The modulation of attention bias modification using transcranial electrical stimulation

Abstract

Attention bias towards threat is implicated in the development, aetiology and maintenance of anxiety. Attention bias modification (ABM) is a cognitive training task which has been seen to manipulate the direction and magnitude of attention biases. ABM training to reduce threat bias has been effective in reducing anxiety. Transcranial electrical stimulation (tES) is a form of non-invasive brain stimulation which is known to modulate the effects of cognitive training. In the present research, two studies investigated the modulation of ABM with tES. In study 1, 172 participants (137 female) received transcranial random noise stimulation (tRNS) of the bilateral inferior frontal gyrus (IFG), anodal transcranial direct current stimulation (tDCS) of the left dorsolateral prefrontal cortex (DLPFC) or sham tES delivered concurrently with active, control or no-training ABM across three consecutive days to assess the effect on attention bias and state anxiety. State anxiety was reduced across participants irrespective of ABM or tES group. Threat bias was reduced for participants with a pre-existing threat bias and neutral bias was reduced for participants with a pre-existing neutral bias. In study 2, 39 participants (27 female) received ABM with anodal or sham tDCS of the left DLPFC during one session. As well as recording reaction times from the attention bias task, the N2pc component was measured as an electrophysiological indicator of attentional selection. The digit span task measured attentional control. State anxiety increased following ABM with sham (but not anodal) tDCS. N2pc suggested no modulation of ABM with anodal tDCS but reaction time data revealed reduced threat bias for participants with a pre-existing threat bias who received anodal (but not sham) tDCS. Digit span score was increased only for low trait anxious participants who received anodal tDCS. Overall, there was no evidence of superior ii reductions in threat bias and anxiety for active ABM relative to non-active ABM or the enhancement of ABM effects with tES. Instead, findings suggested that, for each experiment, outcomes were determined by the interaction of pre-existing cognitive and neural state with task and tES-induced frontal cortex facilitation. Where ABM sufficiently enhanced frontal mechanisms associated with top-down control this resulted in down-regulation of emotional response to anxiety evoking stimuli and its aversive influence on attentional processes. Where training insufficiently recruited these mechanisms, they could be enhanced using tES.

Date of Award	12 Feb 2019
Original language	English
Awarding Institution	University of Roehampton
Supervisor	Amanda Holmes (Supervisor), Margot Crossman (Supervisor) & Jonathan Silas (Supervisor)