Giovanni Tuozzi

Emotional evaluation with and without conscious stimulus identification: evidence from a split-brain patient

Abstract The present study addresses two main aspects of emotional behaviour. The first concerns the role of conscious identification of the stimulus in producing emotional activity, and the second, a possible hemispheric specialisation for an emotional response. These two issues were addressed by studying the cognitive and physiological emotional activity of a split-brain patient under subliminal and above threshold presentation of emotional and nonemotional stimuli. The results show that the brain has a specific mechanism for distinguishing emotional from neutral situations prior to activating the autonomic nervous system, and that evaluation of the affective significance of the stimuli may occur at different levels not necessarily represented in consciousness. Moreover, the results on the split-brain patient seem to be in accordance with evidence that shows that the relationship between right hemisphere damage and disorders of emotional behaviour lies more at the autonomic arousal level, intimately lin...

STORY-LIKE ORGANIZATION OF DREAM EXPERIENCE IN DIFFERENT PERIODS OF REM SLEEP

Four dream reports, collected from each of 16 subjects in an experimental night, were analysed using the criteria of Mandler and Johnsons story grammar. The experimental night was the first of the four nights where subjects had spontaneously given a dream report after each of the four awakenings planned in REM sleep. A multivariate analysis of covariance, taking the order of the nights where the experimental night occurred and the order of reports as factors, the number of stories per report as covariate and the number of statements in the setting, the number of statements in the event structure and number of episodes per story as dependent variables, showed that the greater length and complexity of reports collected in the second half of the night depends on a greater effectiveness of the dream production system rather than on a greater accuracy of recall. This increase concerns the organization of individual stories rather than the number of stories developed in a given time. These findings raise the issue of how dream production is re‐triggered during REM sleep. To cast light on this issue, it seems important to establish whether and how the themes of the various stories developed in a given dream experience are interrelated.

Autonomic Reactivity during Viewing of an Unpleasant Film

The effect of an aversive, high-arousing film on heart rate, respiratory sinus arrhythmia, and electrogastrographic activity (EGG) was investigated. Previous studies have indicated a larger heart-rate deceleration for visual stimuli depicting surgery or blood compared to neutral content, and this phenomenon is similar to the bradycardia observed in animals in response to fear. The heart-rate deceleration is clearly parasympathetically driven, and it is considered a general index of attention. An accurate index of cardiac vagal tone can be obtained by means of quantification of the amplitude of respiratory sinus arrhythmia. The relationship between cardiac vagal tone and EGG is complex, but animal research has shown that suppressing vagal activity dampens gastric motility. We have investigated whether a movie depicting surgery is associated with greater heart-rate deceleration, larger increase in respiratory sinus arrhythmia, and greater increase in EGG activity compared to a neutral movie. In addition, if both respiratory sinus arrhythmia and EGG are indices of vagal tone, a positive correlation between these physiological responses was expected. Analysis indicated an effect of the surgery movie on heart rate and respiratory sinus arrhythmia, but not on EGG activity. Moreover, the expected correlation was not found. Implications for future studies are discussed.

Active processing of declarative knowledge during REM-sleep dreaming

The ability to process recently acquired knowledge is clearly maintained during sleep. Here we assess whether and how far the sleeper controls this processing (in a non‐volitional and non‐conscious manner). We posit that during sleep, the cognitive concerns of previous waking may guide access to, and processing of, items of declarative knowledge with which those concerns are associated. In a delayed recall task, before each of three sleep onsets in the same night, 12 subjects heard a different nonsense sentence. When awakened in rapid eye movement (REM) sleep, they were asked to report their dream experience and to recall the last sentence heard. Occurrences of incorporation into dream content were more frequent for this sentence than for the sentences heard before previous sleep onsets, and also more frequent than occurrences of similar contents in reports from a control night. However, the modalities of elaboration of dream contents did not vary. These findings indicate that cognitive concern can affect the accessing of recently acquired declarative knowledge during sleep, but not the modalities by which this is inserted into dream content. They also suggest that cognitive concern may help consolidate knowledge by increasing the likelihood of it being processed during sleep.

Incorporation of presleep stimuli into dream contents: evidence for a consolidation effect on declarative knowledge during REM sleep?

