<P> The primary auditory cortex is subject to modulation by numerous neurotransmitters, including norepinephrine, which has been shown to decrease cellular excitability in all layers of the temporal cortex . alpha - 1 adrenergic receptor activation, by norepinephrine, decreases glutamatergic excitatory postsynaptic potentials at AMPA receptors . </P> <P> The auditory cortex is the most highly organized processing unit of sound in the brain . This cortex area is the neural crux of hearing, and--in humans--language and music . The auditory cortex is divided into three separate parts: the primary, secondary, and tertiary auditory cortex . These structures are formed concentrically around one another, with the primary cortex in the middle and the tertiary cortex on the outside . </P> <P> The primary auditory cortex is tonotopically organized, which means that neighboring cells in the cortex respond to neighboring frequencies . Tonotopic mapping is preserved throughout most of the audition circuit . The primary auditory cortex receives direct input from the medial geniculate nucleus of the thalamus and thus is thought to identify the fundamental elements of music, such as pitch and loudness . </P> <P> An evoked response study of congenitally deaf kittens by Klinke et al. utilized local field potentials to measure cortical plasticity in the auditory cortex . These kittens were stimulated and measured against a control (an un-stimulated congenitally deaf cat (CDC)) and normal hearing cats . The field potentials measured for artificially stimulated CDC were eventually much stronger than that of a normal hearing cat . This finding accords with a study by Eckart Altenmuller's, in which it was observed that students who received musical instruction had greater cortical activation than those who did not . </P>

Where is auditory information processed in the thalamus