Katja Valli

The threat simulation theory of the evolutionary function of dreaming: Evidence from dreams of traumatized children.

The threat simulation theory of dreaming (TST) () states that dream consciousness is essentially an ancient biological defence mechanism, evolutionarily selected for its capacity to repeatedly simulate threatening events. Threat simulation during dreaming rehearses the cognitive mechanisms required for efficient threat perception and threat avoidance, leading to increased probability of reproductive success during human evolution. One hypothesis drawn from TST is that real threatening events encountered by the individual during wakefulness should lead to an increased activation of the system, a threat simulation response, and therefore, to an increased frequency and severity of threatening events in dreams. Consequently, children who live in an environment in which their physical and psychological well-being is constantly threatened should have a highly activated dream production and threat simulation system, whereas children living in a safe environment that is relatively free of such threat cues should have a weakly activated system. We tested this hypothesis by analysing the content of dream reports from severely traumatized and less traumatized Kurdish children and ordinary, non-traumatized Finnish children. Our results give support for most of the predictions drawn from TST. The severely traumatized children reported a significantly greater number of dreams and their dreams included a higher number of threatening dream events. The dream threats of traumatized children were also more severe in nature than the threats of less traumatized or non-traumatized children.

Can observers link dream content to behaviours in rapid eye movement sleep behaviour disorder? A cross‐sectional experimental pilot study

Motor activity in rapid eye movement (REM) sleep behaviour disorder (RBD) has been linked to dream content. Systematic and controlled sleep laboratory studies directly assessing the relation between RBD behaviours and experienced dream content are, however, largely lacking. We aimed to investigate whether a link can be established between RBD behaviours and dream content when both are systematically sampled in a controlled setting. We investigated six patients with Parkinson syndrome and RBD who underwent 2–3 nights of video–polysomnographic recording during which they were awakened from REM sleep (10 min after the onset of the second and successive REM periods). Spontaneous free‐worded dream reports and a structured dream questionnaire were obtained. Video recordings of motor manifestations were each combined with four dream reports, and seven judges had to match the video clip with the correctly reported dream content from a choice of four possibilities. Of the 35 REM sleep awakenings performed, a total of 17 (48.6%) motor‐behavioural episodes with recalled dream content were obtained. The mean of correctly identified video‐dream pairs was 39.5% (range 0–100%). Our data showed that reported dream content can be linked to motor behaviours above chance level. Matching accuracy was affected mainly by the clarity of dream reports and the specific nature of movements manifest in video recordings.

Dreaming furiously? A sleep laboratory study on the dream content of people with Parkinson's disease and with or without rapid eye movement sleep behavior disorder

OBJECTIVE Rapid eye movement (REM) sleep behavior disorder (RBD) has been related to altered, action-filled, vivid, and aggressive dream content, but research comparing the possible differences in dreams of Parkinsons disease (PD) patients with and without RBD is scarce. The dream content of PD patients with and without RBD was analyzed with specific focus on action-filledness, vividness, emotional valence, and threats. METHODS A total of 69 REM and NREM dream reports were collected in the sleep laboratory, 37 from nine PD patients with RBD and 32 from six PD patients without RBD. A content analysis of (1) action-filledness (actions and environmental events); (2) vividness (emotions and cognitive activity); (3) intensity of actions, events and emotions; (4) emotional valence, and (5) threatening events was performed on the transcripts. RESULTS Altogether 563 dream elements expressing action-filledness and vividness were found. There were no significant between-group differences in the number or distribution of elements reflecting action-filledness or vividness, emotional valence or threats. In within-group analyses, PD patients with RBD had significantly more negative compared to positive dreams (p = 0.012) and compared to PD patients without RBD, a tendency to have more intense actions in their dreams (p = 0.066). CONCLUSIONS Based on the results of this study, there are no major between-group differences in the action-filledness, vividness, or threat content of dreams of PD patients with and without RBD. However, within-group analyses revealed that dreams were more often negatively than positively toned in PD patients with RBD.

Content analysis of subjective experiences in partial epileptic seizures.

A new content analysis method for systematically describing the phenomenology of subjective experiences in connection with partial epileptic seizures is described. Forty patients provided 262 descriptions of subjective experience relative to their partial epileptic seizures. The results revealed that subjective experiences during seizures consist mostly of sensory and bodily sensations, hallucinatory experiences, and thinking. The majority of subjective experiences during seizures are bizarre and distorted; nevertheless, the patients are able to engage in adequate behavior. To the best of our knowledge, this is the first study for which detailed subjective seizure descriptions were collected immediately after each seizure and the first study in which the content of verbal reports of subjective experiences during seizures, including both the ictal and postictal experiences, has been analyzed in detail.

Dreams are more negative than real life: Implications for the function of dreaming

Dream content studies have revealed that dream experiences are negatively biased; negative dream contents are more frequent than corresponding positive dream contents. It is unclear, however, whether the bias is real or due to biased sampling, i.e., selective memory for intense negative emotions. The threat simulation theory (TST) claims that the negativity bias is real and reflects the evolved biological function of dreaming. In the present study, we tested the hypothesis of the TST that threatening events are overrepresented in dreams, i.e., more frequent and more severe in dreams than in real life. To control for biased sampling, we used as a baseline the corresponding negative events in real life rather than the corresponding positive events in dreams. We collected dream reports (N=419) and daily event logs (N=490) from 39 university students during a two-week period, and interviewed them about real threat experiences retrievable from autobiographical memory (N=714). Threat experiences proved to be much more frequent and severe in dreams than in real life, and Current Dream Threats more closely resembled Past than Current Real Threats. We conclude that the TSTs predictions hold, and that the negativity bias is real.

