Evidence for the Re-Enactment of a Recently Learned Behavior during Sleepwalking

Animal studies have shown that sequenced patterns of neuronal activity may be replayed during sleep. However, the existence of such replay in humans has not yet been directly demonstrated. Here we studied patients who exhibit overt behaviors during sleep to test whether sequences of movements trained during the day may be spontaneously reenacted by the patients during sleep

Le trouble comportemental en sommeil paradoxa (un modèle d étude de l activité motrice, onirique et cognitive en sommeil paradoxal)

Le trouble comportemental en sommeil paradoxal (TCSP) se caractérise par des comportements anormaux en sommeil paradoxal, correspondant à l extériorisation de rêves. Nous avons utilisé le TCSP comme un modèle original pour étudier l activité onirique, cognitive et motrice au cours du sommeil paradoxal. En parallèle, nous avons étudié le somnambulisme qui se manifeste par des comportements anormaux en sommeil lent profond. Notre travail a révélé que les TCSP ne se limitaient pas à des comportements violents et primitifs mais englobaient également des comportements élaborés, appris et culturels. Puis, nous avons montré que les mouvements oculaires rapides en sommeil paradoxal n étaient pas la conséquence d une activation aléatoire de leur générateur mais étaient au contraire codés dans la direction de la scène onirique. Notre troisième étude a suggéré que le somnambulisme, comme le TCSP, pouvait correspondre à des rêves agis. En outre, nous avons observé une somnambule ré-exécuter, en dormant, une séquence gestuelle apprise la veille. Nos principaux résultats nous font penser que les rêves en sommeil paradoxal constituent un simulateur du monde réel : un système complexe nous ferait à la fois voir et entendre des scénarios et faire des mouvements du corps et des yeux correspondant grossièrement à ces scénarios. Ce simulateur ne serait toutefois qu une reproduction imparfaite et ébauchée du monde réel. Il pourrait servir à la simulation de menaces primitives, à la consolidation mnésique ou à un remaniement créatif de nos expériences d éveil.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Behavioral and brain responses to verbal stimuli reveal transient periods of cognitive integration of external world during sleep

Behavioral and brain responses to verbal stimuli reveal transient periods of cognitive integration of external world during sleep by Başak Türker, Esteban Munoz Musat, Emma Chabani et al

Memory loss at sleep onset

Every night, we pass through a transitory zone at the borderland between wakefulness and sleep, named the first stage of nonrapid eye movement sleep (N1). N1 sleep is associated with increased hippocampal activity and dream-like experiences that incorporate recent wake materials, suggesting that it may be associated with memory processing. Here, we investigated the specific contribution of N1 sleep in the processing of memory traces. Participants were asked to learn the precise locations of 48 objects on a grid and were then tested on their memory for these items before and after a 30-min rest during which participants either stayed fully awake or transitioned toward N1 or deeper (N2) sleep. We showed that memory recall was lower (10% forgetting) after a resting period, including only N1 sleep compared to N2 sleep. Furthermore, the ratio of alpha/theta power (an electroencephalography marker of the transition toward sleep) correlated negatively with the forgetting rate when taking into account all sleepers (N1 and N2 groups combined), suggesting a physiological index for memory loss that transcends sleep stages. Our findings suggest that interrupting sleep onset at N1 may alter sleep-dependent memory consolidation and promote forgetting.</p

Embracing sleep onset complexity

Sleep is crucial for many vital functions and is extensively studied. In contrast, the sleep onset period, often portrayed as a mere prelude to sleep, has been largely overlooked and remains poorly characterised. However, a recent series of studies has reignited interest in this transitional period, shedding light on its neural mechanisms, cognitive dynamics, and clinical implications. This review synthesises the existing knowledge on the sleep onset period in humans. We first examine the current definition of the sleep onset period and its limits, considering the dynamic and complex electrophysiological changes that accompany the descent to sleep. We then describe how internal and external processing interplay during the wake-to-sleep transition. Finally, we discuss the putative cognitive benefits of the sleep onset period, its scientific value, and identify novel directions to better diagnose sleep onset disorders

Neuro-computational account of how mood fluctuations arise and affect decision making

The influence of mood on choices is a well-established but poorly understood phenomenon. Here, we suggest a three-fold neuro-computational account: (1) the integration of positive and negative events over time induce mood fluctuations, (2) which are underpinned by variations in the baseline activities of critical brain valuation regions, (3) which in turn modulate the relative weights assigned to key dimensions of choice options. We validate this model in healthy participants, using feedback in a quiz task to induce mood fluctuations, and a choice task (accepting vs. declining a motor challenge) to reveal their effects. Using fMRI, we demonstrate the pivotal role of the ventromedial prefrontal cortex and anterior insula, in which baseline activities respectively increase and decrease with theoretical mood level and respectively enhance the weighting of potential gains and losses during decision making. The same mechanisms might explain how decisions are biased in mood disorders at longer timescales

A Pavlovian account for paradoxical effects of motivation on controlling response vigour

International audienceIn high stakes situations, people sometimes choke under pressure, performing below their abilities. Here, we suggest a novel mechanism to account for this paradoxical effect of motivation: the automatic adjustment of action vigour to potential reward. Although adaptive on average, this mechanism may impede fine motor control. Such detrimental effect was observed in three studies (n = 74 in total), using behavioural tasks where payoff depended on the precision of handgrip squeezing or golf putting. Participants produced more force for higher incentives, which aggravated their systematic overshooting of low-force targets. This reward bias was specific to action vigour, as reward did not alter action timing, direction or variability across trials. Although participants could report their reward bias, they somehow failed to limit their produced force. Such an automatic link between incentive and force level might correspond to a Pavlovian response that is counterproductive when action vigour is not instrumental for maximizing reward