Hallucinatory states are experienced not only in connection with drugs and psychopathologies but occur naturally and spontaneously across the human circadian cycle: Our nightly dreams bring multimodal experiences in the absence of adequate external stimuli. The current study proposes a new, tighter measure of these hallucinatory states: Sleep onset, REM sleep, and non-REM sleep are shown to differ with regard to motor imagery indicating interactions with a rich imaginative world, and cognitive agency that could enable sleepers to recognize their hallucinatory (...) state. Mentation reports from the different states were analysed quantitatively with regard to two grammatical–semantic constructs, motor agency and cognitive agency. The present results support earlier physiological and psychological evidence in revealing a decline in cognitive functions and an increase in simulated interactions with a hallucinatory world, en route to normal REM sleep. This leads us to introduce the hypothesis that REM sleep, which exhibits remarkably high levels of sensorimotor processes, may have evolved to serve as a virtual laboratory for the development and rehearsal of embodied cognition. The new measure of hallucinatory states presented here may also hold implications for the study of executive functions and cognitions, which might be interesting, for example, for the investigation of lucid dreaming. (shrink)

We present one of the first quantitative studies on auditory verbal experiences (“hearing voices”) and auditory verbal agency (inner speech, and specifically “talking to (imaginary) voices or characters”) in healthy participants across states of consciousness. Tools of quantitative linguistic analysis were used to measure participants’ implicit knowledge of auditory verbal experiences (VE) and auditory verbal agencies (VA), displayed in mentation reports from four different states. Analysis was conducted on a total of 569 mentation reports from rapid eye movement (REM) sleep, (...) non‐REM sleep, sleep onset, and waking. Physiology was controlled with the nightcap sleep–wake mentation monitoring system. Sleep‐onset hallucinations, traditionally at the focus of scientific attention on auditory verbal hallucinations, showed the lowest degree of VE and VA, whereas REM sleep showed the highest degrees. Degrees of different linguistic‐pragmatic aspects of VE and VA likewise depend on the physiological states. The quantity and pragmatics of VE and VA are a function of the physiologically distinct state of consciousness in which they are conceived. (shrink)

Although the sense of agency is often reduced if not absent in dreams, our agentive dream experiences can at times be similar to or enhanced compared to waking. The sense of agency displayed in dreams is perplexing as we are mostly shut off from real stimulus whilst asleep. Theories of waking sense of agency, in particular, comparator and holistic models, are analysed in order to argue that despite the isolation from the real environment, these models can help account for dream (...) experience. The dreamer might feel an increased sense of control of their dream bodies and a sense that they can directly control elements of the dream world. Such experiences may at times be caused by superstitious or delusional thinking due to altered cognition and changes to the sleeping brain. Here it is argued that some such experiences are akin to specific waking delusions, such as delusions of grandeur, with similar cognitive features. However, other instances of increased sense of agency in dreaming appear to be sui generis and nothing like what we experience when awake. Lucid control dreams, in which the dreamer realises that they are dreaming and that they can control the dream environment, are examples of such an experience although further nuance is required to account for their specific cognitive attributes. Future empirical research should focus on controlled dream reporting conditions in order to clarify the types of experience that occur and determine the relevant cognitive mechanisms that relate to each type. (shrink)

The experience of skilled action occurs in dreams if we take dream reports at face value. However, what these reports indicate requires nuanced analysis. It is uncertain what it means to perform any action in a dream whatsoever. If skilled actions do occur in dreams, this has important implications for both theory of action and theory of dreaming. Here, it is argued that since some dreams generate a convincing, hallucinated world where we have virtual bodies that interact with virtual objects, (...) there is a sense in which we can perform virtual actions. Further, we can also perform skilfully, although not all apparent skilful performance is as it seems. Since the dream world is generated by the dreamer’s own mind, it can be difficult to determine whether the dream world simply allows goals to be achieved without the abilities that would be required in a similar waking scenario. Because of this, individual dream reports alone are insufficient to determine what skills are demonstrated in a particular dream. However, taken with evidence from REM sleep behaviour disorder, incompetent dreams, lucid dreams and motor-skill practise, it is likely that skilled virtual dream performance at times involves both opportunity for virtual behaviour and the display of competence. Evidence from cognitive science suggests that dreamers can also lose competence through forgetting and other cognitive incapacities but, more surprisingly, it is possible to gain abilities in a robust sense, consistent with the idea that some dreams, at least, are virtual realities rather than imagination. (shrink)

