Richard J. Ross

Rapid eye movement sleep disturbance in posttraumatic stress disorder

The subjective sleep disturbance in posttraumatic stress disorder (PTSD), including the repetitive, stereotypical anxiety dream, suggests dysfunctional rapid eye movement (REM) sleep mechanisms. The polysomnograms of a group of physically healthy combat veterans with current PTSD were compared with those of an age-appropriate normal control group. Tonic and phasic REM sleep measures in the PTSD subjects were elevated on the second night of recorded sleep. Increased phasic REM sleep activity persisted in the PTSD group on the subsequent night. During the study, an anxiety dream occurred in a PTSD subject in REM sleep. The results are consistent with the view that a dysregulation of the REM sleep control system, particularly phasic event generation, may be involved in the pathogenesis of PTSD. The finding of a specific disturbance of sleep unique to PTSD may have significant implications for the design of effective treatments for PTSD.

Influence of shock training and explicit fear-conditioned cues on sleep architecture in mice: strain comparison.

Fear conditioning is thought to model anticipatory anxiety. Inbred mouse strains exhibit different levels of reactivity to aversive environmental stimuli, which may reflect anxiety. We examined the effects of fear conditioning on sleep in mouse strains that differ on behavioral measures of anxiety. Mice (BALB/cJ [C], C57BL/6J [B6], CB6F1/J [CB6], n = 7–10 per strain) were implanted with transmitters for recording sleep by telemetry. Baseline sleep was recorded, and the mice were trained to associate a cue (tone) with footshock (15 cue–shock pairings on 4 consecutive days). Sleep was recorded after shock training and again 4 to 5 days later after presentation of the cue alone. Shock training produced a relatively selective suppression of rapid eye movement sleep (REM) that was greater in the C strain compared to the B6 and CB6 mice. Post-training exposure to the cue alone suppressed REM in all strains. The C strain exhibited a relatively greater immediate suppression of REM, and the CB6 hybrid mice showed the greatest overall suppression of REM. These data demonstrate that stimuli associated with an aversive event can alter sleep and suppress REM in much the same way as exposure to the event itself. Fear conditioning may provide a model for examining genetic and neural mechanisms underlying the influence of anxiety on sleep.

A rodent model of sleep disturbances in posttraumatic stress disorder: The role of context after fear conditioning

BACKGROUND A prominent sleep disturbance, likely including a disruption of rapid eye movement sleep (REMS) continuity, characterizes posttraumatic stress disorder (PTSD). We set out to develop a fear conditioning paradigm in rats that displays alterations in sleep architecture analogous to those in PTSD. METHODS Baseline polysomnographic recordings of rats were performed in a neutral context to which the rats had been habituated for several days. Rats were then shock- or mock-trained in a distinctly different context, and their sleep was studied the following day in that context. A separate group of rats was shock-trained and studied in the neutral context on the following 2 days. RESULTS Rats that slept in the neutral context exhibited a REMS-selective increase in sleep 24 hours after training and increases in REMS and non-REMS 48 hours after training. In contrast, rats that slept in the presence of situational reminders of the training context exhibited a REMS-selective decrease in sleep 24 hours later. Animals that were mock-trained showed no changes in sleep. CONCLUSIONS Shock training induced days-long changes in sleep architecture that were disrupted when the animal was exposed to situational reminders of the training context.

Central administration of two 5-HT receptor agonists: Effect on REM sleep initiation and PGO waves

