When the brain takes a break: a model-based analysis of mind wandering.

Mind wandering is an ubiquitous phenomenon in everyday life. In the cognitive neurosciences, mind wandering has been associated with several distinct neural processes, most notably increased activity in the default mode network (DMN), suppressed activity within the anti-correlated (task-positive) network (ACN), and changes in neuromodulation. By using an integrative multimodal approach combining machine-learning techniques with modeling of latent cognitive processes, we show that mind wandering in humans is characterized by inefficiencies in executive control (task-monitoring) processes.

Double dissociation: circadian off-peak times increase emotional reactivity; aging impairs emotion regulation via reappraisal.

This study explored how the effectiveness of specific emotion regulation strategies might be influenced by aging and by time of day, given that in older age the circadian peak in cognitive performance is earlier in the day. We compared the benefit gained by 40 older (60-78 years; 20 women) and 40 younger (18-30 years; 20 women) adults during either on-peak or off-peak circadian times on 2 specific types of cognitive emotion regulation strategies: distraction and reappraisal. Participants rated their negative emotional responses to negative and neutral images under 3 conditions: a baseline nonregulation condition, a distraction condition involving a working memory task, and a reappraisal condition that involved reinterpreting the situation displayed using specific preselected strategies.

The effects of stimulus degradation after 48 hours of total sleep deprivation.

Study Objectives: To test the hypothesis that total sleep deprivation (TSD) slows stimulus detection and evaluation processes. Towards that end we manipulate degradation of the imperative stimulus, a manipulation well established to affect the processes of interest, in a delayed letter recognition (DLR) task and the psychomotor vigilance task (PVT), and predicted that after TSD the ordinary reaction time (RT) slowing effect of stimulus degradation would be increased. These hypotheses were only partially confirmed (see below).

The prefrontal model revisited: double dissociations between young sleep deprived and elderly subjects on cognitive components of performance.

Study Objectives: The prefrontal model suggests that total sleep deprivation (TSD) and healthy aging produce parallel cognitive deficits. Here we decompose global performance on two common tasks into component measures of specific cognitive processes to pinpoint the source of impairments in elderly and young TSD participants relative to young controls and to each other.

Setting: The delayed letter recognition task (DLR) was performed in 3 studies.

fMRI activation during failures to respond key to understanding performance changes with sleep deprivation.

Study Objectives: During sleep deprivation (SD), failures to respond (FR) increase across a variety of tasks. This is the first systematic investigation of neural correlates of FR during SD. We use multivariate analysis to model neural activation separately for FR and responses (R) at each trial phase.

Effects of sleep deprivation on dissociated components of executive functioning.

Study Objectives: We studied the effects of sleep deprivation on executive functions using a task battery which included a modified Sternberg task, a probed recall task, and a phonemic verbal fluency task. These tasks were selected because they allow dissociation of some important executive processes from non-executive components of cognition.

Design: Subjects were randomized to a total sleep deprivation condition or a control condition.

The variable response-stimulus interval effect and sleep deprivation: an unexplored aspect of psychomotor vigilance task performance.

Study Objectives: The Psychomotor Vigilance Task (PVT) contains variable response-stimulus intervals (RSI). Our goal is to investigate the effect of RSI on performance to determine whether sleep deprivation affects the ability to attend to events across seconds and whether this effect is independent of impairment in sustaining attention across minutes, as measured by time on task.

Design: A control group following their normal sleep routines and 3 groups exposed to 54 hours of total sleep deprivation performed a 10-minute PVT every 6 hours for 9 total test runs.

Trait interindividual differences in the sleep physiology of healthy young adults.

Despite decades of sleep research by means of polysomnography (PSG), systematic interindividual differences in PSG-assessed sleep parameters have been scarcely investigated. The present study is the first to quantify interindividual variability in standard PSG-assessed variables of sleep structure in terms of stability and robustness as well as magnitude. Twenty-one carefully screened healthy young adults were studied continuously in a strictly controlled laboratory environment, where their PSGs were recorded for eight nights interspersed with three separate 36 h sleep deprivation periods.