Transcranial Direct Current Stimulation (tDCS) Can Modulate EEG Complexity of Children With Autism Spectrum Disorder

Abstract

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder which affects the developmental trajectory in several behavioral domains, including impairments of social communication, cognitive and language abilities. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique, and it was used for modulating the brain disorders. In this paper, we enrolled 13 ASD children (11 males and 2 females; mean ± SD age: 6.5 ± 1.7 years) to participate in our trial. Each patient received 10 treatments over the dorsolateral prefrontal cortex (DLPFC) once every 2 days. Also, we enrolled 13 ASD children (11 males and 2 females; mean ± SD age: 6.3 ± 1.7 years) waiting to receive therapy as controls. A maximum entropy ratio (MER) method was adapted to measure the change of complexity of EEG series. It was found that the MER value significantly increased after tDCS. This study suggests that tDCS may be a helpful tool for the rehabilitation of children with ASD.

Keywords: autism spectrum disorder (ASD); complexity; electroencephalography (EEG); maximum entropy ratio (MER); transcranial direct current stimulation (tDCS).

Figure 1

Plot of the maximized entropy ratio h′(ε) = logM(ε)/M(ε) as a function of M(ε) in the Equation (7).

Figure 2

MER analysis of an EEG segment of pre-stimulation. (A) The original EEG data from the pre-tDCS state; (B) The recurrence plot of (A), with ε = 13.2; (C) Change of entropy and cardinality with ε; (D) Symbolic recurrence plot; (E) Change of entropy ratio with ε (from 0.01 – 20.34 with 0.01 increment).

Figure 3

MER analysis of an EEG segment of post-stimulation. (A) The original EEG data from the post-tDCS state; (B) The recurrence plot of (A), with ε = 10.88; (C) Change of entropy and cardinality with ε; (D) Symbolic recurrence plot; (E) Change of entropy ratio with ε (from 0.01 – 16.46 with 0.01 increment).

Figure 4

MER analysis of an EEG segment for the controls at the first time. (A) The original EEG data from controls; (B) The recurrence plot of (A), with ε = 11.16; (C) Change of entropy and cardinality with ε; (D) Symbolic recurrence plot; (E) Change of entropy ratio with ε (from 0.01 – 20.00 with 0.01 increment).

Figure 5

MER analysis of an EEG segment for the controls at the second time. (A) The original EEG data from the controls; (B) The recurrence plot of (A), with ε = 10.9; (C) Change of entropy and cardinality with ε; (D) Symbolic recurrence plot; (E) Change of entropy ratio with ε (from 0.01 – 20.00 with 0.01 increment).