Structural MRI-based measures of neuroplasticity in an extended amygdala network as a target for attention bias modification treatment outcome.

Increased attentional bias to threat has been identified as a causal mechanism in the development of anxiety. As such, attention bias modification (ABM) was conceived as a treatment option where anxiety is alleviated through a computerized cognitive training regimen that reduces an individual's attentional bias to threat. Although ABM appears to be a promising treatment option for anxiety, the mechanism of action by which the treatment is effective is unknown. We hypothesize that effective ABM treatment is associated with neuroplasticity-related structural changes in an extended amygdala - prefrontal cortex network that can be detected with standard T-weighted magnetic resonance imaging (MRI). Literature regarding [1] effects of brain damage on attention bias, [2] functional neuroimaging of attention bias, [3] structural neuroimaging of attention bias, and [4] functional neuroimaging of ABM training all support the role of this network as the underlying mechanism of attention bias behavior and neuroplasticity-related changes in attentional bias. Additionally, we provide proof of principle pilot data that ABM training reduces MRI measures of gray matter volume in the basal forebrain/extended amygdala and medial prefrontal cortex. Greater reduction in gray matter volume corresponds to greater reduction in attentional bias. In addition, level of pre-training bias appears to be a strong indicator of treatment outcome. In short, we provide converging evidence for the hypothesis that the mechanism underlying effective ABM training is reduced gray matter volume in an extended amygdala network. MRI-based measures of neuroplasticity in this network could be an important target outcome for the treatment of anxiety with ABM.