bioRxiv Preprint Server
April 12, 2019
Valdas Noreika, Jennifer Windt, Markus Kern et al.
preprint
Applying transcranial direct current stimulation (tDCS) over the sensorimotor cortex during REM sleep reduces reported dream movement, particularly repetitive actions, without affecting other bodily sensations like touch or balance. This effect coincides with reduced interhemispheric coherence in parietal areas and altered muscle activity correlation between arms. The findings indicate that tDCS causally interferes with the neural mechanisms underlying dream movement, confirming the spatial specificity of the stimulation site and suggesting a reorganization of the motor network during dreaming.
Journal of Sleep Research
April 1, 2018
Pilleriin Sikka, Antti Revonsuo, Nils Sandman et al.
Dreams collected at home upon morning awakening are more emotional and more negative than those collected in the lab after early REM sleep awakenings, but not more emotional than those after late REM awakenings. Home dreams also contain a higher density of emotions than lab dreams from either early or late REM sleep. The differences in overall emotionality may be due to the time of night, while the causes of differences in emotion density and negativity—whether from the sleep environment, reporting procedures, or time spent in a sleep stage—remain unclear.
Journal of Cognitive Neuroscience
September 1, 2017
Mika Koivisto, Simone Grassini, Niina Salminen-Vaparanta et al.
Conscious detection of an object and conscious identification of that object rely on different neural processes. In an experiment measuring event-related potentials (ERPs), participants performed tasks requiring either detection or identification of a visual stimulus. Behaviorally, a stimulus could be consciously detected without being identified. A posterior electrophysiological signature occurring 200-300 milliseconds after stimulus onset was sensitive to conscious detection but not to identification, which correlated with later widespread brain activity. These findings provide behavioral and neural evidence for elementary visual experiences that are not yet enriched with higher-level knowledge, suggesting that research on consciousness should focus on early phenomenal experiences to avoid confounding effects of higher-level processes.
Consciousness and Cognition
April 1, 2014
Pilleriin Sikka, Katja Valli, Tiina Virta et al.
Emotional experiences in dreams may appear inconsistent across studies because of whether dream emotions are self-rated or judged by external raters. In a sleep-laboratory study, 17 participants were awakened from REM sleep and provided oral dream reports, then rated their own emotions using a modified scale. External judges rated the same reports with the same scale. Self-ratings yielded higher estimates of emotional dreams, positively valenced dreams, the number of positive and negative emotions per dream, and various discrete emotions compared to external ratings. The discrepancy appears largely due to underrepresentation of positive emotions in dream reports when judged externally.
Advances in Consciousness Research
October 28, 2010
Antti Revonsuo, Katja Valli
Dreaming is a pure form of phenomenality—conscious experience—and the dreaming brain can serve as a model system for studying consciousness. The dreaming brain preserves all essential features of consciousness, making it a challenging but necessary object for any theory aiming to explain consciousness. The argument is grounded in biological realism, the assumption that consciousness is a real natural biological phenomenon in the brain.
International journal of psychophysiology : official journal of the International Organization of Psychophysiology
October 1, 2009
Valdas Noreika, Katja Valli, Hetti Lahtela et al.
A new experimental paradigm called Early-Night Serial Awakenings (ENSA) was tested to assess its usefulness for studying NREM sleep dreaming. Five participants spent 20 nights in a sleep laboratory and were awakened every 24 minutes during Stages 2 and 3 of NREM sleep. Out of 164 awakenings, 30% produced dream reports, 39% reports of white dreaming, and 31% reports of dreamless sleep. Sleep EEG power, dream recall frequency, and dream complexity remained stable across sessions. The authors conclude that ENSA yields static, content-limited dreams and could help reveal the psychophysiological mechanisms of simple early-night NREM dreaming.
Consciousness and Cognition
March 1, 2005
Katja Valli, Antti Revonsuo, Outi Pälkäs et al.
The threat simulation theory (TST) proposes that dreaming evolved as a biological defense mechanism to rehearse threat perception and avoidance, enhancing reproductive success. A key prediction is that real-life threats should increase the frequency and severity of threatening dreams. Analyzing dream reports from severely traumatized Kurdish children, less traumatized Kurdish children, and non-traumatized Finnish children supported most TST predictions. Severely traumatized children reported significantly more dreams, a higher number of threatening dream events, and threats that were more severe in nature compared to less traumatized or non-traumatized children.