TDCS Modulates Baseline fMRI Activity and Population Receptive Fields in the Human Visual Cortex
Poster No:
100
Submission Type:
Abstract Submission
Authors:
Jeongyeol Ahn1, Juhyoung Ryu1, Sangjun Lee2, Chany Lee3, Chang-Hwan Im4, Sang-Hun Lee1
Institutions:
1Seoul National University, Seoul, Seoul, 2University of Minnesota, Minneapolis, MN, 3Korea Brain Research Institute, Daegu, North Gyeongsang, 4Hanyang University, Seoul, Seoul
First Author:
Co-Author(s):
Introduction:
Transcranial direct current stimulation (tDCS) is a widely employed method for modulating various kinds of human cognition. Despite its widespread application, recent neuroimaging studies investigating the impact of tDCS on cortical excitability have yielded highly inconsistent results. This inconsistency underscores the need for a comprehensive understanding of how tDCS affects system-level neural activity, an essential prerequisite for the informed application of tDCS in the field of human cognition. In this study, our objective is to elucidate this understanding by examining the spatial and temporal functional magnetic neuroimaging (fMRI) activity within the human early visual cortex, assessed through diverse parameters, all while carefully controlling the polarity and presence of tDCS. The selection of the early visual cortex as our target allows us to leverage its well-established anatomical and functional architecture, readily accessible through non-invasive quantitative neuroimaging methods.
Methods:
To precisely and effectively create an electric field in the early visual cortex, we tailored high-definition stimulation montages for 15 individuals (25.7 ± 4.17 years, five females) by conducting electric field simulations based on individual head models (Fig. 1). Subsequently, we implemented an fMRI-tDCS experiment on each brain with a sham-controlled crossover design over multiple days. To investigate the impact of tDCS on the temporal and spatial dynamics of cortical activity, we measured fMRI responses to both brief (3 s) whole-field stimuli and traveling-wave stimuli (Fig. 2a-b). The temporal dynamics were characterized by estimating baseline, response amplitude, and sustained response parameters, while the spatial tuning was quantified using a population receptive field (pRF) model. We assessed the significance of these parameters using mixed ANOVA and further validated their robustness against across-voxel and across-subject variability.
Results:
We observed significant impacts of tDCS on the baseline measure and the pRF after anodal tDCS. The offline anodal tDCS resulted in an increase in the baseline of the fMRI time course (z = 7.38, FDR-adjusted p = 3.E-13 across voxels), a decrease in spatial tuning width (z = -5.19, FDR-adjusted p = 4.E-07 across voxels), and an augmentation of surround suppression (z = 4.47, FDR-adjusted p = 1.E-05 across voxels) (Fig. 2c-d).
Conclusions:
Comparisons between our findings and previous studies indicate fundamental differences in the effects of transcranial direct current stimulation (tDCS) on the visual and motor cortices. Our results suggest a prevalence of inhibitory effects in the visual cortex, contrasting with the excitatory effects predominant in the motor cortex. These observations underscore the importance of considering variations in the excitatory-inhibitory recurrent network across different brain regions when predicting or interpreting the effects of tDCS.
Brain Stimulation:
Non-invasive Electrical/tDCS/tACS/tRNS
TDCS 1
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI)
Perception, Attention and Motor Behavior:
Perception: Visual 2
Keywords:
Cortex
MRI
Vision
Other - transcranial Direct Current Stimulation (tDCS)
1|2Indicates the priority used for review