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Visual dream content, graphical representation and EEG alpha activity in congenitally blind subjects.

Helder Bértolo, Teresa Paiva, Lara Pessoa, Tiago Mestre, Raquel Marques, Rosa Santos

Brain research. Cognitive brain research February 2003 DOI: 10.1016/s0926-6410(02)00199-4 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational cohort Peer reviewed
Sample size 19
Population Congenitally blind and normal sighted volunteers
Measures Visual Activity Index (VAI)
Topics Dreaming
Key findings Congenitally blind individuals have visual content in dreams and can draw it, with visual activity indices comparable to sighted participants. Dream recall was lower in the blind (27% vs 42%). Visual Activity Index negatively correlated with alpha power in central and occipital derivations in both groups.

Abstract

It is currently claimed that congenitally blind do not have visual imagery and are therefore unable to present visual contents in their dreams. The aim of our study was to quantitatively evaluate the existence of visual imagery in born-blind dreams and to correlate it with objective measures, such as sleep EEG frequency components, namely with alpha attenuation (regarded as an indicator of visual activity), and graphical analysis of dream pictorial representations. The investigation was carried out via simultaneous recordings of dream reports and polysomnography, during nocturnal sleep at volunteers' homes; scheduled regular awakenings during the night provided the data for dream and EEG analysis. In the morning, subjects were asked to make a drawing of their dream images. Congenitally blind (n=10) were comparable to normal sighted subjects (n=9): the two groups presented equivalent visual activity indices, and no differences in the analysis of graphical representation of dreaming imagery. However, blind subjects presented a lower rate of dream recall than sighted (27% versus 42%). Both groups had significant negative correlation between Visual Activity Index (VAI) and alpha power in the central and occipital O2 derivations (blind: C4: r=-0.615, P<0.005; O2: r=-0.608, P<0.006; sighted: C4: r=-0.633, P<0.01; O2: r=-0.506, P<0.05). This correlation was weaker for the blind in O1 (r=-0.573, P<0.05) and non-existent for the sighted. Blind individuals have significantly lower alpha activity in the central derivation. In conclusion, the congenitally blind have visual content in their dreams and are able to draw it and, as expected, their VAI is negatively correlated with EEG alpha power.

Comparable studies

Other observational and cohort studies on dreaming, most cited first.

Study Year Design Participants
Lucid Dreaming: a State of Consciousness with Features of Both Waking and Non-Lucid Dreaming Student volunteers trained to become lucid and signal lucidity with horizontal eye... 2009 Observational study n = 6
Nightmare Prevalence, Nightmare Distress, and Self-Reported Psychological Disturbance Young adults with a mean age of 20 years 2002 Prospective observational study n = 116
Long-term effects of extreme situational stress on sleep and dreaming Survivors of traumatic events who complained of sleep disturbances, compared with... 1987 Case-control study n = 11
The relationship of nightmare frequency and nightmare distress to well‐being Adults who reported dreams 2004 Observational cohort n = 147
Dreaming in NREM Sleep: A High-Density EEG Study of Slow Waves and Spindles Healthy human subjects 2018 Observational cohort n = 14

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