A single bout of aerobic exercise improves executive function; however, the mechanism(s) underlying this improvement remains unclear. Here, we employed a 20-min bout of aerobic exercise, and at pre- and immediate post-exercise sessions examined executive function via pro- (i.e., saccade to veridical target location) and anti-saccade (i.e., saccade mirror symmetrical to a target) performance and pupillometry metrics. Notably, tonic and phasic pupillometry responses in oculomotor control provided a framework to determine the degree that arousal and/or executive resource recruitment influence behavior. Results demonstrated a pre- to post-exercise decrease in pro- and anti-saccade reaction times (p = 0.01) concurrent with a decrease and increase in tonic baseline pupil size and task-evoked pupil dilations, respectively (ps < 0.03). Such results demonstrate that an exercise-induced improvement in saccade performance is related to an executive-mediated “shift” in physiological and/or psychological arousal, supported by the locus coeruleus norepinephrine system to optimize task engagement.

The present work examined whether oculomotor deficits associated with a sport-related concussion (SRC) reflect an impairment to executive-based planning mechanisms or a taskbased increase in concussion symptomology (e.g., headache, vertigo). Therefore, I employed a standardized measure of SRC symptom severity (SCAT-5), antisaccade performance and pupillometry metrics in persons with a SRC during early (i.e., initial assessment: ≤12 days post-SRC) and later (i.e., follow-up assessment: 14-30 days post-SRC) stages of recovery. In the initial assessment, the SRC group yielded longer reaction times (RT) (p=0.001), increased directional errors (p=0.002) and larger task-evoked pupil dilations (TEPD) (p=0.004) than the control group. The follow-up assessment indicated that RTs did not reliably vary between groups (p=0.155); however, the SRC group demonstrated more directional errors and larger TEPDs (p<0.03). Moreover, SCAT-5 symptom severity indicated that the oculomotor assessment did not increase symptom burden (p=0.622). Accordingly, I propose that a SRC impairs executive-based oculomotor planning mechanisms.

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Recent work proposed that biomechanical constraints in aperture separation limit the utility of Weber's law in determining whether dissociable visual codes support grasping and manual estimation. We tested this assertion by having participants precision grasp, manually estimate and complete a method of adjustment task to targets scaled within and beyond the range of their maximal aperture separation (i.e., from 20 to 140% of participant-specific maximal aperture separation: MAS). For grasping and manual estimation tasks, just-noticeable-difference (JND) scores were computed via the within-participant standard deviations in peak grip aperture, whereas method of adjustment JNDs were computed via the within-participant standard deviations in response output. Method of adjustment JNDs increased linearly across the range of targets; that is, responses adhered to Weber's law. Manual estimation JNDs linearly increased for targets 20-100% of MAS and then decreased for targets 120-140% of MAS. In turn, grasping JNDs for targets 20% through 80% of MAS did not differ and were larger than targets 100-140% of MAS. That manual estimation and grasping showed a decrease in JNDs for the largest targets indicates that participants were at their biomechanical limits in aperture shaping, and the fact that the target showing the JND decrease differed between tasks (i.e., manual estimation = 100% of MAS; grasping = 80% of MAS) is attributed to the fact that grasping-but not manual estimation-requires a safety-margin task-set. Accordingly, manual estimations and grasping across a range of functionally 'graspable' targets, respectively, adhered to and violated Weber's law-a result interpreted to reflect the use of dissociable visual codes.

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Pantomime-grasping is a "simulated" motor response wherein an individual grasps to an area dissociated from a physical target. The task has been used in the apraxia literature as a proxy for natural grasping (i.e., physically grasping a target); however, it is important to recognize that the task's decoupled spatial relations between stimulus and response renders the top-down processing of target features (e.g., size) that accumulating evidence has shown to be mediated by visual information functionally distinct from natural grasping. Here, we examined whether the visual information supporting pantomime-grasps exhibits a visual resolution power commensurate with natural grasps. Participants were presented with a target and nontarget that differed in size below the perceptual threshold (i.e., 0.5 mm or ∼1.3%) and were asked to make a perceptual judgment about the target (i.e., "smaller" or "larger" than the nontarget) before and after completing natural and pantomime-grasps. Results showed that perceptual judgments "before" and "after" natural and pantomime-grasps did not reliably distinguish between target and nontarget. Natural grasp peak grip apertures (PGAs) scaled to target size and were comparable for "before" and "after" perceptual judgment trials-a result indicating that haptic feedback from physically grasping the target did not "boost" perceptual accuracy. Most notably, pantomime-grasp PGAs were insensitive to target size; that is, responses elicited a visual resolution power less than natural grasps. These results provide convergent evidence that pantomime-grasps are mediated by the same visual information as obligatory perceptions and do not provide a proxy for natural grasps. Public Significance StatementThe visual information we use to identify an apple in a bowl of fruit (i.e., a perception) is distinct from the visual information we use to grasp the apple (i.e., an action). The main finding from the present study is that a simulated grasping response (so-called pantomime) is supported by the same visual information as that supporting perceptions.

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