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John Patrick Aggleton - One of the best experts on this subject based on the ideXlab platform.
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Stable encoding of visual cues in the mouse Retrosplenial Cortex
bioRxiv, 2019Co-Authors: Anna Powell, Seralynne Denise Vann, John Patrick Aggleton, Andrew J D Nelson, William M. Connelly, Asta Vasalauskaite, Frank Sengpiel, Adam RansonAbstract:Abstract The rodent Retrosplenial Cortex functions as an integrative hub for sensory and motor signals, serving roles in both navigation and memory. While Retrosplenial Cortex (RSC) is reciprocally connected with the sensory Cortex, the form in which sensory information is represented in the Retrosplenial Cortex and how it interacts with behavioural state is unclear. Here, we used 2-photon cellular imaging of neural activity of putative excitatory (CaMKII expressing) and inhibitory (parvalbumin expressing) neurons to measure visual and running evoked activity in RSC and compare it to primary visual Cortex (V1). We found that stimulus position and orientation information was preserved between V1 and RSC, and additionally that positional information was organised topographically. Stimulus directional preference was biased towards nasal-temporal flow. Locomotion modulation of activity of single neurons, both in darkness and light, was also more pronounced in RSC than V1, and strongest in parvalbumin-positive neurons. Longitudinal measurements of single neurons showed that these response features were stably maintained over many weeks. These data provide evidence for stable representations of visual cues in Retrosplenial Cortex which are highly spatially selective. These may provide sensory data to contribute to the formation of memories of spatial information.
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Lesions of Retrosplenial Cortex spare immediate-early gene activity in related limbic regions in the rat:
Brain and neuroscience advances, 2018Co-Authors: Anna Powell, John Patrick Aggleton, Emma Hindley, Moira Davies, Eman Amin, Andrew Nelson, Seralynne Denise VannAbstract:The Retrosplenial Cortex forms part of a network of cortical and subcortical structures that have particular importance for spatial learning and navigation in rodents. This study examined how Retrosplenial lesions affect activity in this network by visualising the expression of the immediate-early genes c-fos and zif268 after exposure to a novel location. Groups of rats with extensive cytotoxic lesions (areas 29 and 30) and rats with lesions largely confined to area 30 (dysgranular Cortex) were compared with their respective control animals for levels of c-fos expression measured by immunohistochemistry. These cortical lesions had very limited effects on distal c-fos activity. Evidence of a restricted reduction in c-fos activity was seen in the septal dentate gyrus (superior blade) but not in other hippocampal and parahippocampal subareas, nor in the anterior cingulate and prelimbic cortices. Related studies examined zif268 activity in those cases with combined area 29 and 30 lesions. The only clear evidence for reduced zif268 activity following Retrosplenial cell loss came from the septal CA3 area. The confined impact of Retrosplenial tissue loss is notable as, by the same immediate-early gene measures, Retrosplenial Cortex is itself highly sensitive to damage in related limbic areas, showing a marked c-fos and zif268 hypoactivity across all of its subareas. This asymmetry in covert pathology may help to explain the apparent disparity between the severity of learning deficits after Retrosplenial Cortex lesions and after lesions in either the hippocampus or the anterior thalamic nuclei.
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When is the rat Retrosplenial Cortex required for stimulus integration
Behavioral neuroscience, 2018Co-Authors: Andrew J D Nelson, Seralynne Denise Vann, Emma Hindley, John Patrick AggletonAbstract:The rodent Retrosplenial Cortex is known to be vital for spatial cognition, but evidence has also pointed to a role in processing nonspatial information. It has been suggested that the Retrosplenial Cortex may serve as a site of integration of incoming sensory information. To examine this proposal, the current set of experiments assessed the impact of excitotoxic lesions in the Retrosplenial Cortex on two behavioral tasks that tax animals' ability to process multiple and overlapping environmental stimuli. In Experiment 1, rats with Retrosplenial lesions acquired a negative patterning discrimination, a form of configural learning that can be solved only by learning the conjunction of cues. Subsequent transfer tests confirmed that both the lesion and control animals had solved the task by using configural representations. Furthermore, in Experiment 2, a 2nd cohort of Retrosplenial lesion animals successfully acquired conditioned inhibition. Nevertheless, the same animals failed a subsequent summation test that assesses the ability to transfer what has been learned about one stimulus to another stimulus in the absence of reinforcement. Taken together, these results suggest that in the nonspatial domain, the Retrosplenial Cortex is not required for forming associations between multiple or overlapping environmental stimuli and, consequently, Retrosplenial engagement in such processes is more selective than was previously envisaged. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
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The rat Retrosplenial Cortex as a link for frontal functions: A lesion analysis.
