Biodiversity and Human Functioning Following Acquired Cerebrovascular Lesions - Phase 2 (EspertaMente)

Stroke

stroke, natural light, HRV, EEG, exposome

Grounded in the exposome framework and the bio-psycho-social model of health, this study investigated the effects of artificial light simulating natural sunlight on autonomic regulation, cognitive-motor performance and brain activity in 30 chronic stroke survivors. The aim of the study is to evaluate HRV and EEG recording across four successive conditions. Functional mobility and executive function, were evaluated before and after light exposure.

The exposome encompasses the totality of environmental exposures, from light and pollutants to diet, stress and social relationships, and their associated biological responses (internal exposome) across an individual's entire lifetime. The neurovisceral integration model and a bio-psycho-social conception of health converge on a single insight: human functioning is the product of a continuously adaptive dialogue between the body's internal regulatory systems and the external environment, a perspective that places the exposome at the center of understanding human functioning. More than 60% of stroke survivors experience persistent motor and cognitive impairments beyond six months post-stroke, accompanied by dysregulation of autonomic and circadian systems that collectively diminish quality of life and hinder rehabilitation. Multisensory environmental stimulation, including exposure to both natural and artificial light, can reshape lifestyle and social dynamics in ways that sustain rehabilitation gains, in part by modulating the autonomic nervous system. Post-stroke dysautonomia, marked by reduced heart rate variability (HRV), sympathetic hyperactivation, and circadian disruption, is increasingly quantifiable through HRV indexes as a validated biomarker whose endogenous circadian rhythmicity is itself regulated by light via the suprachiasmatic nucleus. In fact, natural light synchronizes the human circadian system via melanopsin-expressing retinal ganglion cells that transmit signals to the suprachiasmatic nucleus, regulating melatonin, cortisol, sleep-wake cycles, autonomic tone and cortical activity. Through these interconnected pathways, light acts as a powerful biological modulator influencing circadian rhythms, HRV, vigilance, stress response and neuronal plasticity, making it a promising therapeutic tool in post-stroke rehabilitation. However, most rehabilitation patients spend the majority of their time indoors under standard artificial lighting that lacks the intensity, spectrum and dynamic variation of natural light, disrupting circadian regulation and potentially worsening recovery. Animal models further show that even low levels of nocturnal light exposure can increase ischaemic lesion size and cerebral inflammation, highlighting the vulnerability of the damaged brain to circadian light pollution. Human-centric LED lighting systems designed to replicate natural light dynamics have shown clinically meaningful results in post-stroke patients, with one randomized controlled trial reporting significant reductions in fatigue, depression and anxiety alongside restored circadian melatonin rhythmicity. Despite promising clinical evidence, there is a critical gap in the literature: no study has simultaneously characterized the direct neurophysiological effects of lighting on autonomic regulation and cognitive-motor performances in chronic post-stroke patients. The present study aims to fill this gap by investigating the effects of exposure to artificial lighting simulating natural light on heart rate variability parameters and on electroencephalographic activity in patients with chronic stroke, as well as to analyze whether the 15 minutes of light source induce changes in cognitive-motor outcomes.

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