Thalamic Activation Modulates the Responses of Neurons in Rat Primary Auditory Cortex: An In Vivo Intracellular Recording Study

Abstract

Auditory cortical plasticity can be induced through various approaches. The medial geniculate body (MGB) of the auditory thalamus gates the ascending auditory inputs to the cortex. The thalamocortical system has been proposed to play a critical role in the responses of the auditory cortex (AC). In the present study, we investigated the cellular mechanism of the cortical activity, adopting an in vivo intracellular recording technique, recording from the primary auditory cortex (AI) while presenting an acoustic stimulus to the rat and electrically stimulating its MGB. We found that low-frequency stimuli enhanced the amplitudes of sound-evoked excitatory postsynaptic potentials (EPSPs) in AI neurons, whereas high-frequency stimuli depressed these auditory responses. The degree of this modulation depended on the intensities of the train stimuli as well as the intervals between the electrical stimulations and their paired sound stimulations. These findings may have implications regarding the basic mechanisms of MGB activation of auditory cortical plasticity and cortical signal processing.

Ventral tegmental area activation promotes firing precision and strength through circuit inhibition in the primary auditory cortex

“…Excitatory thalamic inputs can directly activate pyramidal neurons (PNs) or indirectly modulate PNs through GABAergic interneurons in the sensory cortex, which is known as the thalamocortical pathway. The activity of cortical neurons is determined by the integration of thalamic excitatory inputs, intracortical excitation and feedforward inhibition ( Ojima and Murakami, 2002 ; Sun et al, 2010 ; Han et al, 2012 ). This circuitry model has been verified in various sensory cortices and is considered to be the basic pathway underlying the response properties of cortical neurons in sensory systems ( Douglas and Martin, 1991 , 2004 ; Liu et al, 2007 ; Zhou et al, 2010 ; Constantinople and Bruno, 2013 ).…”