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Tactile force evokes a biphasic BOLD response in ipsilateral primary somatosensory cortex
Anna C Feldbush1,2, Nahid Kalantaryardebily3, Neha A Reddy4
1Fralin Biomedical Research Institute at VTC, Virginia Tech, Blacksburg, VA, United States.
Imaging Neuroscience (Cambridge, Mass.)
|May 25, 2026
Summary
Investigating tactile perception, this study reveals distinct blood-oxygen-level-dependent (BOLD) responses in the ipsilateral somatosensory cortex (S1). Specific areas show biphasic activity, challenging previous understandings of sensory processing.
Area of Science:
- Neuroscience
- Somatosensory System
Background:
- Tactile perception relies on the somatosensory cortex (S1).
- While contralateral S1 processing is known, ipsilateral S1 responses to tactile stimuli are less understood.
Purpose of the Study:
- To characterize the blood-oxygen-level-dependent (BOLD) response pattern in the ipsilateral primary somatosensory cortex (S1) during unilateral tactile stimulation.
- To investigate the nature of observed biphasic responses in specific Brodmann's areas (BAs) of the ipsilateral S1.
Main Methods:
- Utilized an event-related design applying three tactile stimulus force levels.
- Employed multi-echo analysis to assess the BOLD nature of the biphasic response pattern.
Main Results:
- Observed differing BOLD response patterns between contralateral and ipsilateral S1 hemispheres.
- Identified a positive BOLD response in ipsilateral BA2, similar to the contralateral side.
- Found a biphasic (initial negative, then positive) BOLD response in ipsilateral BA1 and BA3b, with the secondary positive phase being force-sensitive.
Conclusions:
- The biphasic BOLD response in ipsilateral BA1 and BA3b is consistent with two distinct periods of neural activity.
- These findings support the hypothesis of bilateral sensory gating.
- The secondary positive phase of the ipsilateral response is more sensitive to tactile stimulus intensity.
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