Medial geniculate neurons show diverse effects in response to electrical stimulation of prefrontal cortex

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Phantom perceptions have been proposed to arise due to dysfunctional sensory gating at the level of the thalamus. Recently, it has been suggested that tinnitus, a phantom perception of sound, may arise from altered cortico-limbic circuitry and its connection with the auditory thalamus, the medial geniculate nucleus (MGN). Indeed, some elements of this cortico-limbic circuitry, such as the prefrontal cortex (PFC), as well as elements of the auditory pathway, have been shown to be altered in humans with tinnitus. However, the functional connectivity between PFC and MGN has not yet been explored. We therefore investigated the effects of activation of the PFC on neuronal activity in MGN in normal anaesthetized Wistar rats. Bipolar electrical stimulation was delivered to the PFC while recording single neuron activity in the MGN. The majority (81%) of MGN neurons sampled showed a change in their spontaneous firing rate in response to electrical stimulation of the PFC. The effects observed varied greatly between neurons and included combinations of inhibitory and excitatory effects with a wide range of latencies. The effects were not dependent on acoustic response type or MGN subdivision. These data demonstrate that PFC activation can modulate MGN neuronal activity and this connection could potentially play a role in sensory gating of auditory signals.

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