Kirsten I. Stordal

Impairment across executive functions in recurrent major depression.

Depression is associated with impairment of cognitive functions, and especially executive functions (EFs). Despite the fact that most depressed patients experience recurrence of episodes, the pattern and the severity of executive impairment have not been well characterized in this group of depressed patients. We asked if and to what extent these patients were impaired on a range of neuropsychological tests measuring EFs, and also when confounding factors were adjusted for. Forty-five patients (aged 19–51 years) with moderate to severe (Hamilton score >18) recurrent major depressive disorder (DSM-IV) were compared to 50 healthy controls matched on age, education, gender and intellectual abilities. The subjects were administered a set of neuropsychological tests that assesses sub-components of EFs. The depressed patients were impaired compared to the control group on all selected tests, with a severity of impairment within −1 standard deviation from the control group mean. The group difference was statistically significant for eight of the 10 EFs that were assessed. These were measures of verbal fluency, inhibition, working memory, set-maintenance and set-shifting. The group difference was still significant for all sub-components except for set-shifting (Wisconsin Card Sorting Test) and planning (Tower of London), when additional medication and retarded psychomotor speed was adjusted for. In conclusion, the depressed subjects were mildly impaired across a wide range of EFs. This may have a negative impact on everyday functioning for this group of patients.

Attention profile in schizophrenia compared with depression: differential effects of processing speed, selective attention and vigilance

Objective: The aim of the study is to investigate whether subjects with schizophrenia and major depression display attention deficits for different reasons.

Executive function improvement upon remission of recurrent unipolar depression

AbstractThe aim of the study was to investigate the improvement of executive function measures upon recovery from unipolar depression. Thirty patients who suffered from recurrent major unipolar depression were retested with regard to their executive function approximately two years after an initial baseline examination. At baseline, patients were depressed (average 17–item HAM–D score 21.8), at retesting they were partially or totally recovered (average HAM–D score 8.2). There was a significant positive association between improvement on the HAM–D and improvement of executive function. In those with complete recovery, overall executive function and most examined executive function measures were no longer different from the baseline performance of healthy controls (with the possible exception of semantic fluency and Stroop Colour–word). In conclusion, recovery from major unipolar depression was accompanied by a recovery of many aspects of executive function to a normal level. Our findings support previous studies that have shown that neuropsychological impairment associated with long–standing depressive symptomatology is reversible (i. e. state–related) in recurrent unipolar depression.

Neuropsychological test profiles in schizophrenia and non-psychotic depression.

Objective:  The study examined to what degree schizophrenia is characterized by a neuropsychological (NP) test profile specific in shape and level compared with depression and normal functioning.

Cortisol level predicts executive and memory function in depression, symptom level predicts psychomotor speed

Objective:  On a group level depression is related to hypercortisolism and to psychomotor retardation, executive dysfunction and memory impairment. However, intra‐group heterogeneity is substantial. Why some are impaired while others remain in the normal range, is not clear. The present study aims at discerning the relative contribution of present symptom severity and hypercortisolism to impairment in the three domains of cognition.

Sensitivity and specificity of memory dysfunction in schizophrenia: A comparison with major depression

Fifty-three schizophrenic subjects were compared to 50 patients with major depression and 50 normal controls on measures of working memory, declarative memory and malingering. The schizophrenic group scored 1–2 SDs below controls on all measures, while depressive patients exposed only lesser deficits in working memory and free recall. The memory deficit of the schizophrenic subjects was disproportionately greater than their intellectual decline. Differences between clinical groups could not be explained by differences in IQ, clinical symptom load or demographic characteristics. This indicates that impaired memory is a particular sensitive symptom of schizophrenia and that the impairment is specific to the illness. Working memory failure was prominent in both clinical groups. The schizophrenic subjects displayed primarily an acquisition failure, while the depressed group showed retrieval difficulties.

Attentional and executive dysfunctions in schizophrenia and depression: evidence from dichotic listening performance

BACKGROUND We compared performance on a dichotic listening (DL) task between schizophrenic, depressed, and healthy control subjects. A variant of the traditional DL paradigm was used in which the subjects were required to focus attention either on the left (forced-left condition) or right (forced-right condition) ear stimulus. METHODS The subjects were 51 patients with a DSM-IV diagnosis of schizophrenia, 49 patients with recurrent unipolar major depression, and 49 healthy control subjects. They were tested with a consonant-vowel syllables dichotic listening task under three attentional instructions. RESULTS There was a significant overall right ear advantage during the nonforced condition, which increased dramatically during the forced-right condition and was eliminated during the forced-left condition. The depressed patients showed no signs of impairments compared with the healthy control group. Thus, they showed a right ear advantage during the nonforced and forced-right conditions, which was shifted to a left ear advantage during the forced left condition. The schizophrenic patients, however, were impaired on the forced-left condition compared with the healthy control and depressed subjects. CONCLUSIONS The results are discussed in terms of separating attentional and inhibitory executive impairments in schizophrenia and depression, taking into consideration illness duration and information-processing demands.

A longitudinal analysis of neurocognitive function in unipolar depression

Neurocognitive function is reduced in major depression, but uncertainties remain about if and to what extent improvement in neurocognitive function follows remission of depressive symptoms. A total of 30 patients with Diagnostic and Statistical Manual of Mental Disorders–Fourth Edition (DSM-IV) diagnosis of unipolar major depressive disorder (MDD) at baseline were tested neuropsychologically again, after a mean test–retest interval of 2 years. At retest, patients were partly or completely recovered from depression. Remission of depression was followed by improvement in verbal memory function up to the level of healthy controls, but no associations between improvement in depression and improvement in other dimensions of neurocognitive function were found. Neurocognitive function at baseline was not predictive of improvement in depressive symptoms over time. The present study provided some support for the state hypothesis as to the association between neurocognitive impairment and depression.

General psychopathology is more important for executive functioning than diagnosis.

Objective:  Impaired executive functioning (EF) has often been reported in patients with major depression or schizophrenia. We hypothesize that the variance in EF is more affected by level of general psychopathology than by diagnosis.

Honig's model of working memory and brain activation: an fMRI study.

The present study investigated changes in neuronal activation with fMRI related to Honigs model of working memory, which is much less studied compared with other working memory models. In contrast to other studies which have applied recognition procedures, the primary aim with the present study was to examine brain activation when subjects had to continuously recall and forget items held in working memory. The results showed that the mid-ventrolateral frontal cortex was particularly activated in the left hemisphere, whereas the mid-dorsolateral frontal cortex was particularly activated in the right hemisphere during execution of the working memory task. The findings are discussed in relation to process- and domain-specific accounts of working memory.