A feed-forward model of spatial and directional selectivity of hippocampal place cells (original) (raw)
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Spatial Processing in the Brain: The Activity of Hippocampal Place Cells
Annual Review of Neuroscience, 2001
The startling discovery by O'Keefe & Dostrovsky (Brain Res. 1971; 34: 171-75) that hippocampal neurons fire selectively in different regions or "place fields" of an environment and the subsequent development of the comprehensive theory by O'Keefe & Nadel (The Hippocampus as a Cognitive Map. Oxford, UK: Clarendon, 1978) that the hippocampus serves as a cognitive map have stimulated a substantial body of literature on the characteristics of hippocampal "place cells" and their relevance for our understanding of the mechanisms by which the brain processes spatial information. This paper reviews the major dimensions of the empirical research on place-cell activity and the development of computational models to explain various characteristics of place fields.
Spatial cognition and neuro-mimetic navigation: a model of hippocampal place cell activity
Biological Cybernetics, 2000
A computational model of hippocampal activity during spatial cognition and navigation tasks is presented. The spatial representation in our model of the rat hippocampus is built on-line during exploration via two processing streams. An allothetic vision-based representation is built by unsupervised Hebbian learning extracting spatio-temporal properties of the environment from visual input. An idiothetic representation is learned based on internal movement-related information provided by path integration. On the level of the hippocampus, allothetic and idiothetic representations are integrated to yield a stable representation of the environment by a population of localized overlapping CA3-CA1 place fields. The hippocampal spatial representation is used as a basis for goal-oriented spatial behavior. We focus on the neural pathway connecting the hippocampus to the nucleus accumbens. Place cells drive a population of locomotor action neurons in the nucleus accumbens. Reward-based learning is applied to map place cell activity into action cell activity. The ensemble action cell activity provides navigational maps to support spatial behavior. We present experimental results obtained with a mobile Khepera robot.
The Hippocampus, Memory, and Place Cells
Neuron, 1999
in humans and nonhuman primates. A major source of this limitation has been the contention that hippocampal processing is dedicated to spatial memory in rodents, in contrast to the global memory deficits observed following damage to the hippocampal region in humans and more recently in animals as well . Furthermore, several recent electrophysiological McGill University Montreal PQH3A 1B1 studies have revealed properties of hippocampal neuronal firing patterns that are inconsistent with the notion Canada ‡ Department of Neuroscience and Neurology of a cognitive map and indicate a broader scope of information processing. This paper will focus on these University and University Hospital of Kuopio 70211 Kuopio studies, reviewing some of the history and basic properties of place cells, and considering both early and recent Finland findings that shed light on the content and organization of information encoded within hippocampal neuronal activity. We will call into question the cognitive map Identifying the scope and nature of memory processing by the hippocampus has proved a formidable challenge. account and offer an alternative view.
Context-specific acquisition of location discrimination by hippocampal place cells
European Journal of Neuroscience, 2003
The spatially localized ®ring of rodent hippocampal place cells is strongly determined by the local geometry of the environment. Over time, however, the cells can acquire additional inputs, including inputs from more distal cues. This is manifest as a change in ®ring pattern (`remapping') when the new inputs are manipulated. Place cells also reorganize their ®ring in response to non-geometric changes in`context', such as a change in the colour or odour of the environment. The present study investigated whether the new inputs acquired by place cells in one context were still available to the cells when they expressed their altered ®ring patterns in a new context. We found that the acquired information did not transfer to the new context, suggesting that the context inputs and the acquired inputs must interact somewhere upstream of the place cells themselves. We present a model of one possible such interaction, and of how such an interaction could be modi®ed by experience in a Hebbian manner, thus explaining the context speci®city of the new learning.
Hippocampus, 2011
To ask if the properties of spatial learning supported by the hippocampus are distinct from the properties of conditioning, we conducted a blocking-like experiment in which the measured variable was not a conditioned response but rather the ability of a novel visual stimulus to control the location of place cell firing fields after being briefly combined with a familiar, salient stimulus to form a compound stimulus. For most rats, we found that rotations of the novel stimulus on the wall of a cylindrical recording chamber produced equal rotations of firing fields, whether exposure to the compound stimulus lasted 10 min or 60 min. Thus, there was little indication that the blocking phenomenon acted to prevent the rapid inclusion of a new stimulus into a previously experienced cue constellation. This result is in agreement with the finding of Doeller and Burgess (2008) that blocking is seen for landmark stimuli inside an arena but not for boundary stimuli that circumscribe the arena. We conclude that the rules governing incidental spatial learning are different for the hippocampal representation of a rat's environment than for conditioning. V V C 2010 Wiley-Liss, Inc.
Hippocampal place cells are topographically organized, but physical space has nothing to do with it
Brain Structure and Function, 2019
Topographical organization can be found in many areas of the cerebral cortex, although its presence in higher order cortices is debated. Some studies evaluated whether this pattern of organization is present in the hippocampus, trying to determine whether hippocampal place cells are organized around a topographical map of space. Those studies indicated that the topographical organization of hippocampal place cells is either very limited or simply nonexistent. In this paper, we argue for a different interpretation of available evidence and suggest that there is a topographical organization in hippocampal place cells, but the topographical map formed is not a map of the physical space. Although place cell firing is correlated with the animal's position and is important to spatial navigation, place cells encode much more information than just location. Thus, we should not expect the topographical map to be organized around physical space, but around an abstract, multidimensional space containing the receptive fields of place cells. We show that this conclusion is supported by two of the main theories of hippocampal function-cognitive map theory and index theory-which, when carefully analyzed, make exactly the same predictions about hippocampal topography. Such abstract topographical map would be extremely hard to find using the methods commonly employed in the literature, but there are some approaches that may, in the future, make possible to characterize the topographical organization in the hippocampus and other high-order brain regions.
Episodes in Space: A Modeling Study of Hippocampal Place Representation
Lecture Notes in Computer Science, 2008
A computer model of learning and representing spatial locations is studied. The model builds on biological constraints and assumptions drawn from the anatomy and physiology of the hippocampal formation of the rat. The emphasis of the presented research is on the usability of a computer model originally proposed to describe episodic memory capabilities of the hippocampus in a spatial task. In the present model two modalities -vision and path integration -are contributing to the recognition of a given place. We study how place cell activity emerges due to Hebbian learning in the model hippocampus as a result of random exploration of the environment. The model is implemented in the Webots mobile robotics simulation software. Our results show that the location of the robot is well predictable from the activity of a population of model place cells, thus the model is suitable to be used as a basic building block of location-based navigation strategies. However, some properties of the stored memories strongly resembles that of episodic memories, which do not match special spatial requirements.
Behavioural Brain Research, 2001
Rats learned to find the baited corner of a box surrounded by a curtain, regardless of whether they had a fixed or random point of entry (POE) through the curtain. On probe trials, rats used an internal direction sense carried from outside the curtain to solve the problem, and only used the visual cue inside the curtain if disoriented and denied access to a view of the room en route. Similar disorientation procedures were required to obtain cue control of hippocampal place fields. The results suggest that: (1) POE effects previously found in the water maze may be task-specific; (2) an undisrupted internal sense of direction carried from one environment to another may provide the preferred solution to spatial problems in the second environment, even when this second environment is a familiar one with stable visual cues; and (3) choice behaviour is sometimes, but not always, representative of the hippocampal representation of space.