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Keywords:

  • dream content;
  • dream enactment behaviour;
  • Parkinson’s disease;
  • REM sleep behaviour disorder;
  • video analysis

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Declarations of interest
  8. Acknowledgements
  9. References
  10. Supporting Information

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.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Declarations of interest
  8. Acknowledgements
  9. References
  10. Supporting Information

Rapid eye movement (REM) sleep behaviour disorder (RBD) is believed to be characterized by acting-out of dreams while sound asleep and unaware of one’s surroundings (Schenck and Mahowald, 2002). This so-called dream enactment has been reported in 64–95% of RBD patients in existing case series (Iranzo et al., 2005; Olson et al., 2000; Schenck et al., 1993; Sforza et al., 1997). The manifest movements are believed to be guided by the phenomenal contents of consciousness and the actions are usually seen as very relevant to the dreamt situation (Olson et al., 2000; Schenck and Mahowald, 2002; Schenck et al., 1993; Sforza et al., 1997). Anecdotally, dream content frequently involves defence against attack (Olson et al., 2000). Despite this, studies showed that violent behaviours represent only a small fraction of motor events in RBD (Frauscher et al., 2007), and that non-violent behaviours may also occur (Frauscher et al., 2007, 2009; Leclair-Visonneau et al., 2010; Oudiette et al., 2009). Regardless, as in RBD the phenomenal contents of consciousness are in potential mismatch with the actual physical environment and circumstances, the actions carried out can lead to potentially lethal behaviours to self or others.

In the present study, we addressed the relationship between the actual actions carried out by RBD patients in the objective physical realm during REM sleep, and dream content. We hypothesized, based on previous literature, that a link can be inferred by blind external judges between RBD behaviours and reported phenomenal dream content when both are sampled systematically.

Methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Declarations of interest
  8. Acknowledgements
  9. References
  10. Supporting Information

Patient population

Fourteen patients with Parkinson syndrome and clinical RBD who had no psychiatric disorder, no dementia defined by a mini-mental state examination (MMSE) <24 and no Parkinson-related hallucinations were screened for the study. Patients who did not manifest actual REM-related movements during the experimental nights (= 3), patients who did not recall any dreams (= 2) and patients who wished to withdraw after the first night (= 3) were excluded from further analysis. The final study population consisted of six patients (five Parkinson’s disease, one multiple system atrophy) with a mean age of 58.5 ± 8.4 years and a disease duration of 8.0 ± 7.4 years. Mean Hoehn and Yahr (H&Y) score was 2.8 ± 1.0. All but one patient were on dopaminergic therapy. The study was approved by the Ethics Committee of Innsbruck Medical University, and subjects’ written informed consent was obtained according to the Declaration of Helsinki.

Procedure

All subjects underwent video–polysomnographic recording for two (four patients) or three nights (two patients). Because polysomnographies were performed before the introduction of the new American Academy of Sleep Medicine (AASM) criteria (Iber et al., 2007), scoring of sleep stages was performed visually in 30-s epochs according to standard criteria (Rechtschaffen and Kales, 1968), with allowance to score REM sleep despite persistence of tonic or phasic muscle activity in case of REM sleep without atonia (Mahowald and Schenck, 2005). For this study, we selected only unambiguous REM sleep episodes.

The first night was used for adaptation, and dream recall and dream content was assessed only in conjunction with spontaneous awakenings. If the patient was familiar with the sleep laboratory setting from previous investigation and known to spend only two nights in the laboratory (four patients), dream data were also collected during the first night. During the experimental nights, the patients were awakened from REM sleep 10 min after the onset of the second and all consecutive REM periods or in the case of apparent dream enactment. Dream recall was also sampled in conjunction with spontaneous awakenings from REM sleep. Altogether, 35 REM sleep awakenings were performed, and spontaneous free-worded dream reports and a structured questionnaire for dream elements, including dreamt actions, were obtained immediately after each REM awakening. The structured questions related directly to movements included: ‘Do you remember taking any actions or conducting any movements in your dream just before you woke up?’ and ‘What kind of movements did you try to conduct?’. All dream reports were recorded digitally and transcribed.