Behavioural brain research, 2017Co-Authors: Anna Powell, John Patrick Aggleton, Andrew J D Nelson, Emma Hindley, Moira Davies, Seralynne Denise VannAbstract:Cohorts of rats with excitotoxic Retrosplenial Cortex lesions were tested on four behavioural tasks sensitive to dysfunctions in prelimbic Cortex, anterior cingulate Cortex, or both. In this way the study tested whether Retrosplenial Cortex has nonspatial functions that reflect its anatomical interactions with these frontal cortical areas. In Experiment 1, Retrosplenial Cortex lesions had no apparent effect on a set-shifting digging task that taxed intradimensional and extradimensional attention, as well as reversal learning. Likewise, Retrosplenial Cortex lesions did not impair a strategy shift task in an automated chamber, which involved switching from visual-based to response-based discriminations and, again, included a reversal (Experiment 2). Indeed, there was evidence that the Retrosplenial lesions aided the initial switch to response-based selection. No lesion deficit was found on an automated cost-benefit task that pitted size of reward against effort to achieve that reward (Experiment 3). Finally, while Retrosplenial Cortex lesions affected matching-to-place task in a T-maze, the profile of deficits differed from that associated with prelimbic Cortex damage (Experiment 4). When the task was switched to a nonmatching design, Retrosplenial Cortex lesions had no apparent effect on performance. The results from the four experiments show that many frontal tasks do not require the Retrosplenial Cortex, highlighting the specificity of their functional interactions. The results show how Retrosplenial Cortex lesions spare those learning tasks in which there is no mismatch between the internal and external representations used to guide behavioural choice. In addition, these experiments further highlight the importance of the Retrosplenial Cortex in solving tasks with a spatial component.
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The Retrosplenial Cortex and object recency memory in the rat.
The European journal of neuroscience, 2017Co-Authors: Anna Powell, Seralynne Denise Vann, John Patrick Aggleton, C.m. Olarte-sánchez, Lisa Kinnavane, Moira Davies, Eman Amin, Andrew J D NelsonAbstract:It has been proposed that the Retrosplenial Cortex forms part of a "where/when" information network. The present study focussed on the related issue of whether Retrosplenial Cortex also contributes to "what/when" information, by examining object recency memory. In Experiment 1, rats with Retrosplenial lesions were found to be impaired at distinguishing the temporal order of objects presented in a continuous series ('Within-Block' condition). The same lesioned rats could, however, distinguish between objects that had been previously presented in one of two discrete blocks ('Between-Block' condition). Experiment 2 used intact rats to map the expression of the immediate-early gene c-fos in Retrosplenial Cortex following performance of a between-block, recency discrimination. Recency performance correlated positively with levels of c-fos expression in both granular and dysgranular Retrosplenial Cortex (areas 29 and 30). Expression of c-fos in the granular Retrosplenial Cortex also correlated with prelimbic Cortex and ventral subiculum c-fos activity, the latter also correlating with recency memory performance. The combined findings from both experiments reveal an involvement of the Retrosplenial Cortex in temporal order memory, which includes both between-block and within-block problems. The current findings also suggest that the rat Retrosplenial Cortex comprises one of a group of closely interlinked regions that enable recency memory, including the hippocampal formation, medial diencephalon, and medial frontal Cortex. In view of the well-established importance of the Retrosplenial Cortex for spatial learning, the findings support the notion that, with its frontal and hippocampal connections, Retrosplenial Cortex has a key role for both what/when and where/when information. This article is protected by copyright. All rights reserved.
Seralynne Denise Vann - One of the best experts on this subject based on the ideXlab platform.
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The Retrosplenial Cortex and long-term spatial memory: from the cell to the network.
