.1152/jn.1999.81.4.1827.
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Effect of reversible inactivation of macaque lateral intraparietal area on visual and memory saccades. Previous studies from our laboratory identified a parietal eye field in the primate lateral intraparietal sulcus, the lateral intraparietal area (area LIP). Here we further explore the role of area LIP in processing saccadic eye movements by observing the effects of reversible inactivation of this area. One to 2 μl of muscimol (8 mg/ml) were injected at locations where saccade-related activities were recorded for each lesion experiment. After the muscimol injection we observed in two macaque monkeys consistent effects on both the metrics and dynamics of saccadic eye movements at many injection sites. These effects usually took place within 10–30 min and disappeared after 5–6 h in most cases and certainly when tested the next day. After muscimol injection memory saccades directed toward the contralesional and upper space became hypometric, and in one monkey those to the ipsilesional space were slightly but significantly hypermetric. In some cases, the scatter of the end points of memory saccades was also increased. On the other hand, the metrics of visual saccades remained relatively intact. Latency for both visual and memory saccades toward the contralesional space was increased and in many cases displayed a higher variance after muscimol lesion. At many injection sites we also observed an increase of latency for visual and memory saccades toward the upper space. The peak velocities for memory saccades toward the contralesional space were decreased after muscimol injection. The peak velocities of visual saccades were not significantly different from those of the controls. The duration of saccadic eye movements either to the ipsilesional or contralesional space remained relatively the same for both visual and memory saccades. Overall these results demonstrated that we were able to selectively inactivate area LIP and observe effects on saccadic eye movements. Together with our previous recording studies these results futher support the view that area LIP plays a direct role in processing incoming sensory information to program saccadic eye movements. The results are consistent with our unit recording data and microstimulation studies, which suggest that area LIP represents contralateral space and also has a bias for the upper visual field.
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Pasternak, Tatiana, and Daniel Zaksas. "Stimulus Specificity and Temporal Dynamics of Working Memory for Visual Motion." Journal of Neurophysiology 90, no. 4 (October 2003): 2757–62. http://dx.doi.org/10.1152/jn.00422.2003.
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When asked to compare two moving stimuli separated by a delay, observers must not only identify stimulus direction but also store it in memory. We examined the properties of this storage mechanism in two macaque monkeys by sequentially presenting two random-dot stimuli, sample and test, in opposite hemifields and introducing a random-motion mask during the delay. The mask interfered with performance only at the precise location of the test, 100–200 ms after the start of the delay, and when its size and speed matched those of the remembered sample. This selective interference suggests that the representation of the motion stimulus in memory preserves its direction, speed, and size and is most fragile shortly after the completion of the encoding phase of the task. This precise preservation of sensory attributes of the motion stimulus suggests that the neural mechanisms involved in the processing of visual motion may also be involved in its storage.
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Watanabe, Yumiko, and Shintaro Funahashi. "Neuronal Activity Throughout the Primate Mediodorsal Nucleus of the Thalamus During Oculomotor Delayed-Responses. II. Activity Encoding Visual Versus Motor Signal." Journal of Neurophysiology 92, no. 3 (September 2004): 1756–69. http://dx.doi.org/10.1152/jn.00995.2003.
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We collected single-neuron activity from the mediodorsal (MD) nucleus of the thalamus, examined the information that was represented by task-related activity during performance of a spatial working memory task, and compared the present results with those obtained in the dorsolateral prefrontal cortex (DLPFC). We used two oculomotor delayed-response (ODR) tasks. In the ordinary ODR task, monkeys were required to make a memory-guided saccade to the location where a visual cue had been presented 3 s previously, whereas in the rotatory ODR task, they were required to make a memory-guided saccade 90° clockwise from the cue direction. By comparing the best directions of the same task-related activity between the two tasks, we could determine whether this activity represented the cue location or the saccade direction. All cue-period activity represented the cue location. In contrast, 56% of delay-period activity represented the cue location and 41% represented the saccade direction. Almost all response-period activity represented the saccade direction. These results indicate that task-related MD activity represents either visual or motor information, suggesting that the MD participates in sensory-to-motor information processing. However, a greater proportion of delay- and response-period activities represented the saccade direction in the MD than in the DLPFC, indicating that more MD neurons participate in prospective information processing than DLPFC neurons. These results suggest that although functional interactions between the MD and DLPFC are crucial to cognitive functions such as working memory, there is a difference in how the MD and DLPFC participate in these functions.
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Pasternak, Tatiana, and Duje Tadin. "Linking Neuronal Direction Selectivity to Perceptual Decisions About Visual Motion." Annual Review of Vision Science 6, no. 1 (September 15, 2020): 335–62. http://dx.doi.org/10.1146/annurev-vision-121219-081816.
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Psychophysical and neurophysiological studies of responses to visual motion have converged on a consistent set of general principles that characterize visual processing of motion information. Both types of approaches have shown that the direction and speed of target motion are among the most important encoded stimulus properties, revealing many parallels between psychophysical and physiological responses to motion. Motivated by these parallels, this review focuses largely on more direct links between the key feature of the neuronal response to motion, direction selectivity, and its utilization in memory-guided perceptual decisions. These links were established during neuronal recordings in monkeys performing direction discriminations, but also by examining perceptual effects of widespread elimination of cortical direction selectivity produced by motion deprivation during development. Other approaches, such as microstimulation and lesions, have documented the importance of direction-selective activity in the areas that are active during memory-guided direction comparisons, area MT and the prefrontal cortex, revealing their likely interactions during behavioral tasks.
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Naya, Yuji, Masatoshi Yoshida, and Yasushi Miyashita. "Forward Processing of Long-Term Associative Memory in Monkey Inferotemporal Cortex." Journal of Neuroscience 23, no. 7 (April 1, 2003): 2861–71. http://dx.doi.org/10.1523/jneurosci.23-07-02861.2003.
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Carlson, Synnöve, Pia Rämä, Heikki Tanila, Ilkka Linnankoski, and Heikki Mansikka. "Dissociation of Mnemonic Coding and Other Functional Neuronal Processing in the Monkey Prefrontal Cortex." Journal of Neurophysiology 77, no. 2 (February 1, 1997): 761–74. http://dx.doi.org/10.1152/jn.1997.77.2.761.
