Electrophysiology of the frontal lobe.

Abstract

The electrophysiology of the frontal lobe appears to be unimpressive when the view is limited to the routine EEG recording of a healthy waking adult. There is usually low voltage fast activity, which becomes more pronounced when recorded with depth leads. Three special EEG patterns of marginal to slightly abnormal character are discussed: a) rhythmical midfrontal 6-7/sec activity of juveniles, b) rhythmical midfrontal sharp 4-6/sec activity of infancy and early childhood with arousal from sleep, and c) frontal intermittent rhythmical delta activity (FIRDA) in waking adults with frontopolar maximum, possibly related to thought processes under abnormal conditions. With extension of the frequency range, ultraslow (DC-like) as well as fast beta (gamma, 40-80/sec) and ultrafast activity (80-1000/sec) are found particularly over the frontal lobes. Ultraslow baseline shifts are arousal-related and mixed with overlying ultrafast waves. Attention control and the "working memory" involve chiefly the dorsolateral prefrontal cortex, investigated with P300 responses and likely to show ultrafast spectra. Perception-related 40-80/sec gamma activity has been thought to be associated with the entrance into consciousness. Initiation and design of motor activity spreads from prefrontal to the frontomotor cortex, associated with powerful event-related potentials: contingent negative variation (CNV) and "Bereitschafts potential" ("readiness potential," RP). Neuroscientific research of the highest frontal lobe functions has become a very active domain of neuroimaging. With the use of the extended frequency range, EEG and also evoked potential studies could add further information with acquisition in real time. Ultrafast frequency ranges presented in computerized frequency analysis and mapping might show impressive correlates of highest frontal lobe functions.