Questionnaire relating to sleep paralysis

Out-of-body experiences in relation to lucid dreaming and sleep paralysis: a theoretical review and conceptual model

Out-of-body experiences (OBEs) are characterized by the subjective experience of being located outside the physical body. Little is known about the neurophysiology of spontaneous OBEs, which are often reported by healthy individuals as occurring during states of reduced vigilance, particularly in proximity to or during sleep (sleep-related OBEs). In this paper, we review the current state of research on sleep-related OBEs and hypothesize that maintaining consciousness during transitions from wakefulness to REM sleep (sleep-onset REM periods) may facilitate sleep-related OBEs. Based on this hypothesis, we propose a new conceptual model that potentially describes the relationship between OBEs and sleep states. The model sheds light on the phenomenological differences between sleep-related OBEs and similar states of consciousness, such as lucid dreaming (the realization of being in a dream state) and sleep paralysis (feeling paralyzed while falling asleep or waking up), and explores the potential polysomnographic features underlying sleep-related OBEs. Additionally, we apply the predictive coding framework and suggest a connecting link between sleep-related OBEs and OBEs reported during wakefulness.

Prevalence and Clinical Characteristics of Sleeping Paralysis: A Systematic Review and Meta-Analysis

Sleep paralysis (SP) is a mixed state of consciousness and sleep, combining features of rapid eye movement (REM) sleep with those of wakefulness. The exact cause of SP is unknown, and its prevalence varies among the studies. We aim to identify SP's global prevalence, the affected population's characteristics, and the SP's clinical picture. We searched three databases (PubMed, Scopus, and Web of Science (WoS)) using a unique search strategy to identify eligible studies. All observational studies identifying the prevalence or frequency of sleeping paralysis were included. No exclusions are made based on country, race, or questionnaire. The analysis was performed using the latest version of R software (R Core Team, Vienna, Austria). The analysis included 76 studies from 25 countries with 167,133 participants. The global prevalence of SP was 30% (95% CI (22%, 39%)). There were similar frequencies of isolated SP and SP (33%, 95% CI (26%, 42%), I2 = 97%, P <0.01; 31%, 95% CI (21%, 43%), I2 = 100%, P = 0, respectively). A subgroup analysis showed that the majority of those who experienced SP were psychiatric patients (35%, 95% CI (20%, 55%), I2 = 96%, P <0.01). The prevalence among non-psychiatric patients was among students (34%, 95% CI (23%, 47%), I2 = 100%, P = 0). Auditory and visual hallucinations were reported in 24.25% of patients. Around 4% had only visual hallucinations. Meta-regression showed no association between the frequency of SP and sex. Publication bias was detected among the included studies through visual inspection of funnel plot asymmetry. Our findings revealed that 30% of the population suffered from SP, especially psychiatric patients and students. The majority of SP cases lacked associated hallucinations, while a noteworthy proportion experienced combined visual and auditory hallucinations.

The incubus phenomenon: Prevalence, frequency and risk factors in psychiatric inpatients and university undergraduates

BACKGROUND

The incubus phenomenon is a paroxysmal sleep-related disorder characterized by the visuotactile sensation of a person or entity exerting pressure on one's thorax during episodes of sleep paralysis and (apparent) wakefulness. This terrifying phenomenon is relatively unknown even though a previous meta-analysis indicated a lifetime prevalence of 0.11 for individuals in the general population and of 0.41 for selected at-risk groups, including people diagnosed with schizophrenia and students. Since the studies reviewed did not always make a strict distinction between the incubus phenomenon and isolated sleep paralysis, we carried out a cross-sectional study in a contemporary patient and student sample to attain current, more detailed data on the incubus phenomenon.

MATERIALS AND METHODS

In a cross-sectional design, we used the Waterloo Unusual Sleep Experience Questionnaire (WUSEQ) to screen patients with severe psychiatric disorders and university undergraduates to establish and compare prevalence rates, frequencies of occurrence, and risk factors for the incubus phenomenon.

RESULTS

Having interviewed 749 people, comprising 606 students and 143 patients with a schizophrenia spectrum or related disorder who had been acutely admitted to a secluded nursing ward, we computed a reported lifetime prevalence of 0.12 and 0.09, respectively, which rates were not statistically different. In both groups, the phenomenon was more common in people with a non-Western European background. Risk factors noted for the students were the use of psychotropic medication and the lifetime presence of an anxiety disorder, eating disorder, or sleeping disorder. We found no associations with age or gender in either group.

