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How is sound frequency organized in the medial geniculate nucleus and auditory cortex?

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Diagram of a human brain showing a median sagittal section, highlighting the fourth ventricle and cerebellum in the hindbrain, with labeled anatomical structures including the pons, medulla oblongata, and central canal of the spinal cord. — thalamus Sagittal section of the human brain, showing structures of the cerebellum, brainstem, and cerebral ventricles.

The medial geniculate nucleus (MGN) and the auditory cortex are organized in a tonotopic fashion, meaning they are structured according to sound frequency.1

Within the MGN, which serves as the thalamic relay for auditory information, the ventral region is specifically responsible for relaying frequency, intensity, and laterality. While the MGN is organized tonotopically, it is further subdivided into three functional regions:1
* Ventral region: Relays frequency, intensity, and laterality.1
* Dorsal region: Relays information regarding complex sounds.1
* Medial region: Encodes relative sound properties.1

Regarding the auditory cortex, while it receives an orderly projection of fibers from the MGN, research indicates that the cortex is not strictly necessary for basic frequency recognition, as this can occur at lower levels of the auditory pathway. Instead, the auditory cortex is considered essential for the recognition of temporal patterns and the analysis of complex auditory stimuli, such as speech and music.23