Frederic Boy | Searcharxiv

arXiv2015

Repeated transcranial direct current stimulation (tDCS) in nondepressed reduces levels of reported negative affects from daily stressors

Negative emotional responses to the daily life stresses have cumulative effects which, in turn, impose wide-ranging negative constraints on emotional well being and neurocognitive performance (Kalueff:2007cp, Charles:2013eq, Nadler:2010hk). Crucial cognitive functions such as memory and problem solving, as well more short term emotional responses (e.g., anticipation of- and response to- monetary rewards or losses) are influenced by mood. The negative impact of these behavioural responses is felt at the individual level, but it also imposes major economic burden on modern healthcare systems. Although much research have been undertaken to understand the underlying mechanisms of depressed mood and design efficient treatment pathways, comparatively little was done to characterize mood modulations that remain within the boundaries of a healthy mental functioning. In one placebo-controlled experiments, we applied daily prefrontal transcranial Direct Current Stimulation (tDCS) at five points in time, and found reliable improvements on self-reported mood evaluation. We replicated this finding in an independent double-blinded placebo-controlled experiment and showed that stimulation over a shorter period of time (3 days) is sufficient to create detectable mood improvements. Taken together, our data show that repeated bilateral prefrontal tDCS can reduce psychological distress in nondepressed individuals.

q-bio.NC↗

arXiv2013

Visibility predicts priming within but not between people: a cautionary tale for studies of cognitive individual differences

With resurgent interest in individual differences in perception, cognition and behavioural control, as early indicators of disease, endophenotypes, or a means to relate brain structure to function, behavioural tasks are increasingly being transferred from within-subject settings to between-group or correlational designs. The assumption is that where we know the mechanisms underlying within-subject effects, these effects can be used to measure individual differences in those same mechanisms. However, between-subject variability can arise from an entirely different source from that driving within-subject effects, and here we report a clear-cut demonstration of this. We examined the debated relationship between the visibility of a masked-prime stimulus and the direction of priming it causes (positive or reversed). Such reversal of priming has been hypothesized to reflect an automatic inhibitory mechanism that controls partially activated responses and allows behavioural flexibility. Within subjects, we found an unambiguous systematic transition from reversed priming to positive priming as prime visibility increased, replicated seven times, and using different stimulus manipulations. However, across individuals there was never a relationship between prime discrimination ability and priming. Specifically, these data resolve the controversial debate on visibility and reversed priming, indicating that they arise from independent processes relying on partially shared stimulus signals. More generally, they stand as an exemplar case in which variance between individuals arises from a different source from that produced by stimulus manipulations.

q-bio.NC↗