Rockwood Memorial Lecture
2006Department of Cognitive Science,Kavli Institute for Brain and Mind, UC San Diego
4:00PM, Tuesday, April 4, 2006
Liebow Auditorium, Basic Science Building, UCSD
Title: "Unwiring the Brain: Neuromorphic Engineering of Motion Detection"
Models of Neural computation rely on accurate understanding of the underlying neural operations of single cells, small overlapping assemblies and interacting populations. Lettvin's "Bug Detector", a specific neuron type in the deepest layer of the optic tectum of all vertebrates, was first described in 1959 in a report to the IEEE. This neuron responds with exquisite sensitivity to extremely small, rapidly moving stimuli over a large portion of the visual world. It responds in a linear manner to motion ("speed") but shows no directionality in its responses. Using a combination of morphological, biophysical, and histochemical methods, (combined with "back-of-the-napkin" modeling) we have uncovered the "microarchitecture" of the motion detecting process of single cells in the tectum. This was found to be consequent to the unique properties of the afferents, geometry of the dendrites relative to the visual inputs, and the intrinsic biophysical properties of the motion detector itself. We are now exploring how the overlapping population of these neurons operate communally to optimize signal detection and reduce error. The next synaptic target in the sequence is able to then extract the direction of motion. This circuit provides the substrate for Weiskrantz's "Blindsight", or, motion detection in the temporal lobe in the presence of scotomata in the visual cortex.
Host: Terry Sejnowski