Spindle-like oscillations in the auditory thalamus and cortex

Abstract

In the present study, we investigated the spindle oscillation in the thalamic reticular nucleus (TRN), medial geniculate body (MGB) and auditory cortex (AC). Neuronal activities in above regions were simultaneously recorded with extracellular and intracellular electrodes. We have found that thalamocortical neurons exhibit membrane oscillations that have spindle frequencies consist of excitatory postsynaptic potentials (EPSP). Acoustic stimuli could trigger membrane oscillation in EPSPs with spikes. TRN lesioning or injection of a combination of GABAA and GABAB antagonists into the MGB resulted in slowed oscillation in the MGB. Injection of GABAA antagonist into the MGB decreased oscillation frequency in the MGB and AC. In preparations in which AC was removed and the TRN was deafferented with glutamate receptor antagonists, oscillation frequency in the MGB was fastened by rhythmic electrical stimulation of the TRN. Our results therefore support the model that cortical spindles in the auditory system are originated in the MGB and are modulated by inhibitory inputs from the TRN. Fast inhibition through GABAA receptors facilitates the internal frequency of the oscillations while slow inhibition through GABAB receptors limits the occurrence of the oscillations. (Supported by CERG PolyU 5610/08M) Keywords: Spindle oscillation; Thalamic reticular nucleus; Medial geniculate body; Auditory cortex; excitatory postsynaptic potential (EPSP); GABA receptor antagonist