Impact of subclinical neck pain on eye and hand movements in goal-directed upper limb aiming movements.

Individuals with untreated, mild-to-moderate recurrent neck pain or stiffness (subclinical neck pain (SCNP)) have been shown to have impairments in upper limb proprioception, and altered cerebellar processing. It is probable that aiming trajectories will be impacted since individuals with SCNP cannot rely on accurate proprioceptive feedback or feedforward processing (body schema) for movement planning and execution, due to altered afferent input from the neck. SCNP participants may thus rely more on visual feedback, to accommodate for impaired cerebellar processing. This quasi-experimental study sought to determine whether upper limb kinematics and oculomotor processes were impacted in those with SCNP. 25 SCNP and 25 control participants who were right-hand dominant performed bidirectional aiming movements using two different weighted styli (light or heavy) while wearing an eye-tracking device. Those with SCNP had a greater time to and time after peak velocity, which corresponded with a longer upper limb movement and reaction time, seen as greater constant error, less undershoot in the upwards direction and greater undershoot in the downwards direction compared to controls. SCNP participants also showed a trend towards a quicker ocular reaction and movement time compared to controls, while the movement distance was fairly similar between groups. This study indicates that SCNP alters aiming performances, with greater reliance on visual feedback, likely due to altered proprioceptive input leading to altered cerebellar processing.

Subclinical Neck Pain Leads to Differential Changes in Early Somatosensory Evoked Potentials in Response to a Novel Force Matching Tracking Task.

BACKGROUND: Neural adaptions in response to sensorimotor tasks are impaired in those with untreated, recurrent mild-to-moderate neck pain (subclinical neck pain (SCNP)), due to disordered central processing of afferent information (e.g., proprioception). Neural adaption to force modulation, a sensorimotor skill reliant on accurate proprioception, is likely to be impaired in those with SCNP. This study examined changes in somatosensory evoked potential (SEP) peak amplitudes following the acquisition of a novel force matching tracking task (FMTT) in those with SCNP compared to non-SCNP. METHODS: 40 (20 female (F) & 20 male (M); average age (standard deviation, SD): 21.6 (3.01)) right-handed participants received controlled electrical stimulation at 2.47 Hz and 4.98 Hz (averaged 1000 sweeps/frequency) over the right-median nerve, to elicit SEPs before and after FMTT acquisition. Participants used their right thumb to match a series of force profiles that were calibrated to their right thumb (abductor pollicis brevis muscle) strength. To determine if motor learning was impacted, retention was assessed 24 to 48 hours later. Outliers were removed before running independent t-tests on normalized SEP peak amplitudes, and repeated measures analysis of variance (ANOVA) with planned contrasts on absolute and normalized motor performance accuracy. Benjamini-hochberg test was used to correct for multiple independent SEP comparisons. RESULTS: SEP peaks: N18 (t(29.058) = 2.031, p = 0.026), N20 (t(35) = -5.460, p < 0.001), and P25 (t(33) = -2.857, p = 0.004) had group differences. Motor performance: Absolute error (n = 38) had a main effect of time, and significant pre-and post-acquisition contrast for time (both p < 0.001). CONCLUSIONS: Group differences in the olivary-cerebellar pathway (N18), and cortical processing at the somatosensory cortex (N20 and P25), suggests that SCNP alters cortical and cerebellar processing compared to non-SCNP in response to FMTT acquisition. The sensory-motor integration differences in the SCNP group suggests that those with SCNP may rely more on feedback loops for discrete sensorimotor tasks dependent on proprioception. Early SEP changes may be used as a marker for altered neuroplasticity in the context of motor skill acquisition of a novel discrete FMTT in those with SCNP.

Cervico-Ocular and Vestibulo-Ocular Reflexes in Subclinical Neck Pain and Healthy Individuals: A Cross-Sectional Study.