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Carlson, Synnöve, Pia Rämä, Heikki Tanila, Ilkka Linnankoski, and Heikki Mansikka. Dissociation of mnemonic coding and other functional neuronal processing in the monkey prefrontal cortex. J. Neurophysiol. 77: 761–774, 1997. Single-neuron activity was recorded in the prefrontal cortex of three monkeys during the performance of a spatial delayed alternation (DA) task and during the presentation of a variety of visual, auditory, and somatosensory stimuli. The aim was to study the relationship between mnemonic neuronal processing and other functional neuronal responsiveness at the single-neuron level in the prefrontal cortex. Recordings were performed in both experimental situations from 152 neurons. The majority of the neurons (92%) was recorded in the prefrontal cortex. Nine of the neurons were recorded in the dorsal bank of the anterior cingulate sulcus and two in the premotor cortex. Of the total number of neurons recorded in the prefrontal area, 32% fired in relation to the DA task performance and 39% were responsive to sensory stimulation or to the movements of the monkey outside of the memory task context. Altogether 42% of the recorded neurons were neither activated by the various stimuli nor by the DA task performance. Three types of task-related neuronal activity were recorded: delay related, delay and movement related, and movement related. The majority of the task-related neurons ( n = 33, 73%) fired in relation to the delay period. Of the delay-related neurons, 26 (79%) were spatially selective. The number of spatially selective delay-related neurons of the whole population of recorded neurons was 18%. Twelve task-related neurons (27%) fired in relation to the response period of the DA task. Five of these neurons changed their firing rate during the delay period and were classified as delay/movement-related neurons. Contrary to the delay-related neurons, less than half (42%) of the response-related neurons were spatially selective. The majority (70%) of the delay-related neurons could not be activated by any of the sensory stimuli used and did not fire in relation to the movements of the monkey. The remaining portion of the delay-related neurons was activated by stationary and moving visual stimuli or by visual fixation of an object. In contrast to the delay-related neurons, the majority (66%) of the task-related neurons firing in relation to the movement period were also responsive to sensory stimulation outside of the task context. The majority of these neurons responded to visual stimulation, visual fixation of an object, or tracking eye movements. One neuron gave a somatomotor and another a polysensory response. The majority ( n = 37, 67%) of all neurons responding to stimulation outside of the task context did not fire in relation to the DA task performance. The majority of their responses was elicited by visual stimuli or was related to visual fixation of an object or to eye movements. Only six neurons fired in relation to auditory, somatosensory, or somatomotor stimulation. This study provides further evidence about the significance of the dorsolateral prefrontal cortex in spatial working memory processing. Although a considerable number of all DA task-related neurons responded to visual, somatosensory, and auditory stimulation or to the movements of the monkey, most delay-related neurons engaged in the spatial DA task did not respond to extrinsic sensory stimulation. These results indicate that most prefrontal neurons firing selectively during the delay phase of the DA task are highly specialized and process only task-related information.
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Wilke, Melanie, Igor Kagan, and Richard A. Andersen. "Effects of Pulvinar Inactivation on Spatial Decision-making between Equal and Asymmetric Reward Options." Journal of Cognitive Neuroscience 25, no. 8 (August 2013): 1270–83. http://dx.doi.org/10.1162/jocn_a_00399.
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The ability to selectively process visual inputs and to decide between multiple movement options in an adaptive manner is critical for survival. Such decisions are known to be influenced by factors such as reward expectation and visual saliency. The dorsal pulvinar connects to a multitude of cortical areas that are involved in visuospatial memory and integrate information about upcoming eye movements with expected reward values. However, it is unclear whether the dorsal pulvinar is critically involved in spatial memory and reward-based oculomotor decision behavior. To examine this, we reversibly inactivated the dorsal portion of the pulvinar while monkeys performed a delayed memory saccade task that included choices between equally or unequally rewarded options. Pulvinar inactivation resulted in a delay of saccade initiation toward memorized contralesional targets but did not affect spatial memory. Furthermore, pulvinar inactivation caused a pronounced choice bias toward the ipsilesional hemifield when the reward value in the two hemifields was equal. However, this choice bias could be alleviated by placing a high reward target into the contralesional hemifield. The bias was less affected by the manipulation of relative visual saliency between the two competing targets. These results suggest that the dorsal pulvinar is involved in determining the behavioral desirability of movement goals while being less critical for spatial memory and reward processing.
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Compte,, Albert, Christos Constantinidis, Jesper Tegnér, Sridhar Raghavachari, Matthew V. Chafee, Patricia S. Goldman-Rakic, and Xiao-Jing Wang. "Temporally Irregular Mnemonic Persistent Activity in Prefrontal Neurons of Monkeys During a Delayed Response Task." Journal of Neurophysiology 90, no. 5 (November 2003): 3441–54. http://dx.doi.org/10.1152/jn.00949.2002.
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An important question in neuroscience is whether and how temporal patterns and fluctuations in neuronal spike trains contribute to information processing in the cortex. We have addressed this issue in the memory-related circuits of the prefrontal cortex by analyzing spike trains from a database of 229 neurons recorded in the dorsolateral prefrontal cortex of 4 macaque monkeys during the performance of an oculomotor delayed-response task. For each task epoch, we have estimated their power spectrum together with interspike interval histograms and autocorrelograms. We find that 1) the properties of most (about 60%) neurons approximated the characteristics of a Poisson process. For about 25% of cells, with characteristics typical of interneurons, the power spectrum showed a trough at low frequencies (<20 Hz) and the autocorrelogram a dip near zero time lag. About 15% of neurons had a peak at <20 Hz in the power spectrum, associated with the burstiness of the spike train; 2) a small but significant task dependency of spike-train temporal structure: delay responses to preferred locations were characterized not only by elevated firing, but also by suppressed power at low (<20 Hz) frequencies; and 3) the variability of interspike intervals is typically higher during the mnemonic delay period than during the fixation period, regardless of the remembered cue. The high irregularity of neural persistent activity during the delay period is likely to be a characteristic signature of recurrent prefrontal network dynamics underlying working memory.
