Neuropsychological correlates of the electroencephalogram in epileptics: II. The waking posterior rhythm and its interaction with epileptiform activity.

Relationships between psychological functions and waking dominant posterior rhythm frequency (DPRF) of the EEG were evaluated with and without simultaneous evaluation of epileptiform discharges. Ninety adult epileptics with uncontrolled seizure disorders treated solely by diphenylhydantoin underwent EEGs during wakefulness and administrations of an extensive battery of neuropsychological tests. The DPRF was particularly related to abilities simultaneously requiring attention an complex mental manipulations. Rhythms slower than 7.5-8.0 Hz were accompanied by relatively poorer performance than rhythms which were faster. When epileptiform discharges were considered in combination with the DPRF, larger differences in abilities were demonstrated, and the psycholoigcal correlates tended to be more substantial for the epileptiform discharge variable than for the DPRF variable. The selection of tests employed and the range of rhythms assessed are critical to these findings, and the substantial construction of these variables by many previous investigators is believed to be related to the negative findings often reported.