In-vivo intracellular recording on the auditory thalamic neurons

The present study investigates the neuronal mechanism of the corticofugal modulation on the thalamic neurons, which transmit auditory information from the periphery to the cortex. It was reported in a previous study that electrical activation of the primary auditory cortex induced both facilitatory and inhibitory effects on the response of the medial geniculate body (MGB) neurons to auditory stimulus. We hypothetized that the direct corticothalamic input to the auditory thalamic neurons is the main cause of the facilitatory effect in the MGB. This was examined by using in vivo intracellular recording method to measure the membrane potential of the MGB neurons during the presentation of sound stimulus and/or cortical activation. The neuronal responses to sound stimulus were studied while the resting potential was manipulated by injecting positive/negative electrical current. For most neurons, the response to sound stimulus increased while it was depolarized and decreased while hyperpolarized. Electrical stimulation on the auditory cortex resulted in either a slow elevation or a slow depression of the membrane potential, thereby leading to an increase or a decrease in the neuronal response to sound stimulus