CONCLUSION

The 0.09 and 0.12 lifetime prevalence rates we recorded for the incubus phenomenon in students and psychiatric inpatients is substantially lower than the 0.41 found in an earlier meta-analysis. We tentatively attribute this difference to an overgeneralization in previous studies but also discuss alternative explanations. The elevated prevalence among non-Western European participants may well be due to the fact that the topic continues to be part of the cultural and religious heritage of many non-Western countries.

Sleep-Related Practices, Behaviors, and Sleep-Related Difficulties in Deployed Active-Duty Service Members Performing Security Duties

Objective: To assess sleep-related difficulties (e.g., trouble staying asleep, oversleeping, falling asleep while on duty, disturbing dreams, sleep paralysis) and behavioral patterns of active-duty service members (ADSMs) performing security duties. Participants: The participants were 1,169 ADSMs (20-44 years of age). Methods: ADSMs completed an online survey (67.3% response rate) with items assessing demographics, the occupational environment, sleep-related attributes, habits, or difficulties, factors affecting sleep, aids and techniques used to improve sleep, and the use of sleep-related products. Results: ADSMs reported sleeping ~6.5 hr/day (~56% reported sleeping < 6 hr). Sleep-related difficulties were reported by ~72% of the ADSMs (i.e., 55.1% had problems staying asleep, 33.1% reported experiencing sleep paralysis, 25.6% reported oversleeping, 21.6% had disturbing dreams, and 4.79% reported falling asleep while on duty). Daily sleep duration and quality, occupational factors (shift work, operational commitments, collateral duties, habitability, taking antimalarial medication, years deployed), and personal factors or behaviors (history of sleep problems, problems in personal life, late exercise times, altering sleep schedule to talk or text with family or friends) were associated with sleep-related difficulties. Some ADSMs reported using alcohol (~14%) or exercising prior to bedtime (~34%) in an attempt to fall sleep faster. Conclusions: We identified a high prevalence of sleep-related difficulties in our military sample. Even though most ADSMs used sleep hygiene practices to improve their sleep, some ADSMs used methods not recommended. Improving ADSMs' daily schedule (to include periods for exercising, and protected sleep periods), and further emphasis on sleep hygiene practices may be viable methods to reinforce behaviors promoting healthy sleep and improve performance.

Prevalence Rates of the Incubus Phenomenon: A Systematic Review and Meta-Analysis

BACKGROUND

The incubus phenomenon is a paroxysmal sleep-related disorder characterized by compound hallucinations experienced during brief phases of (apparent) wakefulness. The condition has an almost stereotypical presentation, characterized by a hallucinated being that exerts pressure on the thorax, meanwhile carrying out aggressive and/or sexual acts. It tends to be accompanied by sleep paralysis, anxiety, vegetative symptoms, and feelings of suffocation. Its prevalence rate is unknown since, in prior analyses, cases of recurrent isolated sleep paralysis with/without an incubus phenomenon have been pooled together. This is unfortunate, since the incubus phenomenon has a much greater clinical relevance than isolated sleep paralysis.

METHODS

PubMed, Embase, and PsycINFO were searched for prevalence studies of the incubus phenomenon, and a meta-analysis was performed.

RESULTS

Of the 1,437 unique records, 13 met the inclusion criteria, reporting on 14 (k) independent prevalence estimates (total N = 6,079). The pooled lifetime prevalence rate of the incubus phenomenon was 0.19 [95% confidence interval (CI) = 0.14-0.25, k = 14, N = 6,079] with heterogeneous estimates over different samples. In selected samples (e.g., patients with a psychiatric disorder, refugees, and students), prevalence rates were nearly four times higher (0.41, 95% CI = 0.25-0.56, k = 4, n = 1,275) than in the random samples (0.11, 95% CI = 0.08-0.14, k = 10, n = 4,804). This difference was significant (P < 0.001).

CONCLUSION

This review and meta-analysis yielded a lifetime prevalence of the incubus phenomenon in the general population of 0.11 and, in selected samples, of 0.41. This is slightly higher than the prevalence rates in previous analyses that included cases of recurrent isolated sleep paralysis without an incubus phenomenon. Based on the condition's robust clinical presentation and the relatively high prevalence rates, we advocate inclusion of the incubus phenomenon as a diagnostic category in major classifications such as the International Classification of Diseases and Related Health Problems and the Diagnostic and Statistical Manual of Mental Disorders. Recommendations are also made for clinical practice and future research.

