The role of thalamic state in dynamic tactile encoding
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Sensory pathways extract information about the local environment to guide our actions and behaviors. The internal representation of the outside world is built on patterns of neural activity, commonly referred to as the ‘neural code’. While we often model the neural code as a linear mapping from stimulus to spikes, it is actually extremely complicated and nonlinear even very early in the sensory pathway. In particular, the neural code explodes in complexity at the thalamocortical circuit where it has been hypothesized that the thalamus gates information flow to the cortex through dynamic transitions in thalamic state. Mechanistically, the baseline membrane potential of an individual thalamic neuron controls its state, or firing mode. Here, we have found that the thalamic state, and presumably the subthreshold membrane potential, can be externally modulated by sensory stimulation, identifying a role for sensory driven state manipulations. Furthermore, we have found that manipulation of thalamic state affects stimulus-evoked cortical dynamics, consistent with the view that the thalamus can gate information flow to cortex. Finally, we linked thalamic state transitions to shifts in the precise stimulus encoding from thalamus to cortex. Through this work, we provide evidence that the state of the thalamus determines what types of information are transmitted to cortex through modulations to thalamic spike timing. Dynamic shifts in thalamic state set the stage for an intricate control strategy upon which cortical computation is built.