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Inoue, Masato, and Akichika Mikami. "Prefrontal Activity During Serial Probe Reproduction Task: Encoding, Mnemonic, and Retrieval Processes." Journal of Neurophysiology 95, no. 2 (February 2006): 1008–41. http://dx.doi.org/10.1152/jn.00552.2005.
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To study the prefrontal neuronal mechanism for the encoding and mnemonic processing of multiple objects, the order of object presentation, and the retrieval of an object among objects in the working memory, we recorded neuronal activity from the lateral prefrontal cortex while two monkeys performed the serial probe reproduction task. In the task, two objects (C1 and C2) were presented sequentially interleaved with a delay (D1) period, and after the second delay (D2) period, a color cue was presented. Monkeys were trained to select one target object on the basis of the color stimulus. During the C1 and C2 periods, we found responses that depended on the order of presentation (order-selective response). During the D1 and/or D2 periods, two-thirds of the neurons with object-selective delay-period activity showed order-selective activity coding either C1 or C2. Neurons with larger response magnitudes during the C2 period showed order-selective delay-period activity during the D2 period. These order-selective responses during the C2 period could also contribute to order-selective delay-period activity, and order-selective delay-period activity during the D1 and D2 periods could play an essential role in storing information on both the object and the temporal order of presentation. During the color cue period, two-thirds of the neurons with responses showed target object selectivity (CT and T responses), although the target object was not presented during this period. The CT and T responses could play a critical role in the retrieval of an item among various items in the working memory.
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Washburn, David A., Jonathan P. Gulledge, Michael J. Beran, and J. David Smith. "With his memory magnetically erased, a monkey knows he is uncertain." Biology Letters 6, no. 2 (October 28, 2009): 160–62. http://dx.doi.org/10.1098/rsbl.2009.0737.
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Although intelligence is associated with what one knows, it is also important to recognize and to respond adaptively when one is uncertain. This competency has been examined developmentally and comparatively, but it is difficult to distinguish between objective versus subjective cues to which organisms may respond. In this study, transcranial magnetic stimulation was used to disrupt cognitive processing by a rhesus monkey ( Macaca mulatta ) in a computerized divided visual field memory task. When magnetic stimulation disrupted neural activity in the cerebral hemisphere that initially processed the visual images, recognition accuracy declined and use of the uncertain response significantly increased, relative to control conditions. Thus, the monkey tended to respond adaptively when he did not know the answer—where uncertainty was produced by targeted disruption of the neural processing of a stimulus—even in the absence of external, objective cues to corroborate his subjective, metacognitive assessment of uncertainty.
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Keller, Edward L., Kyoung-Min Lee, Se-Woong Park, and Jessica A. Hill. "Effect of Inactivation of the Cortical Frontal Eye Field on Saccades Generated in a Choice Response Paradigm." Journal of Neurophysiology 100, no. 5 (November 2008): 2726–37. http://dx.doi.org/10.1152/jn.90673.2008.
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Previous studies using muscimol inactivations in the frontal eye fields (FEFs) have shown that saccades generated by recall from working memory are eliminated by these lesions, whereas visually guided saccades are relatively spared. In these experiments, we made reversible inactivations in FEFs in alert macaque monkeys and examined the effect on saccades in a choice response task. Our task required monkeys to learn arbitrary pairings between colored stimuli and saccade direction. Following inactivations, the percentage of choice errors increased as a function of the number of alternative (NA) pairings. In contrast, the percentage of dysmetric saccades (saccades that landed in the correct quadrant but were inaccurate) did not vary with NA. Saccade latency increased postlesion but did not increase with NA. We also made simultaneous inactivations in both FEFs. The results following bilateral lesions showed approximately twice as many choice errors. We conclude that the FEFs are involved in the generation of saccades in choice response tasks. The dramatic effect of NA on choice errors, but the lack of an effect of NA on motor errors or response latency, suggests that two types of processing are interrupted by FEF lesions. The first involves the formation of a saccadic intention vector from associate memory inputs, and the second, the execution of the saccade from the intention vector. An alternative interpretation of the first result is that a role of the FEFs may be to suppress incorrect responses. The doubling of choice errors following bilateral FEF lesions suggests that the effect of unilateral lesions is not caused by a general inhibition of the lesioned side by the intact side.
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Chelazzi, Leonardo, John Duncan, Earl K. Miller, and Robert Desimone. "Responses of Neurons in Inferior Temporal Cortex During Memory-Guided Visual Search." Journal of Neurophysiology 80, no. 6 (December 1, 1998): 2918–40. http://dx.doi.org/10.1152/jn.1998.80.6.2918.
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Chelazzi, Leonardo, John Duncan, Earl K. Miller, and Robert Desimone. Responses of neurons in inferior temporal cortex during memory-guided visual search. J. Neurophysiol. 80: 2918–2940, 1998. A typical scene will contain many different objects, few of which are relevant to behavior at any given moment. Thus attentional mechanisms are needed to select relevant objects for visual processing and control over behavior. We examined this role of attention in the inferior temporal cortex of macaque monkeys, using a visual search paradigm. While the monkey maintained fixation, a cue stimulus was presented at the center of gaze, followed by a blank delay period. After the delay, an array of two to five choice stimuli was presented extrafoveally, and the monkey was rewarded for detecting a target stimulus matching the cue. The behavioral response was a saccadic eye movement to the target in one version of the task and a lever release in another. The array was composed of one “good” stimulus (effective in driving the cell when presented alone) and one or more “poor” stimuli (ineffective in driving the cell when presented alone). Most cells showed higher delay activity after a good stimulus used as the cue than after a poor stimulus. The baseline activity of cells was also higher preceding a good cue, if the animal expected it to occur. This activity may depend on a top-down bias in favor of cells coding the relevant stimulus. When the choice array was presented, most cells showed suppressive interactions between the stimuli as well as strong attention effects. When the choice array was presented in the contralateral visual field, most cells initially responded the same, regardless of which stimulus was the target. However, within 150–200 ms of array onset, responses were determined by the target stimulus. If the target was the good stimulus, the response to the array became equal to the response to the good stimulus presented alone. If the target was a poor stimulus, the response approached the response to that stimulus presented alone. Thus the influence of the nontarget stimulus was eliminated. These effects occurred well in advance of the behavioral response. When the array was positioned with stimuli on opposite sides of the vertical meridian, the contralateral stimulus appeared to dominate the response, and this dominant effect could not be overcome by attention. Overall, the results support a “biased competition” model of attention, according to which 1) objects in the visual field compete for representation in the cortex, and 2) this competition is biased in favor of the behaviorally relevant object by virtue of “top-down” feedback from structures involved in working memory.
