Journal: Brain Stimulation (2021)
Authors: Alyagon U, Barnea-Ygael N, Carmi L, Zangen A
Background:
Adaptive decision making requires the adjustment of behavior following an error in order to improve future performance, but OCD patients are characterized by abnormal error monitoring. For example, in cognitive tasks like Flanker or Stroop, reaction time (RT) following commission of an error (post-error; PE) is often longer than that of RT following a correct response (post-correct; PC), but this phenomenon, known as PE slowing (PES), is inordinate in OCD patients and associated with increased theta activity over the medial prefrontal cortex (mPFC).
Objective:
Test the hypothesis that multiple stimulation sessions of the mPFC may induce long-term modifications to cognitive functions associated with error monitoring.
Methods:
Data from the OCD pilot randomized controlled trial that included a Stroop task and electrophysiological recording administered before the first and last treatment sessions was revisited. Analysis of total RT distribution (PC+PE) was conducted using extraction of percentiles (5,25,50,75,95) from the RT distribution of each individual during incongruent trials. These were subjected to ANOVA with Percentiles X Time (pre/post treatment) X Treatment (active/sham) X Condition (PC/PE).
Results:
Pre- and Post-treatment Stroop data was available for 12 patients of the active group (7 females) and 10 patients of the sham group (7 females. ANOVA of RTs revealed a three-way Time X Condition X Treatment interaction (F1,19=5.38, p<0.05), and a follow-up Bonferroni corrected post-hoc analysis revealed that active Deep TMS significantly reduced RTs in both task conditions (PC: p<0.005, PE: p<0.00001). A direct comparison between treatments revealed that PES was reduced in the active (F1,19=5.39, p<0.05) but not the sham (F1,19=1.06, p<0.32) group. Comparable analysis of PEA reveled robust reduction of accuracy following errors (F1,19=16.4, p<0.001) but without an interaction effect with treatment or time (F1,19=0.04, p=0.83). Moreover, treatment-induced changes in PES and PEA were significantly correlated with each other in the active (r=0.63, p<0.05), but not in the sham (r=0.03, p=0.93) group.
Conclusions:
Taken together, these results indicate that patients receiving the active Deep TMS course improved their performance in the Stroop task in accordance with task requirements. This suggests that Deep TMS of the mPFC and ACC can induce long-term modifications to cognitive functioning associated with error monitoring.
