EEG components of spontaneous trait inferences.

Can event-related electro-encephalogram (EEG) responses provide support for the occurrence of spontaneous trait inferences (STI)? Participants read sentences describing the behavior of a target person from which a strong trait could be inferred. The last word of each sentence determined the consistency with the trait induced during an introductory paragraph. In comparison with sentences that were consistent with the implied trait, when the sentences were inconsistent, an event-related P300 waveform was observed at parietal scalp regions (Pz). This dependency on behavioral consistency indicates that trait inferences were made spontaneously. Memory measures taken after the presentation of the stimulus material involved sentence completion and trait-cued recall, and also supported the occurrence of spontaneously inferred traits associated with the actor. Interestingly, increased memory for consistent relative to inconsistent behaviors at the trait-cued recall task was significantly correlated with the P300, which supports this latter measure as a valid neural correlate of spontaneous trait inferences.

Is the relationship between frontal EEG alpha asymmetry and depression mediated by implicit or explicit self-esteem?

A robust physiological finding is a higher relative left sided activity in the prefrontal cortex during the experience of positive approach related emotions and a higher relative right sided activity during the experience of negative withdrawal related emotions. Since self-esteem can be conceptualized within a framework of approach/withdrawal tendencies, the present study aimed at investigating if the relation between frontal EEG alpha asymmetry and depressive symptoms is mediated by implicit or explicit self-esteem. Self-esteem was measured by questionnaires (explicit) and in an indirect way (implicit). The mediation analyses showed that only explicit self-esteem acted as a partial mediator in the path from EEG alpha asymmetry to depression.

Neurocognitive effects of obstructive sleep apnea syndrome.

The nature of the neurocognitive deficits found in obstructive sleep apnea is still debatable. What is the extent of higher executive versus alertness-based cognitive dysfunction? Are cognitive impairments caused by nighttime hypoxemia or daytime sleepiness? This paper demonstrates the importance of a sound theoretical neurocognitive framework to be able to answer these questions. A strategy to assess executive function is proposed and illustrated with well-known neuropsychological tests. It seems that the pervasive effects of decreased alertness on higher cognitive functioning were not fully taken into account in those studies in which executive dysfunction has been found and has been related to prefrontal lobe damage caused by intermittent hypoxemia. Therefore, a basal slowing in information processing, primarily due to sleepiness, may explain most of the neurocognitive deficits in sleep apnea. This conjecture appears to be in agreement with recent functional MRI studies indicating sleep loss as the primary cause of neurocognitive deficits, more so than hypoxemia.

Electrophysiological time course and brain areas of spontaneous and intentional trait inferences.

This study measured event-related potentials during spontaneous and intentional trait inferences. Participants read sentences describing the behavior of a target person from which a strong moral trait could be inferred. The last word of each sentence determined the consistency with the trait induced during an introductory paragraph. In comparison with behaviors that were consistent with the implied trait, a P300 waveform was obtained when the behaviors were evaluative inconsistent with that trait. This dependency on behavioral consistency indicates that trait inferences were made previously while reading the preceding behaviors, irrespective of the participants' spontaneous or intentional goals. Overall, the P300 shows considerable parallels between spontaneous and intentional inferences, indicating that the type and timing of the inconsistency process is very similar. In contrast, source localization (LORETA) of the event-related potentials suggest that spontaneous inferences show greater activation in the temporo-parietal junction compared to intentional inferences following an inconsistency. Memory measures taken after the presentation of the stimulus material involved sentence completion and trait-cued recall, and supported the occurrence of trait inferences associated with the actor. They also showed significant correlations with the neural components (i.e. P300 and its current density at the temporo-parietal junction) predominantly following spontaneous instructions, indicating that these components are valid neural indices of spontaneous inferences.

Neurophysiological aspects of primary insomnia: implications for its treatment.

Insomnia has usually been studied from a behavioral perspective. Somatic and/or cognitive conditioned arousal was shown to play a central role in sleep complaints becoming chronic, and was used as a starting point for the development of treatment modalities. The introduction of the neurocognitive perspective, with its focus on cortical or CNS arousal, has given rise to a renewed interest in the neurophysiological characteristics of insomnia. Recent research, using quantitative EEG, neuroimaging techniques and the study of the microstructure of sleep, suggests a state of hyperarousal with a biological basis. Furthermore, insomnia might not be restricted to sleep complaints alone because it appears to be a 24-h disorder, affecting several aspects of daytime functioning as well. These new findings have implications for the treatments used and indicate that a focus on cortical or CNS arousal should be pursued. As such, the use of EEG neurofeedback, a self-regulation method based on the paradigm of operant conditioning, might be a promising treatment modality. Preliminary results for insomnia and successful applications for other disorders suggest that this treatment can have the necessary stabilizing effects on the EEG activity, possibly resulting in a normalizing effect on daytime as well as nighttime functioning.

