MAZZA Stephanie

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The involvement of sleep in cognitive functioning is well known, but only a few studies have examined objective sleep parameters in children with high intellectual potential (HP). The main objective of this study was to compare sleep characteristics of 33 children with high intellectual potentialities (HP) (median 10 years old, 64% of boys) compared to 25 controls (median 11 years old, 64% of boys) and assess the difference between children with a homogeneous vs. a heterogeneous intelligence quotient (IQ) (i.e., a difference ≥15 points between verbal and non-verbal IQ). All children underwent a one-night polysomnography, an evaluation of intellectual quotient (IQ) and filled standardized questionnaires. Using non-parametric tests to compare groups' characteristics, we found that children with HP had more heterogeneous IQ, more rapid eyes movement (REM) sleep and tended to have less stage 1 sleep than controls. They also had more insomnia and sleep complaints. The high amount of REM sleep in children with HP could be advantageous for learning and could partially explain their gift. This study highlights the necessity of investigating sleep disorders in children with HP during clinical routine and reinforces the hypothesis of the involvement of nocturnal sleep, and especially REM sleep, in daytime cognition and behavior.

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How sleep affects memory in older adults is a critical topic, since age significantly impacts both sleep and memory. For declarative memory, previous research reports contradictory results, with some studies showing sleep-dependent memory consolidation and some other not. We hypothesize that this discrepancy may be due to the use of recall as the memory measure, a demanding task for older adults. The present paper focuses on the effect of sleep on relearning, a measure that proved useful to reveal subtle, implicit memory effects. Previous research in young adults showed that sleeping after learning was more beneficial to relearning the same Swahili-French word pairs 12 hours later, compared with the same interval spent awake. In particular, those words that could not be recalled were relearned faster when participants previously slept. The effect of sleep was also beneficial for retention after a one-week and a 6-month delay. The present study used the same experimental design in older adults aged 71 on average but showed no significant effect of sleep on consolidation, on relearning, or on long-term retention. Thus, even when using relearning speed as the memory measure, the consolidating effect of sleep in older adults was not demonstrated, in alignment with some previous findings.

Chronic pain patients often complain of their "poor memory" and numerous studies objectively confirmed such difficulties in reporting working memory (WM) and long-term memory (LTM) dysfunctions. This paper provides a comprehensive review of the literature on memory impairment in chronic pain (CP) patients. Twenty-four observational studies evaluating WM or/and LTM in a chronic pain group and a control group were included in this review. Results showed that studies consistently reported a moderate decline, in both WM and LTM performances in CP patients. Even if CP patients complained about forgetfulness, objective measurements did not permit to conclude to a long-term storage impairment. CP patients exhibited more specifically encoding or retrieving difficulties compared to controls. Results showed that chronic pain selectively impacted the most attention-demanding memory processes, such as working memory and recollection in long-term memory. Results also demonstrated that CP patients exhibited a memory bias directed towards painful events compared to control subjects. Several authors have suggested that CP could be a maladaptive consequence of memory mechanisms. The long-lasting presence of pain continuously reinforces aversive emotional associations with incidental events. The inability to extinguish this painful memory trace could explain the chronic persistence of pain even when the original injury has disappeared. A major concern is the need to extricate pain-related cognitive effects from those resulting from all the co-morbidities associated with CP which both have a deleterious effect on cognitive function.

Numerous studies have explored the effect of sleep on memory. It is well known that a period of sleep, compared to a similar period of wakefulness, protects memories from interference, improves performance, and might also reorganize memory traces in a way that encourages creativity and rule extraction. It is assumed that these benefits come from the reactivation of brain networks, mainly involving the hippocampal structure, as well as from their synchronization with neocortical networks during sleep, thereby underpinning sleep-dependent memory consolidation and reorganization. However, this memory reorganization is difficult to explain within classical memory models. The present paper aims to describe whether the influence of sleep on memory could be explained using a multiple trace memory model that is consistent with the concept of embodied cognition: the Act–In (activation–integration) memory model. We propose an original approach to the results observed in sleep research on the basis of two simple mechanisms, namely activation and integration.

