Temporal and Sensory Experiences in the Dreams of Sighted and Congenital Blind Individuals

Abstract

Dreams compose a unique state of consciousness with information related to people we know (Kahn et al., 2000), events that happened (Nielsen & Stenstrom, 2005), and future outcomes (MacDuffie & Mashour, 2010). During sleep, however, the dimensions of future, past, and present are believed not to be perceptible due to the deactivation of the prefrontal cortex (PFC) that leads to decreased functioning of working memory (Voss et al., 2009). The dreamer, therefore, is considered to be “offline” and “off the clock” (MacDuffie & Mashour, 2010). However, researchers support that the brain is not restricted to silence but rather is prone to hyperassociations that may lead to retrieval of fragmented memories and unstructured recombination of those when dreaming. It has been reported that 65% of the context we experience in dreams is derived from past memories (Fosse et al., 2003), but the chronological event order is fragmented. The question arising, therefore, is how exactly is time experienced in dreams?Events in dreams, apart from the time dimension, also involve rich sensory experiences in the absence of known external stimuli. A series of studies report that sensory imagery in dreams is mainly visual for sighted individuals, whereas in congenital blind individuals the visual experiences are replaced with the senses of sound, smell, touch, and taste (Bulkeley, 2009). However, previous studies are often limited by small sample sizes and measurements limited to word search. Most importantly, previous studies on the sensory experiences in dreams are limited on the use of the Aristotelian theory of the five basic senses, whereas current research supports the existence of at least nine senses. In the present study, we investigate more systematically the temporal references (never examined to-date) and the sensory experiences of dreamers. We analyzed a set of dream reports from the DreamBank database (Schneider & Domhoff, 1999) of sighted and congenitally blind individuals. The analysis was done, not through simple word searches, but with the use of a custom-made linguistic scheme and human annotation through the Callisto annotation tool. The analysis included the following five levels: space, time (age, order, duration-long, short, frequency, and time point-past, future, present), emotion (fear, anger, sadness, love, joy, and surprise), action, and unity (semantic link between any of the previously mentioned levels). Using this scheme, we were able to derive the type and frequency of temporal and sensory references used during dreams and compare the possible links between time, space, emotion, and action in dreams and those known from perceptual (waking) literature.