Date: Wednesday, September 30, 2020
Location: Zoom Webinar – Registration Required
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Speaker: Gordon Fishell, Ph.D.
Affiliation: Professor of Neurobiology, Harvard Medical School; Broad Institute Member, the Stanley Center at the Broad
Host: Dr. Mriganka Sur
Talk title: Sensory priming: how the developmental reshaping of inhibition may give rise to internal representations - A hypothesis
Abstract: Rao and Ballard (1999) proposed a model of cortical function based on the idea that higher cognition depends upon a comparison of an internal representation to sensory information to generate an “error signal” which reconciles the two. Recent experiments in my laboratory suggest that early in development, interneurons both within the deepest and most superficial layers of the cortex transiently receive efferent copies of the bottom-up sensory inputs emanating from the thalamus. During critical period remodeling these inputs are greatly weakened and reshaped such that deep layer somatostatin interneurons change their input to being driven by the adjacent pyramidal neurons within their same layer. Similarly, Layer 1 (Lamp5/Id2) interneurons shift from being thalamically-driven to being primarily activated by long range intracortical inputs. I hypothesize that this remodeling occurs to shift cortical input from a constitutive bottom-up flow of information to a flow that facilitates comparison of bottom-up and top-down information (to generate the “error signal” proposed by Rao and Ballard).
In the adult every point in our primary sensory maps receives convergent information from other cortical areas and reciprocal feedback loops with the thalamus. While useful for adult computation, I posit that these feedforward and feedback systems would confound the formation of primary sensory maps and hence the orderly emergence of an “internal representation”. My hypothesis, which I have dubbed “Sensory priming”, is founded on the supposition that the formation of such internal representations is dependent upon developmentally constraining flow of information. This I suggest is achieved through efferent copy to interneurons in layer 1 and layers 5/6, which during development prevents the premature flow of intracortical and corticothalmic information, respectively.
In this lecture I will discuss evidence that supports this hypothesis.