When the auditory information passes into the cortex, the specifics of what exactly takes place are unclear. The auditory cortex plays an important yet ambiguous role in hearing. This system allows the amplification of the auditory signal and improved analysis of its activity. Each neuron of the MGB that projects to the auditory cortex (C) generates a fiber (f-1) that branches horizontally for a few millimeters and contacts numerous pyramidal cells (B) and puncta (C). Summation corresponds to similar afferentation from both ears, with a contralateral dominance. Cortical columns receive input from both MGBs and are therefore bilateral, working on the principal of summation/suppression. Neurons in AI and AII are functionally organized into columns, first described by Lorent de Nó. Importantly, the change is persistent, in that it lasts throughout the animal’s life, and specific, in that the same exposure outside of that period causes no lasting change in the tonotopy of A1. In the rat, exposure to a single frequency during postnatal day (P) 11 to 13 can cause a 2-fold expansion in the representation of that frequency in A1. This has been best studied using animal models, especially cats and rats. Like many areas in the neocortex, the functional properties of the adult primary auditory cortex (A1) are highly dependent on the sounds encountered early in life. Inverted stellate cells also exist (Martinotti cells) as well as cells with candelabra-shaped dendritic configurations. The remaining 15% are multipolar or stellate cells. In humans, pyramidal cells (including all types) correspond to 85% of AI. The presence of six cell layers in the auditory cortex is common to all mammals, but species differences take the form of the commonality of each cells within each layer. Structure and Functions of Auditory Cortex Secondary auditory cortex (AII) is located more rostrally in the temporal lobe and contains Brodmann area 42.AI is the central region of the auditory cortex and receives direct projections from the ascending auditory pathway, particularly the ventral region of the medial geniculate body (MGB) in the thalamus. Primary auditory cortex (AI) is situated in the posterior third of the superior temporal gyrus (also known as Brodmann area 41), next to Wernicke’s area (W).Unilateral destruction results in slight hearing loss, whereas bilateral destruction results in cortical deafness.Īuditory cortex, narrower in humans than in other mammals, develops from front to back within the Sylvian fissure at the point where it joins Heschl’s gyrus. It is located bilaterally, roughly at the upper sides of the temporal lobes – in humans on the superior temporal plane, within the lateral fissure and comprising parts of Heschl’s gyrus and the superior temporal gyrus, including planum polare and planum temporale (roughly Brodmann areas 41, 42, and partially 22). Auditory cortex is the section of the brain that processes information received through hearing.
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