William Richard Staines

Background: The movement-related cortical potential (MRCP) is generated primarily by the supplementary motor area (SMA) and primary motor cortex (M1). Brain computer interfaces (BCIs) leveraging the MRCP have emerged as a therapeutic option for supporting neurorehabilitation. Objectives: This study aims to investigate whether intermittent theta burst stimulation (iTBS) applied to the primary motor cortex (M1), supplementary motor area (SMA), or both (M1 + SMA) enhances neural activity associated with endogenous motor preparation. Methods: Fifteen participants performed a self-paced ballistic gripping task before and after receiving iTBS to M1, SMA, and M1 + SMA across three experiments. MRCPs were analyzed in four components: readiness potential (RP), negative slope (NS′), motor potential (MP), and peak negativity (PN). Signal-to-noise ratio (SNR) was calculated on individual MRCP trials. Artifacts were removed using independent component analysis, followed by manual inspection of trials to ensure only clear MRCPs were used in the repeated-measures statistical analysis. Results: iTBS over M1 significantly enhanced the MP component. SMA stimulation reduced PN without affecting RP. Sequential M1 + SMA stimulation strongly facilitated the NS′ component and increased SNR. M1 stimulation effects peaked at 10 min post-stimulation, while SMA and sequential iTBS effects were strongest at 30 min. Conclusions: Single- and multi-site iTBS modulated late-phase motor preparation, with early-phase activity remaining unchanged. M1 and sequential stimulation influenced different MRCP components, suggesting the former enhanced corticospinal output while sequential iTBS facilitated earlier cortical activity, perhaps through modulating connections between SMA and M1. Significance: We show that iTBS can selectively enhance late-phase motor preparation, offering a promising avenue for both neurorehabilitation of individuals with motor impairments and performance optimization in athletic context. In improving quality of the MRCP signal, our findings can contribute to more reliable and responsive BCI designs.

Clinical and behavioral studies suggest the right lateral cerebellar hemisphere plays a critical role in cognition, particularly attention. Contralateral connections between the cerebellum and cerebrum via the thalamus support this involvement. When rapid attentional shifts occur between two target stimuli (T1 and T2) in close succession, a phenomenon known as attentional blink (AB) results in decreased accuracy in reporting T2. Continuous theta burst stimulation (cTBS) studies indicate that inhibiting the right cerebellar hemisphere enhances visual AB. However, it is uncertain whether the cerebellum impacts sensory processing when presented with two relevant targets in different sensory modalities, and if lateralization of function is conserved. This study investigated cerebellar involvement in cross‐modal AB, particularly the influence of right cerebellar stimulation on rapid attentional shifts between visual and tactile stimuli. In two experiments, participants completed a cross‐modal attentional blink task pre‐ and post‐cTBS stimulation applied to the left or right cerebellar hemisphere. Stimuli included a visual or tactile T1, followed by a cross‐modal T2 and a mask. In Experiment 1, stimuli were presented to the second and fifth digits of the left hand and left visual space, whereas in Experiment 2, they were presented to the second and fifth digits of the right hand and right visual space. Results revealed that right cerebellar inhibition led to reduced accuracy in reporting tactile T2 targets irrespective of stimulus location. No significant changes following left cerebellar stimulation were observed. These findings suggest hemisphere‐specific cerebellar modulation of cross‐modal AB performance, where the right cerebellum plays a role in managing relevant T2 targets from distractors (mask).

Background/Objectives: Concussions have been associated with deficits in attentional control. The current work examined whether attentional correlates could be enhanced following acute aerobic exercise in those with a history of concussion (CH). Methods: EEG was collected as participants completed a flanker task to evoke stimulus-locked (N2, P3) and response-locked error-related (ERN, Pe) ERPs, before and after participants completed a bout of acute aerobic exercise at moderate intensity. Conflict was modulated with distance (close/far) and congruency (incongruent/congruent) of the distractors relative to the targets. Results: CH individuals had reduced accuracy in high-conflict conditions, with improvements following exercise. No differences were observed in attentional cognitive control across the four conditions (close/far congruent, close/far incongruent); however, reduced interference control was shown in far conditions, when compared to close conditions. When compared to non-concussed controls, increased accuracy with increased response time in individuals with a concussion history was likely attributed to the speed–accuracy trade-off. Close conditions highlighted a decreased Pe amplitude in CH individuals (as opposed to the active controls), suggesting CH individuals may present with challenges when evaluating an error with working memory. Conclusions: The findings demonstrated acute exercise improved accuracy among CH individuals, and performance monitoring is impacted negatively long term following a concussion.