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Paré, Martin, and Robert H. Wurtz. "Progression in Neuronal Processing for Saccadic Eye Movements From Parietal Cortex Area LIP to Superior Colliculus." Journal of Neurophysiology 85, no. 6 (June 1, 2001): 2545–62. http://dx.doi.org/10.1152/jn.2001.85.6.2545.
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Neurons in both the lateral intraparietal area (LIP) of the monkey parietal cortex and the intermediate layers of the superior colliculus (SC) are activated well in advance of the initiation of saccadic eye movements. To determine whether there is a progression in the covert processing for saccades from area LIP to SC, we systematically compared the discharge properties of LIP output neurons identified by antidromic activation with those of SC neurons collected from the same monkeys. First, we compared activity patterns during a delayed saccade task and found that LIP and SC neurons showed an extensive overlap in their responses to visual stimuli and in their sustained activity during the delay period. The saccade activity of LIP neurons was, however, remarkably weaker than that of SC neurons and never occurred without any preceding delay activity. Second, we assessed the dependence of LIP and SC activity on the presence of a visual stimulus by contrasting their activity in delayed saccade trials in which the presentation of the visual stimulus was either sustained (visual trials) or brief (memory trials). Both the delay and the presaccadic activity levels of the LIP neuronal sample significantly depended on the sustained presence of the visual stimulus, whereas those of the SC neuronal sample did not. Third, we examined how the LIP and SC delay activity relates to the future production of a saccade using a delayed GO/NOGO saccade task, in which a change in color of the fixation stimulus instructed the monkey either to make a saccade to a peripheral visual stimulus or to withhold its response and maintain fixation. The average delay activity of both LIP and SC neuronal samples significantly increased by the advance instruction to make a saccade, but LIP neurons were significantly less dependent on the response instruction than SC neurons, and only a minority of LIP neurons was significantly modulated. Thus despite some overlap in their discharge properties, the neurons in the SC intermediate layers showed a greater independence from sustained visual stimulation and a tighter relationship to the production of an impending saccade than the LIP neurons supplying inputs to the SC. Rather than representing the transmission of one processing stage in parietal cortex area LIP to a subsequent processing stage in SC, the differences in neuronal activity that we observed suggest instead a progressive evolution in the neuronal processing for saccades.
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Takeuchi, D., T. Hirabayashi, K. Tamura, and Y. Miyashita. "Reversal of Interlaminar Signal Between Sensory and Memory Processing in Monkey Temporal Cortex." Science 331, no. 6023 (March 17, 2011): 1443–47. http://dx.doi.org/10.1126/science.1199967.
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Peng, Xinmiao, Margaret E. Sereno, Amanda K. Silva, Sidney R. Lehky, and Anne B. Sereno. "Shape Selectivity in Primate Frontal Eye Field." Journal of Neurophysiology 100, no. 2 (August 2008): 796–814. http://dx.doi.org/10.1152/jn.01188.2007.
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Previous neurophysiological studies of the frontal eye field (FEF) in monkeys have focused on its role in saccade target selection and gaze shift control. It has been argued that FEF neurons indicate the locations of behaviorally significant visual stimuli and are not inherently sensitive to specific features of the visual stimuli per se. Here, for the first time, we directly examined single cell responses to simple, two-dimensional shapes and found that shape selectivity exists in a substantial number of FEF cells during a passive fixation task or during the sample, delay (memory), and eye movement periods in a delayed match to sample (DMTS) task. Our data demonstrate that FEF neurons show sensory and mnemonic selectivity for stimulus shape features whether or not they are behaviorally significant for the task at hand. We also investigated the extent and localization of activation in the FEF using a variety of shape stimuli defined by static or dynamic cues employing functional magentic resonance imaging (fMRI) in anesthetized and paralyzed monkeys. Our fMRI results support the electrophysiological findings by showing significant FEF activation for a variety of shape stimuli and cues in the absence of attentional and motor processing. This shape selectivity in FEF is comparable to previous reports in the ventral pathway, inviting a reconsideration of the functional organization of the visual system.
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Fuster, J. M. "Inferotemporal units in selective visual attention and short-term memory." Journal of Neurophysiology 64, no. 3 (September 1, 1990): 681–97. http://dx.doi.org/10.1152/jn.1990.64.3.681.
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1. This research was designed to further clarify how, in the primate, the neurons of the inferotemporal (IT) cortex support the cognitive functions of visually guided behavior. Specifically, the aim was to determine the role of those neurons in 1) selective attention to behaviorally relevant features of the visual environment and 2) retention of those features in temporary memory. Monkeys were trained in a memory task in which they had to discriminate and retain individual features of compound stimuli, each stimulus consisting of a colored disk with a gray symbol in the middle. A trial began with brief presentation of one such stimulus, the sample for the trial. Depending on the symbol in it, the monkey had to memorize the symbol itself or the background color; after 10-20 s of delay (retention period), two compound stimuli appeared, and the animal had to choose the one with the symbol or with the color of the sample. Thus the test required attention to the symbol, in some trials also to the color, and short-term retention of the distinctive feature for each trial, either a symbol or a color. Single-unit activity was recorded from cortex of the IT convexity, lower and upper banks of the superior temporal sulcus (STS), and from striate cortex (V1). Firing frequency was analyzed during intertrial periods and during the entirety of every trial, except for the (match) choice period. 2. In IT cortex, as in V1, many units responded to the sample stimulus. Some responded indiscriminately to all samples, whereas others responded selectively to one of their features, i.e., to one symbol or to one color. Fifteen percent of the IT units were symbol selective and 21% color selective. These neurons appeared capable of extracting individual features from complex stimuli. Some color cells (color-attentive units) responded significantly more to their preferred color when it was relevant (i.e., had to be retained) than when it was not. 3. The latency of IT-unit response to the sample stimulus was, on the average, relatively short in unselective units (mean 159 ms), longer in symbol units (mean 203 ms), and longest in color-attentive units (mean 270 ms). This order of latencies corresponds to the presumed order of participation of those three types of units in the selective attention to the component features of the sample as required by the task. It suggests intervening steps of serial processing before color information reached color-attentive cells.(ABSTRACT TRUNCATED AT 400 WORDS)
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Srinivas, Kavitha, Sarah D. Breedin, H. Branch Coslett, and Eleanor M. Saffran. "Intact Perceptual Priming in a Patient with Damage to the Anterior Inferior Temporal Lobes." Journal of Cognitive Neuroscience 9, no. 4 (July 1997): 490–511. http://dx.doi.org/10.1162/jocn.1997.9.4.490.