Current opinion in behavioral sciences, 2020Co-Authors: Michal M. Milczarek, Seralynne Denise VannAbstract:In this review we briefly outline how lesion studies, temporary inactivation and neural activity assays have helped update functional models of the Retrosplenial Cortex, a region critical for episodic and spatial memory. We advocate for the continued importance of appropriately designed behavioural studies in the context of novel experimental methods, such as optogenetic and chemogenetic manipulations. At the same time, we caution against the overreliance on any given level of analysis or experimental technique. Complementary, multimodal strategies are required for understanding how the Retrosplenial Cortex contributes to the formation and storage of memories both at a structural and systems-level.
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Stable encoding of visual cues in the mouse Retrosplenial Cortex
bioRxiv, 2019Co-Authors: Anna Powell, Seralynne Denise Vann, John Patrick Aggleton, Andrew J D Nelson, William M. Connelly, Asta Vasalauskaite, Frank Sengpiel, Adam RansonAbstract:Abstract The rodent Retrosplenial Cortex functions as an integrative hub for sensory and motor signals, serving roles in both navigation and memory. While Retrosplenial Cortex (RSC) is reciprocally connected with the sensory Cortex, the form in which sensory information is represented in the Retrosplenial Cortex and how it interacts with behavioural state is unclear. Here, we used 2-photon cellular imaging of neural activity of putative excitatory (CaMKII expressing) and inhibitory (parvalbumin expressing) neurons to measure visual and running evoked activity in RSC and compare it to primary visual Cortex (V1). We found that stimulus position and orientation information was preserved between V1 and RSC, and additionally that positional information was organised topographically. Stimulus directional preference was biased towards nasal-temporal flow. Locomotion modulation of activity of single neurons, both in darkness and light, was also more pronounced in RSC than V1, and strongest in parvalbumin-positive neurons. Longitudinal measurements of single neurons showed that these response features were stably maintained over many weeks. These data provide evidence for stable representations of visual cues in Retrosplenial Cortex which are highly spatially selective. These may provide sensory data to contribute to the formation of memories of spatial information.
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Lesions of Retrosplenial Cortex spare immediate-early gene activity in related limbic regions in the rat:
Brain and neuroscience advances, 2018Co-Authors: Anna Powell, John Patrick Aggleton, Emma Hindley, Moira Davies, Eman Amin, Andrew Nelson, Seralynne Denise VannAbstract:The Retrosplenial Cortex forms part of a network of cortical and subcortical structures that have particular importance for spatial learning and navigation in rodents. This study examined how Retrosplenial lesions affect activity in this network by visualising the expression of the immediate-early genes c-fos and zif268 after exposure to a novel location. Groups of rats with extensive cytotoxic lesions (areas 29 and 30) and rats with lesions largely confined to area 30 (dysgranular Cortex) were compared with their respective control animals for levels of c-fos expression measured by immunohistochemistry. These cortical lesions had very limited effects on distal c-fos activity. Evidence of a restricted reduction in c-fos activity was seen in the septal dentate gyrus (superior blade) but not in other hippocampal and parahippocampal subareas, nor in the anterior cingulate and prelimbic cortices. Related studies examined zif268 activity in those cases with combined area 29 and 30 lesions. The only clear evidence for reduced zif268 activity following Retrosplenial cell loss came from the septal CA3 area. The confined impact of Retrosplenial tissue loss is notable as, by the same immediate-early gene measures, Retrosplenial Cortex is itself highly sensitive to damage in related limbic areas, showing a marked c-fos and zif268 hypoactivity across all of its subareas. This asymmetry in covert pathology may help to explain the apparent disparity between the severity of learning deficits after Retrosplenial Cortex lesions and after lesions in either the hippocampus or the anterior thalamic nuclei.
