Biological Basis of the Code

The provided code is part of a computational model that simulates the auditory pathway, focusing on its early stages: from the cochlea to the inferior colliculus. Here's an outline of the biological processes being modeled:

1. Cochlear Function

• Characteristic Frequency (CF): The code models how different cochlear channels respond to various sound frequencies. The CF corresponds to the specific frequency at which each section of the cochlea is most sensitive, mimicking the tonotopic organization of the cochlea.
• Basilar Membrane (BM) Motion: The variable v represents the velocity of the basilar membrane movement, modeling how sound waves cause mechanical vibrations that travel along the cochlea.
• Outer Hair Cells (OHCs): These cells modulate cochlear amplifier effects, influencing the ear canal pressure or otoacoustic emissions (OAEs) seen in the model.

2. Inner Hair Cell (IHC) Responses

• Transduction Process: Inner hair cells convert mechanical vibrations (influenced by the basilar membrane movement) into electrical signals (V_ihc), a key step in auditory transduction.
• IHC Receptor Potential: The code includes the variable ihc to track receptor potential changes in inner hair cells, which directly affect neurotransmitter release onto auditory nerve fibers.

3. Auditory Nerve (AN) Activity

• High, Medium, and Low Spontaneous Rate Fibers: The code distinguishes between high, medium, and low spontaneous rate auditory nerve fibers (HSR, MSR, LSR) to account for different firing patterns, reflecting real physiological distinctions in auditory nerve fibers.
• Summed AN Activity: Summed activity across fibers (AN) shows collective responses to acoustic stimuli.

4. Central Auditory Pathway Processing

• Cochlear Nucleus (CN) and Inferior Colliculus (IC): These central auditory structures process the signals transmitted by the auditory nerve. The code includes CN and IC responses to illustrate signal transformations in central auditory processing.
• Brainstem Evoked Responses: The variables W1, W3, W5, and EFR model the population responses in the brainstem evoked by sound, reflecting physiological signals like evoked potential recordings.

This model attempts to simulate how sound information is processed and interpreted from its initial mechanical movements within the cochlea through various neural transformations up to the midbrain, thereby emulating the peripheral to central auditory processing pathway.