Background: The impact of exogenous explicit knowledge on early motor learning is highly variable and may be influenced by excitability within the procedural sensorimotor network. Recent transcranial magnetic stimulation (TMS) studies suggest that variability in interneuron recruitment by anterior–posterior (AP) currents is linked to differences in functional connectivity between premotor and motor regions. Objectives: This study used controllable pulse parameter TMS (cTMS) to assess how AP-sensitive interneuron excitability interacts with explicit knowledge to influence motor learning. Methods: Seventy-two participants were grouped as AP-positive (n = 36) and AP-negative groups (n = 36) based on whether an AP threshold could be obtained before reaching maximal stimulator output. A narrow (30 µs) stimulus was employed to target the longest latency corticospinal inputs selectively. Participants then practiced a continuous visuomotor tracking task and completed a delayed retention test. Half of each group received explicit knowledge of a repeated sequence embedded between random sequences. Random sequence tracking performance assessed general sensorimotor efficiency; repeated sequence performance assessed sequence-specific learning. Results: Both AP₃₀-positive participants, with and without explicit knowledge, and the AP₃₀-negative without explicit knowledge demonstrated similar improvements in sensorimotor efficiency driven by offline consolidation. However, AP₃₀-negative participants given explicit instruction exhibited significantly reduced improvement in sensorimotor efficiency, primarily due to impaired offline consolidation. Conclusions: These findings suggest that individuals with low excitability in long-latency AP-sensitive inputs may be more vulnerable to interference from explicit instruction. The current results highlight the importance of accounting for individual differences in interneuron excitability when developing instructional strategies for motor learning.

The current work aimed to understand the behavioral manifestations that result from disruptions to the selective facilitation of task-relevant sensory information at early cortical processing stages in those with a history of concussion. A total of 40 participants were recruited to participate in this study, with 25 in the concussion history group (Hx) and 15 in the control group (No-Hx). Somatosensory-evoked potentials (SEPs) were elicited via median nerve stimulation while subjects performed a task that manipulated their focus of attention toward or away from proprioceptive cues. Participants also completed an implicit motor sequence learning task relying solely on proprioceptive cues, as well as a visual attentional blink (AB) task to understand the effect of concussion on rapid shifts in attention. The Hx SEP data replicated past work showing an absence of relevancy-based facilitation at early cortical processing stages (N20-P27) that emerged at later processing stages. Our Hx showed evidence of relevancy-based facilitation at either the P50-N70 or the N70-P100. Performance on the learning task was not significantly different between the Hx and No-Hx. Performance on the AB task revealed greater AB magnitude in the Hx compared to the No-Hx. Collectively, these results suggest a compensatory strategy in the Hx that enables them to learn to the same degree as controls. However, when the attentional system is taxed with high temporal demands there are decrements in performance. These results are of particular importance given that these individuals are at an increased risk of sustaining subsequent concussions, and musculoskeletal injuries.

Recent studies highlight a persistent increase in subsequent injury risk following a sport-related concussion (SRC) despite clinical recovery. However, markers of persistent alterations in sensorimotor integration have yet to be identified. One possibility is that compensatory adaptation following SRC may only be unmasked during transient periods of high task complexity in specific sensorimotor circuits. The current study used short-latency afferent inhibition (SAI) to investigate the long-term sequelae of sport-related concussion (SRC) in different short-latency sensorimotor circuits converging in the motor cortex. Specific sensorimotor circuits sensitive to posterior-anterior current with a positive phase lasting 120µs (PA₁₂₀) and anterior-posterior current with a positive phase lasting 30µs (AP₃₀) were assessed using controllable pulse parameter transcranial magnetic stimulation (cTMS) while young adults with and without a history of SRC were at rest or responded to valid and invalid sensorimotor cues. SAI was quantified as the ratio of the motor-evoked potential (MEP) elicited by peripherally conditioned cTMS stimuli to the unconditioned MEP for each cTMS configuration. Individuals with a SRC history demonstrated persistent adaptation in AP₃₀ SAI, but only in response to invalid cues. Persistent adaptation in AP₃₀ SAI was not apparent at rest or during simple sensorimotor transformations in response to valid cues. PA₁₂₀ SAI demonstrated similar responses at rest and in response to both valid and invalid cues, regardless of SRC history. AP₃₀-sensitive sensorimotor circuits may mark the long-term SRC sequelae and the increased susceptibility to momentary breakdowns in sensorimotor integration during periods of high cognitive-motor demands.