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When is the rat Retrosplenial Cortex required for stimulus integration
Behavioral neuroscience, 2018Co-Authors: Andrew J D Nelson, Seralynne Denise Vann, Emma Hindley, John Patrick AggletonAbstract:The rodent Retrosplenial Cortex is known to be vital for spatial cognition, but evidence has also pointed to a role in processing nonspatial information. It has been suggested that the Retrosplenial Cortex may serve as a site of integration of incoming sensory information. To examine this proposal, the current set of experiments assessed the impact of excitotoxic lesions in the Retrosplenial Cortex on two behavioral tasks that tax animals' ability to process multiple and overlapping environmental stimuli. In Experiment 1, rats with Retrosplenial lesions acquired a negative patterning discrimination, a form of configural learning that can be solved only by learning the conjunction of cues. Subsequent transfer tests confirmed that both the lesion and control animals had solved the task by using configural representations. Furthermore, in Experiment 2, a 2nd cohort of Retrosplenial lesion animals successfully acquired conditioned inhibition. Nevertheless, the same animals failed a subsequent summation test that assesses the ability to transfer what has been learned about one stimulus to another stimulus in the absence of reinforcement. Taken together, these results suggest that in the nonspatial domain, the Retrosplenial Cortex is not required for forming associations between multiple or overlapping environmental stimuli and, consequently, Retrosplenial engagement in such processes is more selective than was previously envisaged. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
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the papez circuit and recognition memory contributions of the medial diencephalon and Retrosplenial Cortex to what where and when aspects of object recognition memory
2018Co-Authors: Andrew John Dudley Nelson, James C Perry, Seralynne Denise VannAbstract:Abstract Both the medial diencephalon and Retrosplenial Cortex are vital for human episodic memory as well as spatial memory in rodents. The contribution of the mammillary bodies, the mammillothalamic tract, anterior thalamic nuclei and Retrosplenial Cortex to different aspects of recognition memory (i.e., what, where, when) will be the focus of the current chapter. Evidence derived from the rodent novel object recognition memory paradigm has confirmed that none of these structures is important for the ability to detect a novel from familiar item. However, consistent impairments emerge when animals are required to make judgements about the spatial arrangement of objects. Similarly, lesions in all three sites impair the ability to discriminate between multiple items on the basis of relative recency. Although there are subtle differences in their respective involvement in recency memory, the profile of deficits associated with these brain regions is remarkably consistent. As well as reviewing this evidence, this chapter will discuss potential explanations for the apparent equivalence of object recognition deficits found after damage to the mammillary bodies, the mammillothalamic tract, anterior thalamic nuclei and Retrosplenial Cortex.
Andrew J D Nelson - One of the best experts on this subject based on the ideXlab platform.
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Stable encoding of visual cues in the mouse Retrosplenial Cortex
bioRxiv, 2019Co-Authors: Anna Powell, Seralynne Denise Vann, John Patrick Aggleton, Andrew J D Nelson, William M. Connelly, Asta Vasalauskaite, Frank Sengpiel, Adam RansonAbstract:Abstract The rodent Retrosplenial Cortex functions as an integrative hub for sensory and motor signals, serving roles in both navigation and memory. While Retrosplenial Cortex (RSC) is reciprocally connected with the sensory Cortex, the form in which sensory information is represented in the Retrosplenial Cortex and how it interacts with behavioural state is unclear. Here, we used 2-photon cellular imaging of neural activity of putative excitatory (CaMKII expressing) and inhibitory (parvalbumin expressing) neurons to measure visual and running evoked activity in RSC and compare it to primary visual Cortex (V1). We found that stimulus position and orientation information was preserved between V1 and RSC, and additionally that positional information was organised topographically. Stimulus directional preference was biased towards nasal-temporal flow. Locomotion modulation of activity of single neurons, both in darkness and light, was also more pronounced in RSC than V1, and strongest in parvalbumin-positive neurons. Longitudinal measurements of single neurons showed that these response features were stably maintained over many weeks. These data provide evidence for stable representations of visual cues in Retrosplenial Cortex which are highly spatially selective. These may provide sensory data to contribute to the formation of memories of spatial information.