Alterations in neck sensory input from recurrent neck pain (known as subclinical neck pain (SCNP)) result in disordered sensorimotor integration (SMI). The cervico-ocular (COR) and vestibulo-ocular (VOR) reflexes involve various neural substrates but are coordinated by the cerebellum and reliant upon proprioceptive feedback. Given that proprioception and cerebellar processing are impaired in SCNP, we sought to determine if COR or VOR gain is also altered. COR and VOR were assessed using an eye-tracking device in 20 SCNP (9 M and 11 F; 21.8 (SD = 2.35) years) and 17 control (7 M and 10 F; 22.40 (SD = 3.66) years) participants. COR gain (10 trials): A motorized chair rotated the trunk at a frequency of 0.04 Hz and an amplitude of 5° while participants gazed at a circular target that disappeared after three seconds. VOR gain (30 trials): Rapid bilateral head movements away from a disappearing circular target while eyes fixated on the last observed target. Independent t-tests on COR and VOR gain were performed. SCNP had a significantly larger COR gain (p = 0.006) and smaller VOR gain (p = 0.487) compared to healthy controls. The COR group differences suggest an association between proprioceptive feedback and SMI, indicating COR may be a sensitive marker of altered cerebellar processing.

Possible Influence of Ethnicity on CT Perfusion Parameter Thresholds in Acute Ischemic Stroke.

Introduction Tissue at risk, as estimated by CT perfusion utilizing Tmax+6, correlates with final infarct volume (FIV) in acute ischemic stroke (AIS) without reperfusion. Tmax thresholds are derived from Western ethnic populations but not from ethnic Asian populations. We aimed to investigate the influence of ethnicity on Tmax thresholds. Methods From a clinical-imaging registry of Australian and Indonesian stroke patients, we selected a participant subgroup with the following inclusion criteria: AIS under 24 hours and absence of reperfusion therapy. Clinical data included demographics, time metrics, stroke severity, premorbid, and 3-month Modified Rankin Score. Baseline CTP and MRI <72 hours were performed. Volumes of Tmax utilizing different thresholds and final infarct volumes (FIV) were calculated. Spearman correlation was used to evaluate relationship involving ordinal variables and calculate the optimal Tmax threshold against FIV in both populations. Results Two hundred patients were included in the study sample 100 in Jakarta and 100 in Geelong. The median National Institutes Health Stroke Scale (IQR) were 6(3-11) and 3(1-5), respectively. The median Tmax+6(IQR) was 0 (0-46.5) in Jakarta group and 0(0-7.5) in Geelong group. The median FIV(IQR) was 0 (0-30.5) and 0 (0-5.5). Tmax +8s in Jakarta population against FIV showed Spearman's coefficient =0.72, representing the optimal Tmax threshold. Tmax+6s showed Spearman's coefficient =0.51 against FIV in the Geelong population. Conclusions Tmax thresholds approximating FIV were possibly different in the Asian when compared with the non-Asian populations. Future studies are required to extend and confirm the validity of our findings.

Source Localization of Somatosensory Neural Generators in Adults with Attention-Deficit/Hyperactivity Disorder.

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder, where differences are often present relating to the performance of motor skills. Our previous work elucidated unique event-related potential patterns of neural activity in those with ADHD when performing visuomotor and force-matching motor paradigms. The purpose of the current study was to identify whether there were unique neural sources related to somatosensory function and motor performance in those with ADHD. Source localization (sLORETA) software identified areas where neural activity differed between those with ADHD and neurotypical controls when performing a visuomotor tracing task and force-matching task. Median nerve somatosensory evoked potentials (SEPs) were elicited, while whole-head electroencephalography (EEG) was performed. sLORETA localized greater neural activity post-FMT in those with ADHD, when compared with their baseline activity (p < 0.05). Specifically, greater activity was exhibited in BA 31, precuneus, parietal lobe (MNI coordinates: X = -5, Y = -75, and Z = 20) at 156 ms post stimulation. No significant differences were found for any other comparisons. Increased activity within BA 31 in those with ADHD at post-FMT measures may reflect increased activation within the default mode network (DMN) or attentional changes, suggesting a unique neural response to the sensory processing of force and proprioceptive afferent input in those with ADHD when performing motor skills. This may have important functional implications for motor tasks dependent on similar proprioceptive afferent input.

