Dichotic Listening before and after Fluoxetine Treatment for Major Depression: Relations of Laterality to Therapeutic Response

Abstract

Despite the wide variance in therapeutic response to antidepressants, there are few clinical or biological predictors of treatment outcome. Studies have suggested the possible value of dichotic listening measures of perceptual asymmetry (PA) as predictors of treatment response. This study examined the relation between outcome of fluoxetine treatment and performance on verbal and nonverbal dichotic tests. As part of a multisite study, 86 outpatients with major depression were tested on dichotic fused-words and complex-tones tests both before and during treatment. Fluoxetine responders differed from nonresponders in having greater right-ear (left-hemisphere) advantage for dichotic words and less left-ear (right-hemisphere) advantage for complex tones. There was no change in PA during fluoxetine treatment, which indicates that PA differences between treatment responders and nonresponders are stable (trait) characteristics. An aggregate, characteristic PA measure was the best predictor of responder status in a logistic regression analysis. Findings from two clinical centers support the hypothesis that a characteristic tendency for relatively greater left-than right-hemispheric activation during dichotic listening is associated with better outcome of fluoxetine treatment.

Dichotic Listening Tests of Functional Brain Asymmetry Predict Response to Fluoxetine in Depressed Women and Men

“…Thus, SSRI responders may have an abnormality of the serotonergic neurotransmitter system that is not shared by patients who do not respond to an SSRI. Our current findings and those of prior studies support the existence of treatment-responsive and -nonresponsive subtypes of depression that differ in functional brain asymmetry (Bruder et al, 1990(Bruder et al, , 1996Stewart et al, 1999). Our findings also suggest the possible clinical value of dichotic listening tests for predicting therapeutic response to an SSRI.…”

“…This was the case in two separate studies, one with patients having an MDD and the other with patients having a mixture of affective disorders, including MDD, dysthymia, or depression not otherwise specified. The consistency of findings across these studies and our prior study (Bruder et al, 1996) indicates that the difference in hemispheric asymmetry between fluoxetine responders and nonresponders is robust and replicable.…”

“…In a prior study of the SSRI fluoxetine (Bruder et al, 1996), unmedicated depressed patients at two clinical centers who subsequently responded to fluoxetine had greater left-hemisphere advantage for dichotic fused words and less right-hemisphere advantage for complex tones when compared to treatment nonresponders. There was no change in PA following treatment, which suggests that the difference between fluoxetine responders and nonresponders represents a stable, state-independent characteristic.…”

Electroencephalographic Alpha Measures Predict Therapeutic Response to a Selective Serotonin Reuptake Inhibitor Antidepressant: Pre- and Post-Treatment Findings

“…Cook et al (16) did not find pretreatment differences between fluoxetine responders and nonresponders in theta, but did find group differences in "cordance", a measure based on a form of surface Laplacian (see Tenke and Kayser [17] for a discussion of methodological limitations). We found a difference in alpha asymmetry between fluoxetine responders and nonresponders (8), which was predicted on the basis of dichotic listening findings (18). Fluoxetine nonresponders showed greater alpha power (less activity) over the left hemisphere than the right, whereas responders tended to have the opposite asymmetry.…”

Surrogate markers of treatment outcome in major depressive disorder

“…Bruder et al (1990) first reported a relationship between perceptual asymmetry following dichotic listening tasks at baseline and outcome during TCA therapy, such that patients with a left-ear advantage were significantly more likely to be responders than those without. This has since been replicated with the SSRI fluoxetine (Bruder et al 1996(Bruder et al , 2004, and the NDRI bupropion (Bruder et al 2007). Unfortunately, studies linking preferential response to antidepressant agents for MDD patients with a right-ear advantage have not been published to date.…”