Does losing sight change how we sleep, dream, and navigate the world? A new study uncovers the hidden links between blindness, brain rhythms, and special awareness.
Study: Investigating the impact of the years of blindness on sleep rhythms, dream patterns, and spatial abilities: The BLINDREAM protocol. Image credit: New Africa/Shutterstick.com
A recent PLOS ONE protocol explored the impact of blindness on sleep processes, dream, and their relationship with spatial perception and memory. Researchers designed the BLINDREAM protocol to enhance the understanding of the impact of blindness on sleep processes and spatial cognition.
How does blindness affect the sleep process?
Scientists have been extremely interested in learning how sensory processing impacts sleep and whether sensory disabilities affect this process. To understand this relationship, blindness has served as a great model for investigating the role of vision in sleep processes.
A lack of vision disrupts the sleep processes through the circadian rhythm, which is influenced by the light-dark cycle. A disrupted circadian process may lead to sleep phase disorders, such as Non-24-Hour Sleep-Wake Disorder (N24SWD). Multiple studies have shown that approximately 72% of blind individuals develop N24SWD because of a misalignment of the internal circadian clock and the 24-hour day. The relationship between the years a person has been blind and the degree of circadian desynchronization remains unclear and underexplored.
Although some research has indicated that alterations in sleep stages and microstructure occur due to potential changes in brain structures induced by visual deprivation, others contradict this observation. In comparison to sighted controls, blind individuals have been found to exhibit a reduction in delta activity and slow-wave sleep (SWS). Furthermore, the observations regarding altered REM features (e.g., the alpha-like rhythm and sawtooth waves) among blind individuals are inconsistent.
Sleep disruptions not only affect sleep architecture but also many daily life activities. A few studies have shown that sleep phase disorders negatively influence alertness, mood, and task performance in blind adults. Previous research has highlighted that insufficient sleep impacts an individual’s ability to process spatial information. Therefore, it is imperative to understand whether sleep mechanisms could further exacerbate the experience of blind individuals in spatial perception and cognition.
Compared to congenitally blind individuals, those with late-onset blindness who had experienced some visual experience earlier in life have a higher percentage of visual content in their dreams, still less than those without any visual impairment. Dreams may serve as a form of mental simulation that integrates sensory input and contributes to developing or reinforcing skills used in daily life.
About the study
From the vast amount of scientific literature, the authors highlight the possibility that visual sensory input can influence an individual’s dreams, which is also linked to their spatial performance. The current study presents the BLINDREAM protocol, aiming to investigate the impact of blindness on the sleep process, dream content, and their relationship in a spatial context.
The study protocol is designed to test the hypothesis that the association between circadian disorders in blind participants and potential alterations in the behavioral tasks depends on the duration and severity of vision loss. Furthermore, the impact of circadian misalignment could affect daily performance.
This study also hypothesized that years of visual deprivation led to a desynchronization of the circadian rhythm in congenitally blind/severely visually Impaired (BSI) individuals and those with late-onset blindness. Greater circadian desynchronization could be associated with poor spatial perception and memory task performance in blind individuals. Furthermore, this study hypothesized a correlation between sleep macro- and microstructure and spatial perceptual and memory performance.
The current study also hypothesized that BSI participants with a typically regulated circadian rhythm may exhibit significant differences compared to controls, involving sleep patterns related to sensorimotor processing and the consolidation of spatial information. An association between the frequency of dream recall and spatial tasks has been hypothesized. A greater presence of dream content could be potentially linked with better spatial performance, which could reveal whether sensory dream contents can influence waking abilities.
It is important to note that this publication outlines a study protocol and has not yet presented experimental results. The hypotheses mentioned are subject to testing through a multi-phase investigation.
The study protocol
The ethical committee approved the study title “The impact of years of blindness on sleep and dream processes and the relationship with spatial abilities”. One week of data from forty adults, including twenty BSI and twenty age- and biological sex-matched Sighted (S) controls, would be collected. All participants must be between 18 and 85 years of age. Those with tactile hypersensitivity, hearing impairments, who have been on neuroactive drugs within six months of the study commencement, and those with a history of central nervous system disorders should be excluded.
A participant selected for the study may withdraw their involvement under specific conditions, such as in the event of logistical or technical issues arising. Scientists have divided the study into three experimental phases, corresponding to three separate visits to the IRCCS San Martino Hospital sleep lab, during which various measurements are taken.
In Phase 1, participants would be assessed for sleep and dream quality using questionnaires, including the Pittsburgh Sleep Quality Index (PSQI), the Morningness-Eveningness Questionnaire (MEQ), and the Dream Recall Frequency Scale (DRFS) to evaluate dream-related aspects. Additionally, a Pre-Screening Questionnaire to Predict N24HSWD in Blind Subjects would be administered. Sleep architecture would be assessed via home-polysomnography (PSG) for one night. Circadian and dream assessment would be performed in phase 2, while neuropsychological evaluations would be conducted in phase 3.
According to the data management plan, each participant will be assigned a general alphanumeric code (e.g., S001) at the beginning of the protocol. Experimental data will be collected via a paper-based Case Report Form (CRF) in a pseudonymized format and transferred to a secure database. Statistical data analysis will be conducted using standard parametric and non-parametric tests, with adjustments for multiple comparisons where needed.
The authors also acknowledge potential limitations in the study, such as the relatively small sample size, difficulty fully characterizing visual impairments, and the challenges of using low-density EEG for microstructural sleep analysis. However, the protocol's exploratory and proof-of-concept nature aims to provide foundational insights for future research.
Conclusions
The current study protocol aims to explain the relationships between clinical, psychological, neurobiological, and electrophysiological factors, to understand how blindness affects these interrelated areas. By investigating sleep rhythms, dream patterns, and spatial abilities in parallel, the study will provide a holistic framework for future investigations.
Although no findings have been reported yet, the results of the completed study may help scientists develop new rehabilitative strategies or tools to enhance the quality of life and cognitive functioning for blind individuals.
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