Biology subjects

Sugata, H.

Publications and source records attributed to Sugata, H..

5 recordsLinked to original sources

bioRxiv2026

Associations between striatal neurochemical changes and resting-state functional connectivity following transcranial temporal interference stimulation

Background Non-invasive modulation of deep brain structures remains a major challenge in human neuroscience and neurorehabilitation. Transcranial temporal interference stimulation (tTIS) has emerged as a promising approach for engaging subcortical regions, but its effects on striatal neurochemical markers and functional connectivity remain unclear. Objective To investigate whether 20-Hz tTIS designed to target the right striatum modulates GABA+ and glutamate-glutamine complex (Glx) levels and whether neurochemical changes are associated with changes in resting-state functional connectivity. Methods Thirty-four healthy right-handed participants were randomly assigned to the tTIS group (20-Hz beat frequency) or sham group (0-Hz frequency difference). Participants underwent proton magnetic resonance spectroscopy (1H-MRS) and resting-state fMRI before and after 30 min of stimulation. One participant in the tTIS group was excluded from the 1H-MRS analyses because of data corruption. Results The direct between-group difference in Glx change did not reach statistical significance, although the tTIS group showed a numerically greater reduction than the sham group (p = 0.066). Exploratory within-group analyses showed a significant decrease in striatal Glx in the tTIS group (p < 0.001), whereas the decrease in the sham group was not significant. No significant GABA+ changes were observed within or between groups. The association between striatal Glx change and functional connectivity change differed between groups in the sensorimotor cortex, right parahippocampal gyrus, and bilateral fusiform gyri. Conclusion These exploratory findings suggest that 20-Hz tTIS may be associated with striatal Glx modulation and group-dependent coupling between neurochemical and cortico-subcortical network changes.

neuroscience↗

bioRxiv2026

Food preference is associated with distinct large-scale cortical functional connectivity patterns during food-image observation

Food preference influences behavior toward food-related stimuli, yet the large-scale neural mechanisms underlying this process remain unclear. This study investigated whether preferred and nonpreferred food cues are associated with distinct patterns of cortical functional connectivity during the observation of food images. Data from 25 of the 40 recruited healthy adults were included in the final analysis after excluding individuals with highly unbalanced response tendencies. Participants viewed 150 food images and rated each image on a four-point preference scale. Trials were classified as favorite food (FF) or disliked food (DF). High-density electroencephalography (EEG) was recorded during the task, and source-level ROI-to-ROI functional connectivity was analyzed using amplitude envelope correlation in the alpha (8-13 Hz) and beta (13-25 Hz) frequency bands over the 1000-ms period after food-picture onset. Response time did not differ significantly between FF and DF trials. However, distinct functional connectivity patterns were observed between conditions in both frequency bands. In the alpha band, FF trials involved a network including the cuneus, parietal regions, cingulate regions, and lateral occipital cortex, whereas DF trials involved the isthmus cingulate, caudal middle frontal gyrus, inferior temporal cortex, superior parietal lobule, and lateral occipital cortex. In the beta band, FF trials involved the isthmus cingulate, precuneus, parietal regions, and pericalcarine cortex, whereas DF trials additionally involved frontal regions, including the superior frontal gyrus and pars triangularis. These findings indicate that food preference is associated with distinct large-scale cortical functional connectivity patterns during food image observation, suggesting differential neural processing of preferred and nonpreferred food cues.

neuroscience↗

bioRxiv2025

Transcutaneous vagus nerve stimulation reduces total striatal GABA content and facilitates early-phase motor learning

BackgroundTranscutaneous vagus nerve stimulation (tVNS) has emerged as a promising non-invasive technique for modulating neuroplasticity. Previous studies have suggested that changes in regional brain GABA signaling contribute to these effects, but empirical neurophysiological evidence remains limited. MethodsWe investigated the neurophysiological and behavioral effects of tVNS (200-s pulses at 20 Hz, alternating 30 s ON-1 s OFF cycles, 30 min total duration) in healthy adults using two experimental paradigms. In Experiment 1, GABA levels were measured in the left striatum (STR), dorsolateral prefrontal cortex (DLPFC), and sensorimotor cortex (SM) of 34 participants by magnetic resonance spectroscopy (MRS) before and after ipsilateral tVNS. In Experiment 2, 28 participants performed a right-hand force-control motor learning task before, during, and after tVNS. ResultsAdministration of tVNS significantly reduced GABA levels in the left STR compared to sham stimulation (p < 0.05), and also significantly improved motor task performance compared to the sham group at 10 minutes after stimulus onset (p < 0.05) ConclusionTranscutaneous VNS may facilitate early-phase motor learning by reducing striatal GABA levels and consequently inducing corticobasal circuit disinhibition. These findings support tVNS as a potential noninvasive intervention to enhance motor learning for neurorehabilitation and motor disorder treatment.

neuroscience↗

bioRxiv2025

Wakeful targeted memory reactivation during short rest periods modulates motor learning via the lateral orbitofrontal cortex network

This study investigated whether wakeful targeted memory reactivation (TMR) during short rest intervals improves motor learning. Participants were randomly assigned to the following four groups and performed a sequential key-press task under each condition: (1) TMRno group: no auditory stimuli, (2) TMRregular group: auditory cues played at the same speed as the previous task, (3) TMRfast group: auditory cues played 1.3 times faster, and (4) TMRrandom group: auditory cues randomized in pitch. The TMRregular group suppressed early learning gains compared with the TMRno and TMRfastgroups. Electroencephalogram revealed reduced functional connectivity centered on the lateral orbitofrontal cortex (lOFC) in the TMRregular group. In contrast, the TMRfastgroup preserved early learning and exhibited improved lOFC-centered functional connectivity compared with the TMRregulargroup. Therefore, wakeful TMR might either hinder or support motor learning, depending on cue timing and structure, emphasizing the need to optimize sensory parameters for effective learning improvement.

neuroscience↗

bioRxiv2024

Cingulate and striatal hubs are linked to early skill learning

Early skill learning develops in the context of activity changes in distributed cortico-subcortical regions. Here, we investigated network hubs--centers of information integration and transmission--within the brain network supporting early skill learning. We recorded magnetoencephalographic (MEG) brain activity in healthy human subjects who learned a moderately difficult sequence skill with their non-dominant left hand. We then computed network hub strength by summing top 10% functional connectivity over 86 parcellated brain regions (AAL3 atlas) and five brain oscillatory frequency bands (alpha, low-, high-beta, low- and high-gamma). Virtually all skill gains developed during rest intervals of early learning (micro-offline gains). MEG hub strength in the alpha band (8-13Hz) in bilateral anterior cingulate (ACC) and caudate and in the low-beta band (13-16Hz) in bilateral caudate and right putamen correlated with micro-offline gains. These regions linked strongly with the hippocampus, parahippocampal cortex, and lingual and fusiform gyri. Thus, alpha and low-beta brain oscillatory activity in cingulate and striatal regions appear to contribute as hubs of information integration and transmission during early skill learning. Significance StatementEarly learning of moderately difficult skill sequences develops over periods of rest interspersed with practice (micro-offline gains). We demonstrate here a link between alpha and low-beta oscillatory activity in a cingulate-hippocampo-striato network hubs and rest intervals of early learning.

neuroscience↗