This paper examines the tremendous similarities between the Parallel Constraint Satisfaction Processes that are a central part of many connectionist models and the Gestalt principles that played a central role in the history of Psychology. Gestalt Psychology played a major role in a number of areas in psychology, such as perception, reasoning and problem solving, causal reasoning, and many key aspects of social psychology, such as social perception, group interaction, and belief consistency. Many of the key assumptions of Gestalt Psychology have resurfaced in recent connectionist models. W e propose that Parallel Constraint Satisfaction Processes provide a computational implementation of many of the central principles of Gestalt Psychology. In this paper we discuss the clear parallels between each of five key assumptions of Gestalt Psychology and aspects of Parallel Constraint Satisfaction Processes. The five assumptions we examine are: (1) psychological processing can be treated as interactions in fields of forces, (2) psychological processing is holistic, (3) the whole is greater than the sum its parts, (4) the importance of the structure of cognitive elements; how things are connected and related, and (5) the emphasis on cognitive dynamics, and such concepts as change, equilibrium, and tension.

Background

There is increasing evidence that the dorso-lateral prefrontal cortex (DLPFC), a brain region related to reward and motivational processes, is involved in effective response inhibition and that decreased activity in this region coincides with reduced inhibitory capacity. Using transcranial direct current stimulation (tDCS) to manipulate cortical activation, this study examined whether cross-hemispheric tDCS over the DLPFC affected performance on an inhibitory control task.

Methods

Neurologically intact participants performed a modified Stroop color-word matching task before and after completing one of two tDCS conditions; (1) anodal stimulation over the left DLPFC or (2) sham tDCS.

Results

There was a statistically significant effect of tDCS condition on Stroop reaction time (RT) pre-post tDCS change scores. Participants who received anodal stimulation over the left DLPFC demonstrated statistically significant faster RT change scores on the Stroop items compared to participants in the sham condition. Although errors on Stroop incongruent items decreased before and after receiving the tDCS treatment, there were no significant differences in errors on Stroop items between the anodal stimulation over left DLPFC and sham tDCS conditions. Anodal tDCS, which is known to elevate neural excitation, may have enhanced activation levels in the left DLPFC and minimized impairment of inhibitory control, resulting in better task performance.

Conclusions

Current findings provide preliminary evidence that increased excitation of the left DLPFC improves inhibitory control and are a step toward understanding the potential of tDCS for moderating deficits in inhibitory control.