Biology subjects

Suviseshamuthu, E. S.

Publications and source records attributed to Suviseshamuthu, E. S..

3 recordsLinked to original sources

bioRxiv2026

Corticospinal Tractometry and Whole-Brain Connectometry of Hand Dexterity in Chronic Stroke and Traumatic Brain Injury

Hand dexterity impairment is a major contributor to long-term disability after acquired brain injury, yet the white matter substrates supporting residual dexterity remain incompletely understood. We investigated diffusion MRI markers of hand dexterity in individuals with chronic stroke (n = 9) and traumatic brain injury (TBI; n = 8) using complementary tract-specific and whole- brain approaches. Partial least squares regression (PLSR) was used to evaluate the cross-validated predictive relevance of bilateral corticospinal tract (CST) diffusion and tractometry features, while quantitative anisotropy (QA)-based correlational tractography was used to identify distributed white matter pathways associated with dexterity performance measured using Box and Block Test (BBT) and MusicGlove Dexterity Test(MGDT). In stroke, CST features predicted BBT performance (Q2 = 0.69, r = 0.85, permutation p = .010) and, more modestly, MGDT performance (Q2= 0.22, r = 0.72, permutation p = .008). In contrast, CST-based models showed no predictive relevance for dexterity outcomes in TBI. Whole-brain connectometry revealed that better dexterity after stroke was associated with greater QA across distributed pathways extending beyond the CST, including commissural, association, and projection fibers. Box and Block Test performance was prominently associated with callosal and cingulum-related pathways, whereas MusicGlove performance showed greater representation of CST and projection pathways. In TBI, significant connectometry findings for the BBT similarly implicated distributed commissural and association pathways, whereas no significant pathways were identified for the MusicGlove test. Together, these findings suggest that the structural correlates of hand dexterity extend beyond the CST and vary across dexterity measures and injury populations. Although preliminary given the small cohorts, the complementary tractometry and connectometry findings support a network-level characterization of residual hand function after acquired brain injury and motivate validation in larger cohorts.

neuroscience↗

bioRxiv2021

Addiction-Related Memory Transfer and Retention in Planaria

Memory retention and transfer in organisms happen at either the neural or genetic level. In humans, addictive behavior is known to pass from parents to offspring. In flatworm planaria (Dugesia tigrina), memory transfer has been claimed to be horizontal, i.e., through cannibalism. Our study is a preliminary step to understand the mechanisms underlying the transfer of addictive behavior to offspring. Since the neural and neurochemical responses of planaria share similarities with humans, it is possible to induce addictions and get predictable behavioral responses. Addiction can be induced in planaria, and decapitation will reveal if the addictive memories are solely stored in the brain. The primary objective was to test the hypothesis that addictive memory is also retained in the brainless posterior region of planaria. The surface preference of the planaria was first determined between smooth and rough surfaces. Through Pavlovian conditioning, the preferred surface was paired with water and the unpreferred surface with sucrose. After the planaria were trained and addicted, their surface preference shifted as a conditioned place preference (CPP) was established. When decapitated, the regenerated segment from the anterior part containing the brain retained the addiction, thus maintaining a shift in the surface preference. Importantly, we observed that the posterior part preserved this CPP as well, suggesting that memory retention is not attributed exclusively to the brain but might also occur at the genetic level. As a secondary objective, the effects of neurotransmitter blocking agents in preventing addiction were studied by administering a D1 dopamine antagonist to planaria, which could provide pointers to treat addictions in humans.

neuroscience↗

bioRxiv2021

EEG-Based Spectral Analysis ShowingBrainwave Changes Related to ModulatingProgressive Fatigue During a ProlongedIntermittent Motor Task

Repeatedly performing a submaximal motor task for a prolonged period of time leads to muscle fatigue comprising a central and peripheral component, which demands a gradually increasing effort. However, the brain contribution to the enhancement of effort to cope with progressing fatigue lacks a complete understanding. The intermittent motor tasks (IMTs) closely resemble many activities of daily living (ADL), thus remaining physiologically relevant to study fatigue. The scope of this study is therefore to investigate the EEG-based brain activation patterns in healthy subjects performing IMT until self-perceived exhaustion. Fourteen participants (median age 51.5 years; age range 26-72 years; 5 males) repeated elbow flexion contractions at 40% maximum voluntary contraction by following visual cues displayed on an oscilloscope screen until subjective exhaustion. Each contraction lasted for approximately 5 s with a 2-s rest between trials. The force, EEG, and surface EMG (from elbow joint muscles) data were simultaneously collected. After preprocessing, we selected a subset of trials at the beginning, middle, and end of the study session representing brain activities germane to mild, moderate, and severe fatigue conditions, respectively, to compare and contrast the changes in the EEG time-frequency (TF) characteristics across the conditions. The outcome of channel- and source-level TF analyses reveals that the theta, alpha, and beta power spectral densities vary in proportion to fatigue levels in cortical motor areas. We observed a statistically significant change in the band-specific spectral power in relation to the graded fatigue from both the steady- and post-contraction EEG data. The findings would enhance our understanding on the etiology and physiology of voluntary motor-action-related fatigue and provide pointers to counteract the perception of muscle weakness and lack of motor endurance associated with ADL. The study outcome would help rationalize why certain patients experience exacerbated fatigue while carrying out mundane tasks, evaluate how clinical conditions such as neurological disorders and cancer treatment alter neural mechanisms underlying fatigue in future studies, and develop therapeutic strategies for restoring the patients ability to participate in ADL by mitigating the central and muscle fatigue.

neuroscience↗