Facilitation of probabilistic classification learning by transcranial direct current stimulation of the prefrontal cortex in the human

The aim of our study was to test if the electrical stimulation of the prefrontal cortex (PFC) could modify probabilistic classification learning (PCL). Transcranial direct current stimulation (tDCS) was administered to the left prefrontal and to the primary visual cortex of 22 healthy subjects while they performed a PCL task. In this task subjects learned which of two outcomes would occur on each trial after presentation of a particular combination of cues. Ten minutes of anodal, but not cathodal, stimulation improved implicit learning only when the left PFC was stimulated. Our results show that implicit PLC can be modified by weak anodal tDCS, which probably increases neural excitability, as has been shown in the motor and visual cortices previously. Our results suggest that further studies on the facilitation of learning and memory processes by tDCS are warranted. (C) 2003 Elsevier Ltd. All rights reserved.