The occurrence and predictive factors of sleep paralysis in university students

The aim of the present study was to assess the occurrence and predictive factors of sleep paralysis (SP) in Czech university students. Our sample included 606 students who had experienced at least one episode of SP. The participants completed an online battery of questionnaires involving questionnaires focused on describing their sleep habits and SP episodes, the 18-item Boundary Questionnaire (BQ-18), the Modified Tellegen Absorption Scale (MODTAS), the Dissociative Experience Scale Taxon, the Beck Depression Inventory II and the State-Trait Anxiety Inventory. The strongest predictive factor for the frequency of SP episodes was nightmares. The strongest predictive factor for the intensity of fear was dream occurrences. In our study sample, SP was more common in women than in men. Those who scored higher in BQ-18 experienced more often pleasant episodes of SP and those who scored higher in MODTAS were more likely to experience SP accompanied with hallucinations. While 62% of respondents answered that their SP was accompanied by intense fear, 16% reported that they experienced pleasant feelings during SP episodes. We suggest that not only the known rapid eye movement sleep dysregulation but also some personality variables may contribute to the characteristics of SP.

A clinician's guide to recurrent isolated sleep paralysis

This review summarizes the empirical and clinical literature on sleep paralysis most relevant to practitioners. During episodes of sleep paralysis, the sufferer awakens to rapid eye movement sleep-based atonia combined with conscious awareness. This is usually a frightening event often accompanied by vivid, waking dreams (ie, hallucinations). When sleep paralysis occurs independently of narcolepsy and other medical conditions, it is termed "isolated" sleep paralysis. Although the more specific diagnostic syndrome of "recurrent isolated sleep paralysis" is a recognized sleep-wake disorder, it is not widely known to nonsleep specialists. This is likely due to the unusual nature of the condition, patient reluctance to disclose episodes for fear of embarrassment, and a lack of training during medical residencies and graduate education. In fact, a growing literature base has accrued on the prevalence, risk factors, and clinical impact of this condition, and a number of assessment instruments are currently available in both self-report and interview formats. After discussing these and providing suggestions for accurate diagnosis, differential diagnosis, and patient selection, the available treatment options are discussed. These consist of both pharmacological and psychotherapeutic interventions which, although promising, require more empirical support and larger, well-controlled trials.

Lifetime prevalence rates of sleep paralysis: a systematic review

OBJECTIVE

To determine lifetime prevalence rates of sleep paralysis.

DATA SOURCES

Keyword term searches using "sleep paralysis", "isolated sleep paralysis", or "parasomnia not otherwise specified" were conducted using MEDLINE (1950-present) and PsychINFO (1872-present). English and Spanish language abstracts were reviewed, as were reference lists of identified articles.

STUDY SELECTION

Thirty five studies that reported lifetime sleep paralysis rates and described both the assessment procedures and sample utilized were selected.

DATA EXTRACTION

Weighted percentages were calculated for each study and, when possible, for each reported subsample.

DATA SYNTHESIS

Aggregating across studies (total N=36,533), 7.6% of the general population, 28.3% of students, and 31.9% of psychiatric patients experienced at least one episode of sleep paralysis. Of the psychiatric patients with panic disorder, 34.6% reported lifetime sleep paralysis. Results also suggested that minorities experience lifetime sleep paralysis at higher rates than Caucasians.

CONCLUSIONS

Sleep paralysis is relatively common in the general population and more frequent in students and psychiatric patients. Given these prevalence rates, sleep paralysis should be assessed more regularly and uniformly in order to determine its impact on individual functioning and better articulate its relation to psychiatric and other medical conditions.

Isolated sleep paralysis and fearful isolated sleep paralysis in outpatients with panic attacks

Isolated sleep paralysis (ISP) has received scant attention in clinical populations, and there has been little empirical consideration of the role of fear in ISP episodes. To facilitate research and clinical work in this area, the authors developed a reliable semistructured interview (the Fearful Isolated Sleep Paralysis Interview) to assess ISP and their proposed fearful ISP (FISP) episode criteria in 133 patients presenting for panic disorder treatment. Of these, 29.3% met lifetime ISP episode criteria, 20.3% met the authors' lifetime FISP episode criteria, and 12.8% met their recurrent FISP criteria. Both ISP and FISP were associated with minority status and comorbidity. However, only FISP was significantly associated with posttraumatic stress disorder, body mass, anxiety sensitivity, and mood and anxiety disorder symptomatology.

