text: The auditory cortex is composed of fields that differ from each other in both structure and function. The number of fields varies in different species, from as few as 2 in rodents to as many as 15 in the rhesus monkey. The number, location, and organization of fields in the human auditory cortex are not known at this time. What is known about the human auditory cortex comes from a base of knowledge gained from studies in mammals, including primates, used to interpret electrophysiological tests and functional imaging studies of the brain in humans.
  When each instrument of a symphony orchestra or jazz band plays the same note, the quality of each sound is different, but the musician perceives each note as having the same pitch. The neurons of the auditory cortex of the brain are able to respond to pitch. Studies in the marmoset monkey have shown that pitch-selective neurons are located in a cortical region near the anterolateral border of the primary auditory cortex. This location of a pitch-selective area has also been identified in recent functional imaging studies in humans.
  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.
  Relationship to the auditory system