Poor sleep quality negatively affects memory performance, and working memory in particular. We investigated sleep habits related to sleep quality including sleep duration, daytime nap duration, nap frequency, and dream content recall frequency (DCRF). Declarative working memory can be subdivided into verbal working memory (VWM) and visuospatial working memory (VSWM). We hypothesized that sleep habits would have different effects on VWM and VSWM. To our knowledge, our study is the first to investigate differences between VWM and VSWM related to daytime (...) nap duration, nap frequency, and DCRF. Furthermore, we tested the hypothesis that the effects of duration and frequency of daytime naps and DCRF on VWM and VSWM differed according to sex. We assessed 779 healthy right-handed individuals (434 males and 345 females; mean age: 20.7 ± 1.8 years) using a digit span forward and backward VWM task, a forward and backward VSWM task, and sleep habits scales. A correlation analysis was used to test the relationships between VWM capacity (VWMC) and VSWM capacity (VSWMC) scores and sleep duration, nap duration, nap frequency, and DCRF. Furthermore, multiple regression analyses were conducted to identify factors associated with VWMC and VSWMC scores and to identify sex-related differences. We found significant positive correlations between VSWMC and nap duration and DCRF, and between VWMC and sleep duration in all subjects. Furthermore, we found that working memory capacity (WMC) was positively correlated with nap duration in males and with sleep duration in females, and DCRF was positively correlated with VSWMC in females. Our finding of sex-related differences in the effects of sleep habits on WMC has not been reported previously. The associations between WMC and sleep habits differed according to sex because of differences in the underlying neural correlates of VWM and VSWM, and effectiveness of the sleep habits in males and females. (shrink)

If both waking and dreaming consciousness are functional, their de-differentiation would be doubly detrimental. Differentiation between waking and dreaming is achieved through neuromodulation. During dreaming, without external sensory data and with mesolimbic dopaminergic input, hyper-cholinergic input almost totally suppresses the aminergic system. During waking, with sensory gates open, aminergic modulation inhibits cholinergic and mesocortical dopaminergic suppresses mesolimbic. These neuromodulatory systems are reciprocally interactive and self-organizing. As a consequence of neuromodulatory reciprocity, phenomenologically, the self and the world that appear during dreaming (...) differ from those that emerge during waking. As a result of self-organizing, the self and the world in both states are integrated.Some loss of self-organization would precipitate a degree of de-differentiation between waking and dreaming, resulting in a hybrid state which would be expressed heterogeneously, both neurobiologically and phenomenologically. As a consequence of progressive de-differentiation, certain identifiable psychiatric disorders may emerge. Ultimately, schizophrenia, a disorganized-fragmented self, may result. (shrink)

Although we are beginning to understand the neurocognitive processes that underlie the emergence of dreaming, what accounts for the bizarre phenomenology of dreams remains debated. I address this question by comparing dreaming with waking mind wandering and challenging previous accounts that utilize bizarreness to mark a sharp divide between conscious experiences in waking and sleeping. Instead, I propose that bizarreness is a common, non-deficient feature of spontaneous offline simulations occurring across the sleep-wake cycle and can be tied to the specific (...) characteristics of spontaneous thought as being dynamic, unconstrained, (hyper)associative and highly variable in content. Rather than misrepresenting waking reality, bizarreness can be employed to investigate the very building blocks of spontaneous cognition. The absence of bizarreness in thought processes is imposed by automatic and deliberate cognitive constraints. By contrast, thought and memory processes operating on their own without such constraints are inherently marked by different degrees and types of bizarreness. (shrink)

Thinking is known to be state dependent but a systematic study of how thinking in dreams differs from thinking while awake has not been done. The study consisted of analyzing the dream reports of 26 subjects who, in addition to providing dream reports also provided answers to questions about their thinking within the dream. Our hypothesis was that thinking in dreams is not monolithic but has two distinct components, one that is similar to wake-state cognition, and another that is fundamentally (...) different. We found that cognition within a dream scenario was similar to that of wake-state cognition, but that thinking about the scenario itself was deficient and very different than wake-state thinking. (shrink)