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انگلیسی:
There is now substantial theoretical and
empirical support for the importance of information processing biases in the
maintenance, and perhaps the etiology, of major depression (1–3). Specifically,
biased attention to depression-relevant material and avoidance of positive
information are hypothesized to maintain the disorder. Recent research has also
demonstrated that modifying these biases reduces symptoms of depression (4–6).
According to a recent cognitive neuropsychological model of depression (7),
antidepressant medications—particularly those that target serotonin and
norepinephrine—may act by modifying emotional information processing. Modified
emotional information processing, in turn, is thought to lead to downstream
antidepressant effects. This model helps explain why antidepressant medication
use is not immediately associated with amelioration of depressed mood. As Harmer
and colleagues note (7), “Rather than acting as direct ‘mood enhancers,’
antidepressants may re-tune how we process personal and socially relevant
affective information” (p. 107). This model follows from a series of studies
suggesting that 1) antidepressants influence emotional information processing
early in treatment; 2) changes in emotional information processing occur earlier
than and in the absence of changes in subjective mood; and 3) early changes in
information processing are associated with eventual therapeutic improvement (see
the review by Harmer et al. [7]). Thus far, much of this research has been
conducted with healthy subjects. For example, Browning et al. (8) randomly
assigned 32 healthy volunteers to receive either one dose of citalopram or a
placebo pill. Consistent with the cognitive neuropsychological hypothesis,
individuals who received the antidepressant demonstrated greater attention to
positive stimuli, as assessed with a visual probe task. More recently,
researchers have begun to evaluate this phenomenon in individuals with
depression. For instance, Harmer et al. (9) conducted a double-blind
placebocontrolled study evaluating patients with depression and healthy
subjects. In line with the cognitive neuropsychological model, depressed
patients who received placebo exhibited lower recognition of positive facial
expressions and lower memory for positive information, as well as slower speed
to respond to positive personality adjectives, compared with healthy subjects.
Notably, these information processing effects in the depressed patients were
reversed with the administration of just a single dose of an antidepressant
(reboxetine). However, there were not corresponding reductions in subjective
ratings of mood or anxiety after this initial administration. In this study, we
built on previous research to focus specifically on the relationship between
antidepressant medication use and selective attention to emotional visual
stimuli, using eye-tracking technology, in a sample of participants with major
depressive disorder as well as a nondepressed comparison group. This research
adds to the small number of studies that have empirically examined the cognitive
neuropsychological model of depression in a clinical sample. The inclusion of a
nondepressed comparison group is also valuable for comparative purposes insofar
as it allows us to more clearly delineate “normal” attention for emotional
information. Our use of an eye-tracking paradigm is particularly valuable
because it allows for multiple dynamic measures of selective attention (10).
This is critical because it enables us to capture the more elaborative stages of
attention that are particularly relevant for patients with major depression
(11). Eye tracking also specifically provides an assessment of overt attention,
since eye movements are necessarily associated with shifts in attention, whereas
the dot-probe task used in previous studies does not always elicit eye movements
and may measure both overt and covert shifts in attention (12, 13). Ours is also
the first study to examine the effects of antidepressant medication, as
prescribed in the community, on emotional information processing. We used eye
tracking to measure selective attention (total gaze duration, mean number of
fixations, mean fixation duration) for dysphoric, threatening, positive, and
neutral emotional scenes in a sample of community participants with major
depression (both medicated and unmedicated) and a never-depressed comparison
group. Consistent with previous work (8, 9), we hypothesized that antidepressant
medication use, compared with nonuse, would be associated with greater selective
attention for positive stimuli. We further predicted that there would not be
significant group differences between the medicated major depression group and
the nondepressed comparison group on selective attention for positive
information, consistent with the idea that antidepressant medication use
normalizes emotional information processing. |
