Subjective versus objective sleep in men with Klinefelter syndrome.

OBJECTIVES: To investigate sleep among men with Klinefelter syndrome (KS). METHOD: We compared the sleep domains latency, disturbance, and efficiency in 30 men with KS (M age = 36.7 years, SD = 10.6) to 21 age-matched non-KS controls (M age = 36.8 years, SD = 14.4). Actigraphs were used to objectively measure sleep across 7 days and nights. Participants also completed a sleep diary over the same period, and the Pittsburgh Sleep Quality Index (PSQI). RESULTS: The mean correlation between the objective and subjective sleep measures was lower for the KS sample (M r = .15) than for controls (M r = .34). Sleep disturbance was significantly larger in the KS sample, as measured by actigraphy (p = .022, d = 0.71) and the PSQI (p = .037, d = 0.61). In regression models predicting sleep domains from KS status, age, educational level, vocational status, IQ, and mental health, KS status was not a significant predictor. Higher age was associated with more actigraphy-measured sleep disturbance. Higher educational level and being employed were associated with better sleep efficiency. CONCLUSIONS: Sleep disturbance may be a particular problem for men with KS and should be measured with complimentary methods.

Differences in Cortical Sources of the Event-Related P3 Potential Between Young and Old Participants Indicate Frontal Compensation.

The event-related P3 potential, as elicited in auditory signal detection tasks, originates from neural activity of multiple cortical structures and presumably reflects an overlap of several cognitive processes. The fact that the P3 is affected by aging makes it a potential metric for age-related cognitive change. The P3 in older participants is thought to encompass frontal compensatory activity in addition to task-related processes. The current study investigates this by decomposing the P3 using group independent component analysis (ICA). Independent components (IC) of young and old participants were compared in order to investigate the effects of aging. Exact low-resolution tomography analysis (eLORETA) was used to compare current source densities between young and old participants for the P3-ICs to localize differences in cortical source activity for every IC. One of the P3-related ICs reflected a different constellation of cortical generators in older participants compared to younger participants, suggesting that this P3-IC reflects shifts in neural activations and compensatory processes with aging. This P3-IC was localized to the orbitofrontal/temporal, and the medio-parietal regions. For this IC, older participants showed more frontal activation and less parietal activation as measured on the scalp. The differences in cortical sources were localized in the precentral gyrus and the parahippocampal gyrus. This finding might reflect compensatory activity recruited from these cortical sources during a signal detection task.

Multimodal imaging of functional networks and event-related potentials in performance monitoring.

The stop-signal task is a prototypical experiment to study cognitive processes that mediate successful performance in a rapidly changing environment. By means of simultaneous recording and combined analysis of electroencephalography and functional magnetic resonance imaging on single trial level, we provide a comprehensive view on brain responses related to performance monitoring in this task. Three types of event-related EEG components were analyzed: a go-related N2/P3-complex devoid of motor-inhibition, the stop-related N2/P3-complex and the error-related negativity with its consecutive error positivity. Relevant functional networks were identified by crossmodal correlation analyses in a parallel independent component analysis framework. Go-related potentials were associated with a midcingulate network known to participate in the processing of conflicts, a left-dominant somatosensory-motor network, and deactivations in visual cortices. Stop-related brain responses in association with the N2/P3-complex were seen with networks known to support motor and cognitive inhibition, including parts of the basal ganglia, the anterior midcingulate cortex and pre-supplementary motor area as well as the anterior insula. Error-related brain responses showed a similar constellation with additional recruitment of the posterior insula and the inferior frontal cortex. Our data clearly indicate that the pre-supplementary motor area is involved in inhibitory mechanisms but not in the processing of conflicts per se.

The role of the cingulate cortex as neural generator of the N200 and P300 in a tactile response inhibition task.

Both the N200 and P300, which are, for example, evoked by Go/Nogo or Stop-Signal tasks, have long been interpreted as indicators for inhibition processes. Such interpretations have recently been challenged, and interest in the exact neural generators of these brain responses is continuously growing. Using recent methodological advancements, source estimations for the N200 and P300 as evoked by a tactile response inhibition task were computed. Current density reconstructions were also calculated accounting for interindividual differences in head geometry by incorporating information from T1-weighted magnetic resonance images. To ease comparability with relevant paradigms, the task was designed to mimic important characteristics of both Go/Nogo and Stop-Signal tasks as prototypes for a larger set of paradigms probing response inhibition. A network of neural generators was revealed, which has previously been shown to act in concert with executive control processes and thus is in full agreement with observations from other modalities. Importantly, a spatial segregation of midcingulate sources was observed. Our experimental data indicate that a left anterior region of the midcingulate cortex (MCC) is a major neural generator of the N200, whereas the midcingulate generator of the P300 is located in the right posterior MCC. Analyses of the P300 also revealed several areas, which have previously been associated with motor functions, for example, the precentral region. Our data clearly suggest a neuroanatomical and therefore also functional dissociation of the N200 and P300, a finding that cannot easily be provided by other imaging techniques.