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When is the rat Retrosplenial Cortex required for stimulus integration
Behavioral neuroscience, 2018Co-Authors: Andrew J D Nelson, Seralynne Denise Vann, Emma Hindley, John Patrick AggletonAbstract:The rodent Retrosplenial Cortex is known to be vital for spatial cognition, but evidence has also pointed to a role in processing nonspatial information. It has been suggested that the Retrosplenial Cortex may serve as a site of integration of incoming sensory information. To examine this proposal, the current set of experiments assessed the impact of excitotoxic lesions in the Retrosplenial Cortex on two behavioral tasks that tax animals' ability to process multiple and overlapping environmental stimuli. In Experiment 1, rats with Retrosplenial lesions acquired a negative patterning discrimination, a form of configural learning that can be solved only by learning the conjunction of cues. Subsequent transfer tests confirmed that both the lesion and control animals had solved the task by using configural representations. Furthermore, in Experiment 2, a 2nd cohort of Retrosplenial lesion animals successfully acquired conditioned inhibition. Nevertheless, the same animals failed a subsequent summation test that assesses the ability to transfer what has been learned about one stimulus to another stimulus in the absence of reinforcement. Taken together, these results suggest that in the nonspatial domain, the Retrosplenial Cortex is not required for forming associations between multiple or overlapping environmental stimuli and, consequently, Retrosplenial engagement in such processes is more selective than was previously envisaged. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
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Retrosplenial Cortex and its role in spatial cognition
bioRxiv, 2017Co-Authors: Anna S Mitchell, Rafal Czajkowski, Ningyu Zhang, Kate J Jeffery, Andrew J D NelsonAbstract:Retrosplenial Cortex (RSC) is a region within the posterior neocortical system, heavily interconnected with an array of brain networks, both cortical and subcortical, that is engaged by a myriad of cognitive tasks. Although there is no consensus as to its precise function, evidence from both human and animal studies clearly points to a role in spatial cognition. However, the spatial processing impairments that follow RSC damage are not straightforward to characterise, leading to difficulties in defining the exact nature of its role. In the present article we review this literature and classify the types of ideas that have been put forward into three broad, somewhat overlapping classes: (i) Learning of landmark location, stability and permanence; (ii) Integration between spatial reference frames, and (iii) Consolidation and retrieval of spatial knowledge (9schemas9). We evaluate these models and suggest ways to test them, before briefly discussing whether the spatial function may be a subset of a more general function in episodic memory.
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The rat Retrosplenial Cortex as a link for frontal functions: A lesion analysis.
Behavioural brain research, 2017Co-Authors: Anna Powell, John Patrick Aggleton, Andrew J D Nelson, Emma Hindley, Moira Davies, Seralynne Denise VannAbstract:Cohorts of rats with excitotoxic Retrosplenial Cortex lesions were tested on four behavioural tasks sensitive to dysfunctions in prelimbic Cortex, anterior cingulate Cortex, or both. In this way the study tested whether Retrosplenial Cortex has nonspatial functions that reflect its anatomical interactions with these frontal cortical areas. In Experiment 1, Retrosplenial Cortex lesions had no apparent effect on a set-shifting digging task that taxed intradimensional and extradimensional attention, as well as reversal learning. Likewise, Retrosplenial Cortex lesions did not impair a strategy shift task in an automated chamber, which involved switching from visual-based to response-based discriminations and, again, included a reversal (Experiment 2). Indeed, there was evidence that the Retrosplenial lesions aided the initial switch to response-based selection. No lesion deficit was found on an automated cost-benefit task that pitted size of reward against effort to achieve that reward (Experiment 3). Finally, while Retrosplenial Cortex lesions affected matching-to-place task in a T-maze, the profile of deficits differed from that associated with prelimbic Cortex damage (Experiment 4). When the task was switched to a nonmatching design, Retrosplenial Cortex lesions had no apparent effect on performance. The results from the four experiments show that many frontal tasks do not require the Retrosplenial Cortex, highlighting the specificity of their functional interactions. The results show how Retrosplenial Cortex lesions spare those learning tasks in which there is no mismatch between the internal and external representations used to guide behavioural choice. In addition, these experiments further highlight the importance of the Retrosplenial Cortex in solving tasks with a spatial component.
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The Retrosplenial Cortex and object recency memory in the rat.