Data analysis

Movements were defined behaviourally as any motor activity that could be observed visually to occur in the video. All patients showed increased muscle tone during REM sleep, whether or not movements could be observed. In 17 of the 35 REM awakenings (48.6%), both REM-related movements and dream recall were present simultaneously (see Table 1).

Table 1.   Characteristics of experimental awakenings
  1. REM, rapid eye movement.

Awakenings, n total35
Frequency of dream recall, n (%)25 (71.4)
Frequency of REM-related movements, n (%)26 (74.3)
Frequency of both dream recall and REM-related movements, n (%)17 (48.6)

For examples of the original data sets (dream reports and video), see Data S1.

Video recordings from these 17 awakenings were cut to include a 5.5-min continuous, unedited clip preceding the awakening. The video clips were assembled randomly together with (i) a dream report given by the patient in the interview immediately after the awakening, (ii) a dream report from another RBD patient from another REM awakening but unrelated to movements and (iii) two REM dream reports from control patients diagnosed with Parkinson’s disease without RBD. The three non-matching dreams were selected randomly from a bigger dream report pool of another project of the Innsbruck sleep laboratory.

The 17 video clips, each combined with four dream reports (one matching the awakening), were presented in randomized order to seven neurologists who acted as blind judges (three movement disorders specialists, three sleep specialists, one movement disorders and sleep specialist). The judges thus had a 25% possibility of matching the correct dream report to the video clip by chance. They were instructed to pay specific attention to the body movements manifested in the video and to the descriptions of body movements in the dream reports. In addition, they were informed that in all cases they had to choose the most matching dream report according to their best estimation (forced-choice design).

Statistical procedures

Statistical analyses were performed with SPSS version 16.0. Due to the nature of the experimental design and data, mainly descriptive statistics were calculated. In addition, a one-sample t-test with test value 0.25 and 95% confidence interval (CI) was conducted for the following variables: individual judge performance, overall judge performance per patient and overall judge performance per each video-dream report pair.

Results

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Declarations of interest
  8. Acknowledgements
  9. References
  10. Supporting Information

Awakenings

The mean number of REM awakenings per patient was 5.8 ± 1.4, with a mean REM duration before an awakening of 11.8 ± 5.1 min. Twenty-five of the total 35 awakenings (71.4%) presented with dream recall. Mean dream recall rate was 71.4 ± 31.8% (range 14–100%).

In 17 awakenings (48.6%) both REM-related movements, independent of their intensity, and dream recall were present simultaneously. These were obtained mainly from the second (seven cases; 41.2%) or third REM stages (six cases; 35.3%), and only once from first, fourth, fifth or sixth REM phases. Minor movements and twitching occurred in conjunction with dream recall in four REM episodes (11% of all awakenings), moderate movements, e.g. jerks and vocalizations, were manifest with dream recall in nine REM episodes (17% of all awakenings) and violent movements coinciding with dream recall (hitting, kicking, screaming) were present in four (11%) of the REM awakenings. Individual video-dream pairs are given in Table 2.

