Left Prefrontal Cortex Supports the Recognition of Meaningful Patterns in Ambiguous Stimuli.

Grégory Bartel,Imani Rameses,Claus Lamm,Martin Marko,Igor Riečanský

doi:10.3389/fnins.2020.00152

Abstract

Processing of ambiguous visual stimuli has been associated with an increased activation of the left lateral prefrontal cortex (PFC) in neuroimaging studies. Nevertheless, the functional role of prefrontal activity in this process is not fully understood. In this experiment we asked participants to evaluate ambiguous inkblots from the Rorschach test, while stimulating the left lateral PFC using excitatory anodal transcranial direct current stimulation (tDCS). In addition, visual insight ability was assessed as a control measure requiring visual and conceptual restructuring and convergent thinking rather than divergent idea generation employed to interpret the equivocal Rorschach inkblots. Using a randomized double-blind design, we demonstrated that anodal tDCS increased the number of meaningful patterns recognized in the inkblots but had no significant effect on visual insight. These findings support the role of left lateral PFC in the processing of ambiguous visual information and object recognition. More generally, we discuss that the PFC may be involved in the mechanisms supporting the activation of stored visual and semantic representations in order to compensate for less informative bottom-up inputs and thus facilitate flexible cognition and idea generation.

Highlights

Seeing is not merely a bottom-up process, and uses the constructive qualities of our perceptual system, which are essential to navigate in a world full of ambiguity and incompleteness (Gregory, 1970, 1990)
A one-way ANCOVA was conducted to evaluate the effect of transcranial direct current stimulation (tDCS) on Rorschach inkblot test (ROR) response fluency in the post-test whilst controlling for the pre-test performance
We have demonstrated that anodal electrical stimulation of the left prefrontal cortex (PFC) enhances response fluency in the Rorschach test

Summary

Introduction

Seeing is not merely a bottom-up process, and uses the constructive qualities of our perceptual system, which are essential to navigate in a world full of ambiguity and incompleteness (Gregory, 1970, 1990). An important aspect of adaptive behavior entails a dynamic interpretation of elements embedded in natural scenes, which are ambiguous due to various forms of noise (i.e., degraded visibility, shading, and occlusion) or intrinsic complexity By virtue of this ambiguity, natural visual scenes frequently produce perceptions of non-existent entities, reflecting approximate or even erroneous matching between sensory inputs and internal representations, commonly referred to as illusory perception, pareidolia, or projection (Voss et al, 2012; Liu et al, 2014). It has been suggested that coarse representations of incoming stimuli are carried rapidly from early visual areas to the prefrontal cortex (PFC) in order to compute the prediction about the most likely interpretation of the input (Summerfield et al, 2006) This top-down prediction precedes and augments the bottom-up processing in the temporal-occipital visual pathway, supporting rapid recognition of objects (Bar, 2004; Bar et al, 2006). Ambiguous or distorted visual inputs may compromise the meticulous bottom-up analysis performed in the temporaloccipital cortices increasing the reliance on prefrontally mediated top-down processes

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Discussion

Conclusion