Biology subjects

Hayashi, M. J.

Publications and source records attributed to Hayashi, M. J..

3 recordsLinked to original sources

bioRxiv2023

Immediate effect of quadri-pulse stimulation on human brain microstructures

Several studies have implied that human brain microstructures can change immediately after a behavioral training. However, since widespread regions are involved in behavioral training, it remains unclear whether the microstructure in the living human brain changes immediately after the change in activity of a specific brain area. Hence, we aimed to examine whether the microstructures in the human brain change after the increase and decrease in the specific brain activity by repetitive transcranial magnetic stimulation, namely quadri-pulse stimulation (QPS). Right-handed healthy adults underwent both the excitatory (QPS5) and inhibitory (QPS50) QPS protocols over the left M1. Before and after QPS, diffusion MRI and resting-state fMRI scans were collected to detect any microstructural (fractional anisotropy [FA] and mean diffusivity [MD] values) and functional (functional connectivity between the bilateral M1) changes after QPS5 and QPS50. As a result, we observed no statistically significant change in FA or MD values after either QPS5 or QPS50 in cerebral cortex. This suggests that the brain activity change in widespread area is required to induce microstructural change immediately.

neuroscience↗

bioRxiv2022

Attentional rhythmic blink: Theta/Alpha balance in neural oscillations determines the rhythmicity in visual sampling

Brain oscillations in the theta (3-7 Hz) and alpha (7-13 Hz) bands are implicated in visual perception and attention. We show that in an attentional blink paradigm, where the task requires detecting two targets presented in rapid succession, perceptual performance varied with the rhythms at these two frequencies, which we name attentional rhythmic blink. In the absence of distractors, second target detection performance fluctuated at the theta rhythm, but the fluctuation frequency shifted toward alpha rhythm when distractors were interspersed with the targets. We further show, in magnetoencephalography experiments, that a change in the dominant frequency of ongoing neural oscillations accompanied those in perceptual performance, with the parietal theta being more pronounced in the no-distractor and the occipital alpha in the distractor conditions, respectively. We propose that perceptual rhythms may depend on the power balance between ongoing neural oscillations, determined by the task-specific demand.

neuroscience↗

bioRxiv2021

Microstructural Properties of Human Brain Revealed by Fractional Anisotropy can Predict the After-effect of Intermittent Theta Burst Stimulation

Intermittent theta burst stimulation (iTBS) delivered by transcranial magnetic stimulation (TMS) produces a long term potentiation (LTP)-like after-effect useful for investigations of cortical function and of potential therapeutic value. However, the iTBS-evoked after-effect over the primary motor cortex (M1) as measured by changes in motor evoked potential (MEP) amplitude exhibits a largely unexplained variability across individuals. Here, we present evidence that individual differences in white and grey matter microstructural properties revealed by fractional anisotropy (FA) predict the magnitude of the iTBS-induced after-effect over M1. The MEP amplitude change in the early phase (5-10 min) post-iTBS was associated with FA values in white matter tracts such as right superior longitudinal fasciculus and corpus callosum. In contrast, the MEP amplitude change in the late phase (15-30 min) post-iTBS was associated with FA in grey matter, primarily in right frontal cortex. These results suggest that the microstructural properties of regions connected directly or indirectly to the target region (M1) are crucial determinants of the iTBS after-effect. FA values indicative of these microstructural differences can predict the potential effectiveness of rTMS for both investigational use and clinical application.

neuroscience↗