Caroline L. Horton

Memory sources of dreams: the incorporation of autobiographical rather than episodic experiences

The present study aimed to explore autobiographical memories (long‐lasting memories about the self) and episodic memories (memories about discrete episodes or events) within dream content. We adapted earlier episodic memory study paradigms and reinvestigated the incorporation of episodic memory sources into dreams, operationalizing episodic memory as featuring autonoetic consciousness, which is the feeling of truly re‐experiencing or reliving a past event. Participants (n = 32) recorded daily diaries and dream diaries, and reported on wake–dream relations for 2 weeks. Using a new scale, dreams were rated for their episodic richness, which categorized memory sources of dreams as being truly episodic (featuring autonoetic consciousness), autobiographical (containing segregated features of experiences that pertained to waking life) or otherwise. Only one dream (0.5%) was found to contain an episodic memory. However, the majority of dreams (>80%) were found to contain low to moderate incorporations of autobiographical memory features. These findings demonstrate the inactivity of intact episodic memories, and emphasize the activity of autobiographical memory and processing within dreams. Taken together, this suggests that memories for personal experiences are experienced fragmentarily and selectively during dreaming, perhaps in order to assimilate these memories into the autobiographical memory schema.

Metaphor and hyperassociativity: the imagination mechanisms behind emotion assimilation in sleep and dreaming

In this paper we propose an emotion assimilation function of sleep and dreaming. We offer explanations both for the mechanisms by which waking-life memories are initially selected for processing during sleep, and for the mechanisms by which those memories are subsequently transformed during sleep. We propose that emotions act as a marker for information to be selectively processed during sleep, including consolidation into long term memory structures and integration into pre-existing memory networks; that dreaming reflects these emotion assimilation processes; and that the associations between memory fragments activated during sleep give rise to measureable elements of dream metaphor and hyperassociativity. The latter are a direct reflection, and the phenomenological experience, of emotional memory assimilation processes occurring during sleep. While many theories previously have posited a role for emotion processing and/or emotional memory consolidation during sleep and dreaming, sleep theories often do not take enough account of important dream science data, yet dream research, when conducted systematically and under ideal conditions, can greatly enhance theorizing around the functions of sleep. Similarly, dream theories often fail to consider the implications of sleep-dependent memory research, which can augment our understanding of dream functioning. Here, we offer a synthesized view, taking detailed account of both sleep and dream data and theories. We draw on extensive literature from sleep and dream experiments and theories, including often-overlooked data from dream science which we believe reflects sleep phenomenology, to bring together important ideas and findings from both domains.

Autobiographical memory and hyperassociativity in the dreaming brain: implications for memory consolidation in sleep

In this paper we argue that autobiographical memory (AM) activity across sleep and wake can provide insight into the nature of dreaming, and vice versa. Activated memories within the sleeping brain reflect one’s personal life history (autobiography). They can appear in largely fragmentary forms and differ from conventional manifestations of episodic memory. Autobiographical memories in dreams can be sampled from non-REM as well as REM periods, which contain fewer episodic references and become more bizarre across the night. Salient fragmented memory features are activated in sleep and re-bound with fragments not necessarily emerging from the same memory, thus de-contextualizing those memories and manifesting as experiences that differ from waking conceptions. The constructive nature of autobiographical recall further encourages synthesis of these hyper-associated images into an episode via recalling and reporting dreams. We use a model of AM to account for the activation of memories in dreams as a reflection of sleep-dependent memory consolidation processes. We focus in particular on the hyperassociative nature of AM during sleep.

THE MEMORY EXPERIENCES AND DREAMS QUESTIONNAIRE (MED-Q): A VALIDATED MEASURE OF DREAM REMEMBERING

Dream recall has been investigated via various means, often relying upon self-report judgments. Such methods, as well as individual differences and cognitive correlates of dream recall, rarely acknowledge models, theory, or empirical work concerning waking memory. Study 1 presents the development and psychometric validation of the Memory Experiences and Dreaming Questionnaire (MED-Q)—a 30-item measure of autobiographical and dream memory sensations incorporating items on dreaming, sensory experiences, and autobiographical remembering behaviors. It produces a single score and can be broken down into its constituent factors: “awareness of dreaming,” “daydreaming,” “dream sensations upon waking,” “déjà-states,” “comprehensibility of dream content,” and “senses.” Study 2 demonstrates the validity of the MED-Q as compared with dream report indices of dream detail. The MED-Q measures the extent to which a person engages with their dream memories through both frequency and subjective characteristic ratings. It is therefore novel in emphasizing the context of autobiographical memory for dreaming.

Correlates of Dream Recall: Implications for Confabulation

This investigation aimed to characterize the personality profile of dream-recallers using a psychometrically-validated measure of dream remembering (the MED-Q) (Horton & Conway, 2009), and considered these relationships in terms of confabulation: the tendency to confuse reality with imaginings and thus create false memories. In Experiment 1, 221 participants completed the MED-Q and a battery of personality measures online. The MED-Q significantly correlated with personality dimensions such as openness, thin boundaries, and fantasy-proneness, reinforcing previous findings. Experiment 2 involved participants (N = 45) recalling a previously-read story, providing measures of true recall and confabulation. A significant relationship was found between the MED-Q (“Awareness of dreaming” factor) and confabulation, but not with other memory scores. Thus, the personality profile described in Experiment 1 gives rise to a tendency to confabulate, reflect upon or rehearse personal memories, as opposed to improving the recall of autobiographical memories, which in turn may lead to an increased awareness of dreaming (Experiment 2). This not only reinforces the overlap between dreaming and constructive autobiographical memory processes, but also acts as a warning to interpret freely recalled dreams with substantial caution.

Consciousness across Sleep and Wake: Discontinuity and Continuity of Memory Experiences As a Reflection of Consolidation Processes

The continuity hypothesis (1) posits that there is continuity, of some form, between waking and dreaming mentation. A recent body of work has provided convincing evidence for different aspects of continuity, for instance that some salient experiences from waking life seem to feature in dreams over others, with a particular role for emotional arousal as accompanying these experiences, both during waking and while asleep. However, discontinuities have been somewhat dismissed as being either a product of activation-synthesis, an error within the consciousness binding process during sleep, a methodological anomaly, or simply as yet unexplained. This paper presents an overview of discontinuity within dreaming and waking cognition, arguing that disruptions of consciousness are as common a feature of waking cognition as of dreaming cognition, and that processes of sleep-dependent memory consolidation of autobiographical experiences can in part account for some of the discontinuities of sleeping cognition in a functional way. By drawing upon evidence of the incorporation, fragmentation, and reorganization of memories within dreams, this paper proposes a model of discontinuity whereby the fragmentation of autobiographical and episodic memories during sleep, as part of the consolidation process, render salient aspects of those memories subsequently available for retrieval in isolation from their contextual features. As such discontinuity of consciousness in sleep is functional and normal.