Primary Auditory Pathway

The final neuron of the primary auditory pathway links the thalamus to the auditory cortex, where the message, already largely decoded during its passage through the previous neurons in the pathway, is recognised, memorised and perhaps integrated into a voluntary response.
A final relay, before the cortex, occurs in the thalamus (median geniculate body); genouillé médian)it's here that an important integration occurs: preparation of a motor response (eg vocal response). 
Leaving this relay, a third neuron carries the mesage up to the level of the mesencephalus (superior colliculus). These two relays play an essential rôle in the localisation of sound.
The second major relay in the brain stem is in the superior olivary complex: the majority of the auditory fibres synapse there having already crossed the midline.
The first relay of the primary auditory pathway occurs in the cochlear nuclei in the brain stem, which receive Type I spiral ganglion axons (auditory nerve); at this level an important decoding of the basic signal occurs: duration, intensity and frequency.