Presleep stimuli to be retained for further recall is often incorporated into dream contents. To establish whether processing for insertion into dream contents may improve consolidation, we compared the retention rate at delayed recall of contents resulting from incorporation of presleep sentence‐stimuli with those of other contents of the same dream experiences. We hypothesized that association with a cognitive task of recall facilitates access to recently acquired items of declarative knowledge such as presleep stimuli, and triggers the deep elaboration of their semantic features, which involves rehearsal. Twelve subjects were given a task of delayed recall for three nonsense sentences delivered once a time before each of the sleep (re‐)onsets over an experimental night. After each awakening in rapid eye movement sleep, subjects were asked to report dream experience and recall the sentence to be retained. In the morning, after spontaneous awakening, subjects were unexpectedly requested to again report their dream experiences and to recall the stimuli. Two pairs of judges independently identified possible incorporations of the stimuli, and parsed dream reports into propositional content units. The proportion of night reports with at least one incorporation of the stimulus delivered (i.e. valid incorporations) was higher than that of reports with contents similar to a stimulus(‐i) not yet delivered (forward pseudo‐incorporations) or delivered prior to an earlier sleep period (backward pseudo‐incorporations). The proportion of content units common to night and morning reports (considered to be better consolidated) was significantly higher for incorporated contents than for other contents, including pseudo‐incorporated contents. Instead, the retention at morning recall of words of sentence‐stimuli corresponding to incorporated contents was not significantly higher than that of other words. The better retention of incorporated contents provides a partial confirmation (that is, limited to the output of the processing) that a generation effect, which benefits retention of actively processed information, is operative during sleep as well as in waking.

Story-like organization of REM-dreams in patients with narcolepsy–cataplexy

Narcolepsy with cataplexy (NC) is a neurological disorder characterized by excessive daytime sleepiness and an altered architecture of sleep. Previous laboratory studies have shown that frightening, bizarre and visually vivid contents are more frequent in dream experiences developed during the first period of REM sleep by NC patients than healthy subjects. As the structural organization of dream experiences of NC patients has not been yet examined, we compared its indicators in dream reports collected from a sample of NC patients and their matched controls. During an experimental night two awakenings were provoked after 8min of REM sleep in the first and third sleep cycle. Dream reports were analyzed using the rules of story grammars, capable of identifying units larger than single contents and describing their story-like organization. While dream recall (about 85%) was comparable in NC patients and controls, 1st-REM dream reports were longer in NC patients. Statistical analyses on the 12 NC patients and their matched controls who reported dreams after both REM periods showed that dream experiences occurring in 1st-REM reports of NC patients were longer and had a more complex organization than those of controls. These findings suggest that the cognitive processes underlying dream generation reach their optimal functioning earlier in the night in NC patients than in normal subjects.

Sleep and time course of consolidation of visual discrimination skills in patients with narcolepsy–cataplexy

The level of procedural skills improves in normal individuals when the acquisition is followed by a period of sleep rather than wake. If sleep plays an important role in the consolidation process the advantage it provides should be reduced or delayed when its organization is altered, as in patients with chronic sleep disorders. To test this prediction in patients with narcolepsy–cataplexy (NC), who usually have a more fragmented organization of sleep than normals, we compared the initial, intermediate and delayed level of consolidation of visual skills. Twenty‐two drug‐naive NC patients and 22 individually‐matched controls underwent training at a texture discrimination task (TDT) and were re‐tested on the next morning (after a night spent in laboratory with polysomnography) and after another six nights (spent at home). TDT performance was worse in patients than controls at training and at both retrieval sessions and the time course of consolidation was different in NC patients (who improved mainly from next‐day to 7th‐day retrieval session) compared with controls. Moreover, the less‐improving patients at next‐day retrieval had a wider disorganization of sleep, probably because of an episode of rapid eye movement (REM) sleep at sleep onset REM, on post‐training night more frequently than more‐improving patients. These findings suggest that the time course of the consolidation process of procedural skills may be widely influenced by the characteristics of sleep organization (varying night‐by‐night much more in NC patients than controls) during post‐training night.

