The effects of constrained left versus right monocular viewing on the autonomic nervous system

Vertical pseudoneglect: Sensory-attentional versus action-intentional

INTRODUCTION

Healthy persons demonstrate an upward bias on the vertical-line bisection test (vertical or "altitudinal" pseudoneglect). This bias might be sensory-attentional or action-intentional in origin. To test the action-intention hypothesis, we analyze whether the direction of action has an effect on altitudinal pseudoneglect.

METHODS

Twenty-four healthy right-handed adults performed vertical-line bisection on an apparatus designed to distinguish the effects of sensory-attention and action-intention. Depending on hand placement, participants estimated line midpoints with a marker that moved in the same (congruent) or opposite (incongruent) direction as their hand movements. Two binary factors - hand movement in the upward versus downward direction and congruent vs incongruent hand movements - produced four conditions.

RESULTS

There was upward deviation from the midline across all conditions. Bisections in the incongruent condition were higher than in the congruent condition. Bisections were also higher with upward hand movements than with downward hand movements. There was not a significant interaction between these factors.

CONCLUSIONS

These results suggest that vertical pseudoneglect is primarily influenced by the allocation of allocentric attention, rather than action-intention. However, action-perceptual spatial incongruence increased this deviation. Perhaps the incongruent condition requires greater allocation of attention, but further exploration is needed. Additionally, these results suggest that visual attention follows the direction of motor action. Future studies of visual attention should consider the potential influence of this factor.

Hyperarousal symptoms and decreased right hemispheric frontolimbic white matter integrity predict poorer sleep quality in combat-exposed veterans

OBJECTIVE

Disrupted sleep is common following combat deployment. Contributors to risk include posttraumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI); however, the mechanisms linking PTSD, mTBI, and sleep are unclear. Both PTSD and mTBI affect frontolimbic white matter tracts, such as the uncinate fasciculus. The current study examined the relationship between PTSD symptom presentation, lateralized uncinate fasciculus integrity, and sleep quality.

METHOD

Participants include 42 combat veterans with and without PTSD and mTBI. Freesurfer and Tracula were used to establish specific white matter ROI integrity via 3-T MRI. The Pittsburgh Sleep Quality Index and PTSD Checklist were used to assess sleep quality and PTSD symptoms.

RESULTS

Decreased fractional anisotropy in the right uncinate fasciculus (β = -1.11, SE = 0.47, p < .05) and increased hyperarousal symptom severity (β = 3.50, SE = 0.86, p < .001) were associated with poorer sleep quality.

CONCLUSION

Both right uncinate integrity and hyperarousal symptom severity are associated withsleep quality in combat veterans. The right uncinate is a key regulator of limbic behavior and sympathetic nervous system reactivity, a core component of hyperarousal. Damage to this pathway may be one mechanism by which mTBI and/or PTSD could create vulnerability for sleep problems following combat deployment.

Pupillary light reflex as a diagnostic aid from computational viewpoint: A systematic literature review

This work presents a detailed and complete review of publications on pupillary light reflex (PLR) used to aid diagnoses. These are computational techniques used in the evaluation of pupillometry, as well as their application in computer-aided diagnoses (CAD) of pathologies or physiological conditions that can be studied by observing the movements of miosis and mydriasis of the human pupil. A careful survey was carried out of all studies published over the last 10 years which investigated, electronic devices, recording protocols, image treatment, computational algorithms and the pathologies related to PLR. We present the frontier of existing knowledge regarding methods and techniques used in this field of knowledge, which has been expanding due to the possibility of performing diagnoses with high precision, at a low cost and with a non-invasive method.

Hemispheric stroke: Mood disorders

Stroke causes many forms of disability, including emotional and mood disorders. Depression is the most common of these, affecting approximately one-third of stroke patients. Other disorders like mania, bipolar disorder, anxiety disorder, or apathy may also develop following stroke, although they are less common. The development of mood and emotional disorders is dependent on the severity of brain injury, the side of injury, and hemispheric location. Whereas a left hemispheric stroke often results in depression or a catastrophic reaction with anxiety, injury to the right hemisphere has predominantly been associated with the development of emotional indifference (anosodiaphoria) or euphoria. In this chapter, we discuss the mood disorders associated with hemispheric strokes and the neuropsychological mechanisms that might account for the clinical manifestations of these affective disorders.

