Cellular Mechanisms of Spatiotemporal Processing

Washington University, Saint Louis MO

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Abstract

DESCRIPTION (provided by applicant): LONG-TERM OBJECTIVE: To understand the synaptic, dendritic and network mechanisms of spatiotemporal processing underlying the computation of visual motion. SPECIFIC AIMS: The aim is to provide a cellular- and systems-level understanding of spatiotemporal processing in the tectal SGC-I motion pathway, thereby providing insight into general neural strategies for visual motion processing. The specific aims are (1) to determine to what extent the retino-tectal dynamics renders the SGC-I response to dynamic visual stimuli largely insensitive to the details of the retinal transformation, (2) to investigate the functional role of dendritic spike initiation and nonlinear dendritic interaction for the neural analysis of space-time pattern in the presynaptic population activity, and (3) to investigate the functional role of neural structure and connectivity for the population coding of motion with interdigitating sets of spiking dendrites. RESEARCH DESIGN AND METHODS: Synaptic, dendritic, and network mechanisms are critical for information processing in all vertebrates, but have been difficult to elucidate in mammals because of anatomical limitations. Therefore a chick tectal slice preparation has been developed which has two features that help to circumvent these limitations: (a) The extensive and sparse spatial distribution of tectal SGC-I neuron dendrites allows the spatiotemporal synaptic stimulation of selected dendritic endings in the slice. (b) Tectal SGC-I neurons receive monosynaptic inputs from a subpopulation of retinal ganglion cells at their dendritic endings. Further, tectal SGC-I neurons are sophisticated spatiotemporal integrators of retinal representations of dynamic visual stimuli and previous tectal SGC-I studies indicate phasic retino-tectal synaptic dynamics, dendritic spike generation in response to synaptic stimulation, and highly nonlinear dendritic interaction of multiple synaptic inputs. The central component of this research program consists of in vitro synaptic stimulation and whole-cell recordings. The interpretation of the in vitro results is supported with computational modeling. HEALTH-RELATEDNESS: The understanding of spatiotemporal processing at the level of synapses and dendrites in a visual pathway provides the key for the pharmacological intervention of visual perceptual impairments.