REM-dreams recall in patients with narcolepsy-cataplexy

An abundant recall of dreams has been observed in clinical studies on patients with narcolepsy-cataplexy (NC), a neurological disorder characterized by an altered sleep architecture. Laboratory studies have shown that dream experiences developed during 1st-rapid eye movement (REM) sleep by NC patients are longer and more complex than those of healthy subjects. To establish whether these features indicate an earlier optimal functioning of the cognitive processes involved in dream generation rather than a more accurate dream recall, we compared the indicators of length and structural organization in reports of REM-dreams collected from 14 NC patients and their matched controls. During an experimental night two awakenings were provoked after 8 min in 1st- and 3rd-REM sleep; participants were asked to report their dream experience (spontaneous report) and then, if possible, further remembered parts of this experience (prompted report). All reports were analyzed using story-grammar rules, which allow us to identify units larger than single contents and describe their story-like organization. While dream recall (about 90%) was comparable in NC patients and controls, 1st-REM spontaneous reports were longer and more complex in NC patients, half of whom also provided prompted reports. After 3rd-REM awakening more than one third of NC patients and controls gave prompted reports, which were fairly comparable in length and complexity with the spontaneous reports. These findings confirm that the cognitive processes underlying dream generation reach their optimal functioning earlier in the night in NC patients than in normal subjects, and raises the question of whether the dream-stories described in spontaneous and prompted reports are part of the same or distinct REM-dreams.

Semantic priming effect during REM-sleep inertia in patients with narcolepsy.

Patients with narcolepsy-cataplexy (NC) present excessive daytime sleepiness (EDS), cataplexy and an altered architecture of nocturnal sleep, with frequent episodes of REM-sleep at sleep onset (SOREM-sleep). This altered organization of nocturnal sleep may be accompanied by some differences in the functioning of the cognitive processes involved in the access, organization and consolidation of information during sleep. This study attempts to ascertain whether the activation of semantic memory during REM-sleep, as measured using a technique of semantic priming (namely, the facilitation of the activation of strongly-related rather than weakly-related and, overall, unrelated pairs of prime-target words) is different in NC patients compared to normal subjects. A lexical decision task (LDT) was carried out twice in wakefulness (at 10a.m. and after a 24h interval) and twice in the period of sleep inertia following awakening from SOREM and 4th-cycle REM-sleep on 12 NC patients and from 1st- and 4th-cycle REM-sleep on 12 matched controls. Reaction time (RT) to target words, taken as a measure of the semantic priming effect, proved to be longer (a) in NC patients than in control subjects; (b) in the period of REM-sleep inertia than in wakefulness; (c) in the first rather than the second session; and (d) for unrelated compared to weakly-related and, overall, strongly-related prime-target pairs. RT in post-REM-sleep sessions was less impaired, compared to waking sessions, and less dependent on the associative strength of prime-target pairs in NC patients than in normal subjects. Finally, RT of NC patients, although longer than that of normal subjects in waking sessions, significantly improved in the second session, as a consequence of either the amount of exercise or the consolidation advantage provided by REM-sleep for the procedural components of the task. The whole picture suggests a greater effectiveness of the activation of semantic memory during (SO)REM-sleep in NC patients rather than in normal subjects, and overall for the organization of new and unexpected relationships (such as those between unrelated pairs) between items of information.

Consolidation effect of the processing of declarative knowledge during human sleep: evidence from long-term retention of interrelated contents of mental sleep experiences

Sleep may partly exert a positive influence on memory through the processing underlying the transformation of items of declarative knowledge into contents of mental sleep experience (MSE). This hypothesis implies that the level of consolidation (and thus, long-term retention) should be enhanced for those items which are repeatedly processed and transformed into identical or very similar (so-called interrelated) contents of distinct MSEs developed over the same night. To test this prediction, we examined accessibility at delayed recall (i.e., the next morning) of the interrelated contents of MSEs reported (immediate recall) by 14 subjects who were awakened during the first four periods of rapid eye-movement (REM) sleep in two experimental nights. Interrelated contents were much more frequent, and at delayed recall much better retained, than other, non-interrelated contents in report pairs of MSEs. Moreover, they were also more frequent and better retained than by-chance similar or identical contents, as estimated in report pairs of MSEs of different subjects. These findings provide partial but coherent evidence in favour of the hypothesis that a generation effect occurs during sleep, with a further consolidation of the input and the output of MSE processing (respectively, the items of declarative knowledge and the contents of MSEs resulting from their elaboration during sleep).