Table 2.   Individual video-dream pairs
No.Video descriptionCorresponding dream report
Description of visible movements and facial emotional expressionThe free-worded dream report as narrated by the patient, and the emotional tone of the dream events as related by the patient
1Raising both arms for several seconds, then grabbing for something. Few lip movements resembling talking without sound. Intermittent small distal limb and head movements. No emotional expressionI was in a competition. There was a race and we had to run, and step into open tubes. Open tubes floating in a lake. We had to get there. We had to run to the tubes, then jump into them and then paddle to the other side of the lake. Then, on the other side, we had bicycles, and we had to ride to our homes. But there was a bridge to cross, it was bottle-like, very narrow. There was a little fight over who was the first. I tried to get to the bridge first. There was a fight for the best position. I was part of this fight. Actually, it was a lot of fun. I was pleased. Positive emotion
2Chewing and lifting left arm. Minor head movements. Slight lip movements resembling talking without sound. No emotional expressionI was talking with a woman about a football game. There were no other feelings but joy, no fear. It was in a room, inside somewhere. It wasn’t a dark room. We were not alone, there were other persons, but I did not recognize them. Positive emotion
3Talking incomprehensively. Gesticulating with both arms like chasing something off. No emotional expressionI can remember an interaction, but it was not a very logical event. There was my father, and it was about a woman and my son. I couldn’t see them very clearly, but it was about them. My son had forgotten something he was supposed to take to my father, and I had brought this to my father. There were many different pathways, the landscape was not clear to me; there were buildings. In the dream, my father wasn’t the way he used to be, he did not behave the way he used to be, he was a little bit different. The behaviour was not typical for him; the father was there, but he would never have acted that way. He was kind of supporting. It was a nice, convenient situation. I thought that this event that happened with my family took place perhaps in a city district in Köln. I thought that my son had again forgotten something. I do not know exactly what he had forgotten. It was something in a box. It was like a musical instrument. J. had forgotten to bring it to my father. I don’t know if it belonged to him, but that was what I brought to my father. I don’t know why, it was just the box without the instrument, perhaps just to store something. In the dream I was walking. Normal speed. Relaxed. I didn’t bump into anything, I only moved. I don’t know what exactly I did in my dream. At some point, J. asked: ‘How are you getting around (transportation)?’, and I said by foot. ‘Where did you leave your father?’, and I said: ‘He’s over there’. ‘D’, J. said, ‘is already gone with the bus’ (D is my spouse, but not J’s parent). There was nothing exiting, it was convenient, nice landscape. There were other persons, but not involved in this event, nevertheless we were not alone. But they didn’t play any role in the event. I can’t remember the others. During the dream everything was OK, brilliant. I felt like the situation was real. As a character in the dream, everything was clear, but now when I think about it, nothing is clear. Emotionally neutral
4Few movements including two whole body jerks and small movements of the right hand. No emotional expressionWe drove with a car and there were people running across the street. It was a bit like chaos. And all the people were dressed in dark clothes. I did not recognize the people. It was in the evening. It was after work, on leisure time and they simply went home very fast. I wasn’t there in the street in person, I only saw it. Like from nowhere, it was just in front of my eyes. It was a wide street, with telephone poles, and also there was a bush. And there was something behind the bush, I don’t know what it was. There were dogs running around. They were frightening. They were running after the people. But they were not aggressive. Big ones. They were darker than shepherds. I can remember no feelings. I felt completely normal, I didn’t care about the things I saw. Emotionally neutral
5Chewing. Incomprehensible vocalization. Few movements including both arms and the head. No emotional expressionIt was a strange situation. I had the all the cables on (the electrodes and other measuring equipment), and in this room (where the patient slept) there was a mass; a priest came in with the children, and everyone got up (I used to do that as a child). I was full of cables, and I was wearing a hat. Then the priest rang the bell and said: ‘in the name of the father, the son…’ In the beginning of the mass I stood up and forgot to take off the hat. That was a strange thing. Actually the priest looked at me; I took off the hat. The priest didn’t say anything, but it was embarrassing. Also, as a child I was a ‘choirboy’, and I know the situation, how I should behave. (Nowadays, I don’t go to the church very often and I don’t have anything to do with the church, I don‘t know why I was dreaming about this.). The cables were attached like they are attached now, and I was supposed to get up. Somehow it was stupid, and I had the hat on. When I had stood up, I sat down too early, and had to get up again. There was perhaps one colleague or colleagues from the past. Negative emotion