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Sleep plays a major role in the learning consolidation process. Subjects' performance in memory test retrieval is better when the learning and retrieval phases are separated by a period of sleep rather than by a period of wakefulness. The effects of sleep on these consolidation processes have been extensively studied in adults, notably with the help of specific sleep deprivation protocols. However, the use of these sleep deprivation protocols in children is not possible for ethical reasons. Our current knowledge of the effects of sleep on sleep-dependent learning consolidation processes is therefore very limited in children. Sleep disorders affect a significant proportion of children and have important daytime repercussions, particularly at the academic level. Surprisingly, although the majority of children with sleep disorders fail at school, the impact of these sleep disorders on the consolidation of sleep-dependent learning processes has very rarely been evaluated. The objective of this thesis project was therefore to evaluate the impact of sleep disorders on these consolidation processes. To achieve this goal, we selected 3 pathologies with specific sleep impairments: narcolepsy, obstructive sleep apnea syndrome (OSA) and benign centrotemporal spike epilepsy (BCSE). We subjected these groups of children and a group of age- and sex-matched control children to memory consolidation tests in which the learning phase was performed at night before bedtime and the retrieval phase in the morning after the post-learning night. In order to have the most complete vision possible of the impact of sleep disorders on learning consolidation processes, these memory consolidation tests involved declarative (verbal, visuo-spatial and emotional tasks) and non-declarative (procedural task) learning. We also measured the children's attentional abilities before learning and before retrieving the memory consolidation tests. Our results suggest that narcolepsy, OSA and PTSD would have a negative impact on the consolidation processes of sleep-dependent visual-spatial learning. On the other hand, these 3 pathologies do not seem to have an influence on these processes in the context of verbal, emotional and procedural learning. These results therefore suggest that aspects concerning the nocturnal consolidation of learning should be integrated into the neuropsychological evaluations that are taken into account in the diagnosis of children with these pathologies. Moreover, the pedagogical and reeducational follow-up of these children should be reconsidered.

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Objective To study the sleep characteristics of HP children and to analyze the responses to questionnaires according to their cognitive profile. Methods Retrospective multicenter study. Thirty HPI children . age 10.7 ± 2.3 years . 20 boys . were seen in consultation in the department of child and adolescent psychopathology of the neurological hospital and in the pediatric sleep unit of the hospital Femme-Mere-Enfant. The control children . n = 28 . age 10.2 ± 2.3 years . 17 boys . were obtained in collaboration with the cognitive science laboratory of the University of Lyon 2. All the children benefited from an ambulatory polysomnographic recording and answered standardized questionnaires. Results Compared to control children, HPI children had significantly less L1 (10.1% vs 11.9%, p = 0.041) and more MS (22.6% vs 18.4%, p = 0.003). The percentage of SP was positively correlated with almost all WISC indices (except IVT). Questionnaire analysis showed a significant difference between HP children and controls for severity of insomnia, hyperactivity and anxiety. Those with a heterogeneous cognitive profile (ICV-IRP ≥ 15) have higher scores for insomnia severity ( p = 0.016), hyperactivity ( p = 0.037) and anxiety disorders ( p = 0.046). Conclusion The percentage of REM sleep is related to intellectual efficiency. The HP children with a heterogeneous profile complain more of insomnia and have more anxiety and depressive disorders.

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In young adults, sleeping after learning has been shown to facilitate relearning and long-term retention, compared to staying awake (Mazza et al., in revision). Children (aged 8) and elderly people (aged 71) learned Swahili-French word pairs to criterion during a learning session taking place in the morning or evening (Wake and Sleep group, respectively). Participants spent 12 hours filled with wakefulness or a night of sleep, then performed a relearning session to criterion either in the evening (Wake) or the following morning (Sleep). One week later, retention was tested. Sleep appeared to affect memory differently according to age. The groups of children did not differ during the relearning session whereas the Sleep outperformed the Wake group after one week. In elderly participants, no effect of sleep was observed. Thus, the enhancing effect of sleep is most pronounced in adults, moderate in children, and weak in elderly people.

