Aging, sex and cognitive Theory of Mind: a transcranial direct current stimulation study

Abstract

Aging is accompanied by changes in cognitive abilities and a great interest is spreading among researchers about aging impact on social cognition skills, such as the Theory of Mind (ToM). Transcranial direct current stimulation (tDCS) has been used in social cognition studies founding evidence of sex-related different effects on cognitive ToM task in a young people sample. In this randomized, double-blind, sham-controlled study, we applied one active and one sham tDCS session on the medial prefrontal cortex (mPFC) during a cognitive ToM task, including both social (i.e., communicative) and nonsocial (i.e., private) intention attribution conditions, in sixty healthy aging individuals (30 males and 30 females). In half of the participants the anode was positioned over the mPFC, whereas in the other half the cathode was positioned over the mPFC. The results showed that: (i) anodal tDCS over the mPFC led to significant slower reaction times (vs. sham) for social intention attribution task only in female participants; (ii) No effects were found in both females and males during cathodal stimulation. We show for the first time sex-related differences in cognitive ToM abilities in healthy aging, extending previous findings concerning young participants.

Figure 1

Changes in RTs in the AI task (Pint and CInt stories) for active and sham tDCS in the four experimental groups. Only in the female group that received anodal tDCS over mPFC the RTs during the CInt task were increased after active tDCS compared to sham stimulation. Asterisk indicates a significant effect (p < 0.05). Errors bars indicate mean standard errors.

Figure 2

Experimental design and Current flow model for anodal tDCS application (anode over mPFC and cathode between Oz and Inion). Active or sham tDCS was started 2 minutes before the beginning of the experimental task and continued throughout the AI task. The anode was over the medial prefrontal cortex and the cathode placed between Inion and Oz. The device utilized two 7 × 5 cm sponge pads and the current flow model is represented in the transverse view and 3D view on the Male 1 model in Soterix HD Targets software (Soterix Medical). Arrows represent the direction of current flow. In the AI task, a short video was played, and the participant was asked to choose the picture representing a logical story ending by pushing one of the two buttons on the button box. One example for each stimulus condition (CInt and PInt) is displayed.