Increased neural activity during overt and continuous semantic verbal fluency in major depression: mainly a failure to deactivate

Abstract

Major depression is associated with impairments in semantic verbal fluency (VF). However, the neural correlates underlying dysfunctional cognitive processing in depressed subjects during the production of semantic category members still remain unclear. In the current study, an overt and continuous semantic VF paradigm was used to examine these mechanisms in a representative sample of 33 patients diagnosed with a current episode of unipolar depression and 33 statistically matched healthy controls. Subjects articulated words in response to semantic category cues while brain activity was measured with functional magnetic resonance imaging (fMRI). Compared to controls, patients showed poorer task performance. On the neural level, a group by condition interaction analysis, corrected for task performance, revealed a reduced task-related deactivation in patients in the right parahippocampal gyrus, the right fusiform gyrus, and the right supplementary motor area. An additional and an increased task-related activation in patients were observed in the right precentral gyrus and the left cerebellum, respectively. These results indicate that a failure to suppress potentially interfering activity from inferior temporal regions involved in default-mode network functions and visual imagery, accompanied by an enhanced recruitment of areas implicated in speech initiation and higher-order language processes, may underlie dysfunctional cognitive processing during semantic VF in depression. The finding that patients with depression demonstrated both decreased performance and aberrant brain activation during the current semantic VF task demonstrates that this paradigm is a sensitive tool for assessing brain dysfunctions in clinical populations.

Disrupted Brain Activation and Deactivation Pattern during Semantic Verbal Fluency Task in Patients with Major Depression

“…This aberrant, symptom-related hyperactivity of the precuneus in MDD patients has not been reported in previous studies using the PVF [12] and indicates that the SVF has an advantage for investigating an MDD patient's neuropathology. In addition, the previous study using the SVF [15] also demonstrated decreased suppression in brain regions related to task-irrelevant self-referential thoughts in MDD patients, and this is in line with the present results.…”

“…The results of these studies suggest that the PVF can reveal MDD patients' impaired executive function related to attenuated left prefrontal cortex (PFC) activity. However, to our knowledge, there is only 1 fMRI study [15] that compares neural activation during SVF between MDD patients and healthy control (HC) subjects directly. They demonstrated aberrant brain activation during SVF in patients with MDD [15].…”

“…However, to our knowledge, there is only 1 fMRI study [15] that compares neural activation during SVF between MDD patients and healthy control (HC) subjects directly. They demonstrated aberrant brain activation during SVF in patients with MDD [15]. In addition, to our knowledge, the modification of neural activation during SVF by pharmacological treatment has never been investigated.…”

Neuropsychological Clustering in Bipolar and Major Depressive Disorder

“…One of the most common patterns of cognitive impairment observed in these conditions is executive dysfunction, which is defined as an alteration in cognitive abilities such as inhibitory control, working memory, cognitive flexibility, planning, and problem solving, collectively known as the executive functions (EFs) (Diamond, 2013). Consistent impairments in related functions such as divided attention and verbal fluency have also been identified in both BD (Allin et al, 2010;Păunescu & Micluţia, 2015) and MDD (Backes et al, 2014), with significant implications for psychosocial and occupational functioning (Evans et al, 2013).…”

Suicide ideation, stability of symptoms and effects of aerobic exercise in major depression

“…In an fMRI study, Backes et al [8] examined brain activation during articulation of words in response to semantic category cues. Compared to healthy controls, patients with unipolar depression showed poorer task performance and after correction for task performance, patients displayed reduced task-related deactivation in the right parahippocampal gyrus, right fusiform gyrus and right supplemental motor area.…”