Objective The saying "practice makes perfect" illustrates that learning is enhanced by practice. When a material is learned repeatedly, each learning session is easier than the last, indicating an economy in relearning. Given the beneficial effect of sleep on memory consolidation, we wondered whether a night's sleep would promote this economy of learning by reducing the number of revisions required to acquire a set of verbal items. Methods Two groups of 20 young adults performed initial learning and then relearning of 16 words from the Swahili language and their translation into French. The number of learning trials required to recall the 16 words without error was measured. The two sessions were spaced 12 hours apart. One group did the learning session at 9:00 am and the re-learning session at 9:00 pm (Awakening group), the other learned at 9:00 pm and re-learned at 9:00 am after a night of sleep (Sleep group). Word retention was also measured one week later. Results The number of trials required to learn the 16 pairs was equivalent in the 2 groups (5.6 ± 1.9 vs. 5.2 ± 1.5 for the Sleep and Wake groups, respectively). When relearning 12 h later, participants who had slept started the test with better performance (10.3 words ± 2.6 vs. 7.4 words ± 3.1 . p p p p Conclusion Sleep thus allows for savings during relearning, while ensuring more effective long-term maintenance. Thus, interspersing a night of sleep between review sessions would allow for less review and longer retention.

While nociceptive cortical activation is now well characterized in humans, understanding of the nociceptive thalamus remains largely fragmentary. We used laser stimuli and intracerebral electrodes in 17 human subjects to record nociceptive-specific field responses in 4 human thalamic nuclei and a number of cortical areas. Three nuclei known to receive spinothalamic (STT) projections in primates (ventro-postero-lateral [VPL], anterior pulvinar [PuA], and central lateral [CL]) exhibited responses with similar latency, indicating their parallel activation by nociceptive afferents. Phase coherence analysis, however, revealed major differences in their functional connectivity: while VPL and PuA drove a limited set of cortical targets, CL activities were synchronized with a large network including temporal, parietal, and frontal areas. Our data suggest that STT afferents reach simultaneously a set of lateral and medial thalamic regions unconstrained by traditional nuclear borders. The broad pattern of associated cortical networks suggests that a single nociceptive volley is able to trigger the sensory, cognitive, and emotional activities that underlie the complex pain experience. The medial pulvinar, an associative nucleus devoid of STT input, exhibited delayed responses suggesting its dependence on descending cortico-thalamic projections. Its widespread cortical connectivity suggests a role in synchronizing parietal, temporal, and frontal activities, hence contributing to the access of noxious input to conscious awareness.

Humans are expert at recognizing facial features whether they are variable (emotions) or unchangeable (gender). Because of its huge communicative value, pain might be detected faster in faces than unchangeable features. Based on this assumption, we aimed to find a presentation time that enables subliminal discrimination of pain facial expression without permitting gender discrimination. For 80 individuals, we compared the time needed (50, 100, 150, or 200 milliseconds) to discriminate masked static pain faces among anger and neutral faces with the time needed to discriminate male from female faces. Whether these discriminations were associated with conscious reportability was tested with confidence measures on 40 other individuals. The results showed that, at 100 milliseconds, 75% of participants discriminated pain above chance level, whereas only 20% of participants discriminated the gender. Moreover, this pain discrimination appeared to be subliminal. This priority of pain over gender might exist because, even if pain faces are complex stimuli encoding both the sensory and the affective component of pain, they signal a danger. This supports the evolution theory relating to the necessity of quickly reading aversive emotions to ensure survival but might also be at the basis of altruistic behavior such as help and compassion.

