Related Experiment Video
Updated: Sep 28, 2026

A Large Lateral Craniotomy Procedure for Mesoscale Wide-field Optical Imaging of Brain Activity
Published on: May 7, 2017
Early secondary somatosensory area (SII) SEPs. Data from intracerebral recordings in humans
Carmen Barba1, M Frot, F Mauguière
1Department of Neurology, Catholic University, Largo A. Gemelli 8, 00168 Rome, Italy. carmen.barba@tiscali.it
Objective:
To record somatosensory evoked potentials (SEPs) to median nerve stimulation by chronically implanted electrodes in the parieto-rolandic opercular area of 9 epileptic patients, in order to evaluate whether somatosensory evoked responses could be generated in the second somatosensory area (SII) earlier than 40 ms after stimulus.
Methods:
Nine patients (4 males, 5 females) with drug-resistant partial epileptic seizures were investigated using stereotactically implanted electrodes in the parietal cortex, posterior to vertical anterior commissure plane and in the frontal opercular region rostral to vertical anterior commissure (VAC).
Results:
The main finding of this study is the recording of an early somatosensory evoked potential, (N30op), by chronically implanted electrodes in the SII area of 8 epileptic patients. In 3 patients where SEPs were performed after ipsilateral median nerve (MN) stimulation, a N30op was recorded 5.8+/-2 ms later than contralateral one.
Conclusions:
This is the first report of early SEPs recorded by electrodes implanted in SII area. The N30op potential, even if less consistent than later potentials, confirmed the important role of the SII area in the early processing of somatosensory inputs.
Related Concept Videos
Somatosensation
Somatosensory, Motor, and Association Cortex
Sensory Perception: Organization of the Somatosensory System
The receptor level:
The receptor level is the first stage of sensation. It involves the detection of a stimulus by specialized sensory receptors. The stimulus must arrive within the receptor's receptive field. Next, the receptor converts the energy of the stimulus...
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.
Overview of Somatic Sensory Pathways
The somatosensory system is divided into three main pathways: the dorsal (or posterior) column-medial lemniscus, spinothalamic (or anterolateral), and spinocerebellar pathways.
The dorsal...

