Superior Parietal Gyrus (Lobule)
The superior parietal lobule is composed of relatively thick cortex (about 3 mm) placed between the horizontal part of the interparietal sulcus and the superior border of the hemisphere, where it becomes continuous on the medial surface with the precuneus.
It has a thick layer IV and numerous pyramidal cells in layer III.
It is the somatosensory association cortex. The primary sensory cortex projects to it. It assembles somatosensory, auditory and visual information received from other cortices. Then, it supplies somatic sensory information through its connections that activate the premotor and supplementary motor cortices, leading to directed movement. Thus, it is involved in spatial reasoning, tool using gestures through hand coordination. It has some involvement also in working memory.
The superior parietal lobule is supplied by the superior division of the middle cerebral artery. A stroke causing a lesion in this area may result in a similar ataxia of the contralateral limbs. Movements become misdirected and dysmetric.
Patients fail to connect to the local environment and ignore it (sensory neglect) on the contralateral space.