Mood and cerebral perfusion revisited.

Klaus P Ebmeier

doi:10.1155/2000/585629

Abstract

Twenty patients with major depression and observed diurnal variations of mood were examined using clinical and neuropsychological measures and perfusion HMPAO-SPECT at 8 a.m. and 8 p.m. In thirteen patients depression scores varied more than 15% although 4 patients with reverse diurnal variation caused mean group depression scores to be not different between morning and evening. There was an overall trend for higher depression scores to be associated with higher perfusion in posterior cingulate. This was mainly accounted for by significant positive correlations in the morning scan in posterior, but also anterior cingulate and medial prefrontal cortex compared with evening scans. This means that morning regression slopes were steeper than evening slopes. This result is discussed with regard to possible interpretations, such as adaptive or habituating changes during the day that may occur in depressed patients.

Highlights

Evidence accumulated in affective disorder research over the last five years points towards the limbic frontal lobes, including the cingulate, the basal ganglia and parts of the temporal lobe as structures underlying symptom formation [24]
As a matter of principle, changes in such studies can be due to regression to the mean or habituation effects that confound the observed associations between symptoms and brain activity patterns
A time-of-day dependent ‘uncoupling’ of the symptom-brain activity relationship in certain areas of the limbic cortex may suggest compensatory brain mechanisms or a habituation of such mechanisms during the course of the day. It may explain some of the difficulties encountered in studies trying to replicate cingulate and medial prefrontal changes in depressed patients [9]

Summary

Introduction

Evidence accumulated in affective disorder research over the last five years points towards the limbic frontal lobes, including the (anterior) cingulate, the basal ganglia and parts of the temporal lobe (such as the amygdala) as structures underlying symptom formation [24] This evidence partly derives from cross-sectional association studies. In order to demonstrate the association between symptoms and brain activity more convincingly, repeat-measures analyses that can link brain activity with symptom changes are necessary. Such studies tend to suffer from order effects that occur, for example, when patients are examined before and after treatment, i.e. first ill and recovered [22]. For economic reasons, balancing studies for order by examining subjects first when well, is impossible apart from very rare occasions, such as lithium withdrawal

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Conclusion