11/20/2023 0 Comments Secondary auditory cortex function![]() 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. However, these contacts represent only 20% of the excitatory fibers that project to cortical neurons: the other 80% comes from other neurons in the ipsilateral cortex. Most ascending fibers originate in the MGB and synapse with the pyramidal cells of layer IV, but this is not always the case. 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 circuitry of the auditory cortex: Columnar organisation Auditory cortex projects to the regions of the frontal lobe involved in motor function for speech (a), the lips (b), jaw (c), tongue (d), larynx (e) and Broca's area (B).ī - Frontal view showing AI inside the Sylvian fissure and Heschl's gyrus. A - Lateral view showing the distribution of AI and AII and Wernicke's area (W). ![]()
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