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We conducted three experiments to examine whether the anterior portion of the inferior temporal (IT) lobe is involved in the processing of visual objects in humans. In monkeys, damage to this region results in severe deficits in perception and in memory for visual objects. Our study was designed to examine both these processes in a patient (DM) with bilateral damage to the anterior portion of the inferior temporal lobe. Neuropsychological examination revealed a significant semantic impairment and a mild deficit in the discrimination of familiar objects from nonobjects. Despite these difficulties, the results of several studies indicated that DM was able to form and retain descriptions of the structure of objects. Specifically, DM showed normal perceptual priming for familiar and novel objects on implicit memory tests, even when the objects were transformed in size and left-right orientation. These results suggest that the anterior IT is not'involved in (1) the storage of pre-existing structural descriptions of known objects, (2) the ability to create new structural descriptions for novel objects, and (3) the ability to compute descriptions that are invariant with respect to changes in size and reflection. Instead, the anterior IT appears to provide the interface between structural descriptions of objects and their meanings.
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Chen, He, and Yuji Naya. "Automatic Encoding of a View-Centered Background Image in the Macaque Temporal Lobe." Cerebral Cortex 30, no. 12 (July 8, 2020): 6270–83. http://dx.doi.org/10.1093/cercor/bhaa183.
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Abstract Perceptual processing along the ventral visual pathway to the hippocampus (HPC) is hypothesized to be substantiated by signal transformation from retinotopic space to relational space, which represents interrelations among constituent visual elements. However, our visual perception necessarily reflects the first person’s perspective based on the retinotopic space. To investigate this two-facedness of visual perception, we compared neural activities in the temporal lobe (anterior inferotemporal cortex, perirhinal and parahippocampal cortices, and HPC) between when monkeys gazed on an object and when they fixated on the screen center with an object in their peripheral vision. We found that in addition to the spatially invariant object signal, the temporal lobe areas automatically represent a large-scale background image, which specify the subject’s viewing location. These results suggest that a combination of two distinct visual signals on relational space and retinotopic space may provide the first person’s perspective serving for perception and presumably subsequent episodic memory.
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Houk, J. C., C. Bastianen, D. Fansler, A. Fishbach, D. Fraser, P. J. Reber, S. A. Roy, and L. S. Simo. "Action selection and refinement in subcortical loops through basal ganglia and cerebellum." Philosophical Transactions of the Royal Society B: Biological Sciences 362, no. 1485 (April 11, 2007): 1573–83. http://dx.doi.org/10.1098/rstb.2007.2063.
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Subcortical loops through the basal ganglia and the cerebellum form computationally powerful distributed processing modules (DPMs). This paper relates the computational features of a DPM's loop through the basal ganglia to experimental results for two kinds of natural action selection. First, functional imaging during a serial order recall task was used to study human brain activity during the selection of sequential actions from working memory. Second, microelectrode recordings from monkeys trained in a step-tracking task were used to study the natural selection of corrective submovements. Our DPM-based model assisted in the interpretation of puzzling data from both of these experiments. We come to posit that the many loops through the basal ganglia each regulate the embodiment of pattern formation in a given area of cerebral cortex. This operation serves to instantiate different kinds of action (or thought) mediated by different areas of cerebral cortex. We then use our findings to formulate a model of the aetiology of schizophrenia.
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Disney, Anita A. "Neuromodulatory Control of Early Visual Processing in Macaque." Annual Review of Vision Science 7, no. 1 (September 15, 2021): 181–99. http://dx.doi.org/10.1146/annurev-vision-100119-125739.
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Visual processing is dynamically controlled by multiple neuromodulatory molecules that modify the responsiveness of neurons and the strength of the connections between them. In particular, modulatory control of processing in the lateral geniculate nucleus of the thalamus, V1, and V2 will alter the outcome of all subsequent processing of visual information, including the extent to and manner in which individual inputs contribute to perception and decision making and are stored in memory. This review addresses five small-molecule neuromodulators—acetylcholine, dopamine, serotonin, noradrenaline, and histamine—considering the structural basis for their action, and the effects of their release, in the early visual pathway of the macaque monkey. Traditionally, neuromodulators are studied in isolation and in discrete circuits; this review makes a case for considering the joint action of modulatory molecules and differences in modulatory effects across brain areas as a better means of understanding the diverse roles that these molecules serve.
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Colby, C. L., J. R. Duhamel, and M. E. Goldberg. "Visual, presaccadic, and cognitive activation of single neurons in monkey lateral intraparietal area." Journal of Neurophysiology 76, no. 5 (November 1, 1996): 2841–52. http://dx.doi.org/10.1152/jn.1996.76.5.2841.
