Effects of Transcranial Magnetic Stimulation on Hemodynamic Responses Measured by Near-Infrared Spectroscopy
Author Information
Author(s): Tiina Näsi, Hanna Mäki, Kalle Kotilahti, Ilkka Nissilä, Petri Haapalahti, Risto J. Ilmoniemi
Primary Institution: Aalto University School of Science
Hypothesis
To what extent do TMS-evoked NIRS responses reflect cerebral hemodynamic responses?
Conclusion
The study found that TMS-evoked NIRS signals include components not directly related to cerebral neuronal activity.
Supporting Evidence
- TMS-evoked NIRS signals include physiological changes that are caused by TMS but do not result from the activation of cerebral neurons.
- The HbT waveforms measured on the stimulated shoulder were similar to the ones recorded on the stimulated hemisphere.
- All circulatory parameters were affected by the stimulation, indicating a systemic arousal effect.
Takeaway
When we use a special technique to stimulate the brain, we also see changes in blood flow that aren't just from brain activity, which means we need to be careful when interpreting the results.
Methodology
The study involved stimulating the left primary motor cortex of 13 subjects with TMS and measuring hemodynamic responses using NIRS, comparing them to responses from shoulder stimulation in another group.
Potential Biases
Potential biases may arise from the small sample size and the specific demographic of participants.
Limitations
The study's findings may not be generalizable beyond the specific conditions tested, and the physiological artifacts could complicate interpretations of NIRS data.
Participant Demographics
13 healthy subjects (1 female, 2 left-handed) aged 22-32 for brain stimulation; 10 healthy subjects (2 female) aged 22-33 for shoulder stimulation.
Statistical Information
P-Value
p<0.05
Statistical Significance
p<0.05
Digital Object Identifier (DOI)
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