Sustained, not habituated, activity in the human amygdala: A pilot fMRI dot-probe study of attentional bias to fearful faces

The effects of yohimbine and hydrocortisone on selective attention to fearful faces: An fMRI study

INTRODUCTION

Selective attention to salient emotional information can enable an advantage in the face of danger. The present study aims to investigate the influence of the stress neuromodulators, norepinephrine and cortisol, on selective attention processes to fearful faces and its neuronal activation.

METHODS AND MATERIALS

We used a randomized, double-blind, placebo-controlled design. 167 healthy men between 18 and 35 years (mean [SD] age: 25.23 [4.24] years) participated in the study. Participants received either: (A) yohimbine (n= 41), (B) hydrocortisone (n = 41), (C) yohimbine and hydrocortisone (n = 42) or (D) placebo only (n= 43) and participated in a dot-probe task with fearful and neutral faces in an fMRI scanner.

RESULTS

We found an attentional bias toward fearful faces across all groups and related neuronal activation in the left cuneus. We did not find any differences between experimental treatment groups in selective attention and its neuronal activation.

DISCUSSION

Our results provide evidence that fearful faces lead to an attentional bias with related neuronal activation in the left cuneus. We did not replicate formerly reported activation in the amygdala, intraparietal sulcus, dorsal anterior cingulate cortex, and thalamus. Suitability of the dot-probe task for fMRI studies and insignificant treatment effects are discussed.

The stability and reliability of attentional bias measures in the dot-probe task: Evidence from both traditional mean bias scores and trial-level bias scores

A new method of calculating attentional bias from the dot-probe task measures fluctuations in bias towards and away from emotional stimuli over time using trial level bias score metrics. We assessed the stability and reliability of traditional attentional bias scores and trial level bias score measures of attentional bias across time in two five-block dot-probe task experiments in non-clinical samples. In experiments 1 and 2, both traditional attentional bias scores and trial level bias score measures of attentional bias did not habituate/decrease across time. In general, trial level bias score metrics (i.e., attention bias variability as well as the mean biases toward and away from threat) were more reliable than the traditional attention bias measure. This pattern was observed across both experiments. The traditional bias score, however, did improve in reliability in the later blocks of the fearful face dot-probe task. Although trial level bias score measures did not habituate and were more reliable across blocks, these measures did not correlate with state or trait anxiety. On the other hand, trial level bias score measures were strongly correlated with general reaction time variability-and after controlling for this effect no longer superior in reliability in comparison to the traditional attention bias measure. We conclude that general response variability should be removed from trial level bias score measures to ensure that they truly reflect attention bias variability.

Cross-species convergence in pupillary response: understanding human anxiety via non-human primate amygdala lesion

Few studies have used matched affective paradigms to compare humans and non-human primates. In monkeys with amygdala lesions and youth with anxiety disorders, we examined cross-species pupillary responses during a saccade-based, affective attentional capture task. Given evidence of enhanced amygdala function in anxiety, we hypothesized that opposite patterns would emerge in lesioned monkeys and anxious participants. A total of 53 unmedicated youths (27 anxious, 26 healthy) and 8 adult male rhesus monkeys (Macaca mulatta) completed matched behavioral paradigms. Four monkeys received bilateral excitotoxic amygdala lesions and four served as unoperated controls. Compared to healthy youth, anxious youth exhibited increased pupillary constriction in response to emotional and non-emotional distractors (F(1,48) = 6.28, P = 0.02, η2p = 0.12). Pupillary response was associated significantly with anxiety symptoms severity (F(1,48) = 5.59, P = 0.02, η2p = 0.10). As hypothesized, lesioned monkeys exhibited the opposite pattern i.e. decreased pupillary constriction in response to distractors, compared to unoperated control monkeys (F(1,32) = 24.22, P < 0.001, η2 = 0.33). Amygdala lesioned monkeys and youth with anxiety disorders show opposite patterns of pupil constriction in the context of an affective distractor task. Such findings suggest the presence of altered amygdala circuitry functioning in anxiety. Future lesion and human neuroimaging work might examine the way in which specific amygdala sub-nuclei and downstream circuits mediate these effects.

Climate change images produce an attentional bias associated with pro-environmental disposition

Humans have developed mechanisms to prioritize certain sensory input(s). Emotionally salient stimuli automatically capture observers' attention at the cost of less salient information. This prioritized processing is called attentional bias. Images of climate change have been found to elicit emotional responses. Yet, to date, there is no research assessing the extent to which climate change-relevant images produce an attentional bias. In a sample of college students (N = 39), we found that (1) climate change-related images capture attention and that (2) this attentional bias is related to individual differences in environmental disposition. Thus, images of climate change are salient-attention grabbing-signals related to pro-environmental orientation.

Extended testing with the dot-probe task increases test-retest reliability and validity

The dot-probe task is used to measure attentional biases toward threat. However, the test-retest reliability and validity of the task have been called into question. No studies to date have included an extended number of testing sessions or tailored the task to individual participants by incorporating self-relevant stimuli-doing so may improve reliability. Here, participants provided 10 words that caused them anxiety and 10 neutral words which were incorporated into a dot-probe task for 6 sessions. The test-retest reliability of their bias indices was stronger in bottom-target trials relative to top-target trials and stronger among later relative to earlier sessions. State and trait anxiety were moderately correlated with bias indices in later sessions, but not earlier sessions. Overall reaction time in each session was moderately correlated with state and trait anxiety. These results suggest that including extended testing may facilitate dot-probe task test-retest reliability and validity.