Baseline cortical excitability determines whether TMS disrupts or facilitates behavior

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Brain Stimulation

Background:

• Transcranial magnetic stimulation (TMS) is a noninvasive technique used to modulate brain activity.
• Understanding the factors influencing TMS efficacy is crucial for its application in research and therapy.
• Variability in TMS outcomes suggests modulation by underlying neural states.

Purpose of the Study:

• To investigate how the baseline activity of a targeted brain region affects the functional outcome of TMS.
• To explore the conditions under which TMS can facilitate or suppress perceptual functions.
• To examine the interaction between on-line TMS and prior neural suppression on behavior.

Main Methods:

• Utilized on-line and off-line repetitive TMS (rTMS) targeting the motion-selective visual area V5/MT.
• Assessed effects on motion-detection performance in human subjects.
• Manipulated the baseline activity of V5/MT through prior rTMS application.

Main Results:

• On-line TMS over V5/MT impaired motion detection when the region was at its baseline activity level.
• Off-line 1 Hz rTMS suppression of V5/MT disrupted subsequent motion detection.
• Paradoxically, on-line TMS facilitated motion detection when V5/MT had been previously suppressed.

Conclusions:

• The efficacy of TMS is state-dependent, modulated by the baseline activation of the targeted neural population.
• TMS can unexpectedly facilitate behavior when applied to a suppressed neural population.
• Findings highlight the importance of considering neural state in TMS experimental design and interpretation.