6Whole body jerk, followed by screaming and holding her left hand in front of her mouth. The patient is apparently frightened. After the awakening, the patient exclaims ‘Oh my god, I must have cried out loudly’In the dream something was broken, like a house falling down. But I woke up before the event had run its course, before all of it had happened. Something big happened. I was afraid, for a moment. There were other persons, too, but not more than one or two. I did not know these people. I was astonished, amazed, I screamed and then I woke up. Negative emotion
7Hitting the wall with both arms. No emotional expression (face is not visible as the patient is facing the wall)This dream was about farming the land. At home, we were planting corn, and there was another man planting corn, too. And there was a situation that I had to rent my land, but the other man couldn’t understand that I gave up the land because I had to retire early due to my illness. I wanted to explain this to him, as he didn’t understand me, and I wanted to tell him that he would have probably done the same thing if he were in my position. I was quite angry because he did not understand me, and then, he wanted to injure me. He had something in his hand, but I do not know what it was. It was so small that he could hold it in his hand. He was a real tough farmer and thought that I cannot just quit farming and give up my land. He told me his opinion and then he started to attack me. I was angry. Negative emotion
8Kicking the legs for several times like defending himself. Intermittent small distal limb movements. Patient seems scaredI dreamt about a train. But what exactly, I cannot really remember. But I know that it was about a train and somewhere in Siberia. I was aboard the train, and I saw the landscape and it looked like in Siberia, there was snow and everything was flat as far as you could see. I don’t know what else happened or what I was doing in the train. I only know that it was about a train, and in Siberia. And then I was standing somewhere and saw a train leave, that I know. Emotionally neutral
9Talking incomprehensibly. Gesticulating with the left arm. No apparent emotionIt was like before. Most of the people are faceless. There is a situation where they need guidance. And I tried to organize them by giving signs with my hands pointing to left and right: You go over there, you over here. I can’t provide them properly, I can’t provide guidance. Negative emotion
10Moaning, moving the lips and the right arm intermittently. No emotional expressionI dreamt that somebody came and wanted certain ashtrays from me. I had three new tablecloths and also ashtrays; somebody wanted the ashtrays and the tablecloths from me. Somebody, I do not know who, but wanted them because they were new. And because this person also wanted to have something beautiful. I don’t know if I gave the items to this person. Then people knocked at the door; it wasn’t a whole house, it was only a half, everything there was open to the street. And then they came in and took everything, the ashtrays and the tablecloths. I can’t say who they were. It was such a colourful dream. Everything was orange. All the things, the carpets, the dishes, all that I saw was orange. They wanted to have them, too. I gave them everything and said: Here, have also something beautiful. I saw the scenery, it was flat, and on the background a hill. I think it was in Innsbruck. Everything went by so fast. Emotionally neutral
11Grapping sth. with both hands. Gesticulating with the right arm and talking soundlessly. No emotional expressionI can’t remember exactly, but I was with my kids (I have two), we were riding bicycles. The kids were still children, six to 10 years old (they are adults now). Then we came home, the boys and I, and then one of the parents, the biological parent (the boys have the same parent but subject has remarried so they have a step-parent and a biological parent) was very annoyed and started to nag at me. Or not so much at me as at the other parent (current spouse; the relationship between both of them is a bit tense). She was nagging because we had been riding bicycles and she doesn’t have control over the kids all the time. She started shouting: ‘What the hell?’ And I said ‘What’s the matter?’ And we had only had a day ride, we didn’t do anything wrong, no harm done. But she became hysteric. My spouse had been with us, I think, and my former spouse was annoyed, because we were having fun. It was summer, and I had felt happy. Both negative and positive emotion
