Corticofugal control of brainstem sensory gating in the rodent whisker system
Final Report Abstract
The project aimed to determine the mechanism of sensory gating in the rodent whisker system. Rodents palpate surrounding objects with their facial whiskers as they navigate through a novel environment or forage for food. Whisker contact with an object can therefore occur either as the animal actively moves the whiskers during exploration (active touches) or when the stationary whisker is displaced in a quiet, non-whisking animal (passive touches). It is well known that across the ascending sensory system, passive touches evoke stronger responses than active touches indicating a gating of sensory processing by the motor state of the animal. Which neural circuits mediate such sensory gating? The currently accepted hypothesis in the field proposes that the descending projections from primary (S1) and secondary (S2) somatosensory cortices mediate this phenomenon by differentially activating or inhibiting the brainstem sensory trigeminal nuclei. In this project, I test this claim using three groups of experiments. First, using anatomical tract tracing I show that although the sensory trigeminal nuclei receive robust projections from S1 and S2 these are largely overlapping thus questioning the complementary action of these cortical regions on brainstem processing. Second by recording in the sensory trigeminal brainstem nuclei I show that an intra-trigeminal inhibitory mechanism can indeed account for such sensory gating. Finally in an ongoing set of experiments, I aim to test the hypothesis that this intra-trigeminal inhibitory mechanism is under cortical control. Taken together this data will for the first time determine the neural substrates for a proposed top down sensorimotor gating mechanism which is vital for active sensing.
Publications
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(2013). Origin of cortical projections to rat brainstem whisker nuclei. Society for Neuroscience Abstract 167.07
Chakrabarti S, Schwarz C
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(2014). Stimulus preference profiles of whisker sensitive neurons in trigeminal nuclei. Society for Neuroscience Abstract 441.23
Chakrabarti S, Maia-Chagas A, Schwarz C
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(2014). Studying motor cortex function using the rodent vibrissal system. e-Neuroforum. 5: 20-27
Chakrabarti S, Schwarz C
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(2015). Corticofugal projection patterns of whisker sensorimotor cortex to the sensory trigeminal nuclei. Front Neural Circuits. 9(53)
Smith JB, Watson GD, Alloway KD, Schwarz C, Chakrabarti S
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(2015). Sensory modulation by whisker movement in the rat brainstem trigeminal complex. Society for Neuroscience Abstract 516.05
Chakrabarti S, Schwarz C
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(2015). The Rodent Vibrissal System as a Model to Study Motor Cortex Function. in Patrik Krieger and Alexander Groh, eds. Sensorimotor Integration in the Whisker System. New York: Springer
Schwarz C, Chakrabarti S
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(2015). Whisking control by motor cortex. in Tony J Prescott, Ehud Ahissar and Eugene Izhikevich, eds. Scholarpedia of Touch. New York: Springer
Chakrabarti S, Schwarz C
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(2015). Whisking control by motor cortex. Scholarpedia. 10(3): 7466
Chakrabarti S, Schwarz C
