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Conférence mensuelle - Edmund T. RollsA theory of hippocampal function, and how it incorporates spatial view cells in primates and place cells in rodents

Abstract :

A quantitative computational theory of the operation of the hippocampus as an episodic memory system is described. The CA3 system operates as a single attractor or autoassociation network to enable rapid, one-trial, associations between any spatial location (place in rodents, or spatial view in primates) and an object or reward, and to provide for completion of the whole memory during recall from any part. The theory is extended to associations between time and object or reward to implement temporal order memory, also important in episodic memory. The dentate gyrus performs pattern separation by competitive learning to produce sparse representations, producing for example neurons with place-like fields from entorhinal cortex grid cells. The dentate granule cells produce by the very small number of mossy fiber connections to CA3 a randomizing pattern separation effect important during learning but not recall that separates out the patterns represented by CA3 firing to be very different from each other, which is optimal for an unstructured episodic memory system in which each memory must be kept distinct from other memories. The direct perforant path input to CA3 is quantitatively appropriate to provide the cue for recall in CA3, but not for learning. The CA1 recodes information from CA3 to set up associatively learned backprojections to neocortex to allow subsequent retrieval of information to neocortex, providing a quantitative account of the large number of hippocampo-neocortical and neocortical-neocortical backprojections. Tests of the theory including hippocampal subregion analyses and hippocampal NMDA receptor knockouts are described, and provide support for the theory.

Recordings from single hippocampal neurons in locomoting macaques reveal that some neurons are tuned to "spatial view". These hippocampal neurons (1) respond to a view of space “out there”, not to the place where the monkey is; (2) have responses that depend on where the monkey is looking, as shown by measuring eye  position; (3) can still occur (especially for CA1 neurons) if the view details are obscured with curtains; (4) that the cells (in e.g. CA1) retain part of their "space" tuning even in complete darkness, for several minutes; (5) that the spatial representation is allocentric; and (6) that the information about spatial view increases linearly with the number of cells in the representation. The spatial representation may be different from that of place cells in rats because of the smaller field of view of primates. It has also been shown that some hippocampal encode for objects, others for places in a room, and others for a combination of objects and places, while a monkey is performing an object-place memory task. This task is prototypical of episodic memory, and provides evidence that the primate hippocampus does associatively link information about objects and allocentric information about places “out-there”.

Selected publications

Rolls, E. T., Dempere-Marco,L. and Deco, G. (2013) Holding multiple items in short term memory: a neural mechanism. PLoS ONE 8(4): e6107

Gabbott,P.L. and Rolls,E.T. (2013). Increased neuronal firing in resting and sleep in areas of the macaque medial prefrontal cortex (mPFC) that are part of the default mode network. European Journal of Neuroscience DOI: 10.1111/ejn.12171.

Walters,D.M., Stringer,S.M. and Rolls,E .T. (2013) Path integration of head direction: updating a packet of neural activity at the correct speed using axonal conduction delays. PLoS ONE 8: e58330.

Rolls,E.T. (2013) A biased activation theory of the cognitive and attentional modulation of emotion. Frontiers in Human Neuroscience 7: 74.

Rolls,E.T. (2012) Taste, olfactory, and food texture reward processing in the brain and the control of appetite. Proceedings of the Nutrition Society 71: 488-501.

Rolls,E.T. (2012) Willed action, free will, and the stochastic neurodynamics of decision-making. Frontiers in Integrative Neuroscience 6: 68.

Rolls,E.T. (2010) A computational theory of episodic memory formation in the hippocampus. Behavioural Brain Research 215: 180-196.

Rolls,E.T. (2008) Memory, Attention, and Decision-Making. Oxford University Press: Oxford.

Rolls,E.T. and Xiang,J-Z. (2006) Spatial view cells in the primate hippocampus, and memory recall.

Reviews in the Neurosciences 17: 175-200.

Rolls,E.T. (2012) Advantages of dilution in the connectivity of attractor networks in the brain. Biologically Inspired Cognitive Architectures 1: 44-54.

Scientific focus :

Professor Rolls is a neuroscientist who has served as Professor of Experimental Psychology at Oxford University; as Fellow, Tutor and Vice President of Corpus Christi College, Oxford; as Associate Director of the MRC Interdisciplinary Research Centre in Cognitive Neuroscience at Oxford; as Secretary of the European Brain and Behaviour Society; and as Secretary of the Council of the European Neuroscience Association. In 2008 he was awarded Institute of Scientific Information HighlyCited.com status, recognising him as among the top 0.5% of neuroscientists in the world in terms of scientific impact.

In Rolls’ theory of emotion (2005) it is argued that emotions are states elicited by reinforcers which are the goals for action, the rewards and punishers. It is argued that emotions solve a fundamental problem in Darwinian evolution, for it is much more efficient for genes to specify goals for actions, rewards and punishers, rather than actions or responses. It is shown that the orbitofrontal cortex is important in emotion for it represents primary, unlearned, gene-specified, reinforcers including the taste and texture of food and face expression, and performs rapid learning, and reversal, of stimulus-reward associations. These reward systems in our brains provide inputs to much of our decision-making (Rolls 2008).

Christophe Mulle (mulle @ u-bordeaux2.fr)

Conférence labellisées "Formation doctorale neurosciences"

Conférences animées par les doctorants. Les étudiants n'ont pas à s'inscrire pour participer à ces conférences. Elles se déroulent en anglais et sont bien entendu ouvertes à tous (à toutes les disciplines même hors neurosciences). Un lunch cloture la conférence (discussion avec l'invité), ll est ouvert sur inscription (4 jours à l'avance auprès de Claire Biard "claire-helene.biard@u-bordeaux2.fr". (Free entrance, registration only if lunch with the speaker). Pas de lunch pour cette séance qui aura lieu à 14h, mais un coffee break.

Focus


Professor Edmund T. Rolls is a psychologist and neuroscientist. He currently serves as an Honorary Fellow in Applied Neuroimaging at the University of Warwick. He has written numerous highly cited publications in the fields of neural networks and computational neuroscience, with his work covering a wide area of topics within neuroscience.(Wikipedia)

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Edmund T. Rolls
Neuroculture: On the implications of brain science. Why do we have emotions? What are the bases of social behaviour? What is the relationship between the mind and the brain? How, and why, do we appreciate art? How do we make decisions? etc..