Identification of Reliable Target Brain Regions for Enhancing Object-Location Memory by Brain Stimulation.

INTRODUCTION

Object-location memory (OLM) is essential for remembering the locations of objects within an environment and is often impaired in aging and neurodegenerative diseases. Transcranial direct current stimulation (tDCS) has shown promise for improving OLM, although study outcomes have varied considerably. This study aimed to identify key brain regions involved in OLM that may serve as stimulation targets for future tDCS research and to assess the test-retest reliability (TRR) of both behavioral and functional magnetic resonance imaging (fMRI) data.

METHODS

Twenty healthy young adults (10 females; mean age = 25.0 years, standard deviation [SD] = 5.56) completed two task-based fMRI sessions using parallel versions of an OLM task. Participants learned associations between house images and their locations on a two-dimensional street map across four feedback-based learning stages. Sham tDCS was administered in both sessions using a focal 3 × 1 electrode montage. TRR was assessed using intraclass correlation coefficients (ICCs) for behavioral performance and task-related fMRI activation.

RESULTS

Behavioral data showed significant improvements in response accuracy (estimate = 0.211, p < 0.001) and a reduction in response latency (estimate = -0.050, p < 0.001) across learning stages. fMRI analysis revealed predominantly right-lateralized activation, including the right hippocampus, the fusiform gyrus, the precuneus, and the lateral temporo-occipital areas. Behavioral measures showed moderate to good TRR (accuracy ICC = 0.801; reaction time ICC = 0.705). Task-related fMRI activity demonstrated good-to-excellent TRR in key regions, including the fusiform and temporo-occipital cortices.

CONCLUSION

These findings support the validity of our OLM paradigm for assessing brain stimulation effects and highlight potential cortical targets for future tDCS interventions. The observed reliability of behavioral and neural measures further reinforces the utility of this protocol in crossover study designs.