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1. Posterior parietal cortex contains neurons that are visually responsive and active in relation to saccadic eye movements. We recorded from single neurons in a subregion of parietal cortex, the lateral intraparietal area (LIP), in alert rhesus monkeys. To characterize more completely the circumstances under which LIP neurons are responsive, we used five tasks designed to test the impact of sensory, motor, and cognitive factors. We obtained quantitative data in multiple tasks in 91 neurons. We measured neural activity during central fixation and in relation to stimulus onset and saccade onset. 2. LIP neurons have visual responses to the onset of a stationary stimulus in the receptive field. These visual responses occurred both in tasks that require a subsequent eye movement toward the stimulus and in tasks in which eye movements are not permitted, indicating that this activity is sensory rather than presaccadic. 3. Visual responses were enhanced when the monkey had to use information provided by the stimulus to guide its behavior. The amplitude of the sensory response to a given stimulus was increased in a task in which the monkey would subsequently make a saccade to the location signaled by the stimulus, as compared with the amplitude of the visual response in a simple fixation task. 4. The visual response was also enhanced when the monkey attended to the stimulus without looking at it. This result shows that enhancement does not reflect saccade preparation because the response is enhanced even when the monkey is not permitted to make a saccade. Instead, enhancement reflects the allocation of attention to the spatial locus of the receptive field. 5. Many LIP neurons had saccade-related activity in addition to their visual responses. The visual response for most neurons was stronger than the saccade-related activation. 6. Saccade-related activity was independent of visual activity. Similar presaccadic activity was observed in trials that included a recent visual stimulus (memory-guided saccade task) and in trials with no visual stimulus (learned saccade task). 7. We observed increases in activity during fixation in tasks in which the monkey could anticipate the onset of a behaviorally significant stimulus. LIP neurons usually showed low levels of background firing in the fixation task during the period before stimulus onset. This background activity was increased in the peripheral attention and memory-guided saccade tasks during the period when the monkey was waiting for a behaviorally relevant stimulus to appear. 8. The results from these several tasks indicate that LIP neurons are activated in a variety of circumstances and are not involved exclusively in sensory processing or motor planning. The modulation of sensory responses by attention and anticipation suggests that cognitive factors play a major role in parietal function.
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Tauste Campo, Adrià, Marina Martinez-Garcia, Verónica Nácher, Rogelio Luna, Ranulfo Romo, and Gustavo Deco. "Task-driven intra- and interarea communications in primate cerebral cortex." Proceedings of the National Academy of Sciences 112, no. 15 (March 30, 2015): 4761–66. http://dx.doi.org/10.1073/pnas.1503937112.
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Neural correlations during a cognitive task are central to study brain information processing and computation. However, they have been poorly analyzed due to the difficulty of recording simultaneous single neurons during task performance. In the present work, we quantified neural directional correlations using spike trains that were simultaneously recorded in sensory, premotor, and motor cortical areas of two monkeys during a somatosensory discrimination task. Upon modeling spike trains as binary time series, we used a nonparametric Bayesian method to estimate pairwise directional correlations between many pairs of neurons throughout different stages of the task, namely, perception, working memory, decision making, and motor report. We find that solving the task involves feedforward and feedback correlation paths linking sensory and motor areas during certain task intervals. Specifically, information is communicated by task-driven neural correlations that are significantly delayed across secondary somatosensory cortex, premotor, and motor areas when decision making takes place. Crucially, when sensory comparison is no longer requested for task performance, a major proportion of directional correlations consistently vanish across all cortical areas.
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Bisley, James W., Daniel Zaksas, Jason A. Droll, and Tatiana Pasternak. "Activity of Neurons in Cortical Area MT During a Memory for Motion Task." Journal of Neurophysiology 91, no. 1 (January 2004): 286–300. http://dx.doi.org/10.1152/jn.00870.2003.
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We recorded the activity of middle temporal (MT) neurons in 2 monkeys while they compared the directions of motion in 2 sequentially presented random-dot stimuli, sample and test, and reported them as the same or different by pressing one of 2 buttons. We found that MT neurons were active not only in response to the sample and test stimuli but also during the 1,500-ms delay separating them. Most neurons showed a characteristic pattern of activity consisting of a small burst of firing early in the delay, followed by a period of suppression and a subsequent increase in firing rate immediately preceding the presentation of the test stimulus. In a third of the neurons, the activity early in the delay not only reflected the direction of the sample stimulus, but was also related to the range of local directions it contained. During the middle of the delay the majority of neurons were suppressed, consistent with a gating mechanism that could be used to ignore task-irrelevant stimuli. Late in the delay, most neurons showed an increase in response, probably in anticipation of the upcoming test. Throughout most of the delay there was a directional signal in the population of MT neurons, manifested by higher firing rates following the sample moving in the antipreferred direction. Whereas some of these effects may be related to sensory adaptation, others are more likely to represent a more active task-related process. These results support the hypothesis that MT neurons actively participate in the successful execution of all aspects of the task requiring processing and remembering visual motion.
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Gruber, Aaron J., Sara A. Solla, D. James Surmeier, and James C. Houk. "Modulation of Striatal Single Units by Expected Reward: A Spiny Neuron Model Displaying Dopamine-Induced Bistability." Journal of Neurophysiology 90, no. 2 (August 2003): 1095–114. http://dx.doi.org/10.1152/jn.00618.2002.
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Single-unit activity in the neostriatum of awake monkeys shows a marked dependence on expected reward. Responses to visual cues differ when animals expect primary reinforcements, such as juice rewards, in comparison to secondary reinforcements, such as tones. The mechanism of this reward-dependent modulation has not been established experimentally. To assess the hypothesis that direct neuromodulatory effects of dopamine on spiny neurons can account for this modulation, we develop a computational model based on simplified representations of key ionic currents and their modulation by D1 dopamine receptor activation. This minimal model can be analyzed in detail. We find that D1-mediated increases of inward rectifying potassium and L-type calcium currents cause a bifurcation: the native up/down state behavior of the spiny neuron model becomes truly bistable, which modulates the peak firing rate and the duration of the up state and introduces a dependence of the response on the past state history. These generic consequences of dopamine neuromodulation through bistability can account for both reward-dependent enhancement and suppression of spiny neuron single-unit responses to visual cues. We validate the model by simulating responses to visual targets in a memory-guided saccade task; our results are in close agreement with the main features of the experimental data. Our model provides a conceptual framework for understanding the functional significance of the short-term neuromodulatory actions of dopamine on signal processing in the striatum.
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Zaitsev, A. V., N. V. Povysheva, G. Gonzalez-Burgos, and D. A. Lewis. "Electrophysiological classes of layer 2/3 pyramidal cells in monkey prefrontal cortex." Journal of Neurophysiology 108, no. 2 (July 15, 2012): 595–609. http://dx.doi.org/10.1152/jn.00859.2011.
