Interhemispheric differences in P1 and N1 amplitude in EEG and MEG differ across older individuals with a concussion compared with age-matched controls

Long-term effects of multiple concussions on prefrontal cortex oxygenation during repeated squat-stands in retired contact sport athletes

BACKGROUND

This study investigated the long-term effects of multiple concussions on prefrontal cortex oxygenation using near-infrared spectroscopy (NIRS) during a squat-stand maneuver that activated dynamic cerebral autoregulation.

METHODS

Active male retired contact sport athletes with a history of 3+ concussions (mTBI; n = 55), and active retired athletes with no concussion history (CTRL; n = 29) were recruited. Participants completed a 5-min squat-stand maneuve (10-s squat, 10-s stand, 0.05 Hz; 15 times). Oxygenated (O₂Hb), deoxygenated (HHb), total (tHb) hemoglobin, and hemoglobin difference (HbDiff) were analyzed through the change in maximal and minimal values during the test (∆MAX), Z-scores, and standard deviations.

RESULTS

mTBI group showed left prefrontal cortex O₂Hb ∆MAX (p = 0.046) and HbDiff ∆MAX (p = 0.018) were significantly higher. Within-group analyses showed significantly higher left HHb ∆MAX (p = 0.003) and lower left HbDiff Z-scores (p = 0.010) only in the mTBI group. The CTRL group demonstrated significantly lower left HbDiff SD (p = 0.039), tHb Z-scores (p = 0.030), and HbDiff ∆MAX (p = 0.037) compared to right prefrontal cortex response.

CONCLUSION

These preliminary results suggest changes in prefrontal cortex oxygenation potentially affecting the brain's ability to adapt to changing cerebral perfusion pressure after multiple previous concussions.

Spatiotemporal Dynamics of Covert Attention With Different Degrees of Central Visual Field Defects: An ERP and sLORETA Study

Purpose

The present study aimed to investigate the spatiotemporal dynamics of covert attention by simulating different degrees of central visual field defects in healthy subjects.

Methods

An electroencephalogram (EEG) was recorded while 40 normal-sighted subjects performed a target discrimination task. Target stimuli simulated different defect degrees of the central visual field by artificially central scotomas (5, 10, 20, and 30 degrees of visual angle) masked on the center of black-and-white checkerboards. Event-related potentials (ERPs) and standardized low-resolution brain electromagnetic tomography (sLORETA) based on ERPs were analyzed.

Results

ERP results indicated that during early perceptual processes, compared with 5-degree and 10-degree defects, N1 amplitudes of 20-degree and 30-degree defects decreased, whereas P2 amplitudes significantly reduced in 30-degree defects. During later discrimination and decision processing, N2 amplitudes gradually increased from 5-degree to 30-degree defects, whereas P3 amplitudes gradually decreased. Source localization indicated that 5-degree and 10-degree defects had stronger activations than 20-degree and 30-degree defects from the occipital cortex to the ventral stream and dorsal streams. Especially, 30-degree defects primarily recruited additional activations in the ventrolateral prefrontal cortex and ventral stream and later caused the disconnection of dorsolateral prefrontal-posterior parietal cortices in the dorsal stream.

Conclusions

Different degrees of central visual field defects differed in distinct spatiotemporal characteristics at multiple stages of covert attention, from top-down forward feedback and attentional allocation to executive controls through ventral and dorsal processing streams, suggesting that the combination of ERP and source localization can reveal the spatiotemporal control capacity of the cortex on central visual field defects.