Sex Mediates the Effects of High-Definition Transcranial Direct Current Stimulation on “Mind-Reading”

Abstract

Sex differences in social cognitive ability are well established, including measures of Theory of Mind (ToM). The aim of this study was to investigate if sex mediates the effects of high-definition transcranial direct current stimulation (HD-tDCS) administered to a key hub of the social brain (i.e., the dorsomedial prefrontal cortex, dmPFC) on the Reading the Mind in the Eyes Test (RMET). Forty healthy young adults (18-35 years) were randomly allocated to receive either anodal or cathodal HD-tDCS in sham HD-tDCS controlled, double blind designs. In each of the two sessions, subjects completed the RMET. Anodal stimulation to the dmPFC increased accuracy on the RMET in females only. To assure regional specificity we performed a follow-up study stimulating the right temporoparietal junction and found no effect in either sex. The current study is the first to show improved performance on the RMET after tDCS to the dmPFC in females only. The polarity-specific effects and use of focal HD-tDCS provide evidence for sex-dependent differences in dmPFC function in relation to the RMET. Future studies using tDCS to study or improve ToM, need to consider sex.

Common and unique effects of HD-tDCS to the social brain across cultural groups

“…Anodal stimulation to the dmPFC also had a unique effect in the SEA cohort of reducing overall memory performance, whereas in the CA, overall memory performance remained the same and only the bias towards self-referential memories was removed.Previous studies have highlighted differential tDCS effects on the social brain based on sex (Adenzato et al, 2017;Martin, Huang, et al, 2017), but this is the first study to provide evidence that cultural background may also be a necessary consideration. Although this effect may be limited to social cognition where culture is a recognised source of variance, performance on other cognitive domains has been shown to be culturally specific (Nisbett & Miyamoto, 2005) and…”

“…The return electrode was 9.2/11.5 cm inner/outer in diameter for the dmPFC site, whereas a smaller electrode of 7.5/9.8 cm was used for the rTPJ site, due to the position of the right ear. Current modelling and safety information for these montages are presented in detail in previous studies (Gbadeyan et al, 2016;Martin, Huang, Hunold, & Meinzer, 2017;Martin, Huang, et al, 2018).…”

“…Prior to the VPT, participants completed a modified version of the Reading the Mind in the Eyes Test (RMET) (Baron-Cohen, Wheelwright, Hill, Raste, & Plumb, 2001), data published elsewhere (Martin, Huang, et al, 2017;Martin, Su, & Meinzer, 2018). The RMET requires participants to select one word from four multiple-choice options to describe the emotion/ mental state that best describes the expression from the eye region of the face.…”

“…Current modelling was conducted for both the dmPFC and rTPJ stimulation sites and is presented in previous manuscripts (Martin, Huang, et al, 2017. Briefly, peak current field strengths (0.36 V/m) were identified at the dmPFC [MNI: 0 54 33] and rTPJ (0.59 V/m) [MNI: 60 -54 13].…”

Improving cross-cultural “mind-reading” with electrical brain stimulation

“…The latter renders the stimulation ineffective while preserving blinding integrity (Gbadeyan, Steinhauser, McMahon, & Meinzer, 2016). Details of the stimulation parameters and biophysical modelling evidence for focal current delivery with both set--ups are provided in greater detail in previous manuscripts (Martin, Huang, Hunold, & Meinzer, 2017;Martin, Huang, & Meinzer, 2018). Sessions were at least three days apart to avoid carryover effects.…”