Spontaneous Entry into an “Offline” State during Wakefulness: A Mechanism of Memory Consolidation?

Moments of inattention to our surroundings may be essential to optimal cognitive functioning. Here, we investigated the hypothesis that humans spontaneously switch between two opposing attentional states during wakefulness—one in which we attend to the external environment (an “online” state) and one in which we disengage from the sensory environment to focus our attention internally (an “offline” state). We created a data-driven model of this proposed alternation between “online” and “offline” attentional states in humans, on a seconds-level timescale. Participants (n = 34) completed a sustained attention to response task while undergoing simultaneous high-density EEG and pupillometry recording and intermittently reporting on their subjective experience. “Online” and “offline” attentional states were initially defined using a cluster analysis applied to multimodal measures of (1) EEG spectral power, (2) pupil diameter, (3) RT, and (4) self-reported subjective experience. We then developed a classifier that labeled trials as belonging to the online or offline cluster with >95% accuracy, without requiring subjective experience data. This allowed us to classify all 5-sec trials in this manner, despite the fact that subjective experience was probed on only a small minority of trials. We report evidence of statistically discriminable “online” and “offline” states matching the hypothesized characteristics. Furthermore, the offline state strongly predicted memory retention for one of two verbal learning tasks encoded immediately prior. Together, these observations suggest that seconds-timescale alternation between online and offline states is a fundamental feature of wakefulness and that this may serve a memory processing function.

[Soft tissue defects following tumor resection in the limbs and trunk : Plastic reconstructive soft tissue and revision concepts]

BACKGROUND

Tissue defects of the trunk and limbs after oncologic surgery and radiation require plastic reconstructive tissue coverage. Depending on the location and size of the wound as well as the interdisciplinary treatment concept, different reconstructive procedures are performed. These range from skin transplantation to local and pedicle flaps, to perforator flaps and free microsurgical tissue transfer.

METHODS

The modern "reconstructive ladder" can be regarded as an orientation for the sequence of the reconstructive options. Considering the patient's wishes and risk profile, an individual reconstructive concept must be devised. The best functional and simultaneously safest procedure with the smallest secondary defect is to be chosen. Wound preconditioning via vacuum-assisted closure can precede definitive tissue coverage in order to optimize local conditions.

CONCLUSION

Safe tissue coverage can be achieved even in advanced stages of oncologic disease and after extensive surgery by performing wound preconditioning and arteriovenous loop grafting to induce safe de novo recipient vessels for two-stage free tissue transfer. The choice between maximum plastic reconstructive options for a curative approach or limited palliative surgery is to be harmonized and balanced with therapeutic goals and the patient's biologic resources. Preservation and restoration of quality of life and functionality is the plastic surgeon's dictum.

Comparing the Effects of Sleep and Rest on Memory Consolidation

INTRODUCTION

There is ample evidence that overnight sleep and daytime naps benefit memory retention, compared to comparable amounts of active wakefulness. Yet recent evidence also suggests that a period of post-training rest (eg, quiet wakefulness with eyes closed) provides a similar memory benefit compared to wake. However, the relative benefits of sleep vs quiet waking rest on memory remain poorly understood. Here, we assessed the extent to which sleep provides a unique memory benefit, above and beyond that conferred by quiet waking rest.

METHODS

In a sample of healthy undergraduate students (N=83), we tested the effect of 30 mins of post-learning sleep, rest, or active wake on concept learning (dot pattern classification) and declarative memory (word pair associates) across a 4-hr daytime training-retest interval.

RESULTS AND CONCLUSIONS

Contrary to our hypotheses, we found no differences in performance between the three conditions for either task. The findings are interpreted with reference to methodological considerations including the length of the experimental interval, the nature of the tasks used, and challenges inherent in creating experimental conditions that can be executed by participants.