Auditory cortex in the context of "Language processing in the brain"

The sensory cortex can refer sometimes to the primary somatosensory cortex, or it can be used as a term for the primary and secondary cortices of the different senses (two cortices each, on left and right hemisphere): the visual cortex on the occipital lobes, the auditory cortex on the temporal lobes, the primary olfactory cortex on the uncus of the piriform region of the temporal lobes, the gustatory cortex on the insular lobe (also referred to as the insular cortex), and the primary somatosensory cortex on the anterior parietal lobes. Just posterior to the primary somatosensory cortex lies the somatosensory association cortex or area, which integrates sensory information from the primary somatosensory cortex (temperature, pressure, etc.) to construct an understanding of the object being felt. Inferior to the frontal lobes are found the olfactory bulbs, which receive sensory input from the olfactory nerves and route those signals throughout the brain. Not all olfactory information is routed to the olfactory cortex: some neural fibers are routed to the supraorbital region of the frontal lobe, while others are routed directly to limbic structures. The direct limbic connection makes the olfactory sense unique.

The brain cortical regions are related to the auditory, visual, olfactory, and somatosensory (touch, proprioception) sensations, which are located lateral to the lateral fissure and posterior to the central sulcus, that is, more toward the back of the brain. The cortical region related to gustatory sensation is located anterior to the central sulcus.

Brodmann areas 41 and 42 are parts of the primary auditory cortex.

Brodmann area 41 is also known as the anterior transverse temporal area 41 (H). It is a cytoarchitectonic division of the cerebral cortex occupying the anterior transverse temporal gyrus (H) in the bank of the lateral sulcus on the dorsal surface of the temporal lobe. Brodmann area 41 is bounded medially by the parainsular area 52 (H) and laterally by the posterior transverse temporal area 42 (H) (Brodmann-1909).

In the study of language processing, Carl Wernicke created an early neurological model of language, that later was revived by Norman Geschwind. The model is known as the Wernicke–Geschwind model.

1. For listening to and understanding spoken words, the sounds of the words are sent through the auditory pathways to area 41, which is the primary auditory cortex (Heschl's gyrus). From there, they continue to Wernicke's area, where the meaning of the words is extracted.
2. In order to speak, the meanings of words are sent from Wernicke's area via the arcuate fasciculus to Broca's area, where morphemes are assembled. The model proposes that Broca's area holds a representation for articulating words. Instructions for speech are sent from Broca's area to the facial area of the motor cortex, and from there instructions are sent to facial motor neurons in the brainstem, which relay movement orders to facial muscles.
3. In order to read, information concerning the written text is sent from visual areas 17, 18, and 19 to the angular gyrus (area 39) and from there to Wernicke's area, for silent reading or, together with Broca's area, for reading out loud.

This model is now obsolete. Nevertheless, it has been very useful in directing research and organizing research results, because it is based on the idea that language consists of two basic functions: comprehension, which is a sensory/perceptual function, and speaking, which is a motor function.
However, the neural organization of language is more complex than the Wernicke–Geschwind model of language suggests. The localization of speech in Broca's area is one of the weakest points of this model.