Tactile contribution extends beyond exteroception during spatially guided finger movements.

Area of Science:

• Neuroscience
• Human motor control
• Somatosensation

Background:

• Touch is traditionally viewed as exteroceptive, with less emphasis on its role in spatial movement control compared to vision.
• The contribution of tactile cues to guiding hand movements during surface interaction remains underexplored.

Purpose of the Study:

• To investigate the role of tactile feedback in controlling sliding finger movements.
• To determine if the central nervous system actively gates somatosensory information during visuo-somatosensory conflict.

Main Methods:

• Developed a technique to isolate and measure tactile involvement in finger movements.
• Utilized a 2D shape tracing task with direct or mirror-reversed visual feedback to induce sensory conflict.
• Employed electroencephalography (EEG) source analysis to examine brain activity in the somatosensory cortex.

Main Results:

• Participants exhibited poorer movement accuracy when relying on direct tactile input during sensory conflict compared to when tactile sensation was dampened.
• EEG source analysis showed reduced activity in the somatosensory cortex when direct touch was involved under conflict conditions.
• The central nervous system demonstrated selective gating of task-irrelevant somatosensory inputs to mitigate visuo-somatosensory conflict.

Conclusions:

• Tactile cues are significantly involved in the real-time control of finger movements over surfaces.
• The brain actively modulates somatosensory processing to manage conflicts between visual and tactile information.
• Findings challenge the predominant view of vision as the sole driver of goal-directed hand movements, highlighting the integrated role of touch.