A new study published in Psychiatry Research: Neuroimaging has shed light on how individuals with high depression scores exhibit increased brain activity in frontal brain regions while performing visuospatial memory tasks, even though their behavioral performance in these tasks is similar to those with low depression scores.
When thinking about depression, there is often a focus on the emotional aspects. However, depression may also impact some cognitive abilities such as memory, attention, and decision-making. Depression can even lead to structural and functional changes in the brain, most often observed in specific areas such as the prefrontal cortex – a region at the front of the brain – and some deeper structures such as the amygdala.
Previous studies have demonstrated mixed results regarding the impact of depression upon test scores that measure these cognitive abilities, in addition to the activity of the brain while completing these tests.
Consequently, Özge Vural Keleş from Bartin University in Turkey and Erol Yıldırım from Istanbul Medipol University in Turkey sought to clarify these inconsistencies in the literature.
The researchers were drawn to investigate how depression impacts visuospatial working memory. This type of memory focuses on where items are located in space, and can be likened to a “temporary mental notepad” specifically for images and locations.
Firstly, the Beck Depression Inventory (BDI) was administered online to assess depression symptoms in 501 volunteer university students and graduates. The individuals who had the lowest and highest BDI scores were invited to the laboratory for further experiments.
In total, the participants included 23 individuals with high depression scores (BDI ≥ 23, on average around 31) and 20 individuals with low depression scores (BDI ≤ 11, on average around 6). Between the groups, age and education levels were found to be similar.
The high BDI and low BDI groups completed a visuospatial 2-back working memory task to measure their working memory performance.
In this task, participants were presented with a sequence of visual stimuli, which included faces or words, and were of an emotional or neutral nature. They were asked 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 (hence, the ”2-back” condition).
During this visuospatial 2-back working memory task, brain responses were recorded with a brain imaging technique known as functional near-infrared spectroscopy (fNIRS) from the prefrontal cortex.
fNIRS utilizes small sensors placed on the head to monitor changes in blood flow and oxygen levels in the brain, which allowed the researchers to pinpoint which areas of the brain were active.
Finally, statistical analyses were conducted to compare behavioral and fNIRS data between the two groups.
No significant behavioral differences were found between the high and low BDI groups in the visuospatial working memory task. In other words, the visuospatial memory abilities of the healthy group was similar to 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, “the group with depressive features exhibited more PFC activation to achieve the same success [as the group with low depression],” and that the high BDI group “made a compensatory effort to achieve the same performance.”
Some limitations are to be noted. While the low BDI score acted as a healthy group for comparison, the lack of an official clinical diagnosis in the high BDI group might limit the validity of the findings. The authors also suggested that the low difficulty of the visuospatial working memory task may have led to similar scores for both low and high BDI groups.
The study, “Depression affects working memory performance: A Functional Near Infrared Spectroscopy (fNIRS) Study”, was authored by Özge Vural Keleş and Erol Yıldırım.
