Sleep electroencephalogram (EEG) oscillations and associated memory processing during childhood and early adolescence.

The architecture of sleep undergoes distinct changes during childhood and early adolescence. Slow wave sleep is involved in memory processing and may support active consolidation of newly encoded representations to support the formation of abstracted "gist" memories. Here, we examined sleep and overnight memory formation in German school children (n = 33) between 7 and 15 years of age, after the encoding phase of a verbal Deese-Roediger-McDermott (DRM) task. Effects of age were analyzed on sleep electroencephalogram (EEG) signatures of memory processing during nonrapid eye movement (NonREM) sleep, and the overnight formation of veridical and gist-based memories. Increasing age decreases time spent in slow wave sleep, and slow wave activity, whereas density and amplitude of fast sleep spindles in NonREM sleep were increased. Moreover, fast spindles were more consistently and more closely coupled to the upstate of the slow oscillation in the older children. Also, veridical and gist-based recall of words after sleep increased with age. Notably, a closer slow oscillation upstate-fast spindle coupling predicted veridical recall of words, and this relationship was found independent of age. Memory performance in the sleeping children did not differ from that of an age-matched control group (n = 32) tested over a daytime wake retention interval, with adolescents even showing superior veridical recall after wake. Our findings suggest that slow oscillation-spindle coupling as a mechanism of sleep-dependent memory formation becomes increasingly relevant during childhood and early adolescence. However, wake-associated mechanisms similarly effective in forming medium-term memory exist in this age as well. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

How do children with autism spectrum disorder form gist memory during sleep? A study of slow oscillation-spindle coupling.

Sleep is assumed to support memory through an active systems consolidation process that does not only strengthen newly encoded representations but also facilitates the formation of more abstract gist memories. Studies in humans and rodents indicate a key role of the precise temporal coupling of sleep slow oscillations (SO) and spindles in this process. The present study aimed at bolstering these findings in typically developing (TD) children, and at dissecting particularities in SO-spindle coupling underlying signs of enhanced gist memory formation during sleep found in a foregoing study in children with autism spectrum disorder (ASD) without intellectual impairment. Sleep data from 19 boys with ASD and 20 TD boys (9-12 years) were analyzed. Children performed a picture-recognition task and the Deese-Roediger-McDermott (DRM) task before nocturnal sleep (encoding) and in the next morning (retrieval). Sleep-dependent benefits for visual-recognition memory were comparable between groups but were greater for gist abstraction (recall of DRM critical lure words) in ASD than TD children. Both groups showed a closely comparable SO-spindle coupling, with fast spindle activity nesting in SO-upstates, suggesting that a key mechanism of memory processing during sleep is fully functioning already at childhood. Picture-recognition at retrieval after sleep was positively correlated to frontocortical SO-fast-spindle coupling in TD children, and less in ASD children. Critical lure recall did not correlate with SO-spindle coupling in TD children but showed a negative correlation (r = -.64, p = .003) with parietal SO-fast-spindle coupling in ASD children, suggesting other mechanisms specifically conveying gist abstraction, that may even compete with SO-spindle coupling.

Signs of enhanced formation of gist memory in children with autism spectrum disorder - a study of memory functions of sleep.

