Inject 2-deoxyglucose (2-DG) to an animal. Then, expose the animal to a ton of a particular frequency. 2-DG is taken up into the neurons, predominantly the most active neurons. Postmortem processing of the 2-DG distripution shows which area of the inferior colliculus was activated in responce to the specific tone. The most active areas will hve the most 2-DG.

Method of mapping the inferior coliculus

The levels of auditory pathway display are spatially arranged based on frequency from high to low frequency.  

Grinnell College

The auditory pathway in the human brain represents the sequence of structures and processes that transmit auditory information. It begins with the mechanical activation of hair cells, which generates neural impulses. These impulses travel along the auditory nerve to the brain. The auditory information is then shuttled sequentially to the inferior colliculus, the medial geniculate nucleus of the thalamus, and finally to the auditory cortex in the temporal lobe for higher-level processing.

Auditory Pathways in the human brain

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

The brainstem nuclei that recieves imput from the auditory hairs sent from the vestibulochochlear nerve (cranial nerve VIII). The cochlear nucleus diverges into multiple pathways in the brain.

Cochlear nucleus

Tonotopic mapping of the Inferior Colliculus

The A1 is located at the upper surface of the temporal lobes. The A1 is activated by multiple stimuli, such as speech sounds and the process of lip-reading in hearing individuals. This suggests an integration of senses to process information.

Primary auditory cortex (A1)

Similar to the visual system, the brain processes different aspects of auditory information through parallel streams. Evidence suggests that distinct pathways are used for auditory recognition (identifying what a sound is) and localization (determining where a sound is coming from).

Auditory Parallel Processing

A patient has a small, localized brainstem lesion. While they can still hear sounds clearly with both ears and identify what the sounds are (e.g., a bell, a voice), they have significant difficulty determining the direction or location of the sound source. This specific deficit in sound localization suggests damage to which of the following structures?

Similar to the visual system, evidence suggests that information regarding auditory recognition and auditory localization is processed in parallel streams within the brain.

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