Within-subject reliability of concurrent TMS-fMRI during a single session

Area of Science:

• Neuroscience
• Cognitive Science
• Biomedical Engineering

Background:

• Concurrent transcranial magnetic stimulation with functional MRI (TMS-fMRI) enables causative probing of brain connectivity.
• Technical limitations, safety, and patient tolerability can restrict the number of trials in TMS-fMRI experiments.

Purpose of the Study:

• To assess the reliability of the blood-oxygen-level-dependent (BOLD) response evoked by TMS during concurrent TMS-fMRI.
• To determine the minimum number of trials required for reliable spatial changes in brain activity detection.

Main Methods:

• Utilized an existing dataset of 100 active TMS trials versus a sub-threshold control condition.
• Split trials into subsets (10-50 trials) to create single-subject brain activity maps.
• Calculated reliability using correlations (R) between t-maps from paired trial subsets within individuals.

Main Results:

• Moderate-to-high reliability (mean R = 0.695) was observed with 50 trials, decreasing with fewer trials.
• Spatial patterns of reliability varied individually but correlated with TMS-evoked activity magnitude.
• Concurrent TMS-fMRI demonstrates reliable individual-level activity patterns at higher trial counts, especially in localized regions.

Conclusions:

• Concurrent TMS-fMRI yields reliable individual brain activity patterns, particularly with sufficient trials.
• The spatial distribution of reliability is unique to each individual and linked to their specific evoked brain activity patterns.