Preliminary Evidence for the Clinical Utility of Tactile Somatosensory Assessments of Sport-Related mTBI

Objectives To evaluate the clinical utility of tactile somatosensory assessments to assist clinicians in diagnosing sport-related mild traumatic brain injury (SR-mTBI), classifying recovery trajectory based on performance at initial clinical assessment, and determining if neurophysiological recovery coincided with clinical recovery. Research Design Prospective cohort study with normative controls. Methods At admission (n = 79) and discharge (n = 45/79), SR-mTBI patients completed the SCAT-5 symptom scale, along with the following three components from the Cortical Metrics Brain Gauge somatosensory assessment (BG-SA): temporal order judgement (TOJ), TOJ with confounding condition (TOJc), and duration discrimination (DUR). To assist SR-mTBI diagnosis on admission, BG-SA performance was used in logistic regression to discriminate cases belonging to the SR-mTBI sample or a healthy reference sample (pooled BG-SA data for healthy participants in previous studies). Decision trees evaluated how accurately BG-SA performance classified SR-mTBI recovery trajectories. Results BG-SA TOJ, TOJc, and DUR poorly discriminated between cases belonging to the SR-mTBI sample or a healthy reference sample (0.54–0.70 AUC, 47.46–64.71 PPV, 48.48–61.11 NPV). The BG-SA evaluated did not accurately classify SR-mTBI recovery trajectories (> 14-day resolution 48%, ≤14–day resolution 54%, lost to referral/follow-up 45%). Mann-Whitney U tests revealed differences in BG-SA TOJc performance between SR-mTBI participants and the healthy reference sample at initial clinical assessment and at clinical recovery (p < 0.05). Conclusions BG-SA TOJ, TOJc, and DUR appear to have limited clinical utility to assist clinicians with diagnosing SR-mTBI or predicting recovery trajectories under ecologically valid conditions. Neurophysiological abnormalities persisted beyond clinical recovery given abnormal BG-SA TOJc performance observed when SR-mTBI patients achieved clinical recovery.

EXPRESS: Is the attentional SNARC effect truly attentional? Using temporal order judgments to differentiate attention from response

The spatial-numerical association of response codes (SNARC) effect reflects the phenomenon that low digits are responded to faster with the left hand and high digits with the right. Recently, a particular variant of the SNARC effect known as the attentional SNARC (which reflects that attention can be shifted in a similar manner) has had notable replicability issues. However, a potentially useful method for measuring it was revealed by Casarotti et al. (2007) using a temporal order judgement (TOJ) task. Accordingly, the present study evaluated whether Casarotti et al.’s results were reproducible by presenting a low (1) or high (9) digit prior to a TOJ task where participants had to indicate which of two peripherally presented targets appeared first (Experiment 1) or second (Experiment 2). In Experiment 1, it was revealed that the findings of Casarotti et al.’s were indeed observable upon replication. In Experiment 2, when attention and response dimensions were put in opposition, the SNARC effect corresponded to the side of response rather than attention. Taken together, the present study confirms the robustness of the attentional SNARC in TOJ tasks, but that it is not likely due to shifts in attention.

Evaluating the Effect of Semantic Congruency and Valence on Multisensory Integration

Previous studies demonstrate that semantics, the higher level meaning of multi-modal stimuli, can impact multisensory integration. Valence, an affective response to images, has not yet been tested in non-priming response time (RT) or temporal order judgement (TOJ) tasks. This study aims to investigate both semantic congruency and valence of non-speech audiovisual stimuli on multisensory integration via RT and TOJ tasks (assessing processing speed (RT), point of subjective simultaneity (PSS), and time-window when multisensory stimuli are likely to be perceived as simultaneous (Temporal Binding Window; TBW)). Forty participants (mean age: 26.25; females=17) were recruited from Prolific Academic resulting in 37 complete datasets. Both congruence and valence have a significant main effect on RT (congruent and high valence decrease RT) as well as an interaction effect (congruent/high valence condition being significantly faster than all others). For TOJ, images high in valence require visual stimuli to be presented significantly earlier than auditory stimuli in order for the audio and visual stimuli to be perceived as simultaneous. Further, a significant interaction effect of congruence and valence on the PSS revealed that the congruent/high valence condition was significantly earlier than all other conditions. A subsequent analysis shows there is a positive correlation between the TBW width (b-values) and RT (as the TBW widens, the RT increases) for the categories that differed most from 0 in their PSS (Congruent/High and Incongruent/Low). This study provides new evidence that supports previous research on semantic congruency and presents a novel incorporation of valence into behavioural responses.

