Symbol Digit and the Quantitative EEG

  • Kirtley E. Thornton
  • Dennis P. Carmody


The coordination of allocation resource model of brain functioning examines the relations between quantitative EEG (QEEG) variables and cognitive performance on specific tasks. The Digit Symbol (DS) subtest of the Wechsler Adult Intelligence Scales has proven to be a sensitive measure in a variety of clinical conditions. A conceptually and empirically similar task (Symbol Digit [SD]) was employed to examine the QEEG correlates of successful functioning. A sample of 119 participants engaged in a modified SD test for 200 seconds while QEEG data were obtained. The participant verbally provided the matching number to the examiner to avoid any motor component of the task. There were negative relations between performance and magnitudes across almost all locations and across a wide bandwidth (0–64 Hz). Negative relations to SD performance were also observed for increased relative power of
beta1, whereas positive relations were found for absolute values of coherences of alpha, beta1 (13–32 Hz), and beta2 (32–64 Hz). The results showed the importance of spectral correlation coefficients (SCC) in cognitive functioning, in particular the SCC values within the frontal
region and in the 13–64 frequency range.