The gustatory area is a part of the human brain that receives nerve signals from the tongue. It is located in a part of the parietal lobe, near the rear of the brain, called the parietal operculum. Scientists are not certain as to the exact location of where taste is processed in this area, as of 2011. When taste buds are activated, the signals are transmitted by one of three nerves that go from the tongue, through the brain stem, to the gustatory area. Tests such as functional magnetic resonance imaging (fMRI) can show where in the brain electrical activity increases when tastes are sensed, so the general location has been approximated.
Sweet, sour, bitter, and salty flavors are sensed by different parts of the tongue. Most of the sweet taste buds are at the front, while sour, salty, and bitter receptors are found in sequence going toward the back. Each taste bud has a pore with small hairs called microvilli, and a cluster of cells that relay taste information to a nerve fiber. Up to 30 nerve fibers can interact with one cell, and up to 60 taste cells can be clustered in one taste bud. The neural fibers converge into three main nerves; the facial nerve, the glossopharyngeal nerve, and the vagus nerve, which lead to the gustatory area in the brain.
The gustatory cortex is thought by researchers to be located on the cerebrum at the parietal lobe. Speech is controlled by this area as well as sensory information received from touch stimuli. In back of this area is the visual cortex. Even into the 21st century, the exact structure and location of the brain's taste processing area are still not fully known to scientists. Studies, based on electrical stimulation in brain surgery patients, suggest that part of the temporal lobe might also be involved in processing taste.
Research has also shown that taste might be processed in different locations depending on species. For example, the primary gustatory area in humans could be in a different place than it is in primates or other species. Tests on the visual cortex have shown that vision is processed in slightly different areas. Electrical stimulation and blood flow measurements have enabled biologists to approximate the general location of the gustatory area. A non-living brain does not have the responses that are typically needed to locate such activity, and the cells generally can’t be identified by what they look like.