A new study published in Psychiatry Research: Neuroimaging has uncovered how individuals with high depression scores demonstrate increased brain activity in frontal brain regions while performing visuospatial memory tasks, despite their behavioral performance being similar to those with low depression scores.
When considering depression, the focus is often on its emotional aspects. However, depression can also impact cognitive abilities such as memory, attention, and decision-making. Moreover, it can lead to structural and functional changes in the brain, particularly in areas like the prefrontal cortex and the amygdala.
Previous studies have produced mixed results regarding the effect of depression on test scores that measure these cognitive abilities, as well as the brain activity during these tests.
Given these inconsistencies in the literature, Özge Vural Keleş from Bartin University in Turkey and Erol Yıldırım from Istanbul Medipol University in Turkey aimed to clarify the matter.
The researchers chose to investigate how depression influences visuospatial working memory, which pertains to the spatial location of items and can be likened to a “temporary mental notepad” for images and locations.
Initially, the Beck Depression Inventory (BDI) was administered online to evaluate depression symptoms in 501 volunteer university students and graduates. The individuals with the lowest and highest BDI scores were then invited to the laboratory for further experiments.
In total, the study included 23 individuals with high depression scores (BDI ≥ 23, averaging around 31) and 20 individuals with low depression scores (BDI ≤ 11, averaging around 6). The groups were matched in age and education levels.
The high and low BDI groups performed a visuospatial 2-back working memory task to assess their working memory performance.
In this task, participants were presented with a sequence of visual stimuli, including faces or words with emotional or neutral connotations. Their objective was to remember the location of the face or word within a circular display. Participants had to determine whether the current face or word matched the one presented two steps back in the sequence (referred to as the “2-back” condition).
During the visuospatial 2-back working memory task, brain responses were measured using a technique called functional near-infrared spectroscopy (fNIRS) targeting the prefrontal cortex.
fNIRS utilizes small sensors placed on the head to track changes in blood flow and oxygen levels in the brain, enabling researchers to identify active brain areas.
Statistical analyses were then conducted to compare the behavioral and fNIRS data between the two groups.
No significant differences in behavior were found between the high and low BDI groups in the visuospatial working memory task. This means that the visuospatial memory abilities of the healthy group were similar to those of the depressed group.
However, fNIRS revealed that individuals with high BDI scores exhibited increased activation in the right dorsolateral prefrontal cortex during the visuospatial working memory task compared to the low BDI group.
Keleş and Yıldırım concluded that the group with depressive features displayed more prefrontal cortex activation to achieve the same level of success as the low depression group, suggesting that the high BDI group exerted compensatory effort to attain the same performance.
It is important to note some limitations. While the low BDI score served as a healthy group for comparison, the absence of an official clinical diagnosis in the high BDI group may undermine the validity of the findings. Additionally, the researchers suggested that the relatively low difficulty of the visuospatial working memory task could have contributed to similar scores for both the low and high BDI groups.
The study, titled “Depression affects working memory performance: A Functional Near Infrared Spectroscopy (fNIRS) Study,” was authored by Özge Vural Keleş and Erol Yıldırım.