Sensorimotor integration and motor learning during a novel visuomotor tracing task in young adults with attention-deficit/hyperactivity disorder.

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that has noted alterations to motor performance and coordination, potentially affecting learning processes and the acquisition of motor skills. This work will provide insight into the role of altered neural processing and sensorimotor integration (SMI) while learning a novel visuomotor task in young adults with ADHD. This work compared adults with ADHD (n = 12) to neurotypical controls (n = 16), using a novel visuomotor tracing task, where participants used their right-thumb to trace a sinusoidal waveform that varied in both frequency and amplitude. This learning paradigm was completed in pre, acquisition, and post blocks, where participants additionally returned and completed a retention and transfer test 24 h later. Right median nerve short latency somatosensory-evoked potentials (SEPs) were collected pre and post motor acquisition. Performance accuracy and variability improved at post and retention measures for both groups for both normalized (P < 0.001) and absolute (P < 0.001) performance scores. N18 SEP: increased in the ADHD group post motor learning and decreased in controls (P < 0.05). N20 SEP: increased in both groups post motor learning (P < 0.01). P25: increased in both groups post motor learning (P < 0.001). N24: increased for both groups at post measures (P < 0.05). N30: decreased in the ADHD group and increased in controls (P < 0.05). These findings suggest that there may be differences in cortico-cerebellar and prefrontal processing in response to novel visuomotor tasks in those with ADHD.NEW & NOTEWORTHY Alterations to somatosensory-evoked potentials (SEPs) were present in young adults with attention-deficit/hyperactivity disorder (ADHD), when compared with neurotypical controls. The N18 and N30 SEP peak had differential changes between groups, suggesting alterations to olivary-cerebellar-M1 processing and SMI in those with ADHD when acquiring a novel visuomotor tracing task. This suggests that short-latency SEPs may be a useful biomarker in the assessment of differential responses to motor acquisition in those with ADHD.

Differential changes in somatosensory evoked potentials and motor performance: pursuit movement task versus force matching tracking task.

Force modulation relies on accurate proprioception, and force-matching tasks alter corticocerebellar connectivity. Corticocerebellar (N24) and corticomotor pathways are impacted following the acquisition of a motor tracing task (MTT), measured using both somatosensory evoked potentials (SEPs) and transcranial magnetic stimulation. This study compared changes in early SEP peak amplitudes and motor performance following a force-matching tracking task (FMTT) to an MTT. Thirty (18 females) right-handed participants, aged 21.4 ± 2.76, were electrically stimulated over the right-median nerve at 2.47 Hz and 4.98 Hz (averaged 1,000 sweeps/rate) to elicit SEPs, recorded via a 64-channel electroencephalography cap, before, and after task acquisition using the right abductor pollicis brevis muscle. Retention was measured 24 h later. Significant time-by-group interactions occurred for the N20 SEP: 6.3% decrease post-FMTT versus 5.5% increase post-MTT (P = 0.013); P25 SEP: 4.0% decrease post-FMTT versus 10.3% increase post-MTT (P = 0.006); and N18 SEP: 113.4% increase post-FMTT versus 4.4% decrease post-MTT (P = 0.006). N18 and N30 showed significant effect of time (both P < 0.001). Motor performance: significant time-by-group interactions-postacquisition: FMTT improved 15.3% versus 24.3% for MTT (P = 0.025), retention: FMTT improved 17.4% and MTT by 30.1% (P = 0.004). Task-dependent differences occurred in SEP peaks associated with cortical somatosensory processing (N20 and P25), and cerebellar input (N18), with similar changes in sensorimotor integration (N30), with differential improvements in motor performance, indicating important differences in cerebellar and sensory processing for tasks reliant on proprioception.NEW & NOTEWORTHY This study demonstrates neurophysiological differences in cerebellar and somatosensory cortex pathways when learning a motor task requiring visuomotor tracking versus a task that requires force-matching modulation, in healthy individuals. The clear neurophysiological differences in early somatosensory evoked potentials associated with cortical somatosensory processing, cerebellar input, and sensorimotor integration between these two tasks demonstrate some of the neural correlates of force modulation and validate the force-matching task for use in future work.