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The activity of supragranular pyramidal neurons in the dorsolateral prefrontal cortex (DLPFC) neurons is hypothesized to be a key contributor to the cellular basis of working memory in primates. Therefore, the intrinsic membrane properties, a crucial determinant of a neuron's functional properties, are important for the role of DLPFC pyramidal neurons in working memory. The present study aimed to investigate the biophysical properties of pyramidal cells in layer 2/3 of monkey DLPFC to create an unbiased electrophysiological classification of these cells. Whole cell voltage recordings in the slice preparation were performed in 77 pyramidal cells, and 24 electrophysiological measures of their passive and active intrinsic membrane properties were analyzed. Based on the results of cluster analysis of 16 independent electrophysiological variables, 4 distinct electrophysiological classes of monkey pyramidal cells were determined. Two classes contain regular-spiking neurons with low and high excitability and constitute 52% of the pyramidal cells sampled. These subclasses of regular-spiking neurons mostly differ in their input resistance, minimum current that evoked firing, and current-to-frequency transduction properties. A third class of pyramidal cells includes low-threshold spiking cells (17%), which fire a burst of three-five spikes followed by regular firing at all suprathreshold current intensities. The last class consists of cells with an intermediate firing pattern (31%). These cells have two modes of firing response, regular spiking and bursting discharge, depending on the strength of stimulation and resting membrane potential. Our results show that diversity in the functional properties of DLPFC pyramidal cells may contribute to heterogeneous modes of information processing during working memory and other cognitive operations that engage the activity of cortical circuits in the superficial layers of the DLPFC.
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Tudusciuc, Oana, and Andreas Nieder. "Contributions of Primate Prefrontal and Posterior Parietal Cortices to Length and Numerosity Representation." Journal of Neurophysiology 101, no. 6 (June 2009): 2984–94. http://dx.doi.org/10.1152/jn.90713.2008.
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The ability to understand and manipulate quantities ensures the survival of animals and humans alike. The frontoparietal network in primates has been implicated in representing, along with other cognitive abilities, abstract quantity. The respective roles of the prefrontal and parietal areas and the way continuous quantities, as opposed to discrete ones, are represented in this network, however, are unknown. We investigated this issue by simultaneously analyzing recorded single-unit activity in the prefrontal cortex (PFC) and the fundus of the intraparietal sulcus (IPS) of two macaque monkeys while they were engaged in delayed match-to-sample tasks discriminating line length and numerosity. In both areas, we found anatomically intermingled neurons encoding either length, numerosity, or both types of quantities. Even though different sets of neurons coded these quantities, the representation of length and numerosity was similar within the IPS and PFC. Both length and numerosity were coded by tuning functions peaking at the preferred quantity, thus supporting a labeled-line code for continuous and discrete quantity. A comparison of the response characteristics between parietal and frontal areas revealed a larger proportion of IPS neurons representing each quantity type in the early sample phase, in addition to shorter response latencies to quantity for IPS neurons. Moreover, IPS neurons discriminated quantities during the sample phase better than PFC neurons, as quantified by the receiver operating characteristic area. In the memory period, the discharge properties of PFC and IPS neurons were comparable. These single-cell results are in good agreement with functional imaging data from humans and support the notion that representations of continuous and discrete quantities share a frontoparietal substrate, with IPS neurons constituting the putative entry stage of the processing hierarchy.
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Beiser, David G., and James C. Houk. "Model of Cortical-Basal Ganglionic Processing: Encoding the Serial Order of Sensory Events." Journal of Neurophysiology 79, no. 6 (June 1, 1998): 3168–88. http://dx.doi.org/10.1152/jn.1998.79.6.3168.
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Beiser, David G. and James C. Houk. Model of cortical-basal ganglionic processing: encoding the serial order of sensory events. J. Neurophysiol. 79: 3168–3188, 1998. Several lines of evidence suggest that the prefrontal (PF) cortex and basal ganglia are important in cognitive aspects of serial order in behavior. We present a modular neural network model of these areas that encodes the serial order of events into spatial patterns of PF activity. The model is based on the topographically specific circuits linking the PF with the basal ganglia. Each module traces a pathway from the PF, through the basal ganglia and thalamus, and back to the PF. The complete model consists of an array of modules interacting through recurrent corticostriatal projections and collateral inhibition between striatal spiny units. The model's architecture positions spiny units for the classification of cortical contexts and events and provides bistable cortical-thalamic loops for sustaining a representation of these contextual events in working memory activations. The model was tested with a simulated version of a delayed-sequencing task. In single-unit studies, the task begins with the presentation of a sequence of target lights. After a short delay, the monkey must touch the targets in the order in which they were presented. When instantiated with randomly distributed corticostriatal weights, the model produces different patterns of PF activation in response to different target sequences. These patterns represent an unambiguous and spatially distributed encoding of the sequence. Parameter studies of these random networks were used to compare the computational consequences of collateral and feed-forward inhibition within the striatum. In addition, we studied the receptive fields of 20,640 model units and uncovered an interesting set of cue-, rank- and sequence-related responses that qualitatively resemble responses reported in single unit studies of the PF. The majority of units respond to more than one sequence of stimuli. A method for analyzing serial receptive fields is presented and utilized for comparing the model units to single-unit data.
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Gore, Alex. "Monkeys' memory." New Scientist 193, no. 2587 (January 2007): 18. http://dx.doi.org/10.1016/s0262-4079(07)60144-4.
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Ito, M., H. Tamura, I. Fujita, and K. Tanaka. "Size and position invariance of neuronal responses in monkey inferotemporal cortex." Journal of Neurophysiology 73, no. 1 (January 1, 1995): 218–26. http://dx.doi.org/10.1152/jn.1995.73.1.218.
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1. Object vision is largely invariant to changes of retinal images of objects in size and position. To reveal neuronal mechanisms of this invariance, we recorded activities from single cells in the anterior part of the inferotemporal cortex (anterior IT), determined the critical features for the activation of individual cells, and examined the effects of changes in stimulus size and position on the responses. 2. Twenty-one percent of the anterior IT cells studied here responded to ranges of size > 4 octaves, whereas 43% responded to size ranges < 2 octaves. The optimal stimulus size, measured by the distance between the outer edges along the longest axis of the stimulus, ranged from 1.7 to 30 degrees. 3. The selectivity for shape was mostly preserved over the entire range of effective size and over the receptive field, whereas some subtle but statistically significant changes were observed in one half of the cells studied here. 4. The size-specific responses observed in 43% of the cells are consistent with recent psychophysical data that suggest that images of objects are stored in a size-specific manner in the long-term memory. Both size-dependent and -independent processing of images may occur in anterior IT.
