The parietal lobe in the brain helps to integrate sensory information and to determine object positions in space, among other functions. An important section of this part of the brain is the inferior parietal lobe (IPL), also known as the inferior parietal lobule. This area lies just superior to the temporal lobe, and consists of two ridges, known as gyri.
Several functions have been attributed to the inferior parietal lobe, some of which can be determined based on which parts of the brain they receive signals from. Studies have shown that the hippocampus, cerebellum, and superior colliculus all have strong neuronal connections with this lobule. These brain regions help individuals orient themselves in space, and are involved in motor function.
Connections such as these contribute to certain functions of the IPL, like establishing maps of the outside world. Other functions that these connections are involved in include adjusting hand-eye coordination, and attention behaviors involving eye motion. Such attention-related actions include directing one's gaze toward objects of interest. Integrating sensory input and motion is an important feature of the inferior parietal lobe.
The inferior parietal lobe is not equally large in both hemispheres. There are also gender-related size differences in this part of the cortex. Males have a larger IPL in the left hemisphere, and women show greater IPL size in the right hemisphere. Overall, the size of this region is more massive in males, as well.
Differences in size between hemisphere underscore functional differences. Neurons in the inferior parietal lobe tend to be more dominant in their activity in the right hemisphere. Therefore, they will respond more readily to events detected by sensory neurons in the body, particularly on the left side.
According to research, the left side of the body can detect sensory and tactile changes with greater sensitivity. The left hand detects weight disparities between objects more easily. It can also determine temperature differences better than the right hand. This dominance is due to the activity and sensitivity of neurons in the IPL, not because of differences in the sensory cells in the left side of the body.
Along with integrating sensory input pertaining to touch and vision, the IPL also integrates pain signals. Portions of one gyrus of the IPL, known as the supramarginal gyrus, show sensitivity to pain. One of these portions helps the body to determine where the source of pain is originating. Damage to these areas can result in a larger pain tolerance, or an inability to assign emotional significance to pain.