Cognitive theory of depression predicts that the illness is associated with an information processing bias that interprets ambiguous information in a mood-congruent or depressive fashion. This negative interpretative bias may serve as a vulnerability factor or maintenance mechanism for a depressive illness. The majority of studies investigating such interpretative biases rely primarily on subjective experimental methodologies (eg., evaluative feedback and self-report) that are vulnerable to experimenter demand effects, response selection biases, and the influence of autobiographical memories. In addition, the results from these studies have been mixed, leading to no firm evidence for the existence of a depression-linked interpretative bias for ambiguous material. In order to avoid the limitations that have plagued subjective research, the present study utilised two of the most promising objective physiological measures of assessing interpretation: the Rapid Serial Viewing Presentation (RSVP) procedure and the affective modulation of the human eye blink reflex. The modified RSVP experiment recorded the reaction time of participants reading a textual scenario that was composed of an opening ambiguous sentence and various emotionally valenced continuations. Interpretation of the ambiguous sentence could be inferred from the reaction time as comprehension latency is inversely related to perceived plausibility. The affective modulation experiment recorded the blink amplitudes of participants startled while performing an imagery task. Blink amplitudes are augmented by negative stimuli and inhibited by hedonic stimuli. Thus, the affective interpretation of ambiguous stimuli could be inferred from the size of the recorded blink response. The results of both experiments did not support the predictions made by cognitive theory. There was no difference in the reaction time responses to the various textual stimuli between 2 depressed outpatients and healthy controls. However, antidepressant medication did have an influence upon the ability of patients to correctly judge the plausibility of the emotionally valenced continuation sentences. With regard to the eye blink experiment, there was also no difference between the depressed outpatients and the controls in terms of size of blink amplitude to the various categories of affective stimuli. Depressive, ambiguous, and distorted stimuli did not augment blink amplitudes in healthy controls or depressed patients without social anxiety disorder. However, depressed patients with a comorbid diagnosis of social anxiety disorder did react to the ambiguous stimuli in an aversive and anxious manner as indicated by increased blink amplitudes. This may be due to the social aspect of the experimental context, which engenders fears of evaluation and performance anxiety. The eye blink procedure can therefore be compromised by group selection, as the comorbidity of anxiety and depression can confound the investigation of depression-linked interpretative biases. In addition, the failure of depressive stimuli to augment blink amplitudes may render the procedure insensitive to the selection of such biases
| Identifer | oai:union.ndltd.org:ADTP/221160 |
| Date | January 2005 |
| Creators | Goggin, Leigh S. |
| Publisher | University of Western Australia |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Leigh S. Goggin, http://www.itpo.uwa.edu.au/UWA-Computer-And-Software-Use-Regulations.html |
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