Primary and secondary auditory cortex stimulation for intractable tinnitus.

INTRODUCTION: Recent research suggests tinnitus is a phantom phenomenon based on hyperactivity of the auditory system, which can be visualized by functional neuroimaging, and transiently modulated by transcranial magnetic stimulation (TMS). We present the results of the first implanted electrodes on the primary and secondary auditory cortex after a successful TMS suppression. METHODS AND MATERIALS: Twelve patients underwent an auditory cortex implantation, 10 for unilateral and 2 for bilateral tinnitus, based on >50% suppression applying TMS. Results were analyzed for pure tone tinnitus and white noise tinnitus. RESULTS: TMS results in 77% pure tone tinnitus and 67% white noise reduction. Electrical stimulation via an implanted electrode results in a mean of 97% pure tone tinnitus and 24% white noise suppression. Mean Visual Analogue Scale score decreases from 9.5 to 1.5 for pure tone and from 8.8 to 6.8 for white noise postoperatively. DISCUSSION: Pure tone tinnitus might be the conscious percept of focal neuronal hyperactivity of the auditory cortex. Once visualized, this hyperactivity can be modulated by neurostimulation. CONCLUSION: The preliminary results of the first implantations suggest that patients with unilateral pure tone tinnitus are good surgical candidates for electrode implantation and permanent electrical stimulation of the auditory cortex, provided that the tinnitus is of recent origin and can be suppressed by TMS.

Transcranial magnetic stimulation for tinnitus: influence of tinnitus duration on stimulation parameter choice and maximal tinnitus suppression.

OBJECTIVE: Tinnitus is a distressing symptom for which few treatments exist. It leads to an important decrease in quality of life in 2 to 3% of the population. Tinnitus is considered a phantom sound, the result of cortical reorganization. Transcranial magnetic stimulation (TMS) is a noninvasive method to modulate cortical reorganization and has been shown to be able to influence tinnitus perception. STUDY DESIGN: Retrospective analysis. SETTING: Tertiary referral center. PATIENTS: The effect of TMS of the contralateral auditory cortex in 114 patients with unilateral tinnitus is investigated as one of the selection criteria used for surgical implantation of electrodes on the auditory cortex. INTERVENTION: TMS is performed at 90% of motor threshold at 1, 3, 5, 10, and 20 Hz, with each stimulation session consisting of 200 pulses. Results were classified as no effect (0-19% improvement), partial effect (20-79% improvement), and good effect (80-100 suppression). MAIN OUTCOME MEASURES: TMS had a good effect in 25% of the patients studied, partial effect in 28% patients, and no effect in 47%. RESULTS: TMS at 200 pulses is capable of tinnitus suppression for seconds only. The results were influenced by tinnitus duration: the longer the tinnitus exists, the lower the stimulation frequency that yields maximal tinnitus suppression (p < 0.001). The maximal amount of tinnitus suppression decreases in time (p < 0.01), resulting in a 2% decrease of potential tinnitus suppression per year. CONCLUSION: TMS of the auditory cortex is capable of modifying tinnitus perception for a very short time. The maximal amount of suppression and best stimulation frequency depends on the tinnitus duration.

Executive function in sleep apnea: controlling for attentional capacity in assessing executive attention.