Exploring Reference Frame Integration Using Response Demands in a Tactile Temporal-Order Judgement Task

Exploring the world through touch requires the integration of internal (e.g., anatomical) and external (e.g., spatial) reference frames — you only know what you touch when you know where your hands are in space. The deficit observed in tactile temporal-order judgements when the hands are crossed over the midline provides one tool to explore this integration. We used foot pedals and required participants to focus on either the hand that was stimulated first (an anatomical bias condition) or the location of the hand that was stimulated first (a spatiotopic bias condition). Spatiotopic-based responses produce a larger crossed-hands deficit, presumably by focusing observers on the external reference frame. In contrast, anatomical-based responses focus the observer on the internal reference frame and produce a smaller deficit. This manipulation thus provides evidence that observers can change the relative weight given to each reference frame. We quantify this effect using a probabilistic model that produces a population estimate of the relative weight given to each reference frame. We show that a spatiotopic bias can result in either a larger external weight (Experiment 1) or a smaller internal weight (Experiment 2) and provide an explanation of when each one would occur.

Haptic awareness changes when lying down

Accurate localization of touch requires the integration of two reference frames—an internal (e.g., anatomical) and an external (e.g., spatial). Using a tactile temporal order judgement task with the hands crossed over the midline, we investigated the integration of these two reference frames. We manipulated the reliability of the visual and vestibular information, both of which contribute to the external reference frame. Visual information was manipulated between experiments (Experiment 1 was done with full vision and Experiment 2 was done while wearing a blindfold). Vestibular information was manipulated in both experiments by having the two groups of participants complete the task in both an upright posture and one where they were lying down on their side. Using a Bayesian hierarchical model, we estimated the perceptual weight applied to these reference frames. Lying participants on their side reduced the weight applied to the external reference frame and produced a smaller deficit; blindfolding resulted in similar reductions. These findings reinforce the importance of the visual system when weighting tactile reference frames, and highlight the importance of the vestibular system in this integration.

The Impact of Auditory White Noise on Cognitive Performance

Although noise has often been characterized as a distractor, contemporary studies have emphasized how some individuals’ cognitive performance could benefit from task-irrelevant noise. Usually these studies focus on sub-attentive individuals and/or those who have been diagnosed with ADHD. An example of task-irrelevant noise is white noise (WN). Research regarding the effectiveness of WN in healthy adults has provided mixed results and therefore, the implications of WN remain unknown. The objective of this study was to determine the effects of WN on the cognitive performance of the neurotypical population. To test this, participants were asked to complete simultaneous amplitude discrimination and temporal order judgement (TOJ) tests several times in the presence of varying levels of WN. Participants were split into two groups––one containing individuals with regular prior WN exposure and the other with no previous experience with WN. The performances of participants with prior exposure to WN, but not those without prior exposure, resembled a U-shaped tuning curve for simultaneous amplitude discrimination. This indicates that familiarity with WN moderates its effectiveness on cognitive improvement. TOJ was not found to be affected by varying levels of WN intensity. The results of this study emphasized that there is a possibility that WN could facilitate higher levels of cognitive performance, though there is likely an adjustment period associated with its introduction to daily life. This warrants that additional research should be conducted in order to cultivate a definitive conclusion about the effects of WN.

