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Welcome to the all-new INC web site. We welcome any comments.
Please bear with us during this transition. Click here to get back to the original home page. Note that some links will automatically redirect you to the new site.
See recording of lecture (.mp4)
Who:
Dr. Bruce McNaughton
Distinguished Professor, Department of Neurobiology and Behavior Center for the Neurobiology of Learning and Memory University of California, Irvine
When:
4:00 - 5:30, Monday, April 14, 2014
Where:
San Diego Supercomputer Center Auditorium, Floor B-2, 10100 Hopkins Dr., La Jolla, CA 92093
Abstract:
The hippocampal formation is crucial to the storage and consolidation of 'episodic' memories: memories for experiences that unfold in space and time. It accomplishes its role in memory using so-called 'place-cells', which provide a unique code reflecting the spatio-temporal context of experiences. This code serves as a tag or 'index' that links together sub-components of a given experience which are stored in distributed form throughout the neocortex. The index code is generated by complex interactions of cellular and network mechanisms whose understanding has been greatly facilitated by technologies that enable monitoring cellular activity from large numbers of neurons in the brains of behaving animals. These interactions enable integration of self-motion information to keep track of spatial location, and append information about external and internal events onto the resulting internal spatial coordinate system, thus generating a 'cognitive map'. Networks in thalamus and midbrain ('head-direction cells') compute relative head orientation (azimuth) as animals rotate their heads; cells in medial entorhinal cortex ('grid cells') fire in a regular, 2-D periodic, spatial pattern ('grid field') when an animal moves about its world. Head-direction and grid cells can be explained by a theory in which pre-wired synaptic matrices determine ring (1-D) or toroidal (2-D; 'doughnut-like') manifolds of allowed states ('attractors') of network activity. The speed by which the neuronal state is updated relative to the animal's physical motion in space sets the scale of the 2-D grid field, and there are multiple such grid cell modules, each with a different movement gain, and thus each expressing a different spatial scale. Next, hippocampal place cells, which receive grid field information at multiple spatial scales, provide unique codes for spatial location, possibly by a Fourier synthesis-like summation on their inputs. Finally, inputs from other brain regions, representing features and events in the world, or internal states such as goals, modulate the rate (but not relative location) of place cell firing, thus generating a unique, conjunctive code for 'what' happened 'where'. Although they exhibit a high degree of experience-dependent plasticity, these networks appear to be wired up by a self-organizing process in early post-natal development in a manner that is independent of experience (a priori). Thus, in a sense, Immanuel Kant was correct: "Space⦠originates from the mind's nature in accord with a stable law as a scheme, as it were, for coordinating everything sensed externally".