Source Localization of Audiovisual Multisensory Neural Generators in Young Adults with Attention-Deficit/Hyperactivity Disorder.

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that exhibits unique neurological and behavioural characteristics. Our previous work using event-related potentials demonstrated that adults with ADHD process audiovisual multisensory stimuli somewhat differently than neurotypical controls. This study utilised an audiovisual multisensory two-alternative forced-choice discrimination task. Continuous whole-head electroencephalography (EEG) was recorded. Source localization (sLORETA) software was utilised to determine differences in the contribution made by sources of neural generators pertinent to audiovisual multisensory processing in those with ADHD versus neurotypical controls. Source localization techniques elucidated that the controls had greater neural activity 164 ms post-stimulus onset when compared to the ADHD group, but only when responding to audiovisual stimuli. The source of the increased activity was found to be Brodmann Area 2, postcentral gyrus, right-hemispheric parietal lobe referenced to Montreal Neurological Institute (MNI) coordinates of X = 35, Y = −40, and Z = 70 (p < 0.05). No group differences were present during either of the unisensory conditions. Differences in the integration areas, particularly in the right-hemispheric parietal brain regions, were found in those with ADHD. These alterations may correspond to impaired attentional capabilities when presented with multiple simultaneous sensory inputs, as is the case during a multisensory condition.

The impact of subclinical neck pain on goal-directed upper limb movement in the horizontal plane.

Subclinical neck pain (SCNP) refers to recurrent neck pain and/or stiffness for which individuals have not yet sought treatment. Prior studies have shown that individuals with SCNP have altered cerebellar processing that exhibits an altered body schema. The cerebellum also plays a vital role in upper limb reaching movements through refining internal models and integrating sensorimotor information. However, the impact of SCNP on these processes has yet to be examined in the context of a rapid goal-directed aiming response that relies on feedforward and feedback processes to guide the limb to the target. To address this, SCNP and control participants performed goal-directed upper limb movements with the dominant and non-dominant hands using light and heavy styli in the horizontal plane. The results show greater peak accelerations in SCNP participants using the heavy stylus. However, there were no other group differences seen, possibly due to the fact that reaching behavior predominantly relies on vision such that any proprioceptive deficits seen in those with SCNP can be compensated. This study illustrates the robust compensatory nature of the CNS when performing end-effector reaching tasks, suggesting studies altering visual feedback may be needed to see the full impact of SCNP on upper limb aiming.

Sensorimotor integration and motor learning during a novel force-matching task in young adults with attention-deficit/hyperactivity disorder.

