The Experts below are selected from a list of 42 Experts worldwide ranked by ideXlab platform
Elizabeth A Buffalo - One of the best experts on this subject based on the ideXlab platform.
-
a map of visual space in the primate entoRhinal cortex
Nature, 2012Co-Authors: Nathaniel J Killian, Michael J Jutras, Elizabeth A BuffaloAbstract:Examination of spatial representations in the entoRhinal cortex of monkeys performing a visual memory task reveals individual neurons that emit action potentials when the monkey fixates multiple discrete locations in the visual field, and suggests that entoRhinal cortex neurons encode space during visual exploration, even without locomotion. Grid cells — neurons located in the entoRhinal cortex that exhibit place-modulated activity — provide the brain with the spatial information and spatial memory needed during navigation. The cells have been extensively studied in rodents, but there have been no single-unit analyses of grid cells in primates. Here, Elizabeth Buffalo and colleagues record entoRhinal cortex neural activity in monkeys performing a visual memory task involving images on a computer monitor. The resulting data directly demonstrate the existence of grid cells in primates, and show that these cells are active during visuospatial exploration, even when the animal is not moving and is simply searching with its eyes. Place-modulated activity among neurons in the hippocampal formation presents a means to organize contextual information in the service of memory formation and recall1,2. One particular spatial representation, that of grid cells, has been observed in the entoRhinal cortex (EC) of rats and bats3,4,5, but has yet to be described in single units in primates. Here we examined spatial representations in the EC of head-fixed monkeys performing a free-viewing visual memory task6,7. Individual neurons were identified in the primate EC that emitted action potentials when the monkey fixated multiple discrete locations in the visual field in each of many sequentially presented complex images. These firing fields possessed spatial periodicity similar to a triangular tiling with a corresponding well-defined hexagonal structure in the spatial autocorrelation. Further, these neurons showed theta-band oscillatory activity and changing spatial scale as a function of distance from the Rhinal Sulcus, which is consistent with previous findings in rodents4,8,9,10. These spatial representations may provide a framework to anchor the encoding of stimulus content in a complex visual scene. Together, our results provide a direct demonstration of grid cells in the primate and suggest that EC neurons encode space during visual exploration, even without locomotion.
Martin D Cassell - One of the best experts on this subject based on the ideXlab platform.
-
periRhinal cortex projections to the amygdaloid complex and hippocampal formation in the rat
The Journal of Comparative Neurology, 1999Co-Authors: C J Shi, Martin D CassellAbstract:The differential efferent projections of the periRhinal cortex were traced by using anterograde and retrograde tracing techniques. The dorsal bank cortex (area 36) projected lightly to the lateral entoRhinal cortex and more strongly to the lateral, posterolateral cortical, and posterior basomedial amygdaloid nuclei and amygdalostriatal transition zone. The ventral bank (dorsolateral entoRhinal cortex) projected to the lateral entoRhinal cortex, dorsal subiculum, and subfield CA1 and mainly targeted the basolateral amygdaloid nucleus. Corticocortical projections from the dorsal and ventral banks targeted different cortical areas. The fundus of the Rhinal Sulcus (area 35) projected to both lateral and medial entoRhinal cortices, ventral subiculum, lateral and basolateral nuclei, and amygdalostriatal transition zone. Corticocortical projections targeted areas projected to by both dorsal and ventral banks and also by second somatosensory area, first temporal cortical area, and striate cortex. Neurons projecting to the lateral nucleus were distributed in all layers of the dorsal bank, wheras those projecting to CA1 and subiculum were found in superfical layers (mostly layer III) of the ventral bank. Projections to the basolateral nucleus arose from superfical layers (mostly layer II) of the fundus and deep layers of the ventral bank. Furthermore, projections to the amygdala mostly arose from rostral levels, whereas hippocampal projections primarily originated caudally. The rat periRhinal cortex is heterogeneous in its efferent connectivity, and distinct projections arise from the dorsal and ventral banks and fundus of the Rhinal Sulcus. The widespread cortical connectivity of the fundus suggests that only this part of the periRhinal cortex is similar to area 35 of the primate brain.
Nathaniel J Killian - One of the best experts on this subject based on the ideXlab platform.