STUDY OBJECTIVES: As the effects of general slowness and decreased attentional capacity on higher executive attention have not been fully taken into account in the sleep apnea literature, we statistically controlled for basic attentional performance in evaluating executive attention per se in sleep apnea patients. DESIGN: A case-controlled design was used with comparison of basic and executive attentional tasks. PARTICIPANTS: Thirty-six polysomnographically diagnosed patients (mean apnea-hypopnea index = 60.5 +/- SD 31.6) participated, together with 32 healthy controls. MEASUREMENTS AND RESULTS: Neuropsychological tests included Trail Making part A and B, Symbol Digit Modalities (SDMT), Digit Span forward and backward, Stroop Color-Word, Five-Point design fluency, and an Attentional Flexibility task. Patients' vigilance data indicated time-on-task decrements after 10 minutes. Moreover, their performance was significantly reduced on the SDMT (effect size d = 0.93), the Digit Span forward task (d = 0.44), the number of errors on the basic 2-choice reaction time subtest of the Attentional Flexibility task (d = 0.74) and the mean RT on the actual Attentional Flexibility subtest (d = 0.54). It has been argued that the latter poor performance was probably primarily related to the task's phonologic loop component of working memory rather than to an attentional switching deficit per se. No other performance differences were found between patients and healthy controls. CONCLUSIONS: In addition to vigilance decrements, attentional capacity deficits clearly emerge, ie, slowed information processing and decreased short-term memory span. However, no specific clinical indications for executive attentional deficits--such as disinhibition, distractibility, perseveration, attentional switching dysfunction, decreased design fluency, or an impaired central executive of working memory--are found in patients with severe sleep apnea. Their cognitive performance seems very similar to the cognitive decline found after sleep loss and qualitatively different from patients with chronic obstructive pulmonary disease, suggesting sleepiness as the primary factor in a parsimonious explanation for the attention deficits in sleep apnea, without the need to assume prefrontal brain damage.

Executive control of attention in sleep apnea patients: theoretical concepts and methodological considerations.

Sleep apnea patients' nocturnal breathing disturbances cause daytime sleepiness and cognitive impairments. Attentional capacity and vigilance deficits have often been observed. Moreover, some studies have suggested executive dysfunction, usually assumed to be related to (pre)frontal lobe dysfunction caused by intermittent hypoxemia. However, sleep disruption itself has a pervasive influence on cognitive function and affects not only underlying 'lower-level' processes such as arousal and alertness, but also 'higher-level' cognitive processes such as executive attention. This methodological caveat has not been fully taken into account in the sleep apnea literature. In order to be able to disentangle these cognitive processes on different levels, sound theoretical neurocognitive frameworks are needed to attain careful analyses and interpretations of neuropsychological data. Therefore, this paper firstly presents an overview of relevant theoretical concepts and models of arousal, attention, and executive function. Then, it is being argued that these theoretical considerations have important methodological implications. These methodological concerns are being addressed by specific experimental and statistical approaches, illustrated by some well-known neuropsychological tests. It can be concluded that the reported executive deficits in sleep apnea patients should be regarded as tentative, and that more case-controlled studies are needed using fine-grained analyses to parcel complex cognitive abilities into their subcomponents.

Attentional switching-related human EEG alpha oscillations.

Alpha oscillations during cognitive performance have mostly been studied in memory and/or basic attention tasks. This study investigates task-related alpha power desynchronization during an attentional switching task requiring higher executive attentional control. Low 8-10 Hz and high 10-12 Hz alpha power responses are studied in good versus poor performers based upon normative data. Accurate, fast and stable performers showed significant task-related desynchronization in the 8-10 Hz range during attentional switching, whereas inaccurate performers hypersynchronized in the 10-12 Hz range, and slow and unstable performers did not demonstrate significant alpha reactivity. These preliminary findings indicate, in agreement with previous research, functional differences in these narrow frequency bands. The 8-10 Hz power decrease is likely to be related to phasic arousal or alertness, whereas the 10-12 Hz power increase appears to be associated with inaccurate attentional switching.

Daytime sleepiness and its evaluation.

Basic models of sleepiness, focusing on the homeostatic and circadian components of sleepiness, are able to predict important fluctuations of sleepiness. However, they fail in explaining certain sleepiness phenomena, as for instance in insomnia patients. To meet this shortcoming, modern models incorporate the arousal component of sleepiness, in addition to the sleep drive. While these models mainly concentrate on short-term changes in sleepiness, "state" sleepiness, there are indications that a stable characteristic level of sleepiness, "trait" sleepiness, is also an important determinant of a person's level of sleepiness. This leads to a conceptualization of sleepiness in which situational factors modify a basal level of sleep drive and arousal. It implies that sleepiness is not a unitary concept and can reflect essentially different states. Multiple sleepiness assessment tools have been proposed in the past. The majority of them offer valuable information, but they do not grasp all aspects of sleepiness. We should bear in mind that tools for assessing sleepiness are always operationalizations reflecting the theoretical framework the investigator has on sleepiness. Hence, rather than searching for a gold standard for the measurement of sleepiness, future research effort should be aimed at linking the various measurement techniques with the hypothesized underlying components of sleepiness on a sound empirical basis.