Key points. Sleep spindle are usually considered to play a major role in inhibiting sensory inputs. Using nociceptive stimuli in humans, we tested the effect of spindles on behavioural, autonomic and cortical responses in two experiments using surface and intracerebral electroencephalographic recordings. We found that sleep spindles do not prevent arousal reactions to nociceptive stimuli and that autonomic reactivity to nociceptive inputs is not modulated by spindle activity. Moreover, neither the surface sensory, nor the insular evoked responses were modulated by the spindle, as detected at the surface or within the thalamus. The present study comprises the first investigation of the effect of spindles on nociceptive information processing and the results obtained challenge the classical inhibitory effect of spindles. . . Abstract. Responsiveness to environmental stimuli declines during sleep, and sleep spindles are often considered to play a major role in inhibiting sensory inputs. In the present study, we tested the effect of spindles on behavioural, autonomic and cortical responses to pain, in two experiments assessing surface and intracerebral responses to thermo-nociceptive laser stimuli during the all-night N2 sleep stage. The percentage of arousals remained unchanged as a result of the presence of spindles. Neither cortical nociceptive responses, nor autonomic cardiovascular reactivity were depressed when elicited within a spindle. These results could be replicated in human intracerebral recordings, where sleep spindle activity in the posterior thalamus failed to depress the thalamocortical nociceptive transmission, as measured by sensory responses within the posterior insula. Hence, the assumed inhibitory effect of spindles on sensory inputs may not apply to the nociceptive system, possibly as a result of the specificity of spinothalamic pathways and the crucial role of nociceptive information for homeostasis. Intriguingly, a late scalp response commonly considered to reflect high-order stimulus processing (the ‘P3’ potential) was significantly enhanced during spindling, suggesting a possible spindle-driven facilitation, rather than attenuation, of cortical nociception.

Numerous studies have looked at the influence of sleep on memory. A period of sleep compared to a period of wakefulness reduces forgetfulness, improves performance but also reorganizes memory traces, thus favoring creativity and rule extraction. These studies are based on classical models of memory and explain these observations by an interaction between implicit and explicit processes during sleep. However, classical models of memory seem limited to describe the totality of the processes of reorganization of memory traces observed after a period of sleep. In this thesis, we have tried to understand the influence of sleep on the reorganization of traces through the Act-In model, a model of memory with multiple traces in the line of embodied cognition.We have developed our research around four experimental axes. First, we wanted to verify if a period of sleep allows us to passively transform an implicit trace into an explicit one. We then wanted to study the effect of sleep on the processes of multi-component integration and inter-trace activation. According to us, sleep would allow to reinforce the integration of components within a trace and it would also allow to promote the linking of several traces, leading to the emergence of common elements. Finally, in the last axis of this research work, we were interested in the consequences of age-related nocturnal modifications on memory consolidation during sleep.

Despite sleep-induced drastic decrease of self-awareness, human sleep allows some cognitive processing of external stimuli. Here we report the fortuitous observation in a patient who, while being recorded with intra-cerebral electrodes, was able, during paradoxical sleep, to reproduce a motor behaviour previously performed at wake to consciously indicate her perception of nociceptive stimulation. Noxious stimuli induced behavioural responses only if they reached the cortex during periods when mid-frontal networks (pre-SMA, pre-motor cortex) were pre-activated. Sensory responses in the opercular cortex and insula were identical whether the noxious stimulus was to evoke or not a motor behaviour. conversely, the responses in mid-anterior cingulate were specifically enhanced for stimuli yielding motor responses. Neuronal networks implicated in the voluntary preparation of movements may be reactivated during paradoxical sleep, but only if behavioural-relevant stimuli reach the cortex during specific periods of "motor awareness". These local activation appeared without any global sleep stage change. This observation opens the way to further studies on the currently unknown capacity of the sleeping brain to interact meaningfully with its environment.

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Excessive daytime sleepiness is the main complaint of patients with sleep apnea syndrome. Therefore, daytime vigilance is the attentional component most often investigated during this pathology. The objective of this work was to highlight the extent of attentional deficits in apneic patients, in order to understand if only sleepiness could explain the cognitive impairment of these patients. Our results showed that all the attentional functions were deficient, vigilance, but also selective and divided attention as well as the executive control of attention could be altered in a specific and isolated way. Our research conducted in a real driving situation also showed that these patients had a marked increase in their reaction times while driving and that these performances were correlated with those of a divided attention test carried out in the laboratory. Taken together, these results indicate that apneic patients have multiple attentional deficits not only involving daytime vigilance.