The European journal of neuroscience, 2017Co-Authors: Anna Powell, Seralynne Denise Vann, John Patrick Aggleton, C.m. Olarte-sánchez, Lisa Kinnavane, Moira Davies, Eman Amin, Andrew J D NelsonAbstract:It has been proposed that the Retrosplenial Cortex forms part of a "where/when" information network. The present study focussed on the related issue of whether Retrosplenial Cortex also contributes to "what/when" information, by examining object recency memory. In Experiment 1, rats with Retrosplenial lesions were found to be impaired at distinguishing the temporal order of objects presented in a continuous series ('Within-Block' condition). The same lesioned rats could, however, distinguish between objects that had been previously presented in one of two discrete blocks ('Between-Block' condition). Experiment 2 used intact rats to map the expression of the immediate-early gene c-fos in Retrosplenial Cortex following performance of a between-block, recency discrimination. Recency performance correlated positively with levels of c-fos expression in both granular and dysgranular Retrosplenial Cortex (areas 29 and 30). Expression of c-fos in the granular Retrosplenial Cortex also correlated with prelimbic Cortex and ventral subiculum c-fos activity, the latter also correlating with recency memory performance. The combined findings from both experiments reveal an involvement of the Retrosplenial Cortex in temporal order memory, which includes both between-block and within-block problems. The current findings also suggest that the rat Retrosplenial Cortex comprises one of a group of closely interlinked regions that enable recency memory, including the hippocampal formation, medial diencephalon, and medial frontal Cortex. In view of the well-established importance of the Retrosplenial Cortex for spatial learning, the findings support the notion that, with its frontal and hippocampal connections, Retrosplenial Cortex has a key role for both what/when and where/when information. This article is protected by copyright. All rights reserved.
Douglas A. Nitz - One of the best experts on this subject based on the ideXlab platform.
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Conjunctive coding in an evolved spiking model of Retrosplenial Cortex.
Behavioral neuroscience, 2018Co-Authors: Emily L. Rounds, Andrew S. Alexander, Douglas A. Nitz, Jeffrey L. KrichmarAbstract:Retrosplenial Cortex (RSC) is an association Cortex supporting spatial navigation and memory. However, critical issues remain concerning the forms by which its ensemble spiking patterns register spatial relationships that are difficult for experimental techniques to fully address. We therefore applied an evolutionary algorithmic optimization technique to create spiking neural network models that matched electrophysiologically observed spiking dynamics in rat RSC neuronal ensembles. Virtual experiments conducted on the evolved networks revealed a mixed selectivity coding capability that was not built into the optimization method, but instead emerged as a consequence of replicating biological firing patterns. The experiments reveal several important outcomes of mixed selectivity that may subserve flexible navigation and spatial representation: (a) robustness to loss of specific inputs, (b) immediate and stable encoding of novel routes and route locations, (c) automatic resolution of input variable conflicts, and (d) dynamic coding that allows rapid adaptation to changing task demands without retraining. These findings suggest that biological Retrosplenial Cortex can generate unique, first-trial, conjunctive encodings of spatial positions and actions that can be used by downstream brain regions for navigation and path integration. Moreover, these results are consistent with the proposed role for the RSC in the transformation of representations between reference frames and navigation strategy deployment. Finally, the specific modeling framework used for evolving synthetic Retrosplenial networks represents an important advance for computational modeling by which synthetic neural networks can encapsulate, describe, and predict the behavior of neural circuits at multiple levels of function. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
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Spatially Periodic Activation Patterns of Retrosplenial Cortex Encode Route Sub-spaces and Distance Traveled.
Current biology : CB, 2017Co-Authors: Andrew S. Alexander, Douglas A. NitzAbstract:Traversal of a complicated route is often facilitated by considering it as a set of related sub-spaces. Such compartmentalization processes could occur within Retrosplenial Cortex, a structure whose neurons simultaneously encode position within routes and other spatial coordinate systems. Here, Retrosplenial Cortex neurons were recorded as rats traversed a track having recurrent structure at multiple scales. Consistent with a major role in compartmentalization of complex routes, individual Retrosplenial Cortex (RSC) neurons exhibited periodic activation patterns that repeated across route segments having the same shape. Concurrently, a larger population of RSC neurons exhibited single-cycle periodicity over the full route, effectively defining a framework for encoding of sub-route positions relative to the whole. The same population simultaneously provides a novel metric for distance from each route position to all others. Together, the findings implicate Retrosplenial Cortex in the extraction of path sub-spaces, the encoding of their spatial relationships to each other, and path integration.
