Final answer:
The third/fourth order neurons in the auditory pathway are located in the medial geniculate body of the thalamus and project from there to the primary auditory cortex.
Step-by-step explanation:
The third/fourth order neurons in the auditory pathway are part of the complex journey of auditory information processing from the ear to the brain. After the initial processing in the cochlea and the cochlear nuclei, the auditory information ascends through various brainstem nuclei to reach the inferior colliculus in the midbrain.
Axons from the inferior colliculus then project to two destinations: the medial geniculate body (MGB) of the thalamus, which represents the third-order neuron in the auditory pathway, and the superior colliculus.
From the MGB, the information is sent to the primary auditory cortex in the temporal lobe, which involves fourth-order neurons.
In summary, the third-order neurons are located in the medial geniculate body of the thalamus and the fourth-order neurons project from the MGB to the primary auditory cortex.
This auditory pathway is essential for processing and perceiving sound, enabling sound localization and allowing us to react to auditory stimuli.