BACKGROUND: Autism spectrum disorder (ASD) is characterized by impaired cognitive and social skills, including emotional dysregulation, and symptoms have been suspected to partly arise from impaired formation of memory representations regulating these behaviours. Sleep, which is subjectively impaired in ASD, is critical for forming long-term memories and abstracted gist-based representations. We expected a generally reduced memory benefit from sleep in children with ASD, and a diminished enhancement of gist representations, in particular. METHODS: We compared effects of sleep on memory consolidation between boys (9-12 years) with ASD (n = 21) and typically developing (TD, n = 20) boys, matched for age and IQ, in a within-subjects crossover design. We employed an emotional picture recognition task and the Deese-Roediger-McDermott (DRM) word list task for assessing gist memory formation in the emotional and nonemotional domain, respectively. Learning took place before retention intervals of nocturnal sleep and daytime wakefulness, and retrieval was tested afterwards. RESULTS: Surprisingly, on the DRM task, children with ASD showed an enhanced sleep-dependent formation of gist-based memory (i.e. more recall of 'critical lure words' after sleep compared to wakefulness) than TD children, with this effect occurring on top of a diminished veridical word memory. On the picture recognition task, children with ASD also showed a stronger emotional enhancement in memory (i.e. relatively better memory for negative than neutral pictures) than TD children, with this enhancement occurring independent of sleep. Sleep polysomnography was remarkably comparable between groups. CONCLUSIONS: Children with ASD show well-preserved sleep-dependent memory consolidation. Enhanced gist memory formation in these children might reflect a compensatory response for impairments at earlier stages of memory processing, that is during encoding.

Imagine squeezing a cactus: Cortical activation during affective motor imagery measured by functional near-infrared spectroscopy.

The activation of different brain areas during kinaesthetic and visual motor imagery has been extensively studied, whereas little is known about affective motor imagery, i.e. the imagery of pleasant/unpleasant movements. In the present neuroimaging study we investigated cortical activation of kinaesthetic motor imagery (KMI) based on emotional stimulus content by means of functional near infrared spectroscopy (fNIRS). Twenty healthy adult participants were instructed to imagine affective, and neutral motor tasks while multichannel fNIRS was recorded simultaneously. In the affective MI condition they had to imagine e.g. squeezing a cactus with their right hand several times, eliciting an unpleasant emotion. In the neutral condition their task was to imagine squeezing a ball. Significant differences in oxy-hemoglobin [oxy-Hb] concentration changes during KMI including affective objects in different brain regions were found. Specifically activation in left parietal and frontal regions was increased during the imagery of squeezing a cactus which induced a painful feeling. Both areas are also involved in the perception of pain and commonly labelled as parts of the "pain matrix". Our study provides novel insights in cortical activation patterns during affective motor imagery and its psychological and cognitive mechanisms underlying pain experience.

Towards using fNIRS recordings of mental arithmetic for the detection of residual cognitive activity in patients with disorders of consciousness (DOC).

BACKGROUND: Recently, fNIRS has been proposed as a promising approach for awareness detection, and a possible method to establish basic communication in patients with disorders of consciousness (DOC). AIM: Using fNIRS, the present study evaluated the applicability of auditory presented mental-arithmetic tasks in this respect. METHODS: We investigated the applicability of active attention to serial subtractions for awareness detection in ten healthy controls (HC, 21-32 y/o), by comparing the measured patterns to patterns induced by self-performance of the same task. Furthermore, we examined the suitability of ignoring the given task as additional control signal to implement a two-class brain-computer interface (BCI) paradigm. Finally, we compared our findings in HC with recordings in one DOC patient (78 y/o). RESULTS AND CONCLUSION: Results of the HC revealed no differences between the self-performance and the attention condition, making the attention task suitable for awareness detection. However, there was no general difference between the ignore and attend condition, making the tasks less suitable for BCI control. Despite inconsistent correlations between the patient data and the HC group, single runs of the patient recordings revealed task-synchronous patterns - however, we cannot conclude whether the measured activation derives from instruction based task performance and thus awareness.

Improved concept and first results of an auditory single-switch BCI for the future use in disorders of consciousness patients.

A promising approach to establish basic communication for disorders of consciousness (DOC) patients, is the application of Brain-Computer Interface (BCI) systems, especially the use of single-switch BCIs (ssBCIs). Recently we proposed the concept of a novel auditory ssBCI paradigm and presented first classification results. In this study we report on the evaluation of four different modifications of the original paradigm with the intention to increase the suitability. Therefore we investigated different sound types and the inclusion of additional spatial information. Finally, the classification investigation with the most encouraging modifications shows an enhancement compared to our original paradigm, within healthy subjects, implicating better results for the future use in DOC patients.