Introduction: Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that exhibits unique neurological and behavioral characteristics. Those with ADHD often have noted impairments in motor performance and coordination, including during tasks that require force modulation. The present study provides insight into the role of altered neural processing and SMI in response to a motor learning paradigm requiring force modulation and proprioception, that previous literature has suggested to be altered in those with ADHD, which can also inform our understanding of the neurophysiology underlying sensorimotor integration (SMI) in the general population. Methods: Adults with ADHD (n = 15) and neurotypical controls (n = 15) performed a novel force-matching task, where participants used their right-thumb to match a trace template that varied from 2-12% of their Abductor Pollicis Brevis maximum voluntary contraction. This motor task was completed in pre, acquisition, and post blocks. Participants also completed a retention test 24 h later. Median nerve somatosensory-evoked potentials (SEPs) were collected pre and post motor acquisition. SEPs were stimulated at two frequencies, 2.47 Hz and 4.98 Hz, and 1,000 sweeps were recorded using 64-electrode electroencephalography (EEG) at 2,048 Hz. SEP amplitude changes were normalized to each participant's baseline values for that peak. Results: Both groups improved at post measures (ADHD: 0.85 ± 0.09; Controls: 0.85 ± 0.10), with improvements maintained at retention (ADHD: 0.82 ± 0.11; Controls: 0.82 ± 0.11). The ADHD group had a decreased N18 post-acquisition (0.87 ± 0.48), while the control N18 increased (1.91 ± 1.43). The N30 increased in both groups, with a small increase in the ADHD group (1.03 ± 0.21) and a more pronounced increase in controls (1.15 ± 0.27). Discussion: Unique neural differences between groups were found after the acquisition of a novel force-matching motor paradigm, particularly relating to the N18 peak. The N18 differences suggest that those with ADHD have reduced olivary-cerebellar-M1 inhibition when learning a novel motor task dependent on force-modulation, potentially due to difficulties integrating the afferent feedback necessary to perform the task. The results of this work provide evidence that young adults with ADHD have altered proprioceptive processing when learning a novel motor task when compared to neurotypical controls.

Effect of Neck Muscle Fatigue on Hand Muscle Motor Performance and Early Somatosensory Evoked Potentials.

Even on pain free days, recurrent neck pain alters sensorimotor integration (SMI) measured via somatosensory evoked potentials (SEPs). Neck muscle fatigue decreases upper limb proprioception, and thus may interfere with upper limb motor task acquisition and SMI. This study aimed to determine the effect of cervical extensor muscle (CEM) fatigue on upper limb motor acquisition and retention; and SMI, measured via early SEPs. Twenty-four healthy right-handed individuals were randomly assigned to control or CEM fatigue. Baseline SEPs were elicited via median nerve stimulation at the wrist. Participants then lay prone on a padded table. The fatigue group supported a 2 kg weight until they could no longer maintain the position. The control group rested their neck in neutral for 5 min. Participants completed pre- and post-motor skill acquisition while seated, SEPs were again collected. Task retention was measured 24 h later. Accuracy improved post acquisition and at retention for both groups (p < 0.001), with controls outperforming the fatigue group (p < 0.05). The fatigue group had significantly greater increases in the N24 (p = 0.017) and N30 (p = 0.007) SEP peaks. CEM fatigue impaired upper limb motor learning outcomes in conjunction with differential changes in SEP peak amplitudes related to SMI.

Proximal Upper Limb Sensorimotor Integration in Response to Novel Motor Skill Acquisition.

Previous studies have shown significant changes in cortical and subcortical evoked potential activity levels in response to motor training with the distal upper-limb muscles. However, no studies to date have assessed the neurological processing changes in somatosensory evoked potentials (SEPs) associated with motor training whole-arm movements utilizing proximal upper-limb muscles. The proximal upper-limb muscles are a common source of work-related injuries, due to repetitive glenohumeral movements. Measuring neurophysiological changes following performance of a proximal motor task provide insight into potential neurophysiological changes associated with occupational postures and movements involving proximal upper limb muscles. This study sought to assess the impact of a novel motor skill acquisition task on neural processing of the proximal upper-limb muscle groups, through the measurement of short-latency median nerve SEPs. One group of 12 participants completed a novel motor training task, consisting of tracing a sinusoidal waveform varying in amplitude and frequency. Baseline SEP measurements were recorded from each participant, followed by a mental recitation control task. Pre-test SEP measurements were then recorded, followed by the motor training task, and post-test SEP recordings. The participants completed the tracing with their right thumb, using glenohumeral rotation only to move their hand. Significant improvements in task accuracy were demonstrated, indicating that motor acquisition had occurred. Significant changes were also seen in the N11, N13, N20, N24, P25, and the N30 SEP peaks were seen following the motor training task. Conclusion: Early SEPs appear to be a sensitive measure of changes in sensorimotor integration in response to novel motor skill acquisition within the proximal upper-limb muscles.

