Cortical activations associated with spatial remapping of finger touch using EEG

Area of Science:

• Neuroscience
• Somatosensory System
• Human Perception

Background:

• Tactile information is crucial for shape perception and motor control.
• The transformation of tactile signals from the somatotopic to spatiotopic frame in the brain is not fully understood.

Purpose of the Study:

• To investigate how hand position and posture influence cortical processing of tactile information.
• To understand the spatiotemporal dynamics of tactile remapping.

Main Methods:

• Twenty-two healthy subjects underwent electrical stimulation on the thumb (D1) or little finger (D5).
• Stimulation was applied in three conditions: baseline (palm down), crossing body midline, and altered posture (palm up).
• Somatosensory-evoked potentials (SEPs) were recorded using electroencephalography (EEG).

Main Results:

• Distinct neurophysiological components (P50, P1, N125, P200, N250) were identified for both fingers.
• Hand crossing modulated SEPs at P1 (D1) and P50/N125 (D5).
• Altered posture significantly affected SEPs at N125 (D5), with effects predominantly seen at centro-parietal electrodes.

Conclusions:

• Tactile remapping, the adjustment of sensory input to body position, occurs in the parietal cortex.
• This remapping process, observed via SEPs, happens approximately 100-125 milliseconds post-stimulation.
• Hand position and posture dynamically influence how the brain processes tactile information.