Neurophysiological correlates of cognitive development: changes in long-latency event-related potentials from childhood to adulthood.

Event-related brain potentials (ERPs) to tachistoscopically flashed slides were recorded from subjects ranging from 6 to 36 years of age. Subjects counted the number of presentations of target slides (P = 0.12) randomly interposed in sequences of background slides (either P = 0.76 or P = 0.88). Also interposed (P = 0.12) in these sequences of targets and backgrounds were one of two types of slides: those (termed dims) bearing any one of the letters from C to Z or those bearing 'novel' patterns, each consisting of a different, quasi-random, 'unrecognizable' color pattern. Targets and backgrounds elicited N1, P2, N2 and P3 waves in subjects of every age tested, suggesting that the mode of processing such explicitly important events and the neuronal substrate for such processing, is similar in children and adults. However, P3 latencies and reaction times in response to these events decreased with age, suggesting that the speed of such processing increases with age. On the other hand, dims and novels elicited ERPs in young children and adults characterized by different late waves. ERPs in 6--8 year olds were characterized by Nc waves (ca. 410 msec and 30 muV) and Pc waves (ca. 900 msec and 30 muV), while ERPs in adults were characterized by P3 waves (ca. 420 msec and 15 muV. The transition from the childhood to adulthood wave form occured in the mid-teens. It is suggested that these differences in ERP wave forms reflect differences in the way children and adults categorize events.