Neck muscle fatigue impacts plasticity and sensorimotor integration in cerebellum and motor cortex in response to novel motor skill acquisition.

The cerebellum undergoes neuroplastic changes in response to motor learning. Healthy human individuals demonstrate reduced cerebellar inhibition (CBI) following motor learning. Alterations in neck sensory input due to muscular fatigue are known to impact upper limb sensorimotor processing, suggesting that neck fatigue may also impact cerebellum to motor cortex (M1) pathways in response to motor learning. Therefore, this study aimed to determine whether cervical extensor muscle (CEM) fatigue alters CBI in response to motor learning. We examined 16 participants (8 CEM fatigue and 8 CEM control). A double cone transcranial magnetic stimulation (TMS) coil stimulated the ipsilateral cerebellar cortex 5 ms before application of contralateral test stimuli of the M1 to the right first dorsal interosseous muscle. Cerebellar-M1 activity curves were established pre- and post-motor skill acquisition (consisting of tracing sinusoidal-pattern waves with the index finger) and following either the CEM fatigue or control intervention. The control group showed greater cerebellar disinhibition than the fatigue group following motor skill acquisition (P < 0.006), while the fatigue group showed similar levels of CBI pre- and post-motor skill acquisition. Both groups improved in accuracy following acquisition (P = 0.012) and retention (P = 0.007), but the control group improved significantly more (17% at acquisition and 22% at retention) versus lower (6% and 9%) improvements for the fatigue group. Lessened cerebellar disinhibition in the CEM fatigue versus control group, coupled with diminished motor learning, suggests that CEM fatigue affects the cerebellar-M1 interaction, influencing the cerebellum's ability to adjust motor output to acquire and learn a novel motor task.NEW & NOTEWORTHY Normally motor learning decreases cerebellar inhibition (CBI) to facilitate learning of a novel skill. In this study, neck fatigue before motor skill acquisition led to less of a decrease in CBI and significantly less improvement in performance accuracy relative to a control group. This study demonstrated that neck fatigue impacts the cerebellar-motor cortex interaction to distal hand muscles, a highly relevant finding due to the altered neck postures and fatigue accompanying increased technology use.

Differential Changes in Early Somatosensory Evoked Potentials between the Dominant and Non-Dominant Hand, Following a Novel Motor Tracing Task.

During training in a novel dynamic environment, the non-dominant upper limb favors feedback control, whereas the dominant limb favors feedforward mechanisms. Early somatosensory evoked potentials (SEPs) offer a means to explore differences in cortical regions involved in sensorimotor integration (SMI). This study sought to compare differences in SMI between the right (Dom) and left (Non-Dom) hand in healthy right-handed participants. SEPs were recorded in response to median nerve stimulation, at baseline and post, a motor skill acquisition-tracing task. One group (n = 12) trained with their Dom hand and the other group (n = 12), with their Non-Dom hand. The Non-Dom hand was significantly more accurate at baseline (p < 0.0001) and both groups improved with time (p < 0.0001), for task accuracy, with no significant interaction effect between groups for both post-acquisition and retention. There were significant group interactions for the N24 (p < 0.001) and the N30 (p < 0.0001) SEP peaks. Post motor acquisition, the Dom hand had a 28.9% decrease in the N24 and a 23.8% increase in the N30, with opposite directional changes for the Non-Dom hand; 22.04% increase in N24 and 24% decrease in the N30. These SEP changes reveal differences in early SMI between Dom and Non-Dom hands in response to motor acquisition, providing objective, temporally sensitive measures of differences in neural mechanisms between the limbs.

Audiovisual Multisensory Processing in Young Adults With Attention-Deficit/Hyperactivity Disorder.

