Transcranial magnetic stimulation entrains alpha oscillatory activity in occipital cortex

Abstract

BackgroundParieto-occipital alpha rhythms (8-12 Hz) have been shown to underlie cortical excitability and influence visual performance. However, how the occipital cortex responds to an externally imposed alpha rhythm via transcranial magnetic stimulation (TMS) is an open question.Hypotheses10-Hz rhythmic TMS can entrain intrinsic alpha oscillators in the occipital cortex. Specifically, we predicted: (1) progressive enhancement of entrainment across time windows, (2) output frequency specificity, (3) dependence on the intrinsic oscillation phase, and (4) input frequency specificity to individual alpha frequency (IAF) in the neural signatures.MethodsWe delivered 4-pulse rhythmic TMS at 10 Hz to entrain local neural activity targeting the right V1/V2 regions while participants performed a visual orientation discrimination task.Concurrent electroencephalogram (EEG) recorded TMS-driven changes of local oscillatory activity. There were two control conditions: arrhythmic-active and rhythmic-sham stimulation, both with an equal number of pulses and duration.ResultsThe results were consistent with the first three hypotheses. Relative to both controls, rhythmic TMS bursts significantly entrained local neural activity. Near the stimulation site, evoked oscillation amplitude and inter-trial phase coherence (ITPC) was increased for 2 and 3 cycles, respectively, after the last TMS pulse. Critically, regarding hypothesis 4, ITPC following entrainment positively correlated with IAF, rather than with the degree of similarity between IAF and the input frequency (10 Hz).ConclusionsWe entrained alpha-band activity in occipital cortex for ~3 cycles (~300 ms) with our 4-pulse 10 Hz TMS protocol. IAF predicts the strength of entrained occipital alpha phase synchrony indexed by ITPC.Highlights* online, trial-by-trial entrainment of local neural synchrony in V1/V2 (rhythmic TMS)* occipital entrainment with concurrent neural stimulation (TMS) and recording (EEG)* 4-pulse TMS at 10 Hz yields lasting (300 ms) phase-locking at the alpha-band* individual alpha frequency positively correlated with inter-trial phase coherence

α Phase-Amplitude Tradeoffs Predict Visual Perception

“…Participants were selected based on their ability to perceive TMS-induced phosphenes in the left visual field. A train of 7 pulses at 20 Hz and 70% of the TMS machine output intensity, i.e., suprathreshold, was applied over the right occipital pole (i.e., V1/V2; Dugué et al, 2011a; see also Dugué et al, 2016;Lin et al, 2021) while participants kept fixating at a central fixation. 24% of the participants did not perceive any phosphene (4 out of 17) and were thus excluded from the main experiment.…”

Use of transcranial magnetic stimulation (TMS) for studying cognitive control in depressed patients: A systematic review

“…TMS has emerged as a promising treatment modality for improving attention, primarily through its ability to modulate neural oscillations, particularly alpha rhythms (Lin et al, 2021). Alpha oscillations, crucial for attention regulation, are influenced by TMS application to specific brain areas, such as the DLPFC, where LF TMS increases alpha power, enhancing attentional focus.…”

“…This effect is attributed to neural entrainment, wherein TMS synchronizes neural networks, leading to more efficient information processing and attentional control (Luber & Lisanby, 2014). The left dorsolateral prefrontal cortex serves as a key target for TMS due to its involvement in executive function, cognitive training, and working memory encoding, making it relevant for addressing attention deficits (Liu et al, 2020). Moreover, networks, such as the frontoparietal control network (FPCN) and default mode network (DMN), play critical roles in attention functions, with the FPCN coordinating goal-driven behaviour and the DMN facilitating introspective thought, indicating their involvement in attentional processes.…”

Targeting prefrontal cortex GABAergic microcircuits for the treatment of alcohol use disorder

“…While the cells and mechanisms through which PFC brain stimulation can reduce alcohol cravings remain unresolved, we propose that cortical INs represent compelling candidates. TMS modifies neural circuits through repetitive rhythmic stimulations thought to entrain oscillatory activities (Lin et al, 2021). In addition, the long-term efficacy of brain stimulation approaches is thought to be related to persistent effects on synaptic plasticity (Hanlon et al, 2018).…”