Daniel Butts

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  Detecting the many roles of inhibition in shaping sensory processing
  Daniel Butts
  Inhibition is a component of nearly every neural system, and increasingly prevalent component in theoretical network models. However, its role in sensory processing is often difficult to directly measure and/or infer. Using a nonlinear modeling framework that can infer the presence and stimulus tuning of inhibition using extracellular and intracellular recordings, I will both describe different forms of inferred inhibition (subtractive and multiplicative), and suggest multiple roles in sensory processing. I will primarily refer to studies in the retina, where it likely contributes to contrast adaptation, the generation of precise timing, and also to diversity of computation among different retinal ganglion cell types. I will also describe roles of shaping sensory processing in other areas, including the auditory areas and the visual cortex. Understanding the role of inhibition in neural processing both can inform a richer view of how single neuron processing can contribute to network behavior, as well as provide tools to validate network models using neural data.
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  Coordination of visual processing in cortex by network activity during natural viewing
  Daniel Butts

  In addition to visual information from thalamus, neurons in primary visual cortex (V1) receive inputs from other V1 neurons, as well as from higher cortical areas. This “non-classical� input to V1 neurons, which can be inferred in part from the local field potential, can modulate the “classical� feed-forward responses of V1 neurons to visual stimuli. Using multielectrode recordings in awake primate, we can characterize this modulation in a variety of stimulus contexts. Because this network activity is by definition shared, it can serve to coordinate single neuron responses across a given region of cortex. Such network modulation plays a clear role during natural viewing, where saccadic eye movements result in stereotyped network activity. Thus these network influences to V1 neuron activity, which likely represent both coordinated processing within V1 and top-down influences, play a fundamental role in natural visual processing.