Cholinergic neurons in the pedunculopontine tegmental (PPT) and the laterodorsal tegmental (LDT) nuclei are implicated in the generation of rapid eye movement sleep (REM) and ponto-geniculo-occipital (PGO) waves. Serotonin (5-HT) has a role in sleep-wake regulation and appears to inhibit PGO wave generation. We studied the effects of the central infusion of the relatively specific 5-HT1A receptor agonist 8-hydroxy-2-(n-dipropylamino)tetralin (DPAT) and the less specific 5-HT1 receptor agonist 1(3-chlorophenyl)piperazine (mCPP) on the regulation of REM and on PGO wave generation. DPAT (0.0, 0.002, 0.01, 0.08, and 0.8 microgram/0.5 microliter normal saline) and mCPP (0.0, 0.02, 0.2, 2.0, and 20.0 micrograms/0.5 microliter normal saline) were infused unilaterally into the peribrachial region of PPT (PB) in cats. Additionally, DPAT (0.01 microgram/0.5 microliter) was infused bilaterally into PB in a separate experiment. Low dosages of DPAT (unilateral or bilateral) decreased successful entrances into REM (0.01 microgram) and time spent asleep (0.002 microgram and 0.01 microgram) without affecting outward behavior. No dosage of mCPP significantly decreased the number of REM episodes, and neither drug decreased REM episode duration once REM had been entered. Neither drug affected the rate of PGO waves independently of modulating behavioral state. We propose that 5-HT1A receptor mechanisms have an inhibitory role in actual REM initiation, possibly by facilitating endogenously generated excitation of brainstem startle mechanisms at the onset of REM.

Stress-Induced Changes in Sleep in Rodents: Models and Mechanisms

Psychological stressors have a prominent effect on sleep in general, and rapid eye movement (REM) sleep in particular. Disruptions in sleep are a prominent feature, and potentially even the hallmark, of posttraumatic stress disorder (PTSD) (Ross, R.J., Ball, W.A., Sullivan, K., Caroff, S., 1989. Sleep disturbance as the hallmark of posttraumatic stress disorder. American Journal of Psychiatry 146, 697-707). Animal models are critical in understanding both the causes and potential treatments of psychiatric disorders. The current review describes a number of studies that have focused on the impact of stress on sleep in rodent models. The studies are also in Table 1, summarizing the effects of stress in 4-h blocks in both the light and dark phases. Although mild stress procedures have sometimes produced increases in REM sleep, more intense stressors appear to model the human condition by leading to disruptions in sleep, particularly REM sleep. We also discuss work conducted by our group and others looking at conditioning as a factor in the temporal extension of stress-related sleep disruptions. Finally, we attempt to describe the probable neural mechanisms of the sleep disruptions. A complete understanding of the neural correlates of stress-induced sleep alterations may lead to novel treatments for a variety of debilitating sleep disorders.

Imagery Rehearsal for Posttraumatic Nightmares: A Randomized Controlled Trial

One hundred twenty-four male Vietnam War veterans with chronic, severe posttraumatic stress disorder (PTSD) were randomly assigned to imagery rehearsal (n = 61) or a credible active comparison condition (n = 63) for the treatment of combat-related nightmares. There was pre-post change in overall sleep quality and PTSD symptoms for both groups, but not in nightmare frequency. Intent-to-treat analyses showed that veterans who received imagery rehearsal had not improved significantly more than veterans in the comparison condition for the primary outcomes (nightmare frequency and sleep quality), or for a number of secondary outcomes, including PTSD. Six sessions of imagery rehearsal delivered in group format did not produce substantive improvement in Vietnam War veterans with chronic, severe PTSD. Possible explanations for findings are discussed.

REM sleep: a sensitive index of fear conditioning in rats.

To examine the influence of conditioned fear stimuli on sleep‐wake states, we recorded sleep in Sprague–Dawley rats after exposure to tones previously paired with footshock. After habituation to a recording chamber and the recording procedure, a baseline sleep recording was obtained the next day. One day later, experimental animals were exposed to shock training designed to induce conditioned fear (FC), consisting of five tone‐footshock pairings. The 5‐s tones (conditioned stimuli; CS) co‐terminated with 1‐s footshocks (unconditioned stimuli; US). The next day sleep was recorded for 4 h in the recording chamber after presentation of five CSs alone. Sleep efficiency (total sleep time/recording period) and REM sleep (REM) and non‐REM (NREM) measures were determined. While sleep efficiency was not significantly changed after CS presentation, the percentage of total sleep time spent in REM (REM percentage) was reduced in the FC animals. The reduction in REM percentage in the FC animals was due to a decrease in the number of REM bouts. In a separate experiment, we repeated the procedures, except the tones and shocks were presented in an explicitly unpaired (UP) fashion. The next day, presentation of the tones increased REM percentage in the UP group. Results are discussed in terms of the decreases in REM as a response to conditioned fear, and the relevance of these findings to the sleep changes seen in post‐traumatic stress disorder (PTSD).

