The intraparietal sulcus (IPS) is located on the lateral surface of the parietal lobe, and consists of an oblique and a horizontal portion. The IPS contains a series of functionally distinct subregions that have been intensively investigated using both single-cell neurophysiology in primates and human functional neuroimaging.

The IPS separates the superior parietal lobule and inferior parietal lobule.

IPS demonstrated an interrupted course in 36% of the specimens while its branching pattern was variable. The sulcus anterior half was found to overly the atrium on all occasions. Four discrete, consecutive white matter layers were identified en route to the atrium, ie, the arcuate fibers, the arcuate segment of the superior longitudinal fasciculus, the corona radiata and tapetum, with the arcuate segment being near to the dissection trajectory.

Given the angle of brain transgression during the intraparietal approach, Koutsarnakis et al. found the optimal dissection area to be the very middle of the sulcus. The IPS-postcentral sulcus meeting point, in contrast to previous thought, proved to risk potential injury to the arcuate segment of the superior longitudinal fasciculus, thus affecting surgical outcome ¹⁾.

Its principal functions are related to perceptual-motor coordination (e.g., directing eye movements and reaching) and visual attention, which allows for visually-guided pointing, grasping, and object manipulation that can produce a desired effect.

The IPS is also thought to play a role in other functions, including processing symbolic numerical information, visuospatial working memory and interpreting the intent of others.

A case report of a patient, who suffered from acalculia following an infarct restricted to the left IPS (intraparietal sulcus) showed deficits in an arithmetic battery and in basic numerical processing tasks. Compared to matched controls, showed a larger distance effect in numerical comparisons, an abnormal size congruity indicated by a lack of facilitation by irrelevant numerical values in physical comparisons, a deficiency in counting in comparison tasks, and a deficiency in subitizing in number naming tasks and comparison tasks. This suggests that the underlying deficit was a difficulty in the perception and manipulation of quantity. Moreover, it indicates the essential role of IPS in basic numerical processing ²⁾.

A between-task comparison (mirror versus masked mirror) revealed significant activation in the ipsilateral hemisphere in the anterior intraparietal sulcus (aIP) while performing all tasks, regardless of which hand was used. The right aIP was significantly activated while moving the right hand. In contrast, in the left aIP, a small number of voxels showed a tendency toward activation during both left and right hand movement. The enhancement of ipsilateral aIP activity by the mirror image observation of finger action suggests that bimodal aIP neurons can be activated by visual information. We propose that activation in the M1 ipsilateral to the moving hand can be induced by information passing through the ventral premotor area from the aIP ³⁾.

Seizure onset in superior parietal lobule and IPS caused epileptic kinetopsia and direction of illusionary movement lateralized to the contralateral hemisphere ⁴⁾.