The assessment of the phenomenology of sleep paralysis: the Unusual Sleep Experiences Questionnaire (USEQ)

Previous research has found a relationship between sleep paralysis (SP) and anxiety states and higher rates have been reported among certain ethnic groups. To advance the cross-cultural study of SP, we developed a brief assessment instrument (which can be self-administered), the Unusual Sleep Experiences Questionnaire (USEQ). In this article, we report on a pilot study with the USEQ in a sample of 208 college students. The instrument was easily understood by the participants, with one quarter reporting at least one lifetime episode of SP. As in previous studies, SP was associated with anxiety (in particular, panic attacks).

Risk factors for isolated sleep paralysis in an African American sample: a preliminary study

Isolated sleep paralysis (ISP) is a temporary period of involuntary immobility that can occur at sleep onset or offset. It has previously been reported in association with both panic disorder (PD) and posttraumatic stress disorder (PTSD). The current study examined the association between ISP and several possible risk factors--anxiety sensitivity, trauma exposure, life stress, and paranormal beliefs--in a sample of African American participants with and without a history of ISP. Significant between-group differences were found for PD and PTSD diagnoses, anxiety sensitivity, life stress, and certain aspects of paranormal belief, with the ISP group being higher on all of these indices. No differences were found with regard to trauma exposure. Hierarchical regression analyses indicated that PD, anxiety sensitivity, and life stress each contributed unique variance to ISP cognitive symptoms, whereas PTSD and paranormal beliefs did not. These results provide preliminary support for an association between ISP and anxiety sensitivity and corroborate previous reports of ISP's association with PD and life stress. The current trauma/PTSD findings are mixed, however, and warrant future research.

Sleep paralysis and trauma, psychiatric symptoms and disorders in an adult African American population attending primary medical care

The occurrence of sleep paralysis (SP) absent narcolepsy appears to not be uncommon in African Americans and probably other non-European groups. Prior research has linked SP to trauma and psychiatric disorders and suggested a specific relationship to panic disorder in African Americans. The objective of our study was to evaluate relationships of SP with trauma, concurrent psychiatric symptoms and lifetime psychiatric diagnoses in an adult African American population recruited from primary care. Cross sectional study with surveys and diagnostic interviews; Patients attending primary care clinics filled out a survey that determined the 6 month prevalence and associated features of SP, a panic disorder screen, the self-rated Hamilton Depression Scale, and an inventory of trauma exposure. A subset of trauma-exposed participants (N = 142) received comprehensive diagnostic interviews that incorporated the Structured Clinical Interview for DSM-IV and the Clinician Assessed PTSD Scale. Four hundred and forty-one adults participated (mean age-40.0 SD = 13.3, 68% female, 95% African American). Fourteen percent endorsed recent SP. In approximately 1/3 of those with SP, episodes also featured panic symptoms. SP was strongly associated with trauma history, and concurrent anxiety and mood symptoms. SP was not associated with specific psychiatric disorders other than lifetime (but not current) alcohol or substance use disorders. Our findings suggest that SP is not uncommon in adult African Americans and is associated with trauma and concurrent distress but not with a specific psychiatric diagnosis.

Sensed presence as a correlate of sleep paralysis distress, social anxiety and waking state social imagery

Isolated sleep paralysis (ISP) is a common parasomnia characterized by an inability to move or speak and often accompanied by hallucinations of a sensed presence nearby. Recent research has linked ISP, and sensed presence more particularly, with social anxiety and other psychopathologies. The present study used a large sample of respondents to an internet questionnaire (N=193) to test whether these associations are due to a general personality factor, affect distress, which is implicated in nightmare suffering and hypothesized to involve dysfunctional social imagery processes. A new measure, ISP distress, was examined in relation to features of ISP experiences, to self-reported psychopathological diagnosis, to scores on the Leibowitz Social Anxiety Scale and to scores on a new questionnaire subscale assessing social imagery in a variety of waking states. Three main results were found: (1) ISP experiences are only weakly associated with a prior diagnosis of mental disorder, (2) sensed presence during ISP is associated preferentially with ISP distress, and (3) ISP distress is associated with dysfunctional social imagery. A general predisposition to affective distress may influence the distress associated with ISP experiences; overly passive social imagery may, in turn, be implicated in this affect distress influence.