Acute Impact of Mindfulness Meditation on Cognitive Performance

The beneficial effects of mindfulness meditation on higher-order cognitive performance as well as physiological parameters, such as decreased cortisol levels, blood pressure, pulse rate, and reaction time, have been studied extensively. However, most of these studies have been conducted over a relatively long term, comparing subjects who meditate on a regular basis with those who have never meditated. In this study, the acute effects of mindfulness meditation are investigated by examining the differences between tactile reaction time and temporal-order judgement (TOJ) obtained before and after a 10-minute meditation session in several case studies. Additionally, the participants reported their mood and stress levels in a survey before and after the meditation session. The results demonstrate that mindfulness meditation improves performance on the tactile reaction time and TOJ tasks, and it also promotes a peaceful state of mind.

Sensory testing as a predictor of short vs. long term trajectory of recovery from concussion

There have been numerous reports of neurological assessments of post-concussed athletes. However, the majority of the methods commonly deployed are either qualitative assessments that are simply symptom based or are psycho-social questionnaires. The information provided from those studies does not provide insight into the neural mechanisms impacted by concussion, and more importantly, does not contribute to a prognostic view of overall brain health that would facilitate or predict the recovery of the concussed individual. Cortical metrics are measures that were designed to probe brain function via the somatosensory system (i.e., with high fidelity tactile inputs) and have been demonstrated to be both objective, quantifiable and physiologically based. The methods have also been recently reported to parallel findings in a neurophysiological animal model of brain injury (Challener et al, 2020) that support the concept that these metrics parallel alterations in specific neural mechanisms post-injury. In this report, the battery of tactile based measures are reaction time (RT), reaction time variability (RTvar), sequential and simultaneous amplitude discrimination, temporal order judgement (TOJ) and duration discrimination (DD). These methods are administered with a computer mouse sized tactile stimulator (the Brain Gauge) that delivers sinusoidal stimuli to digits 2 and 3 with precision control of both amplitude and frequency. The results obtained during the first week of observation post-injury predict the recovery trajectory of the concussed individual. Interestingly, some of the metrics of the individuals who take longer to recover from injury obtained during the first week outperform the metrics of individuals that recover quickly, and these findings parallel the findings from the animal model.

Click Trains do not Alter Auditory Temporal Order Judgements

Brief periods of repetitive stimulation (click trains) presented either contiguous or simultaneous to an interval have been previously shown to impact on its perceived duration. In the current investigation we asked whether the perception of temporal order can be altered in a similar way. Participants completed a dichotic spectral temporal order judgement task with the stimuli titrated to their individual thresholds. Immediately prior to the judgement, participants were presented with five seconds of click trains, white noise or silence. We extended previous work on this topic by using each participant’s accuracy and response time data to estimate diffusion model parameters so that the cognitive mechanisms underlying any effect of click trains on the response could be disentangled. There was no effect of stimulation condition on participant’s accuracy, or diffusion model parameters (drift rate, boundary separation or non-decision time). The present findings therefore suggest that click trains do not influence temporal order perception. Additionally, the previous suggestion that click trains induce an increase in the rate of information processing was not supported for this temporal order task. Further work probing the limits and conditions of the click train effect will help to constrain and extend theoretical accounts of subjective timing.

Reliability of the Crossed-Hands Deficit in Tactile Temporal Order Judgements

Crossing the hands over the midline impairs performance on a tactile temporal order judgement (TOJ) task, resulting in the crossed-hands deficit. This deficit results from a conflict between two reference frames — one internal (somatotopic) and the other external (spatial) — for coding stimulus location. The substantial individual differences observed in the crossed-hands deficit highlight the differential reliance on these reference frames. For example, women have been reported to place a greater emphasis on the external reference frame than men, resulting in a larger crossed-hands deficit for women. It has also been speculated that individuals with an eating disorder place a greater weight on the external reference frame. Further exploration of individual differences in reference frame weighing using a tactile TOJ task requires that the reliability of the task be established. In Experiment 1, we investigated the reliability of the tactile TOJ task across two sessions separated by one week and found high reliability in the magnitude of the crossed-hands deficit. In Experiment 2, we report the split-half reliability across multiple experiments (both published and unpublished). Overall, tactile TOJ reliability was high. Experiments with small to moderate crossed-hands deficits showed good reliability; those with larger deficits showed even higher reliability. Researchers should try to maximize the size of the effect when interested in individual differences in the use of the internal and external reference frames.