Multisensory integration is a fundamental form of sensory processing that is involved in many everyday tasks. Those with Attention-Deficit/Hyperactivity Disorder (ADHD) have characteristic alterations to various brain regions that may influence multisensory processing. The overall aim of this work was to assess how adults with ADHD process audiovisual multisensory stimuli during a complex response time task. The paradigm used was a two-alternative forced-choice discrimination task paired with continuous 64-electrode electroencephalography, allowing for the measurement of response time and accuracy to auditory, visual, and audiovisual multisensory conditions. Analysis revealed that those with ADHD ( n = 10) respond faster than neurotypical controls ( n = 12) when presented with auditory, visual, and audiovisual multisensory conditions, while also having race model violation in early response latency quantiles. Adults with ADHD also had more prominent multisensory processing over parietal-occipital brain regions at early post-stimulus latencies, indicating that altered brain structure may have important outcomes for audiovisual multisensory processing. The present study is the first to assess how those with ADHD respond to multisensory conditions during a complex response time task, and demonstrates that adults with ADHD have unique multisensory processing when assessing both behavioral response time measures and neurological measures.

The Influence of Subclinical Neck Pain on Neurophysiological and Behavioral Measures of Multisensory Integration.

Multisensory integration (MSI) is necessary for the efficient execution of many everyday tasks. Alterations in sensorimotor integration (SMI) have been observed in individuals with subclinical neck pain (SCNP). Altered audiovisual MSI has previously been demonstrated in this population using performance measures, such as reaction time. However, neurophysiological techniques have not been combined with performance measures in the SCNP population to determine differences in neural processing that may contribute to these behavioral characteristics. Electroencephalography (EEG) event-related potentials (ERPs) have been successfully used in recent MSI studies to show differences in neural processing between different clinical populations. This study combined behavioral and ERP measures to characterize MSI differences between healthy and SCNP groups. EEG was recorded as 24 participants performed 8 blocks of a simple reaction time (RT) MSI task, with each block consisting of 34 auditory (A), visual (V), and audiovisual (AV) trials. Participants responded to the stimuli by pressing a response key. Both groups responded fastest to the AV condition. The healthy group demonstrated significantly faster RTs for the AV and V conditions. There were significant group differences in neural activity from 100-140 ms post-stimulus onset, with the control group demonstrating greater MSI. Differences in brain activity and RT between individuals with SCNP and a control group indicate neurophysiological alterations in how individuals with SCNP process audiovisual stimuli. This suggests that SCNP alters MSI. This study presents novel EEG findings that demonstrate MSI differences in a group of individuals with SCNP.

Audiovisual Multisensory Integration and Evoked Potentials in Young Adults With and Without Attention-Deficit/Hyperactivity Disorder.

The purpose of this study was to assess how young adults with attention-deficit/hyperactivity disorder (ADHD) process audiovisual (AV) multisensory stimuli using behavioral and neurological measures. Adults with a clinical diagnosis of ADHD (n = 10) and neurotypical controls (n = 11) completed a simple response time task, consisting of auditory, visual, and AV multisensory conditions. Continuous 64-electrode electroencephalography (EEG) was collected to assess neurological responses to each condition. The AV multisensory condition resulted in the shortest response times for both populations. Analysis using the race model (Miller, 1982) demonstrated that those with ADHD had violation of the race model earlier in the response, which may be a marker for impulsivity. EEG analysis revealed that both groups had early multisensory integration (MSI) occur following multisensory stimulus onset. There were also significant group differences in event-related potentials (ERPs) in frontal, parietal, and occipital brain regions, which are regions reported to be altered in those with ADHD. This study presents results examining multisensory processing in the population of adults with ADHD, and can be used as a foundation for future ADHD research using developmental research designs as well as the development of novel technological supports.

Neck muscle fatigue affects performance of an eye-hand tracking task.

