Cathodal stimulation over left ventral posterior parietal cortex decreases response time in multimodal source memory task.

Juliana Silva de Deus ¹, Júlia Feminella Duarte da Costa ², Tainara Castro Parreira ², Luscélia Pereira Castro ², Juliana Santos Siqueira ², Luciano Grüdtner Buratto ¹

¹ Department of Basic Psychological Processes, Institute of Psychology, University of Brasília; ² Institute of Psychology, University of Brasília.

OBJECTIVE: Previous studies suggested that the left ventral posterior parietal cortex (vPPC) is involved in the retrieval of multimodal episodic memories (i.e., information from different sensory modalities; Yazar et al., 2017). The aim of this study is to investigate whether cathodal tDCS over the vPPC can disrupt the retrieval of multimodal memories.

METHODS: In the study, participants (N = 53) memorized objects in a scene, each object comprising two visuospatial and two auditory features. In the test phase, under sham or cathodal stimulation (25 cm² electrodes, 1.5 mA, 30 min over P5), participants were instructed to (a) recognize the objects presented during study phase, (b) retrieve visual and/or auditory contextual details about these objects. After each trial, participants also provided confidence judgments.

RESULTS: Cathodal stimulation did not affect measures of memory accuracy, nor did it affect confidence judgements. However, cathodal tDCS decreased RT in visual trials (Figure 1). Participants also reported difficulties during retrieval of auditory information.

CONCLUSIONS: The accuracy and confidence results do not support the view that the vPPC acts as an integrator of multimodal information during retrieval. The RT results, however, support the alternative view that the intraparietal sulcus, a region near the vPPC, functions as an evidence accumulator that tracks information availability during retrieval (mnemonic accumulator; Wagner et al., 2005). The RT results suggest that cathodal tDCS may have affected the accumulation of retrieved auditory and visual information necessary for decision making during the test phase.


Response Times as a Function of ModalityNote: Cathodal tDCS decreased visual response times, but had no effect on the other modalities. Bars represent standard error of the mean *** p < 0.001

 KEYWORDS: episodic memory, Parietal lobe, recognition memory, mnemonic accumulator, transcranial direct current stimulation.

ACKNOWLEDGMENTS: We thank Julya Rodrigues for assistance with data collection.

FUNDING/FINANCIAL SUPPORT: This study was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brazil, Finance Code 001.