Reduced verbal learning associated with posterior temporal lobe slow wave activity

Functional imaging has revealed that during verbal-word learning there is activation of the left posterior temporo-parictal region (PTPL). The purpose of this study was to learn if differences in the ability of normal people to learn might be accounted for by differences in electrophysiological (EEG) measures of activation of their left, but not right, PTPL. The Rey Auditory Verbal Learning Test (RAVLT) was administered to 42 men without neurological diseases. Delta magnitude, as measured by quantitative electroencephalography (QEEG), was recorded from the left and right PTPL while the participants sat quietly with their eyes closed. The magnitude of delta EEG activity is inversely proportional to cerebral activation. Based on delta magnitude, comparison groups were created by separating those with low and high delta at the left and right PTPL. Cumulative word learning (CWL) on the RAVLT was computed by subtracting the number of words recalled on the first learning trial from the highest number of words recalled on the fourth or fifth trial and multiplying this difference by the total words recalled during all 5 learning trials. The group with a greater magnitude of left PTPL delta activity had a significantly poorer CWL scores than those with less delta, but the CWL scores of the group with a greater magnitude of delta of the right PTPL was no different that the group with less right-sided delta. No significant differences emerged at any frontal or parietal electrode site. Decreased activation of the left, but not right, PTPL appears to be associated with a decreased verbal leaning ability.