ABSTRACT
Like most other sensory pathways, signals enter the auditory pathway via a specific sensory nerve, the eighth cranial or vestibulocochlear nerve. The pathway progresses from the brain stem level where simple motor reflexes tend to be mediated, through to the midbrain where integration with other senses (e.g., vision) starts to occur. It then reaches the main sensory relay station of the brain, the thalamus, which appears to sort the signals that it receives prior to sending them on to the most appropriate overlying areas of cortex for further analysis. Cortical connections then permit comparisons of patterns of activity produced by auditory stimuli with those in other sensory areas of the cortex, as well as with those in limbic regions involved in memory and emotion, and frontal regions involved in cognition. This process ultimately allows complex sound stimuli, such as speech or music, to be recognized. The auditory pathway interacts for most of its ascent to the cortex with other brain areas, and for this reason it is perhaps inappropriate to describe it separately, as is done in this chapter. However, this chapter provides a brief and necessarily simplified sketch of the main anatomical features of the ascending auditory pathway from cochlea to cortex in an attempt to provide a basis for further discussion of the role of its major structures in audition and speech.