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Issar, Deepa, Ryan C. Williamson, Sanjeev B. Khanna, and Matthew A. Smith. "A neural network for online spike classification that improves decoding accuracy." Journal of Neurophysiology 123, no. 4 (April 1, 2020): 1472–85. http://dx.doi.org/10.1152/jn.00641.2019.
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Separating neural signals from noise can improve brain-computer interface performance and stability. However, most algorithms for separating neural action potentials from noise are not suitable for use in real time and have shown mixed effects on decoding performance. With the goal of removing noise that impedes online decoding, we sought to automate the intuition of human spike-sorters to operate in real time with an easily tunable parameter governing the stringency with which spike waveforms are classified. We trained an artificial neural network with one hidden layer on neural waveforms that were hand-labeled as either spikes or noise. The network output was a likelihood metric for each waveform it classified, and we tuned the network’s stringency by varying the minimum likelihood value for a waveform to be considered a spike. Using the network’s labels to exclude noise waveforms, we decoded remembered target location during a memory-guided saccade task from electrode arrays implanted in prefrontal cortex of rhesus macaque monkeys. The network classified waveforms in real time, and its classifications were qualitatively similar to those of a human spike-sorter. Compared with decoding with threshold crossings, in most sessions we improved decoding performance by removing waveforms with low spike likelihood values. Furthermore, decoding with our network’s classifications became more beneficial as time since array implantation increased. Our classifier serves as a feasible preprocessing step, with little risk of harm, that could be applied to both off-line neural data analyses and online decoding. NEW & NOTEWORTHY Although there are many spike-sorting methods that isolate well-defined single units, these methods typically involve human intervention and have inconsistent effects on decoding. We used human classified neural waveforms as training data to create an artificial neural network that could be tuned to separate spikes from noise that impaired decoding. We found that this network operated in real time and was suitable for both off-line data processing and online decoding.
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Sereno, Anne B., and Silvia C. Amador. "Attention and Memory-Related Responses of Neurons in the Lateral Intraparietal Area During Spatial and Shape-Delayed Match-to-Sample Tasks." Journal of Neurophysiology 95, no. 2 (February 2006): 1078–98. http://dx.doi.org/10.1152/jn.00431.2005.
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When a monkey attends to, remembers, and looks toward targets, the activity of some neurons in the lateral intraparietal area (LIP) changes. We recorded from isolated neurons during both a spatial and a shape match-to-sample task to examine and characterize voluntary active processes in LIP. Many LIP neurons show spatially selective activity during the delay period that depends on the location of the sample, but for most cells, this activity does not differ between the two tasks. Although much past work in posterior parietal cortex has explained responses in this region in terms of active processes such as decision-making and motor planning, our findings suggest that much of that activity represents more passive processing. Nevertheless, we do see a significant minority of units that demonstrate instruction-dependent activity during the delay period, suggesting that these units could represent the neural correlates of voluntary or active processes. Separately, we found that during the presentation of the sample stimulus and test array, some units show stronger responses to the stimulus in the shape-matching task when the animal must attend to the shape of a stimulus. This elevated response to the sample during the shape task provides evidence for feature-based attention in LIP. Attention to shape is a property that has not previously been described in primate cortex.
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Chafee, Matthew V., and Patricia S. Goldman-Rakic. "Matching Patterns of Activity in Primate Prefrontal Area 8a and Parietal Area 7ip Neurons During a Spatial Working MemoryTask." Journal of Neurophysiology 79, no. 6 (June 1, 1998): 2919–40. http://dx.doi.org/10.1152/jn.1998.79.6.2919.
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Chafee, Matthew V. and Patricia S. Goldman-Rakic. Matching patterns of activity in primate prefrontal area 8a and parietal area 7ip neurons during a spatial working memory task. J. Neurophysiol. 79: 2919–2940, 1998. Single-unit recording studies of posterior parietal neurons have indicated a similarity of neuronal activation to that observed in the dorsolateral prefrontal cortex in relation to performance of delayed saccade tasks. A key issue addressed in the present study is whether the different classes of neuronal activity observed in these tasks are encountered more frequently in one or the other area or otherwise exhibit region-specific properties. The present study is the first to directly compare these patterns of neuronal activity by alternately recording from parietal area 7ip and prefrontal area 8a, under the identical behavioral conditions, within the same hemisphere of two monkeys performing an oculomotor delayed response task. The firing rate of 222 posterior parietal and 235 prefrontal neurons significantly changed during the cue, delay, and/or saccade periods of the task. Neuronal responses in the two areas could be distinguished only by subtle differences in their incidence and timing. Thus neurons responding to the cue appeared earliest and were more frequent among the task-related neurons within parietal cortex, whereas neurons exhibiting delay-period activity accounted for a larger proportion of task-related neurons in prefrontal cortex. Otherwise, the task-related neuronal activities were remarkably similar. Cue period activity in prefrontal and parietal cortex exhibited comparable spatial tuning and temporal duration characteristics, taking the form of phasic, tonic, or combined phasic/tonic excitation in both cortical populations. Neurons in both cortical areas exhibited sustained activity during the delay period with nearly identical spatial tuning. The various patterns of delay-period activity—tonic, increasing or decreasing, alone or in combination with greater activation during cue and/or saccade periods—likewise were distributed to both cortical areas. Finally, similarities in the two populations extended to the proportion and spatial tuning of presaccadic and postsaccadic neuronal activity occurring in relation to the memory-guided saccade. The present findings support and extend evidence for a faithful duplication of receptive field properties and virtually every other dimension of task-related activity observed when parietal and prefrontal cortex are recruited to a common task. This striking similarity attests to the principal that information shared by a prefrontal region and a sensory association area with which it is connected is domain specific and not subject to hierarchical elaboration, as is evident at earlier stages of visuospatial processing.