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)
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.