The role of naturally occurring differences in norepinephrine availability in modulating electrocortical indices of affectively biased attention

[摘要] It is well established that emotionally salient stimuli implicitly guide attention and enhance visual cortex activation. Yet when emotional salience is pitted against task-relevant goals, mixed effects have been observed, with salient stimuli sometimes hampering task performance (competition), and sometimes improving it (facilitation). Non-human animal research suggests norepinephrine (NE) plays a role in enhancing the gain of neural populations tuned to both affectively salient and goal-relevant stimuli. In humans, genotyping for a common (~50%) deletion variant of the ADRA2b gene, which codes for alpha2b NE receptors, provides a window into the role of NE availability. The goals of the present study were: (1) To examine allocation of cortical resources to task demands in the presence of emotionally salient distractors, and (2) to employ genotyping to explore the role of noradrenergic processes. We measured steady-state visual evoked potentials (ssVEPs) during a change detection task wherein task-relevant Gabor patches were overlaid on task-irrelevant happy, angry, or neutral faces. The overlapping stimuli were driven at distinct frequencies (15 Hz or 20 Hz, counterbalanced within participants). Observers were asked to report phase reversals in the Gabor patch and ssVEP amplitude at driving frequencies was extracted to measure allocation of attention. Observers showed greater accuracy and higher ssVEP amplitudes for targets overlaid on angry faces than on happy or neutral faces, indicating a pronounced facilitation in the presence of negative stimuli. ssVEP amplitudes for faces showed an effect of arousal, with higher amplitudes for happy and angry faces, suggesting there was not a trade-off between resources allocated to targets vs. distractors. Preliminary genotyping results (N = 126) indicate that carrying the ADRA2b deletion variant enhanced the facilitation effect, suggesting that, rather than playing a requisite role, greater NE availability functions to enhance existing patterns facilitation of focused attention by negative affect.

[学科分类] 眼科学