Transcranial direct current stimulation of the prefrontal cortex

Abstract

Targeting memory processes by noninvasive interventions is a potential gateway to modulate fear memories as shown by animal and human studies in recent years. Modulation of fear memories by noninvasive brain stimulation techniques might be an attractive approach, which, however, has not been examined so far. We investigated the effect of transcranial direct current stimulation (tDCS) applied to the right dorsolateral prefrontal cortex and left supraorbital region on fear memories in humans. Seventy-four young, healthy individuals were assigned randomly to two groups, which underwent fear conditioning with mild electric stimuli paired with a visual stimulus. Twenty-four hours later, both groups were shown a reminder of the conditioned fearful stimulus. Shortly thereafter, they received either tDCS (right prefrontal--anodal, left supraorbital--cathodal) for 20 min at 1 mA current intensity or sham stimulation. A day later, fear responses of both groups were compared by monitoring skin conductance. On day 3, during fear response assessment, the tDCS group had a significantly (P<0.05) higher mean skin conductance in comparison with the sham group. These results suggest that tDCS (right prefrontal--anodal, left supraorbital--cathodal) enhanced fear memories, possibly by influencing the prefrontal cortex-amygdala circuit underlying the memory for fear.

Exploring prefrontal cortex functions in healthy humans by transcranial electrical stimulation

“…In a task in which the participants are instructed to downregulate or upregulate emotional responses to the presentation of negative or neutral pictures, anodal tDCS of the right DLPFC improves the amount of intended emotion regulation [76] . Finally, anodal tDCS over the right DLPFC combined with left frontopolar cathodal tDCS applied in the re-consolidation phase of a fear-conditioning paradigm improves fear memories, which is in accord with an involvement of the prefrontal cortices in fear memory consolidation [77] .…”

Transcranial direct current stimulation may modulate extinction memory in posttraumatic stress disorder

“…The first trial was omitted from analyses to account for an orienting response (Mungee, Burger, & Bajbouj, 2016; Mungee et al., 2014; van ‘t Wout et al., 2013). Before discarding any data, adequacy of conditioning was examined as defined by CS+ > CS− during conditioning, and CS+ during conditioning >CS+ during habituation (Asthana et al., 2013; Mungee et al., 2014, 2016; Phelps et al., 2004; van ‘t Wout et al., 2013).…”

“…Before discarding any data, adequacy of conditioning was examined as defined by CS+ > CS− during conditioning, and CS+ during conditioning >CS+ during habituation (Asthana et al., 2013; Mungee et al., 2014, 2016; Phelps et al., 2004; van ‘t Wout et al., 2013). Following this definition, five participants did not condition appropriately and were removed from subsequent analyses.…”

“…This protocol was designed to deliver current to the vmPFC and avoid cathodal effects on the prefrontal cortex. However, other brain regions involved in fear processing (i.e., the dorsolateral prefrontal cortex, Mungee et al., 2014; Asthana et al., 2013; Delgado, Nearing, LeDoux, & Phelps, 2008; and anterior cingulate cortex, Etkin, Egner, & Kalisch, 2011; Milad et al., 2007) may have been inadvertently stimulated. Also, tDCS was applied once for a duration of 10 min total and effects of tDCS may be expected to increase with greater duration and number of sessions (Brunoni et al., 2016).…”

“…tDCS was chosen as it can modulate intrinsic neuronal activity using a weak, constant electrical current (Nitsche et al., 2008) to facilitate cognitive processing including learning and memory (Asthana et al., 2013; Coffman, Clark, & Parasuraman, 2014; Mungee et al., 2014). This work aligns with the rapidly growing body of research that indicates tDCS may have beneficial effects for psychiatric conditions associated with altered prefrontal activity or connectivity, including depression (Drevets, Price, & Furey, 2008), schizophrenia (Meyer‐Lindenberg et al., 2002), and obsessive–compulsive disorder (Chamberlain et al., 2008).…”