ECT : de la neuroplasticité aux mécanismes d’action

Neuroimaging correlates of cognitive disorders secondary to electroconvulsive therapy: A systematic review

OBJECTIVES

Electroconvulsive therapy is known as an efficient therapy, which is sometimes recommended for the management of severe and resistant depression. However, ECT is associated with cognitive adverse effects. The study of the neurobiological correlates of the cognitive adverse effects of ECT has been covered in few published reviews. However, these mechanisms have been investigated in an increasing number of studies in recent years, particularly in neuroimaging. This systematic review of the literature focuses on correlates between changes in structural or functional neuroimaging and impairment of cognitive functions during the ECT treatment.

METHODS

We conducted a systematic review of the literature using PRISMA methodology. Searches were performed on the Medline and Web of Science databases using the following equation: "electroconvulsive therapy AND (MRI OR fMRI OR DTI OR neuroimaging) AND depression AND cogniti*".

RESULTS

This article highlights the significant heterogeneity of the results. In structural imaging, approximately 50% of the studies did not report any correlation between volumetric changes and neuropsychological changes. In studies that did highlight a correlation, the latter was mainly reported with changes in the hippocampus. From a functional perspective, we highlighted a correlation between changes in the connectivity of the hippocampal region and cognition.

CONCLUSION

These results demonstrate a growing interest in understanding the neurobiological mechanisms underlying cognitive disorders secondary to ECT treatment. The ultimate aim behind this understanding is to adopt a more effective prevention strategy vis-à-vis these adverse effects.

Hippocampal Volume and Plasma Brain-Derived Neurotrophic Factor Levels in Patients With Depression and Healthy Controls

The aim of the present study was to investigate associations between hippocampal subfield volumes and plasma levels of brain-derived neurotrophic factor (BDNF) in patients experiencing a first episode of major depression (MD) (n = 30) as compared to healthy controls (HC) (n = 49). Covariate-adjusted linear regression was performed to compare the MD and healthy groups, adjusting for age, sex, and total estimated intracranial volume. We demonstrated that there were no differences in total hippocampal volume between the MD and HC groups. However, the volumes of the hippocampus-amygdala-transition-area (HATA) on the left side of the brain as well as the parasubiculum, presubiculum, and fimbria on the right side were statistically significantly smaller in the MD group than in the HC group. Furthermore, the volume of the hippocampal fissure on the right side was statistically significantly smaller in the HC group than in the MD group. In the MD group, we found a positive linear correlation between hippocampal volume and plasma BDNF concentrations in the CA4 area on the left side (p = 0.043). In contrast, in the HC group, we found a negative linear correlation between parasubiculum volume on the right side and plasma BDNF concentrations (p = 0.04). These results suggest that some hippocampal subfields may already be atrophic at the start of MD. In addition, our findings suggest that the sensitivity of the right parasubiculum region to BDNF may differ between MD and HC groups. These findings guide future research directions and, if confirmed, may ultimately inform medical guidelines.

The expression of non-clustered protocadherins in adult rat hippocampal formation and the connecting brain regions

Non-clustered protocadherins (PCDHs) are calcium-dependent adhesion molecules which have attracted attention for their possible roles in the neuronal circuit formation during development and their implications in the neurological disorders such as autism and mental retardation. Previously, we found that a subset of the non-clustered PCDHs exhibited circuit-dependent expression patterns in thalamo-cortical connections in early postnatal rat brain, but such patterns disappeared in adulthood. In this study, we identified that the non-clustered PCDHs showed differential expression patterns along the septotemporal axis in the subregions of adult hippocampus and dentate gyrus with topographical preferences. The expressions of PCDH1, PCDH9, PCDH10 and PCDH20 showed septal preferences, whereas the expressions of PCDH8, PCDH11, PCDH17 and PCDH19 showed temporal preferences, suggesting that they play roles in the formation/maintenance of intrahippocampal circuits. PCDHs also exhibited the region-specific expression patterns in the areas connected to hippocampal formation such as entorhinal cortex, lateral septum, and basolateral amygdaloid complex. Furthermore, the expression levels of three PCDHs (PCDH8, PCDH19 and PCDH20) were regulated by the electroconvulsive shock stimulation of the brain in the adult hippocampus and dentate gyrus. These results suggest that non-clustered PCDHs are involved in the maintenance and plasticity of adult hippocampal circuitry.