Effects of Transcendental Meditation in Veterans of Operation Enduring Freedom and Operation Iraqi Freedom With Posttraumatic Stress Disorder: A Pilot Study

We conducted an uncontrolled pilot study to determine whether transcendental meditation (TM) might be helpful in treating veterans from Operation Enduring Freedom or Operation Iraqi Freedom with combat-related posttraumatic stress disorder (PTSD). Five veterans were trained in the technique and followed for 12 weeks. All subjects improved on the primary outcome measure, the Clinician Administered PTSD Scale (mean change score, 31.4; p = 0.02; df = 4). Significant improvements were also observed for 3 secondary outcome measures: Clinicians Global Inventory-Severity (mean change score, 1.60; p < 0.04; df = 4), Quality of Life Enjoyment and Satisfaction Questionnaire (mean change score, -13.00; p < 0.01; df = 4), and the PTSD Checklist-Military Version (mean change score, 24.00; p < 0.02; df = 4). TM may have helped to alleviate symptoms of PTSD and improve quality of life in this small group of veterans. Larger, placebo-controlled studies should be undertaken to further determine the efficacy of TM in this population.

Differential effect of sleep-wake states on lingual and dorsal neck muscle activity in rats

Postural tone is reduced during slow-wave sleep (SWS) and absent during rapid eye movement sleep (REMS). In obstructive sleep apnea subjects, upper airway dilating muscles, including those of the tongue, show a similar pattern; this contributes to sleep-related airway obstructions. However, in healthy subjects, state-dependent changes in the activity of pharyngeal muscles are variable. In seven chronically instrumented Sprague-Dawley rats, an animal model used to study sleep and sleep-disordered breathing, we quantified lingual and postural muscle activity across the sleep-wake states by measuring the root mean square levels of the electromyograms (EMG) in successive 10s intervals collected during 2h of recording at a constant circadian time (1-3p.m.). The nuchal EMG was low and steady during SWS and further reduced with occasional twitches during REMS. In contrast, the mean lingual EMG during SWS was only 5.9+/-1.6% (S.E.) of its mean in wakefulness, and during REMS, it increased to 46+/-15% (S.E.) (p<0.03) due to the appearance of phasic bursts, the intensity of which progressively increased. The lingual and nuchal activities also had different time courses during state transitions. In obstructive sleep apnea subjects, the sleep-wake changes in the activity of pharyngeal muscles may become similar to those in postural muscles as a result of pharyngeal tone adaptations to the disorder.

Sleep patterning and behaviour in cats with pontine lesions creating REM without atonia

SUMMARY  Lesions of the dorsal pontine tegmentum release muscle tone and motor behaviour, much of it similar to orienting during wakefulness, into rapid eye movement sleep (REM), a state normally characterized by paralysis. Sleep after pontine lesions may be altered, with more REM‐A episodes of shorter duration compared to normal REM. We examined behaviour, ponto‐geniculo‐occipital (PGO) waves (which may be central markers of orienting) and sleep in lesioned cats: (i) to characterize the relationship of PGO waves to behaviour in REM‐A; (ii) to determine whether post‐lesion changes in the timing and duration of REM‐A episodes were due to activity‐related awakenings; and (iii) to determine whether alterations in sleep changed the circadian sleep/wake cycle in cats. Behavioural release in REM‐A was generally related to episode length, but episode length was not necessarily shorter than normal REM in cats capable of full locomotion in REM‐A. PGO wave frequency was reduced overall during REM‐A, but was higher during REM‐A with behaviour than during quiet REM‐A without overt behaviour. Pontine lesions did not significantly alter the circadian sleep/wake cycle; REM‐A had approximately the same Light/Dark distribution as normal REM. Differences in the patterning of normal REM and REM‐A within sleep involve more than mere movement‐induced awakenings. Brainstem lesions that eliminate the atonia of REM may damage neural circuitry involved in REM initiation and maintenance; this circuitry is separate from circadian control mechanisms.