Vigilance, alertness, or sustained attention: physiological basis and measurement.

We assessed working memory load during computer use with neural network pattern recognition applied to EEG spectral features. Eight participants performed high-, moderate-, and low-load working memory tasks. Frontal theta EEG activity increased and alpha activity decreased with increasing load. These changes probably reflect task difficulty-related increases in mental effort and the proportion of cortical resources allocated to task performance. In network analyses, test data segments from high and low load levels were discriminated with better than 95% accuracy. More than 80% of test data segments associated with a moderate load could be discriminated from high- or low-load data segments. Statistically significant classification was also achieved when applying networks trained with data from one day to data from another day, when applying networks trained with data from one task to data from another task, and when applying networks trained with data from a group of participants to data from new participants. These results support the feasibility of using EEG-based methods for monitoring cognitive load during human-computer interaction.

Monitoring Working Memory Load during Computer-Based Tasks with EEG Pattern Recognition Methods

An overview of the use of EEG to assess hemispheric differences in cognitive and affective processes is presented. Some of the advantages of using EEG to assess asymmetric hemispheric differences in the study of complex mental activity are described. Following this brief introduction, two conceptual issues which are central to studies of EEG asymmetries are introduced: (1) the distinction between hemispheric specialization and activation, and (2) the importance of rostral-caudal differences for the understanding of both specialization and activation. Three methodological issues in the use of EEG to assess hemispheric differences are then presented: (1) the use of asymmetry metrics, (2) muscle artifact, and (3) appropriate reference electrode location. Finally, some empirical examples of using EEG to assess affective and cognitive processes which illustrate these conceptual and methodological issues are described.

EEG measures of cerebral asymmetry: conceptual and methodological issues

(2003). Neurophysiological measures of cognitive workload during human-computer interaction. Theoretical Issues in Ergonomics Science: Vol. 4, No. 1-2, pp. 113-131.

Neurophysiological measures of cognitive workload during human-computer interaction

NeuroMarker combines EEG and ERP measures with neurocognitive tests in a fully computerized and standardized testing system. It is designed for use across the lifespan and has a large normative database of over 1,000 subjects. This study was a preliminary evaluation of "NeuroMarker" in subjects spanning four decades. Twenty-one healthy subjects (12-57 years) were tested at baseline and four weeks later. From the "Neuromarker" battery, the authors analyzed EEG data (eyes open and closed) and ERPs elicited during auditory oddball (N100, P200, N200, P300) and working memory (P150, P300) tasks. Concomitant neuropsychological data, acquired using a touch-screen system, comprised measures of sensori-motor, attention, verbal, executive, and memory function. Test-retest data were examined using analyses of variance and correlational procedures (corrected for multiple comparisons), with parallel analyses of age. EEG data did not differ across sessions, and showed high test-retest reliability (.71-.95), particularly for theta and delta (>.85). ERP components also showed sound reliability, particularly for sites where components are maximal: fronto-central N100 (.76-.77), centro-parietal P300 (.78-.81) to oddball targets, N100 and P200 (.74-.86) to oddball non-targets, and P150 amplitude and latency (.84-.93) to working memory stimuli. Neuropsychological tests showed a similarly sound level of consistency (on average, .70), with the most consistent tests tapping simple motor function, estimated intelligence, switching of attention (Part 2), verbal interference response time and memory intrusions (.71-.89). Age and sex did not have a differential impact on reliability for EEG, ERP, or neuropsychology measures. These findings provide preliminary evidence that the "NeuroMarker" battery is reliable for test-retest assessments. The results suggest that the standardized approach has utility for providing sensitive clinical and treatment evaluations across age groups.

S Ancoli

Papers

On-line computer rejection of EEG artifact☆

Computer rejection of EEG artifact. II. Contamination by drowsiness