Event-related potentials in the frontal lobe during performance of a visual duration discrimination task.

An event-related potential (ERP) study was conducted to elucidate the role of the prefrontal cortex (PFC) in time estimation. Subjects discriminated between three pairs of visual stimuli lasting from 100 ms and 2 seconds by determining whether the second stimulus was longer or briefer than the first. Event-related potentials were recorded in frontal and prefrontal regions after offset of the second stimulus (S2). The results indicated that the accuracy of the performances depended on stimulus duration and presentation order. In the brief-long order, the number of successful responses was higher as a function of stimulus duration. A time-related late positive component (LPCt) was revealed at prefrontal and frontal electrodes whose latency and amplitude differed depending on stimulus duration and order. The amplitude of this positive wave was higher when performance levels increased in the brief-long but not the reverse order. These results indicate that the LPCt may reflect successful decision-making or retrieval during time estimation as a result of neuronal activity in the PFC.