Electrophysiological correlates of selective attention: a lifespan comparison.

BACKGROUND: To study how event-related brain potentials (ERPs) and underlying cortical mechanisms of selective attention change from childhood to old age, we investigated lifespan age differences in ERPs during an auditory oddball task in four age groups including 24 younger children (9-10 years), 28 older children (11-12 years), 31 younger adults (18-25), and 28 older adults (63-74 years). In the Unattend condition, participants were asked to simply listen to the tones. In the Attend condition, participants were asked to count the deviant stimuli. Five primary ERP components (N1, P2, N2, P3 and N3) were extracted for deviant stimuli under Attend conditions for lifespan comparison. Furthermore, Mismatch Negativity (MMN) and Late Discriminative Negativity (LDN) were computed as difference waves between deviant and standard tones, whereas Early and Late Processing Negativity (EPN and LPN) were calculated as difference waves between tones processed under Attend and Unattend conditions. These four secondary ERP-derived measures were taken as indicators for change detection (MMN and LDN) and selective attention (EPN and LPN), respectively. To examine lifespan age differences, the derived difference-wave components for attended (MMN and LDN) and deviant (EPN and LPN) stimuli were specifically compared across the four age groups. RESULTS: Both primary and secondary ERP components showed age-related differences in peak amplitude, peak latency, and topological distribution. The P2 amplitude was higher in adults compared to children, whereas N2 showed the opposite effect. P3 peak amplitude was higher in older children and younger adults than in older adults. The amplitudes of N3, LDN, and LPN were higher in older children compared with both of the adult groups. In addition, both P3 and N3 peak latencies were significantly longer in older than in younger adults. Interestingly, in the young adult sample P3 peak amplitude correlated positively and P3 peak latency correlated negatively with performance in the Identical Picture test, a marker measure of fluid intelligence. CONCLUSION: The present findings suggest that patterns of event-related brain potentials are highly malleable within individuals and undergo profound reorganization from childhood to adulthood and old age.

Electromyographic activity of the lip muscle as a measure of puffing on a cigarette.

The electromyographic activity (EMG) of the upper lip muscle (m. orbicularis oris) during sucking on a cigarette was examined as a potential new measure of smoking behaviour. This parameter was examined under conditions of actual smoking, sham smoking and sucking on a straw. We applied psychophysical procedures (methods of magnitude production), normal and paced smoking, two conventional means to confirm puffing (video recording and changes in air pressure in a cigarette holder) on different groups of smokers (heavy and light). The data revealed that lip-EMG is a valid and reliable means to quantify sucking on a cigarette in a variety of situations common to the study of smoking. It was concluded that lip-EMG may be a sensitive and selective measure of motor activity associated with smoking. The lip-EMG may also be applied together with hand activity and breathing to identify individual puffing, particularly in heavy smokers and during actual smoking. Discussed were several applications of this method to the study of smoking and other motivated behaviour such as consumption of water and palatable fluids.