Our sensory systems gather stimuli as elemental physical features yet we perceive a world made up of familiar objects, not wavelengths or vibrations. Perception occurs when the neuronal representation of physical parameters is transformed into the neuronal representation of meaningful objects. How does this recoding occur? An ideal platform for the inquiry is the rat whisker sensory system: it produces fast and accurate judgments of complex stimuli, yet can be broken down into accessible neuronal mechanisms. CONCEPT will examine the process that begins with whisker motion and ends with perception of the contacted object. Understanding the general principles for the construction of perception will help explain why we experience the world as we do.
The main hypothesis is that graded neuronal representations at early processing stages are “fractured” to generate discrete object representations at late processing stages. Of particular interest is the emergence of object representations as the meaning of new stimuli is acquired.
We will collect multi-site single-unit and local field potential signals simultaneously with precise behavioral indices, and will interpret data through advanced computational methods. We will begin by quantifying whisker motion as rats discriminate texture, thus defining the raw material on which the brain operates. Next, we will characterize the transformation of texture along an intracortical stream from sensory areas (where we expect that neurons encode whisker kinematics) to frontal and rhinal areas (where we expect that neurons encode objects extracted from the graded physical continuum) and hippocampus (where we expect that neurons encode objects in conjunction with context). We will test candidate processing schemes by manipulating perception on single trials using optogenetic methods.
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