-
a map of visual space in the primate entoRhinal cortex
Nature, 2012Co-Authors: Nathaniel J Killian, Michael J Jutras, Elizabeth A BuffaloAbstract:Examination of spatial representations in the entoRhinal cortex of monkeys performing a visual memory task reveals individual neurons that emit action potentials when the monkey fixates multiple discrete locations in the visual field, and suggests that entoRhinal cortex neurons encode space during visual exploration, even without locomotion. Grid cells — neurons located in the entoRhinal cortex that exhibit place-modulated activity — provide the brain with the spatial information and spatial memory needed during navigation. The cells have been extensively studied in rodents, but there have been no single-unit analyses of grid cells in primates. Here, Elizabeth Buffalo and colleagues record entoRhinal cortex neural activity in monkeys performing a visual memory task involving images on a computer monitor. The resulting data directly demonstrate the existence of grid cells in primates, and show that these cells are active during visuospatial exploration, even when the animal is not moving and is simply searching with its eyes. Place-modulated activity among neurons in the hippocampal formation presents a means to organize contextual information in the service of memory formation and recall1,2. One particular spatial representation, that of grid cells, has been observed in the entoRhinal cortex (EC) of rats and bats3,4,5, but has yet to be described in single units in primates. Here we examined spatial representations in the EC of head-fixed monkeys performing a free-viewing visual memory task6,7. Individual neurons were identified in the primate EC that emitted action potentials when the monkey fixated multiple discrete locations in the visual field in each of many sequentially presented complex images. These firing fields possessed spatial periodicity similar to a triangular tiling with a corresponding well-defined hexagonal structure in the spatial autocorrelation. Further, these neurons showed theta-band oscillatory activity and changing spatial scale as a function of distance from the Rhinal Sulcus, which is consistent with previous findings in rodents4,8,9,10. These spatial representations may provide a framework to anchor the encoding of stimulus content in a complex visual scene. Together, our results provide a direct demonstration of grid cells in the primate and suggest that EC neurons encode space during visual exploration, even without locomotion.
C J Shi - One of the best experts on this subject based on the ideXlab platform.
-
periRhinal cortex projections to the amygdaloid complex and hippocampal formation in the rat
The Journal of Comparative Neurology, 1999Co-Authors: C J Shi, Martin D CassellAbstract:The differential efferent projections of the periRhinal cortex were traced by using anterograde and retrograde tracing techniques. The dorsal bank cortex (area 36) projected lightly to the lateral entoRhinal cortex and more strongly to the lateral, posterolateral cortical, and posterior basomedial amygdaloid nuclei and amygdalostriatal transition zone. The ventral bank (dorsolateral entoRhinal cortex) projected to the lateral entoRhinal cortex, dorsal subiculum, and subfield CA1 and mainly targeted the basolateral amygdaloid nucleus. Corticocortical projections from the dorsal and ventral banks targeted different cortical areas. The fundus of the Rhinal Sulcus (area 35) projected to both lateral and medial entoRhinal cortices, ventral subiculum, lateral and basolateral nuclei, and amygdalostriatal transition zone. Corticocortical projections targeted areas projected to by both dorsal and ventral banks and also by second somatosensory area, first temporal cortical area, and striate cortex. Neurons projecting to the lateral nucleus were distributed in all layers of the dorsal bank, wheras those projecting to CA1 and subiculum were found in superfical layers (mostly layer III) of the ventral bank. Projections to the basolateral nucleus arose from superfical layers (mostly layer II) of the fundus and deep layers of the ventral bank. Furthermore, projections to the amygdala mostly arose from rostral levels, whereas hippocampal projections primarily originated caudally. The rat periRhinal cortex is heterogeneous in its efferent connectivity, and distinct projections arise from the dorsal and ventral banks and fundus of the Rhinal Sulcus. The widespread cortical connectivity of the fundus suggests that only this part of the periRhinal cortex is similar to area 35 of the primate brain.
M W Brown - One of the best experts on this subject based on the ideXlab platform.
-
neuronal activity related to visual recognition memory long term memory and the encoding of recency and familiarity information in the primate anterior and medial inferior temporal and Rhinal cortex
Experimental Brain Research, 1993Co-Authors: F L Fahy, I P Riches, M W BrownAbstract:Recordings of the activity of 2705 single neurones were made in entoRhinal and periRhinal cortex, area TG of the temporal lobe, and the inferior temporal cortex both during monkeys' performance of a serial recognition memory task using complex pictures and when monkeys were shown objects. Responses of 120 (9.7%) of the visually responsive neurones recorded were significantly smaller to the second than to the first presentations of unfamiliar stimuli. The incidence of such responses was highest in periRhinal cortex plus areas TE1 and TE2 of the temporal lobe, intermediate in lateral entoRhinal cortex and areas TE3 and TG, and lowest in other parts of entoRhinal and inferior temporal cortex. Response decrements were maintained across 20 or more intervening presentations of other stimuli for the majority of the neurones tested. Responses of 43 (14.4%) of the visually responsive neurones tested were significantly greater to unfamiliar than to highly familiar stimuli. Such differential responses were found only in lateral entoRhinal and periRhinal cortex plus areas TG, TE1, TE2 and TE3. For 6 neurones the response difference was significant even when the familiar stimuli had not been seen for more than 24 h: such neurones demonstrate access to information stored in long-term memory for more than 24 h. Seven familiarity neurones signalled information concerning the relative familiarity of stimuli but not information concerning how recently they were last seen; 58 recency neurones signalled information concerning the recency of presentation of stimuli, but not their relative familiarity. Thus certain neurones demonstrate the separable encoding of recency and familiarity information. Neurones signalling information of use for recognition memory are found in cortex close to the Rhinal Sulcus where lesions result in major deficits in the performance of recognition memory tasks. The conjunction of these findings provides strong evidence for the importance of these neurones and this cortex for processes (recency and familiarity discrimination) necessary for recognition and working memory. The possible relation of the neuronal responses to priming memory is also discussed.