Paranoid delusions and threatening hallucinations: a prospective study of sleep paralysis experiences

Previously we reported a three-factor structure for hallucinations accompanying sleep paralysis (SP). These earlier analyses were, however, based on retrospective accounts. In a prospective study, 383 individuals reported individual episodes online providing further evidence for the three-factor structure as well as clearer conceptually meaningful relations among factors than retrospective studies. In addition, reports of individual episodes permitted a more fine-grained analysis of the internal structure of factors to assess predictions based on the hypothesis that a sensed or felt presence (FP) is a core experience affecting other SP hallucinations. Results were generally consistent with this hypothesis. In particular, associations among, and temporal stability of, sensory hallucinations were largely explained by their common association with FP. The findings are consistent with REM initiation of a threat activated vigilance system with pervasive effects on the SP experience and suggest a potential model for the thematic organization of nightmares and dreams more generally.

Mental representation of space: Insights from an oblique distribution of hallucinations

Three-dimensional spatial distributions of hypnagogic and hypnopompic hallucinations associated with sleep paralysis were used to investigate the internal representation of space. Left-right asymmetries in human preferences and abilities are well established. Parallel effects are also observed as lower-upper asymmetries. These parallels could reflect common underlying mechanisms or additive effects of independently evolved horizontal and vertical asymmetries. This study adds to the growing literature on multidimensional spatial biases in a context free from the influence of task-related factors. We present evidence of an oblique bias in the projection of both sensory and motor hallucinations toward lower-left and especially upper-right external space exceeding that accounted for by an additive model of separate horizontal and vertical biases. These observations are consistent with theories regarding a systematic functional relation of hemispheric with ventral and dorsal cerebral organization.

Timing of spontaneous sleep-paralysis episodes

The objective of this prospective naturalistic field study was to determine the distribution of naturally occurring sleep-paralysis (SP) episodes over the course of nocturnal sleep and their relation to bedtimes. Regular SP experiencers (N = 348) who had previously filled out a screening assessment for SP as well as a general sleep survey were recruited. Participants reported, online over the World Wide Web, using a standard reporting form, bedtimes and subsequent latencies of spontaneous episodes of SP occurring in their homes shortly after their occurrence. The distribution of SP episodes over nights was skewed to the first 2 h following bedtime. Just over one quarter of SP episodes occurred within 1 h of bedtime, although episodes were reported throughout the night with a minor mode around the time of normal waking. SP latencies following bedtimes were moderately consistent across episodes and independent of bedtimes. Additionally, profiles of SP latencies validated self-reported hypnagogic, hypnomesic, and hypnopompic SP categories, as occurring near the beginning, middle, and end of the night/sleep period respectively. Results are consistent with the hypothesis that SP timing is controlled by mechanisms initiated at or following sleep onset. These results also suggest that SP, rather than uniquely reflecting anomalous sleep-onset rapid eye movement (REM) periods, may result from failure to maintain sleep during REM periods at any point during the sleep period. On this view, SP may sometimes reflect the maintenance of REM consciousness when waking and SP hallucinations the continuation of dream experiences into waking life.

Sleep paralysis in African Americans with panic disorder

Studies have reported a wide range in lifetime prevalence of sleep paralysis (SP). This variation may stem from cultural factors, stressful life events and genetic differences in studied populations. We found that recurrent SP was more common among African-American participants, especially those with panic disorder. Recurrent SP was reported by 59% of African Americans with panic disorder, 7% of whites with panic disorder, 23% of African-American community volunteers and 6% of white community volunteers. Significantly more early life stressors were reported by African Americans than whites. Higher levels of psychosocial stressors, including poverty, racism and acculturation, may contribute to the higher rates of SP experienced by African Americans.