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Spatially periodic activation patterns of Retrosplenial Cortex encode route sub-spaces and distance travelled
2017Co-Authors: Andrew S. Alexander, Douglas A. NitzAbstract:Traversal of a complicated route is often facilitated by considering it as a set of related sub-spaces. Such compartmentalization processes could occur within Retrosplenial Cortex, a structure whose neurons simultaneously encode position within routes and other spatial coordinate systems. Here, Retrosplenial Cortex neurons were recorded as rats traversed a track having recurrent structure at multiple scales. Consistent with a major role in compartmentalization of complex routes, individual RSC neurons exhibited periodic activation patterns that repeated across route segments having the same shape. Concurrently, a larger population of RSC neurons exhibited single-cycle periodicity over the full route, effectively defining a framework for encoding of sub-route positions relative to the whole. The same population simultaneously provides a novel metric for distance from each route position to all others. Together, the findings implicate Retrosplenial Cortex in the extraction of path sub-spaces, the encoding of their spatial relationships to each other, and path integration.
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Retrosplenial Cortex maps the conjunction of internal and external spaces
Nature Neuroscience, 2015Co-Authors: Andrew S. Alexander, Douglas A. NitzAbstract:Intelligent behavior demands not only multiple forms of spatial representation, but also coordination among the brain regions mediating those representations. Retrosplenial Cortex is densely interconnected with the majority of cortical and subcortical brain structures that register an animal's position in multiple internal and external spatial frames of reference. This unique anatomy suggests that it functions to integrate distinct forms of spatial information and provides an interface for transformations between them. Evidence for this was found in rats traversing two different routes placed at different environmental locations. Retrosplenial ensembles robustly encoded conjunctions of progress through the current route, position in the larger environment and the left versus right turning behavior of the animal. Thus, the Retrosplenial Cortex has the requisite dynamics to serve as an intermediary between brain regions generating different forms of spatial mapping, a result that is consistent with navigational and episodic memory impairments following damage to this region in humans. Intelligent behavior demands coordination among the multiple forms of spatial representation generated in distinct neural structures. Here, Alexander and Nitz show that Retrosplenial Cortex neuron ensembles conjunctively encode progression through routes, environmental position, and the actions of the animal. Thus, the region may serve as a critical interface between brain regions generating different forms of spatial mapping.
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Retrosplenial Cortex maps the conjunction of internal and external spaces
Nature neuroscience, 2015Co-Authors: Andrew S. Alexander, Douglas A. NitzAbstract:Intelligent behavior demands coordination among the multiple forms of spatial representation generated in distinct neural structures. Here, Alexander and Nitz show that Retrosplenial Cortex neuron ensembles conjunctively encode progression through routes, environmental position, and the actions of the animal. Thus, the region may serve as a critical interface between brain regions generating different forms of spatial mapping.
Andrew S. Alexander - One of the best experts on this subject based on the ideXlab platform.
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Egocentric boundary vector tuning of the Retrosplenial Cortex.
Science advances, 2020Co-Authors: Andrew S. Alexander, Lucas C. Carstensen, James R. Hinman, Florian Raudies, G. William Chapman, Michael E. HasselmoAbstract:The Retrosplenial Cortex is reciprocally connected with multiple structures implicated in spatial cognition, and damage to the region itself produces numerous spatial impairments. Here, we sought to characterize spatial correlates of neurons within the region during free exploration in two-dimensional environments. We report that a large percentage of Retrosplenial Cortex neurons have spatial receptive fields that are active when environmental boundaries are positioned at a specific orientation and distance relative to the animal itself. We demonstrate that this vector-based location signal is encoded in egocentric coordinates, is localized to the dysgranular Retrosplenial subregion, is independent of self-motion, and is context invariant. Further, we identify a subpopulation of neurons with this response property that are synchronized with the hippocampal theta oscillation. Accordingly, the current work identifies a robust egocentric spatial code in Retrosplenial Cortex that can facilitate spatial coordinate system transformations and support the anchoring, generation, and utilization of allocentric representations.
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Egocentric boundary vector tuning of the Retrosplenial Cortex
2019Co-Authors: Andrew S. Alexander, Lucas C. Carstensen, James R. Hinman, Florian Raudies, G. William Chapman, Michael E. HasselmoAbstract:Abstract The Retrosplenial Cortex is reciprocally connected with a majority of structures implicated in spatial cognition and damage to the region itself produces numerous spatial impairments. However, in many ways the Retrosplenial Cortex remains understudied. Here, we sought to characterize spatial correlates of neurons within the region during free exploration in two-dimensional environments. We report that a large percentage of Retrosplenial Cortex neurons have spatial receptive fields that are active when environmental boundaries are positioned at a specific orientation and distance relative to the animal itself. We demonstrate that this vector-based location signal is encoded in egocentric coordinates, localized to the dysgranular Retrosplenial sub-region, independent of self-motion, and context invariant. Further, we identify a sub-population of neurons with this response property that are synchronized with the hippocampal theta oscillation. Accordingly, the current work identifies a robust egocentric spatial code in Retrosplenial Cortex that can facilitate spatial coordinate system transformations and support the anchoring, generation, and utilization of allocentric representations.
