Related Experiment Video
Updated: May 10, 2026

Assessing Corticospinal Excitability During Goal-Directed Reaching Behavior
Published on: December 2, 2022
Role of posterior parietal cortex in reaching movements in humans: clinical implication for 'optic ataxia'
Morito Inouchi1, Riki Matsumoto, Junya Taki
1Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Objective:
To clarify the spatio-temporal profile of cortical activity related to reaching movement in the posterior parietal cortex (PPC) in humans.
Methods:
Four patients with intractable partial epilepsy who underwent subdural electrode implantation were studied as a part of pre-surgical evaluation. We investigated the Bereitschaftspotential (BP) associated with reaching and correlated the findings with the effect of electrical stimulation of the same cortical area.
Results:
BPs specific for reaching, as compared with BPs for simple movements by the hand or arm contralateral to the implanted hemisphere, were recognized in all patients, mainly around the intraparietal sulcus (IPS), the superior parietal lobule (SPL) and the precuneus. BPs near the IPS had the earlier onset than BPs in the SPL. Electrical stimulation of a part of the PPC, where the reach-specific BPs were recorded, selectively impaired reaching.
Conclusions:
Intracranial BP recording and cortical electrical stimulation delineated human reach-related areas in the PPC.
Significance:
The present study for the first time by direct cortical recording in humans demonstrates that parts of the cortices around the IPS and SPL play a crucial role in visually-guided reaching.
Related Concept Videos
Association Areas of the Cortex
Prefrontal Association Area: This area is located in the frontal lobe and is involved in planning, decision-making, and moderating social behavior. It connects with primary motor areas,...
Somatosensory, Motor, and Association Cortex
Motor and Sensory Areas of the Cortex
Motor Areas
The motor areas located in the frontal lobe are central to controlling voluntary movements. This region is further subdivided into the primary motor cortex and the premotor cortex.
Major Somatic Sensory Pathways
Somatosensation
Indirect Motor Pathways
The vestibulospinal tract originates in the vestibular nuclei of the brainstem. The vestibular system detects changes in...

