Jason J. Braithwaite

Visual discomfort or visual stress is an uncomfortable subjective experience that occurs in response to specific visual stimuli. It affects a large proportion of the population to various degrees, disproportionately impacting those with heightened sensory sensitivities, particularly neurodivergent individuals. We argue that this might stem from a mismatch between the statistical properties of visual stimuli in human-made environments and those in natural environments that the visual system can process efficiently. We discuss the inefficiency with which images with certain spatial, chromatic and temporal characteristics are processed by the visual system and propose a cerebral mechanism to account for the discomfort they induce. The mechanism offers a potential explanation for the large individual differences in susceptibility to discomfort. We highlight two avenues for intervention: (1) environmental modifications aimed at reducing the prevalence of visually stressing stimuli in urban settings, and (2) individual-level strategies, such as personalised optical treatments. Addressing these challenges requires an interdisciplinary effort bridging neuroscience, vision science, interior and urban design and typography to create visually accessible and inclusive environments.

The increased multisensory integration and weaker attentional control experienced by older adults during audiovisual processing can result in inaccurate perceptions of their dynamic, everyday environment. These inaccurate representations of our environment can contribute to increased fall risk in older adults. A neural correlate of the attentional difference between younger and older adults could be oscillatory alpha activity (8-12Hz), indexing inhibitory processes during multisensory integration. The current study investigated whether age-related changes in alpha activity underlie weaker attentional control in older adults during a multisensory task, and if alpha associates with fall risk. Thirty-six younger (18-35 years old) and thirty-six older (60-80 years old) adults completed a cued-spatial-attention stream-bounce task, assessing audiovisual integration when attending to validly-cued or invalidly-cued locations, at 0ms or 300ms stimulus-onset asynchronies. Oscillatory alpha activity was recorded throughout using EEG to index participants’ inhibitory abilities. Functional ability and balance were measured to index fall risk. Multiple linear regression models revealed that even when attending to the validly-cued location, less accurate multisensory integration was exhibited by older adults compared to younger adults, suggesting that older adults demonstrate weaker top-down modulation of multisensory integration through failing to inhibit task-irrelevant information. However, alpha power across the trials did not predict the extent of multisensory integration within the task. A significant interaction between age and functional ability scores predicted alpha power, suggesting that older adults may rely on attentional mechanisms for functional ability more than younger adults do. Potential implications in the design of clinical treatments to reduce falls are discussed.

Anomalous phantom visual perceptions coupled to an aversion to some visual patterns has been associated with aberrant cortical hyperexcitability in migraine patients. Previous literature has found fluctuations of alpha oscillation (8-14 Hz) over the visual cortex to be associated with the gating of the visual stream. In the current study, we examined whether alpha activity was differentially modulated in migraineurs in anticipation of an upcoming stimulus as well as post-stimulus periods. We used EEG to examine the brain activity in a group of 28 migraineurs (17 with aura/11 without) and 29 non-migraineurs and compared the modulations of alpha power in the pre/post-stimulus period relative to onset of stripped gratings of 3 spatial frequencies 0.5, 3, and 13 cycles per degree (cpd). Overall, we found that that migraineurs had significantly less alpha power prior to the onset of the stimulus relative to controls. Moreover, relative to the control group, migraineurs had significantly greater post-stimulus alpha suppression (i.e event-related desynchronization) induced by the 3 cpd grating at the 2 ^nd half of the experiment, the stimulus most often reported to induce visual disturbances. These findings taken together provide strong support of the presence of elevated cortical excitability in the visual cortex of migraine sufferers. We speculate that cortical hyperexcitation could be the consequence of impaired perceptual learning driven by the dysfunction of GABAergic inhibitory mechanism.

It has been argued that disorders in body-ownership and aberrant experiences in self-consciousness are due to biases in multisensory integration. Here we examine whether such biases are also associated with spontaneous out-of-body experiences (OBEs) in a nonclinical population. One-hundred and 80 participants took part in a rubber hand illusion (RHI) experiment with synchronous and asynchronous visual and tactile stimulation. A realistic threat was delivered to the rubber hand after a fixed period of stimulation. Self-report exit questionnaires measured the subjective strength of the illusion and psychophysiological measures (skin conductance responses/finger temperature) provided an objective index of fear/anxiety toward the threat. Control participants reported a stronger RHI, and revealed larger threat-related skin conductance responses during synchronous compared with asynchronous brushing. For participants predisposed to OBEs, the magnitude of the skin conductance was not influenced by brushing synchrony-fear responses were just as strong in the asynchronous condition as they were in the synchronous condition. There were also no reliable effects of finger temperature for either group. Collectively, these findings are taken as support for the presence of particular biases in multisensory integration (perhaps via predictive coding mechanisms) in which imprecise top-down tuning occurs resulting in aberrant experiences in self-consciousness even in nonclinical hallucinators. (PsycINFO Database Record