Subjective cognitive decline in major depressive patients is associated with altered entropy and connectivity changes of temporal and insular region

Abstract

Depressive cognitive impairment is seen in a significant number of patients with depression. However, it remains challenging to differentiate between patients with amnestic (those with subjective cognitive impairment complaints) and non-amnestic major depressive disorder, highlighting the urgent need for additional objective tools to help classify these patients more accurately. We analyzed cognitive state, alterations in regional entropy and functional connectivity measures of the brain between patients with major depression and healthy controls. The depressed cohort was categorized as either "amnestic" or "non-amnestic," depending on self-reported experiences of forgetfulness. The superior temporal region and insula exhibited altered entropy and connectivity measures in individuals with depression and subjective cognitive impairment, which was correlated with impaired executive functions, a pattern not being evident in the control group. Our findings support the notion that insular and superior temporal entropic alterations are linked to subjective cognitive changes in the pathology of depression. These regions also hold potential as biomarkers for determining the underlying objective cognitive deficits in subjective cognitive complaints in patients with major depressive disorder (MDD). This underscores the need for improved diagnostic approaches and the implementation of practical dynamic neuroimaging modalities capable of addressing the current challenges in diagnosing subjective cognitive impairment in MDD, offering promise for the future management of patients with depression.

Fig. 1

The left insular cortex and right anterior superior temporal gyrus demonstrated decreased entropy in amnestic depressive patients compared to non-amnestic depression patients.

Fig. 2. Effect size of ROIs showing functional connectivity differences between non-amnestic depression, amnestic depression, and control groups.

The effect sizes (Fisher z-transformed correlation coefficients) are shown for three groups: the blue bars represent the non-amnestic depression group, the red bars represent the amnestic depression group and the yellow bars represent the control group. The effect size reflects the strength of functional connectivity in ROIs, which shows significant connectivity differences between the three groups. Panels A and B represent the left posterior STG, and right insular cortex seeds, respectively. The coordinates on the x-axis correspond to the peak MNI coordinates (from Table 3), related to the ROIs that exhibited functional connectivity differences between the three groups.

Fig. 3. The seed-based connectivity results of the left posterior STG and right insular cortex.

The left posterior STG, in the non-amnestic depression group, exhibited higher connectivity to the anterior cingulate compared to the amnestic depression group. The right insular cortex, in the non-amnestic depression group exhibited higher connectivity to the left cerebellum and bilateral occipital regions compared to the control group. The red patches indicate an increase in functional connectivity. The colour bars present the F-statistics. The regions depicted on brain maps are described in Table 3. Abbreviation: STG, superior temporal gyrus.