Altered afferent input from the neck due to fatigue alters upper limb proprioception and is likely to impact upper limb performance accuracy. This study examined the effect of cervical extensor muscle (CEM) fatigue on eye-hand tracking accuracy in healthy participants. Twenty-four healthy right-handed individuals were randomly assigned to either a control or CEM fatigue group. Each participant performed a tracking task which required shoulder rotation to move a circular object to a square target on a touchscreen computer. The task was performed with vision of the target and with the target hidden. A prone lying position, CEM fatigue protocol required participants to hold a 2 kg weight against gravity with their head in a neutral posture. The control intervention rested for 5 min, in a prone position, with the head supported in a neutral posture. Participants performed 3 trials with vision and 3 without at 5 different time points: (1) pre-intervention (fatigue or control), (2) immediately post-intervention, (3) 5 min, (4) 10 min, and (5) 20 min post-intervention. There were significant differences between the target with vision and the hidden condition for both groups between pre- and post-fatigue trials in angle of trajectory (p = 0.0001), and distance from release point to the target (p = 0.0001). Significant differences occurred in the hidden target condition for the fatigue group immediately post fatigue (p = 0.018) for distance from release to the target. Neck muscle fatigue reduced the accuracy of an upper limb tracking task to a hidden target, suggesting that altered afferent input from the neck due to fatigue may impair body schema and result in decreased upper limb performance accuracy.

The Interactive Effect of Tonic Pain and Motor Learning on Corticospinal Excitability.

Prior work showed differential alterations in early somatosensory evoked potentials (SEPs) and improved motor learning while in acute tonic pain. The aim of the current study was to determine the interactive effect of acute tonic pain and early motor learning on corticospinal excitability as measured by transcranial magnetic stimulation (TMS). Two groups of twelve participants (n = 24) were randomly assigned to a control (inert lotion) or capsaicin (capsaicin cream) group. TMS input⁻output (IO) curves were performed at baseline, post-application, and following motor learning acquisition. Following the application of the creams, participants in both groups completed a motor tracing task (pre-test and an acquisition test) followed by a retention test (completed without capsaicin) within 24⁻48 h. Following an acquisition phase, there was a significant increase in the slope of the TMS IO curves for the control group (p < 0.05), and no significant change for the capsaicin group (p = 0.57). Both groups improved in accuracy following an acquisition phase (p < 0.001). The capsaicin group outperformed the control group at pre-test (p < 0.005), following an acquisition phase (p < 0.005), and following a retention test (p < 0.005). When data was normalized to the pre-test values, the learning effects were similar for both groups post-acquisition and at retention (p < 0.005), with no interactive effect of group. The acute tonic pain in this study was shown to negate the increase in IO slope observed for the control group despite the fact that motor performance improved similarly to the control group following acquisition and retention. This study highlights the need to better understand the implications of neural changes accompanying early motor learning, particularly while in pain.

Audiohaptic Feedback Enhances Motor Performance in a Low-Fidelity Simulated Drilling Task.

When used in educational settings, simulations utilizing virtual reality (VR) technologies can reduce training costs while providing a safe and effective learning environment. Tasks can be easily modified to maximize learning objectives of different levels of trainees (e.g., novice, intermediate, expert), and can be repeated for the development of psychomotor skills. VR offers a multisensory experience, providing visual, auditory, and haptic sensations with varying levels of fidelity. While simulating visual and auditory stimuli is relatively easy and cost-effective, similar representations of haptic sensation still require further development. Evidence suggests that mixing high- and low-fidelity realistic sensations (e.g., audition and haptic) can improve the overall perception of realism, however, whether this also leads to improved performance has not been examined. The current study examined whether audiohaptic stimuli presented in a virtual drilling task can lead to improved motor performance and subjective realism, compared to auditory stimuli alone. Right-handed participants (n = 16) completed 100 drilling trials of each stimulus type. Performance measures indicated that participants overshot the target during auditory trials, and undershot the target during audiohaptic trials. Undershooting is thought to be indicative of improved performance, optimizing both time and energy requirements.