12Moving the right leg (PLM-like), the right arm, followed by a whole body jerk. No emotional expressionThe mayor of our province came to our house, and I ran away, because I don’t like the authorities. But that wasn’t the important thing in the dream. I stood in front of our house and watched at the wall of the house, and I saw big beetles on the wall. I wanted to catch them and thread on them, trample them. I wanted to scratch the beetles down from the wall with a pitchfork. Then I heard, from the inside of the house where the mayor was, shouting, my father shouting: ‘Who is making that noise?’ (He is not alive any more). It was me, sweeping the beetles down from the wall with a pitchfork. Then one beetle fell on me, somewhere on my shoulder. I startled, and then I woke up, as it was so disgusting. I was not afraid, but just disgusted. Negative emotion
13Gesticulating, talking incomprehensively, chewing. The patient seems to be excitedThis was a dream about telling opinions. We were waiting for some event to take place, and were eating dinner. We had all come from work and wanted to discuss what we shall do. I don’t know where it was, exactly, in a bar certainly not. It was kind of a city place, where you can stop (take a break) on your way home. A kind of buffet, I can’t tell. It could have been a sports bar. There were acquaintances, but I didn’t see their faces. I don’t know who they were, but there were two people: I was talking with one of them, and the other only listened. It was an intense discussion: when we shall do it, and so on. The discussion was interesting, we made plans for a bigger meeting. It was like when you plan something. It must have been something important, what, I don’t know. I noticed only two people, but there could have been more, but I didn’t see them. It was a heated discussion of what will happen. But nothing hostile. We discussed how we will arrange it. It was getting hot, but not aggressive. Emotionally neutral
14Moving the lips like talking to somebody. Elevating right arm. No emotional expressionI dreamt that me and some friends were cooking. The food was amazingly good. Somebody made peach soufflé. We invited all the people we saw on the street, and ate it. There were about seven to eight people. I did not know the people I was together with. It is possible that it was in Dornbirn. At the beginning two people brought me some sugar, and at the end we ran from the stove with a bowl in our hands, from the kitchen to another room. I had good emotions, because I was looking forward so much to the meal. We did talk about cooking. Positive emotion
15Hitting several times with the right arm into the air. No emotional expression (the patient is facing the wall)The dream was about an animal that was in our garage. There was a marten in the garage, and it was killing the other animals, animals that were my pets. Small dogs or something like that. I wanted to lure it out from its hiding place and I hit something several times to make noise, scare it, to drive it out from its hiding place. I was angry. I just wanted to lure the animal out from its hiding place. It was a small animal but it was killing our little animals (dogs or cats), and I wanted to catch it. There was only me and all the animals. Then I woke up. Negative emotion
16Moving right arm, hand and fingers. Vocalization. Whole body jerk. No emotional expressionI dreamt about getting up. I was lying across a double bed and thought I will have to get up soon. I was stretching myself: I had two funny hair bands in my hair. Actually I did not want to get up; I thought that we had to leave, there was already someone in the car, who waited for us. And I was still lying in bed and thought: ‘Do I have to go now?’. They were two men, they waited for me, one of them was familiar to me, but I don’t know who it was. There was a house and an open square and there were two cars. The cars were dirty inside. And I did not want to go with them (in the dirty car). I was lying in the bed and thought: ‘Oh, come on’. It was, I think, a carnival party where I was supposed to go, because I had these coloured bands in my hair. They were silly. I had dreamt before that we had been to a party, and that’s why I had these bands in my hair. But it wasn’t anything special. I thought we had got out of the bed, already, and suddenly I just saw myself lying across the bed, and I wasn’t in a mood to go with them. Now there were both men and women. There were also more cars. They were acquaintances, like the ones I would know from the parties. Two or three cars. And on the other side, other cars passed by. The people were friendly. Somebody was acquainted to us, he also came with us, acquaintances were with us and they told that two other persons will also come along with us. Like, you were making plans for a carnival party. We were supposed to go. I’m not sure, maybe someone else was also lying across the bed, I don’t know who exactly it was. I went in (to the room), I thought I was going to fetch somebody, and then I saw someone lying there. First I thought it was me, but then it wasn’t me. I though the one who was lying across the bed was offended because of something. It was a small room. Emotionally neutral
17Whole body jerk, small movements of the head and limbs. No emotional expressionThere was a storm, the window was open and the curtains were blowing in the wind through the window. I didn’t do anything. Emotionally neutral

