Right frontal eye field has perceptual and oculomotor functions during optokinetic stimulation and nystagmus

Assessing perceptual chromatic equiluminance using a reflexive pupillary response

Equiluminant stimuli help assess the integrity of colour perception and the relationship of colour to other visual features. As a result of individual variation, it is necessary to calibrate experimental visual stimuli to suit each individual's unique equiluminant ratio. Most traditional methods rely on training observers to report their subjective equiluminance point. Such paradigms cannot easily be implemented on pre-verbal or non-verbal observers. Here, we present a novel Pupil Frequency-Tagging Method (PFTM) for detecting a participant's unique equiluminance point without verbal instruction and with minimal training. PFTM analyses reflexive pupil oscillations induced by slow (< 2 Hz) temporal alternations between coloured stimuli. Two equiluminant stimuli will induce a similar pupil dilation response regardless of colour; therefore, an observer's equiluminant point can be identified as the luminance ratio between two colours for which the oscillatory amplitude of the pupil at the tagged frequency is minimal. We compared pupillometry-based equiluminance ratios to those obtained with two established techniques in humans: minimum flicker and minimum motion. In addition, we estimated the equiluminance point in non-human primates, demonstrating that this new technique can be successfully employed in non-verbal subjects.

Altered Sexual Response-Related Functional Connectivity and Morphometric Changes Influenced by Sex Hormones across Menopausal Status

Our study retrospectively investigated differential patterns of the functional connectivity (FC) of core brain regions synchronous with morphometric changes associated with sexual dysfunction in menopausal women, and their correlations with sexual hormones. Twenty-three premenopausal women (mean age: 41.52 ± 7.38 years) and 21 menopausal women (mean age: 55.52 ± 2.80 years) underwent sex hormone level measurements with high-resolution T1 and functional magnetic resonance imaging (MRI) during rest, neutral, and sexual arousal conditions. Analysis of covariance adjusted for age was used to compare the FC and gray matter (GM) volume between the two groups. Menopausal women showed lower GM volumes in the superior frontal gyrus (SFG), superior temporal pole, parahippocampal gyrus (PHG), hippocampus (Hip), amygdala (Amg), and cerebellum (Cb) compared to premenopausal women (p < 0.05). In addition, compared to premenopausal women, menopausal women showed decreased FC of seed regions involved in the SFG, frontal eye fields, and Amg, as well as target regions involved in the PHG, Hip, inferior frontal gyrus, Cb, and vermis (p < 0.005). Furthermore, the FC between the right Amg and right Cb and between the left Amg and right Cb during sexual arousal in both groups was positively correlated with total estrogen and estradiol levels, respectively (p < 0.01). The GM volume values in the right Amg and right Cb were positively correlated with total estrogen and estradiol levels (p < 0.05). Our study demonstrated an association between menopause-related differential FC and GM volume variations and fluctuating sex hormones. Our findings highlight that overlapping brain regions with functional alterations and morphometric changes are closely linked with menopausal symptom-related decreases in sexual arousal and hormone levels.

Elements of exogenous attentional cueing preserved during optokinetic motion of the visual scene

Navigating through our environment raises challenges for perception by generating salient background visual motion, and eliciting prominent eye movements to stabilise the retinal image. It remains unclear if exogenous spatial attentional orienting is possible during background motion and the eye movements it causes, and whether this compromises the underlying neural processing. To test this, we combined exogenous orienting, visual scene motion, and EEG. 26 participants viewed a background of moving black and grey bars (optokinetic stimulation). We tested for effects of non-spatially predictive peripheral cueing on visual motion discrimination of a target dot, presented either at the same (valid) or opposite (invalid) location as the preceding cue. Valid cueing decreased reaction times not only when participants kept their gaze fixed on a central point (fixation blocks), but even when there was no fixation point, so that participants performed intensive, repetitive tracking eye movements (eye movements blocks). Overall, manual response reaction times were slower during eye movements. Cueing also produced reliable effects on neural activity on either block, including within the first 120 milliseconds of neural processing of the target. The key pattern with larger ERP amplitudes on invalid versus valid trials showed that the neural substrate of exogenous cueing was highly similar during eye movements or fixation. Exogenous peripheral cueing and its neural correlates are robust against distraction from the moving visual scene, important for perceptual cognition during navigation.

Can a Theater Acting Intervention Enhance Inhibitory Control in Older Adults? A Brain-Behavior Investigation

Purpose: Studies of reactive and proactive modes of inhibitory control tend to show age-related declines and are accompanied by abnormalities in the prefrontal cortex. We explored which mode of inhibitory control would be more amenable to change and accrue greater benefits following engagement in a 4-week theater acting intervention in older adults. These gains were evaluated by performance on the AX-CPT task. We hypothesized that an increase in proactive control would relate to an increase in AY errors and a decrease in BX errors. In contrast, an increase in reactive control would be associated with a decrease in AY errors, no change in AY reaction time, and an increase in BX response time. Further, we posited that an increase in behavioral proactive control would accompany greater cue versus probe activity for previously identified regions in the prefrontal cortex. In contrast, an increase in behavioral reactive control would be accompanied by greater probe activation in these identified brain areas.

Materials and Methods: The participants were 179 community-dwelling adults aged 60–89 years who were on average, college-educated. Participants were pseudo-randomly assigned to either an active-experiencing acting intervention condition (n = 93) or the active control condition (n = 86); participant assignment was subject to time of enrollment. Participants in both groups were trained by theater-actor researchers with expertise in acting interventions. In contrast to the active control participants who attended a course on theater acting, the acting-intervention group was required to consistently deploy proactive and reactive control mechanisms. Both groups met two times/week for 75-min for 4 weeks. Participant brain-behavioral performance on the AX-CPT task was evaluated prior to and after this four-week period.

Results: No intervention effects were found in favor of proactive control. Behavioral evidence in favor of reactive control was weak. Brain-related benefits to reactive control was illustrated by greater probe-activation in Brodmann areas 6 and 8, relative to controls and pre-intervention.

Conclusion: We found some evidence for improvements in reactive control via brain measures, attributed to engagement in the acting intervention.

Update on Nystagmus and Other Ocular Oscillations

This review reports on recent advances in understanding nystagmus and other involuntary eye movements. Advances in quantitative evaluations of eye movements using oculography, computational model simulations, genetics, and imaging technologies have markedly improved our understanding of the pathophysiology of involuntary eye movements, as well as their diagnosis and management. Patient-initiated capture of eye movements, especially when paroxysmal, and the online transfer of these data to clinicians would further enhance the ability to diagnose involuntary eye movements.