Fractal Dimension in ECT: New Imaging Markers

 Out on PubMed, from researchers in Switzerland and the US, is this paper:

Analyzing Fractal Dimension in Electroconvulsive Therapy: Unraveling Complexity in Structural and Functional Neuroimaging.

Denier N, Grieder M, Jann K, Breit S, Mertse N, Walther S, Soravia LM, Meyer A, Federspiel A, Wiest R, Bracht T.Neuroimage. 2024 Jun 18:120671. doi: 10.1016/j.neuroimage.2024.120671. Online ahead of print.PMID: 38901774

The abstract is copied below:

Background: Numerous studies show that electroconvulsive therapy (ECT) induces hippocampal neuroplasticity, but findings are inconsistent regarding its clinical relevance. This study aims to investigate ECT-induced plasticity of anterior and posterior hippocampi using mathematical complexity measures in neuroimaging, namely Higuchi's fractal dimension (HFD) for fMRI time series and the fractal dimension of cortical morphology (FD-CM). Furthermore, we explore the potential of these complexity measures to predict ECT treatment response.

Methods: Twenty patients with a current depressive episode (16 with major depressive disorder and 4 with bipolar disorder) underwent MRI-scans before and after an ECT-series. Twenty healthy controls matched for age and sex were also scanned twice for comparison purposes. Resting-state fMRI data were processed, and HFD was computed for anterior and posterior hippocampi. Group-by-time effects for HFD in anterior and posterior hippocampi were calculated and correlations between HFD changes and improvement in depression severity were examined. For FD-CM analyses, we preprocessed structural MRI with CAT12's surface-based methods. We explored group-by-time effects for FD-CM and the predictive value of baseline HFD and FD-CM for treatment outcome.

Results: Patients exhibited a significant increase in bilateral hippocampal HFD from baseline to follow-up scans. Right anterior hippocampal HFD increase was associated with reductions in depression severity. We found no group differences and group-by-time effects in FD-CM. After applying a whole-brain regression analysis, we found that baseline FD-CM in the left temporal pole predicted reduction of overall depression severity after ECT. Baseline hippocampal HFD did not predict treatment outcome.

Conclusion: This study suggests that HFD and FD-CM are promising imaging markers to investigate ECT-induced neuroplasticity associated with treatment response.

Keywords: Electroconvulsive therapy; connectivity; depression; functional MRI; neuroimaging; neuroplasticity.

The article is here.

And from the text:

This is a fascinating pilot study using innovative imaging markers to explore the link between hippocampal neuroplasticity and ECT treatment response.

More evidence that the hippocampus in ECT is not just relevant for adverse cognitive effects.

Of course, this needs to be replicated, but kudos to these investigators for such pioneering research.