Oculometric behavior assessed by pupil response is altered in adolescent depression

Oculometric behaviour assessed by pupil response provides important information about central autonomic activity and emotional regulation. However, studies regarding pupil response to emotional stimuli in adolescent depression are rare. We aimed to study emotional-linked pupil response in adolescent depression. Twenty depressive adolescents (average age: 15.4+/-1.2 years) and 20 age/gender-matched healthy subjects were examined. Average pupil diameter assessed by eye-tracking and pupillary light reflex were evaluated during protocol - baseline, free-view task, recovery phase. Regarding right eye, significantly greater initial pupil diameter and pupil dilation to positive pictures free-viewing (p=0.013, p=0.031, respectively), significantly slower average and maximum constriction velocity in baseline and positive pictures free-viewing (p=0.036, p=0.050, p=0.021, p=0.015, respectively), significantly slower maximum constriction velocity in recovery phase (p=0.045), and significantly faster average dilation velocity in negative pictures free-viewing (p=0.042) were observed in depressive group. Regarding left eye, significantly lower constriction percentual change in negative pictures free-viewing (p=0.044) and significantly greater baseline pupil diameter and pupil diameter at the peak of constriction in positive vs. negative pictures free-viewing (p=0.002, p=0.015, respectively) were observed in depressive group. Our study revealed discrete central autonomic dysregulation - parasympathetic hypoactivity associated with relative sympathetic dominance influenced by impairments in emotional processing already in adolescent depression.

Asymmetrical responses of skin blood flow in ischemic hindlimbs to electrical stimulation of the unilateral forelimb

The regulation of skin blood flow (SBF) is primarily mediated by the sympathetic nervous system, but the effects of electrical stimulation (ES) of one limb on SBF in the other limbs remain unknown. The present study investigated the effects of unilateral forelimb ES on SBF in the bilateral hindlimbs in anesthetized rats. Bilateral hindlimb ischemia was induced by tourniquet application for 60min. After reperfusion for 24h, ES (3 or 125Hz) was applied to the upper one-fourth of the triceps brachii muscle of the left or right forelimb for 30min. Rats that did not receive ES were used as the controls. Bilateral hindlimb SBF was measured by a laser Doppler line scanner for 20min before ES, 30min during ES, and 9min after ES. The results showed significant differences in SBF in the right but not left hindlimb between the control group and experimental group that received 125-Hz ES of the right forelimb. Right hindlimb SBF significantly increased within 3min following the application of 125-Hz ES to the right forelimb. No significant changes in SBF were observed in the left or right hindlimb when 125-Hz ES was applied to the left forelimb. Moreover, 3-Hz ES of the left or right forelimb did not significantly change SBF in either hindlimb compared with the control group. These results indicate that unilateral forelimb ES causes a differential SBF response in the hindlimb via a specific somatosympathetic reflex, and ES-induced SBF improvements in the ischemic hindlimb are frequency-dependent.

Pupil-size asymmetry is a physiologic trait related to gender, attentional function, and personality

A small difference in the size of the two pupils is common in healthy individuals, a condition termed benign or physiologic anisocoria (BA). Past research indicates that BA is probably caused by asymmetry in sympathetic nervous system (SNS) function [e.g., Rosenberg (2008). Physiologic anisocoria: A manifestation of a physiologic sympathetic asymmetry. Neuro-Ophthalmology, 32, 147-149]. This study is the first to show that BA varies with psychological factors linked to brain asymmetry and autonomic arousal, including gender, attention, and personality. Males exhibited a more directional BA than females, consistent with greater hemispheric lateralization in males. BA also varied with a self-report measure of attentional function, consistent with evidence of hemispheric asymmetry in visuospatial attention networks. Finally, BA varied with personality traits linked to autonomic arousal. Individuals exhibiting higher Meanness and Boldness, and lower Empathy scores tended to show more directional BA. This link between personality traits and BA may be related to brain asymmetries in autonomic arousal and emotion-related processing. If future studies employing direct measures of lateralized brain activity confirm the link between BA and SNS asymmetries, this new metric may prove useful in discovering new relationships between brain organization and psychological function, and how these relationships vary across individuals.

Autonomic responses to lateralized cold pressor and facial cooling tasks

Asymmetry in central nervous system (CNS) control of autonomic nervous system (ANS) activity, a widely debated topic, was investigated via lateralized presentation of two ANS challenges: cold pressor, which elicits primarily sympathetic activation, and facial cooling, a predominantly vagal task. Seventy-three university students (37 female) engaged in these tasks while cardiovascular and electrodermal measures were acquired. Compared to right-side cold pressor, left cold pressor elicited generally larger cardiac, blood pressure, and skin conductance responses, but did not evoke asymmetric changes in heart rate variability. Facial cooling elicited significant increases in vagally mediated heart rate variability, but they were also not lateralized. These findings are consistent with reports of right hemisphere dominance in sympathetic regulation, but indicate that CNS vagal control is relatively symmetric. These results are framed in terms of polyvagal theory and neurovisceral integration two influential models of CNS-ANS integration in the service of adaptive environmental engagement.