How to assess ictal consciousness

Despite the complexity and methodological difficulties in defining the concept of consciousness, it is a central concept in epileptology, and should thus be tractable for scientific analysis. In the present article, a two-dimensional model consisting of concepts related to the level and the contents of consciousness will be presented. This model has been found to be well suited for the description of seizure-induced alterations of consciousness, and is supported both by findings from neuroimaging and electrophysiological studies as well as from phenomenological studies. Further, we will review both traditional introspective methods as well as methods that have recently been developed or utilized in epilepsy research, summarize the main findings concerning first person experiences during epileptic seizures acquired with some of these methods, and discuss their strengths and weaknesses.

Winter is coming: nightmares and sleep problems during seasonal affective disorder

Sleep problems, especially nightmares and insomnia, often accompany depression. This study investigated how nightmares, symptoms of insomnia, chronotype and sleep duration associate with seasonal affective disorder, a special form of depression. Additionally, it was noted how latitude, a proxy for photoperiod, and characteristics of the place of residence affect the prevalence of seasonal affective disorder and sleep problems. To study these questions, data from FINRISK 2012 study were used. FINRISK 2012 consists of a random population sample of Finnish adults aged 25–74 years (n = 4905) collected during winter from Finnish urban and rural areas spanning the latitudes of 60°N to 66°N. The Seasonal Pattern Assessment Questionnaire was used to assess symptoms of seasonal affective disorder. Participants with symptoms of seasonal affective disorder had significantly increased odds of experiencing frequent nightmares and symptoms of insomnia, and they were more often evening chronotypes. Associations between latitude, population size and urbanicity with seasonal affective disorder symptoms and sleep disturbances were generally not significant, although participants living in areas bordering urban centres had less sleep problems than participants from other regions. These data show that the prevalence of seasonal affective disorder was not affected by latitude.

How to test the threat-simulation theory

Malcolm-Smith, Solms, Turnbull and Tredoux [Malcolm-Smith, S., Solms, M.,Turnbull, O., & Tredoux, C. (2008). Threat in dreams: An adaptation? Consciousness and Cognition, 17, 1281-1291.] have made an attempt to test the Threat-Simulation Theory (TST), a theory offering an evolutionary psychological explanation for the function of dreaming [Revonsuo, A. (2000a). The reinterpretation of dreams: An evolutionary hypothesis of the function of dreaming. Behavioral and Brain Sciences, 23(6), 877-901]. Malcolm-Smith et al. argue that empirical evidence from their own study as well as from some other studies in the literature does not support the main predictions of the TST: that threatening events are frequent and overrepresented in dreams, that exposure to real threats activates the threat-simulation system, and that dream threats contain realistic rehearsals of threat avoidance responses. Other studies, including our own, have come up with results and conclusions that are in conflict with those of Malcolm-Smith et al. In this commentary, we provide an analysis of the sources of these disagreements, and their implications to the TST. Much of the disagreement seems to stem from differing interpretations of the theory and, consequently, of differing methods to test it.

Recurrent dreams: Recurring threat simulations?

Zadra, Desjardins, and Marcotte (2006) have made a valuable contribution to the empirical testing of the Threat Simulation Theory (TST) (Revonsuo, 2000a) in recurrent dreams. For the most part, their results are in accordance with the theory, while some findings seem to conflict with the predictions of TST. In our commentary, we consider some alternative ways to interpret the results, and we conclude that many prominent features of most recurrent dreams seem to be manifestations of a threat simulation function, leading to repeated rehearsal of threat perception and avoidance, but a minority of recurrent dreams seem to have origins unrelated to threat simulation.

The Avatars in the Machine: Dreaming as a Simulation of Social Reality

The idea that dreaming is a simulation of the waking world is currently becoming a far more widely shared and accepted view among dream researchers. Several philosophers, psychologists, and neuroscientists have recently characterized dreaming in terms of virtual reality, immersive spatiotemporal simulation, or realistic and useful world simulation. Thus, the conception of dreaming as a simulated world now unifies definitions of the basic nature of dreaming within dream and consciousness research. This novel concept of dreaming has consequently led to the idea that social interactions in dreams, known to be a universal and abundant feature of human dream content, can best be characterized as a simulation of human social reality, simulating the social skills, bonds, interactions, and networks that we engage in during our waking lives. Yet this tempting idea has never before been formulated into a clear and empirically testable theory of dreaming. Here we show that a testable Social Simulation Theory (SST) of dreaming can be formulated, from which empirical predictions can be derived. Some of the predictions can gain initial support by relying on already existing data in the literature, but many more remain to be tested by further research. We argue that the SST should be tested by directly contrasting its predictions with the major competing theories on the nature and function of dreaming, such as the Continuity Hypothesis (CH) and the Threat Simulation Theory (TST) . These three major theories of dreaming make differing predictions as to the quality and the quantity of social simulations in dreams. We will outline the first steps towards a theory-and-hypothesis-driven research program in dream research that treats dreaming as a simulated world in general and as a social simulation in particular. By following this research program it will be possible to find out whether dreaming is a relatively unselective and thus probably non-functional simulation of the waking world ( CH ), a simulation primarily specialized in the simulation of dangerous and threatening events that present important challenges for our survival and prosperity ( TST ), or whether it is a simulation primarily specialized in training the social skills and bonds most important for us humans as a social species ( SST ). Whatever the evidence for or against the specific theories turn out to be, in any case the conception of dreaming as a simulated world has already proved to be a fruitful theoretical approach to understanding the nature of dreaming and consciousness.