Evidence suggests that trait anxiety relates to cognitive processing and behavior. However, the relationships between trait anxiety and sensory processing, goal‐directed performance and sensorimotor function are unclear, particularly in a multimodal context. This study used electroencephalography to evaluate whether trait anxiety influenced visual and tactile event‐related potentials (ERPs), as well as behavioral distractor cost, in a bimodal sensorimotor task. Twenty‐nine healthy young adults completed the State–Trait Anxiety Inventory. Participants were directed to focus on either tactile or visual stimuli while disregarding the other modality, responding to target stimulus amplitude with a proportional grip. Previous research suggests that somatosensory N70 and visual P2 ERPs serve as markers of attentional relevance, with attention also impacting the visual P3 ERP. It was hypothesized that trait anxiety would modulate the ERPs susceptible to attentional modulation (tactile N70, visual P2 and P3) and not affect behavioral performance. Trait anxiety showed a large, significant interaction with attention for visual P3 latency in response to unimodal visual stimuli, with a positive relationship between P3 latencies and trait anxiety when attending toward the stimulus and negative when attending away. A large, positive main effect of trait anxiety on visual N1 amplitude for bimodal stimuli was also detected. As predicted, trait anxiety related to ERPs but not behavioral distractor cost. These findings suggest that trait anxiety modulates visual but not somatosensory processing correlates based on attention. The absence of overt behavioral performance effects suggests compensatory mechanisms may offset underlying differences in sensory processing.

Enhancing cerebellar activity influences motor cortical activity and contributes to motor adaptation, though it is unclear which neurophysiological mechanisms contributing to adaptation are influenced by the cerebellum. Pre-movement beta event-related desynchronization (β-ERD), which reflects a release of inhibitory control in the premotor cortex during movement planning, is one mechanism that may be modulated by the cerebellum through cerebellar-premotor connections. We hypothesized that enhancing cerebellar activity with intermittent theta burst stimulation (iTBS) would improve adaptation rates and increase β-ERD during motor adaptation. Thirty-four participants were randomly assigned to an active (A-iTBS) or sham cerebellar iTBS (S-iTBS) group. Participants performed a visuomotor task, using a joystick to move a cursor to targets, prior to receiving A-iTBS or S-iTBS, following which they completed training with a 45° rotation to the cursor movement. Behavioural adaptation was assessed using the angular error of the cursor path relative to the ideal trajectory. The results showed a greater adaptation rate following A-iTBS and an increase in β-ERD, specific to the high β range (20–30 Hz) during motor planning, compared to S-iTBS, indicative of cerebellar modulation of the motor cortical inhibitory control network. The enhanced release of inhibitory activity persisted throughout training, which suggests that the cerebellar influence over the premotor cortex extends beyond adaptation to other stages of motor learning. The results from this study further understanding of cerebellum-motor connections as they relate to acquiring motor skills and may inform future skill training and rehabilitation protocols.

Exercise may influence components of executive functioning, specifically cognitive control and action monitoring. We aimed to determine whether high level exercise improves the efficacy of cognitive control in response to differing levels of conflict. Fitter individuals were expected to demonstrate enhanced action monitoring and optimal levels of cognitive control in response to changing task demands. Participants were divided into the highly active (HA) or low-active group based on self-reported activity using the International Physical Activity Questionnaire. A modified flanker task was then performed, in which the level of conflict was modulated by distance of distractors from the target (close, far) and congruency of arrows (incongruent, congruent). Electroencephalography (EEG) was collected during 800 trials; trials were 80% congruent, 20% incongruent, 50% close, and 50% far. The error-related negativity (ERN) and error positivity (Pe) were extracted from the difference wave of correct and incorrect response locked epochs, the N2 from the difference wave of congruent and incongruent stimulus locked epochs and the P3 from stimulus locked epochs. The HA group showed a larger Pe amplitude compared to the low-active group. Close trials elicited a larger N2 amplitude than far trials in the HA group, but not the low-active group, the HA group also made fewer errors on far trials than on close trials. Finally, the P3 was smaller in the lowest conflict condition in the HA, but not the low-active group. These findings suggest that habitual, high levels of exercise may influence the endogenous processing involved in pre-response conflict detection and the post-error response.