In the remaining awakenings with dream recall (= 8), no movements were observed during preceding REM sleep. There was no significant difference in the presence of movements when stratified for whether or not dream recall was present.

Judge performance

The mean agreement percentage between all judges was 59.6% (±0.87), and between individual judge pairs the inter-rater reliability varied from 47% to 77%. All judges performed above expected chance levels, and mean matching accuracy rate was 39.5% (±7.4%, range 29.0–53.0%), which differed significantly from what could be expected by chance (t(6) = 5.2, < 0.01). There was great variability in judges’ performance concerning individual video-dream pairs, and matching rates differed significantly from the expected 25% accuracy (t(16) = 2.3, < 0.05). Although the mean matching rate accuracy was 39.5%, one video-dream pair was matched with 100% accuracy by all judges, and three others with 85%, 71% and 57% accuracy levels, respectively. In contrast, one video-dream pair was not matched correctly by any judge, three cases were matched well below chance level (14%), five slightly above (29%) and four moderately above chance level (43%). Of note, despite the presence of positive emotions in four dream reports (Table 2), the four most accurately matched dream-video pairs were the ones with negative dream emotions.

Further, overall judge performance varied considerably concerning individual patients. This seeming difference was not statistically significant. However, as the patients contributed uneven number of video-dream pairs to analysis (ranging from 1 to 5, see Fig. 1), the individual characteristics of the person contributing the data might show a statistical effect on matching accuracy in a larger sample.

image

Figure 1.  Judges’ performance accuracy with data from individual patients varied, but did not reach statistical significance, due possibly to unevenly distributed and small patient sample.

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Discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Declarations of interest
  8. Acknowledgements
  9. References
  10. Supporting Information

The main aim of the present pilot study was to address the question whether a content-related connection can be established by blind judges between actual RBD behaviours and reported dream content when both are systematically sampled in controlled conditions. We demonstrated that dream content can be linked to motor behaviours above chance level. However, while all judges performed above expected chance level, they did not perform particularly well. Nevertheless, the accuracy of matching the correct dream report to behaviours observed in the video was statistically significant compared to chance level. The clarity of dream reports produced by the patient, the emotional tone of the dream and the special nature of movements displayed on the video affected matching accuracy. Based on our data, in case of clear, coordinated and seemingly purposeful behaviour and a well-recalled dream the hypothesis of dream content–behavioural isomorphism can be confirmed. Ongoing dream mentation, however, also occurred during background jerking.

Of note, our findings also indicate that dreaming in RBD may occur without behavioural manifestation, and that REM-related movements in RBD may occur without recalled dream imagery. Indeed, in only approximately half of all REM sleep awakenings, patients had both dream recall and REM-related movements, while during other REM awakenings patients either reported dreams but expressed no movements, or vice versa. In addition, dream recall also varied between our participants, some providing a dream report from almost every awakening, whereas one failed to recall dreams on most awakenings. In general, in Parkinson’s disease, frequency of dream recall is compatible with normative data for the elderly, and varies in relation to cognitive functioning and language comprehension, but not in relation to age, illness duration and dose of levodopa (Cipolli et al., 1992). Our findings are, nevertheless, mainly in accordance with the findings of Santamaria et al. (2004), who reported that dream recall increases with the intensity of the movements, although in our small sample this did not reach significance.

