Abstract
Functional connectivity is linked to several degenerative brain diseases prevalent in our aging society. Electrical stimulation is used for the clinical treatment and rehabilitation of patients with many cognitive disorders. In this study, the effects of high-definition transcranial direct current stimulation (HD-tDCS) on resting-state brain networks in the human prefrontal cortex were investigated by using functional near-infrared spectroscopy (fNIRS). The intrahemispheric as well as interhemispheric connectivity changes induced by 1 mA HD-tDCS were examined in 15 healthy subjects. Pearson correlation coefficient-based correlation matrices were generated from filtered time series oxyhemoglobin (ΔHbO) signals and converted into binary matrices. Common graph theory metrics were computed to evaluate the network changes. Systematic interhemispheric, intrahemispheric, and intraregional connectivity analyses demonstrated that the stimulation positively affected the resting-state connectivity in the prefrontal cortex. The poststimulation connectivity was increased throughout the prefrontal region, while focal HD-tDCS effects induced an increased rate of connectivity in the stimulated hemisphere. The graph theory metrics clearly distinguished the prestimulation and poststimulation networks for a range of thresholds. The results of this study suggest that HD-tDCS can be used to increase functional connectivity in the prefrontal cortex. The increase in functional connectivity can be explored clinically for neurorehabilitation of patients with degenerative brain diseases.
Highlights
Today’s rapidly aging society is increasingly confronting degenerative brain diseases, such as mild cognitive impairment (MCI) and Alzheimer’s disease (AD)
The results of this study suggest that high-definition transcranial direct current stimulation (HD-Transcranial direct current stimulation (tDCS)) can be used to increase functional connectivity in the prefrontal cortex
The effects of HD-tDCS on ΔHbO were examined in the pre, intra, and poststimulation phases
Summary
Today’s rapidly aging society is increasingly confronting degenerative brain diseases, such as mild cognitive impairment (MCI) and Alzheimer’s disease (AD). Patients with AD face difficulties in their daily tasks due to impairments in cognitive functions like working memory, episodic memory, and executive attention [1, 2]. The prefrontal cortex is involved in working memory and several executive tasks [6]. Functional near-infrared spectroscopy (fNIRS) has been employed to study the functional activation and connectivity in relation to working memory, AD, and multiple neuropsychiatric disorders [7] such as schizophrenia [8], various types of affective disorders [9,10,11,12,13,14], and the treatment and rehabilitative effects in psychiatric disorders [15]. Functional connectivity in the human brain is critical for the performance of our daily tasks. This study was conducted to develop a better understanding of resting-state functional connectivity and its dynamic changes in light of stimulation
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