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Conjunctive coding in an evolved spiking model of Retrosplenial Cortex.
Behavioral neuroscience, 2018Co-Authors: Emily L. Rounds, Andrew S. Alexander, Douglas A. Nitz, Jeffrey L. KrichmarAbstract:Retrosplenial Cortex (RSC) is an association Cortex supporting spatial navigation and memory. However, critical issues remain concerning the forms by which its ensemble spiking patterns register spatial relationships that are difficult for experimental techniques to fully address. We therefore applied an evolutionary algorithmic optimization technique to create spiking neural network models that matched electrophysiologically observed spiking dynamics in rat RSC neuronal ensembles. Virtual experiments conducted on the evolved networks revealed a mixed selectivity coding capability that was not built into the optimization method, but instead emerged as a consequence of replicating biological firing patterns. The experiments reveal several important outcomes of mixed selectivity that may subserve flexible navigation and spatial representation: (a) robustness to loss of specific inputs, (b) immediate and stable encoding of novel routes and route locations, (c) automatic resolution of input variable conflicts, and (d) dynamic coding that allows rapid adaptation to changing task demands without retraining. These findings suggest that biological Retrosplenial Cortex can generate unique, first-trial, conjunctive encodings of spatial positions and actions that can be used by downstream brain regions for navigation and path integration. Moreover, these results are consistent with the proposed role for the RSC in the transformation of representations between reference frames and navigation strategy deployment. Finally, the specific modeling framework used for evolving synthetic Retrosplenial networks represents an important advance for computational modeling by which synthetic neural networks can encapsulate, describe, and predict the behavior of neural circuits at multiple levels of function. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
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Spatially Periodic Activation Patterns of Retrosplenial Cortex Encode Route Sub-spaces and Distance Traveled.
Current biology : CB, 2017Co-Authors: Andrew S. Alexander, Douglas A. NitzAbstract:Traversal of a complicated route is often facilitated by considering it as a set of related sub-spaces. Such compartmentalization processes could occur within Retrosplenial Cortex, a structure whose neurons simultaneously encode position within routes and other spatial coordinate systems. Here, Retrosplenial Cortex neurons were recorded as rats traversed a track having recurrent structure at multiple scales. Consistent with a major role in compartmentalization of complex routes, individual Retrosplenial Cortex (RSC) neurons exhibited periodic activation patterns that repeated across route segments having the same shape. Concurrently, a larger population of RSC neurons exhibited single-cycle periodicity over the full route, effectively defining a framework for encoding of sub-route positions relative to the whole. The same population simultaneously provides a novel metric for distance from each route position to all others. Together, the findings implicate Retrosplenial Cortex in the extraction of path sub-spaces, the encoding of their spatial relationships to each other, and path integration.
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Spatially periodic activation patterns of Retrosplenial Cortex encode route sub-spaces and distance travelled
2017Co-Authors: Andrew S. Alexander, Douglas A. NitzAbstract:Traversal of a complicated route is often facilitated by considering it as a set of related sub-spaces. Such compartmentalization processes could occur within Retrosplenial Cortex, a structure whose neurons simultaneously encode position within routes and other spatial coordinate systems. Here, Retrosplenial Cortex neurons were recorded as rats traversed a track having recurrent structure at multiple scales. Consistent with a major role in compartmentalization of complex routes, individual RSC neurons exhibited periodic activation patterns that repeated across route segments having the same shape. Concurrently, a larger population of RSC neurons exhibited single-cycle periodicity over the full route, effectively defining a framework for encoding of sub-route positions relative to the whole. The same population simultaneously provides a novel metric for distance from each route position to all others. Together, the findings implicate Retrosplenial Cortex in the extraction of path sub-spaces, the encoding of their spatial relationships to each other, and path integration.
