A. Gevins et Me. Smith, Neurophysiological measures of working memory and individual differences in cognitive ability and cognitive style, CEREB CORT, 10(9), 2000, pp. 829-839
The capacity to deliberately control attention in order to hold and manipul
ate information in working memory is critical to higher cognitive functions
. This suggests that between-subject differences in general cognitive abili
ty might be related to observable differences in the activity of brain syst
ems that support working memory and attention control. To test this notion,
electroencephalograms were recorded from 80 healthy young adults during sp
atial working memory tasks. Measures of task-related neurophysiological and
behavioral variables were derived from these data and compared to scores o
n a test battery commonly used to assess general cognitive ability (the WAI
S-R). Subjects who scored high on the psychometric test also tended to resp
ond faster in the experimental tasks without any loss of accuracy. The ampl
itude of the late positive component of the event-related potential was lar
ger in high-ability subjects, and the frontal midline theta component of th
e EEG signal was also selectively enhanced in this group under conditions o
f sustained performance and high working memory load. These results suggest
that subjects who scored high on the WAIS-R were better able to focus and
sustain attention to task performance. Changes in the EEG alpha rhythm in r
esponse to manipulations of task practice and load were also examined and c
ompared between frontal and parietal regions. The results indicated that hi
gh-ability subjects developed strategies that made relatively greater use o
f parietal regions, whereas low-ability subjects relied more exclusively on
frontal regions. Other analyses indicated that hemispheric asymmetries in
alpha band measures distinguish between individuals with relatively high ve
rbal aptitude and those with relatively high nonverbal aptitude. In particu
lar, subjects with a verbal cognitive style tended to make greater use of t
he left parietal region during task performance, and subjects with a nonver
bal style tended to make greater use of the right parietal region. These re
sults help clarify relationships between task related brain activity and in
dividual differences in cognitive ability and style.