Prevalence and illness beliefs of sleep paralysis among Chinese psychiatric patients in China and the United States

To investigate the prevalence and illness beliefs of sleep paralysis (SP) among Chinese patients in a psychiatric out-patient clinic, consecutive Chinese/Chinese-American patients who attended psychiatric out-patient clinics in Boston and Shanghai were asked about their lifetime prevalence, personal experience and perceptions regarding the causes, precipitating factors, consequences, and help-seeking of SP. During the 4-month study period, 42 non-psychotic psychiatric out-patients from the Boston site and 150 patients from the Shanghai site were interviewed. The prevalence of SP was found to be 26.2% in Boston and 23.3% in Shanghai. Patients with post-traumatic stress disorder (PTSD) or panic disorder reported a higher prevalence of SP than did patients without these disorders. Patients attributed SP to fatigue, stress, and other psychosocial factors. Although the experience has traditionally been labeled 'ghost oppression' among the Chinese, only two patients, one from each site, endorsed supernatural causes of their SP. Sleep paralysis is common among Chinese psychiatric out-patients. The endorsement of supernatural explanations for SP is rare among contemporary Chinese patients.

Sleep paralysis, sexual abuse, and space alien abduction

Sleep paralysis accompanied by hypnopompic ('upon awakening') hallucinations is an often-frightening manifestation of discordance between the cognitive/perceptual and motor aspects of rapid eye movement (REM) sleep. Awakening sleepers become aware of an inability to move, and sometimes experience intrusion of dream mentation into waking consciousness (e.g. seeing intruders in the bedroom). In this article, we summarize two studies. In the first study, we assessed 10 individuals who reported abduction by space aliens and whose claims were linked to apparent episodes of sleep paralysis during which hypnopompic hallucinations were interpreted as alien beings. In the second study, adults reporting repressed, recovered, or continuous memories of childhood sexual abuse more often reported sleep paralysis than did a control group. Among the 31 reporting sleep paralysis, only one person linked it to abuse memories. This person was among the six recovered memory participants who reported sleep paralysis (i.e. 17% rate of interpreting it as abuse-related). People rely on personally plausible cultural narratives to interpret these otherwise baffling sleep paralysis episodes.

The Primary Parasomnias

BACKGROUND

Primary parasomnias are undesirable motor or verbal phenomena which occur during sleep and result in abnormal arousals. They occur out of all sleep stages or during transitions between sleep and awake. Secondary parasomnias are sleep disturbances that are caused by disorders of other organ systems. This review addresses only primary parasomnias. Arousal disorders and the parasomnias associated with REM sleep are the primary parasomnias most likely to be seen in a neurology practice. Sleep-wake transition disorders are also discussed with nocturnal leg cramps, probably the most common in this group.

REVIEW SUMMARY

The salient clinical features of the primary parasomnias are discussed. Emphasis is placed on the differential diagnosis of the different conditions and the best management strategies. Parasomnias encountered in infancy, such as infant sleep apnea, are not discussed in this review.

CONCLUSIONS

Parasomnias are common disturbances of sleep that may significantly affect the patient's quality of life and that of the bed partner. Most parasomnias can be diagnosed with careful history taking and polysomnography, and management is usually safe and effective.

Spatial characteristics of hallucinations associated with sleep paralysis

INTRODUCTION

Spatial properties of hallucinations have received relatively little systematic investigation. We present evidence from a web-based study of the spatial properties of a broad array of hallucinations associated with sleep paralysis. Predictions regarding spatial characteristics of hallucinations were based on proposed neurophysiological mechanisms underlying different types of hallucinations.

METHOD

Distributions in three dimensions as well as distance and dispersion measures were assessed for 279 experient for two general categories of hallucinations: Intruder hallucinations--including presence, visual, and auditory hallucinations; and Vestibular-Motor (V-M) hallucinations--including floating, flying, illusory motor movements, out-of-body experiences (OBEs), and autoscopy.

RESULTS

For all spatial measures, Confirmatory Factor Analysis revealed that Intruder and V-M hallucinations constituted distinctive factors. In addition, Intruder hallucinations were experienced as occurring close to, usually within a meter of, the experient, whereas V-M hallucinations involved excursions of considerable distance, often beyond the immediate environment. V-M hallucination distance was positively associated with vividness of V-M hallucinations, whereas Intruder hallucination distance was negatively correlated with theoretically related contact hallucinations (pressure, obstructed breathing, pain, choking, and touch).

CONCLUSION

The differences in the spatial characteristics of Intruder and V-M hallucinations largely corroborated predictions based on the respective hypothesised neural substrates of a threat activated vigilance system and a bodily-self neuromatrix.