Interestingly, RBD patients often indicate that their dream content has changed alongside the development of RBD (Boeve et al., 1998; Comella et al., 1998; Fantini et al., 2005; Schenck et al., 1993; Sharf et al., 1978), and even their dream recall seems to be increased compared to healthy controls (Fantini et al., 2005). According to Fantini et al. (2005), dream content does not differ between patients with idiopathic RBD and symptomatic RBD, but as the patients with symptomatic RBD were on dopaminergic treatment, the effects of medication cannot be ruled out. In Parkinson’s disease (which so often coincides with RBD), altered dream content was described before RBD was officially identified (Nausieda et al., 1984; Sharf et al., 1978). We do not know, however, whether in the reported cases altered dream content reflects changes in dream content due to Parkinson’s disease or its dopaminergic treatment or represents RBD specific alterations, as no information on dream enactment is given in the papers published before 1986 (Nausieda et al., 1984; Sharf et al., 1978). Dreams of patients with early Parkinson’s disease contain significantly more physical aggression and animal-related features than those of healthy controls, and dopaminergic doses and depressive symptoms did not affect these results (Bugalho and Paiva, 2011). Thus, Parkinson’s disease itself may relate to altered dreams, irrespective of RBD.

Apart from characteristic violent or scenic behaviours with negative emotional content, two recent papers have reported specifically non-violent behaviours, including positive emotional content such as laughing in RBD (Oudiette et al., 2009; Siclari et al., 2011). Interestingly, despite the presence of positive emotions in four dream reports in our sample, only one such dream was matched to behaviour above chance level, and the most accurately matched dream-video pairs were all related to negatively toned dream emotions. Whether scenic behaviours coinciding with positive emotional content are less probable than violent behaviours with negative dream mentation remains to be determined in further studies with larger patient samples.

A major strength of the present study is that we performed systematic REM sleep awakenings, assessed dream recall and content in detail, and recorded simultaneously any behaviours with an infrared camera. Instead of basing our conclusions on anecdotal evidence or single cases of videotaped dream enactment behaviours, we sampled REM dreaming and movements systematically in a controlled setting. This design allowed us to use blind judges to match behavioural data to phenomenal dream content, a design never utilized previously. With regard to limitations, our patient sample was small, and more than half of the patients who were screened could not be included. Further, our sample was biased, in the sense that some participants contributed more data to the analyses than others. This is paradigmatic to dream studies. In addition, it was very difficult, even with patients who reported frequent nocturnal behaviours at home, to capture elaborate behavioural episodes on video. Indeed, even in severe RBD scenic or violent manifestations present the tip of the iceberg (Frauscher et al., 2007), while simple minor or major motor activity is frequent. In order to counterbalance this challenge and to obtain not only movements, but behavioural episodes, the number of patients has to be increased. Therefore, the present study can only be considered to be a pilot study. All our patients were also diagnosed with Parkinsonism, and—although cognitively preserved—were on anti-Parkinsonian medication, which might also have influenced RBD manifestation and dream recall and content.

In summary, our data showed that in RBD the experienced dream content can be linked to actual motor behaviours above chance level by external blind judges. Matching accuracy was affected mainly by the clarity of dream reports and the specific nature of movements displayed on the video. In future studies, systematic online sampling of extreme eye movement sleep-related behaviours with regard to dream content should be performed in larger series of RBD patients to explore the link between behaviours and dream content.

Declarations of interest

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Declarations of interest
  8. Acknowledgements
  9. References
  10. Supporting Information

None of the authors have either personal or financial disclosures in the subject matter of the paper, nor are they involved with organizations with financial interest in the subject matter of the paper.

Acknowledgements

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Declarations of interest
  8. Acknowledgements
  9. References
  10. Supporting Information

We thank Heinz Hackner for the always excellent technical realization of video-polysomnographies, and our patients for participation. Dr Valli was financed by the Graduate School of Psychology, and the Academy of Finland (project no. 8124623), and received a grant for working abroad from the Helsingin Sanomat 100th Anniversary Foundation. The project was supported by Grant 9223 of the National Bank of Austria to Birgit Högl.

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Declarations of interest
  8. Acknowledgements
  9. References
  10. Supporting Information
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Supporting Information

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Declarations of interest
  8. Acknowledgements
  9. References
  10. Supporting Information

Data S1. Examples of video dream report combinations.

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JSR_938_sm_Supplementarymaterial.doc26KSupporting info item

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