John G. Keilp

Prefrontal Dopamine D1 Receptors and Working Memory in Schizophrenia

Studies in nonhuman primates documented that appropriate stimulation of dopamine (DA) D1 receptors in the dorsolateral prefrontal cortex (DLPFC) is critical for working memory processing. The defective ability of patients with schizophrenia at working memory tasks is a core feature of this illness. It has been postulated that this impairment relates to a deficiency in mesocortical DA function. In this study, D1 receptor availability was measured with positron emission tomography and the selective D1 receptor antagonist [11C]NNC 112 in 16 patients with schizophrenia (seven drug-naive and nine drug-free patients) and 16 matched healthy controls. [11C]NNC 112 binding potential (BP) was significantly elevated in the DLPFC of patients with schizophrenia (1.63 ± 0.39 ml/gm) compared with control subjects (1.27 ± 0.44 ml/gm; p = 0.02). In patients with schizophrenia, increased DLPFC [11C]NNC 112 BP was a strong predictor of poor performance at the n-back task, a test of working memory. These findings confirm that alteration of DLPFC D1 receptor transmission is involved in working memory deficits presented by patients with schizophrenia. Increased D1 receptor availability observed in patients with schizophrenia might represent a compensatory (but ineffective) upregulation secondary to sustained deficiency in mesocortical DA function.

The cognitive effects of electroconvulsive therapy in community settings.

Despite ongoing controversy, there has never been a large-scale, prospective study of the cognitive effects of electroconvulsive therapy (ECT). We conducted a prospective, naturalistic, longitudinal study of clinical and cognitive outcomes in patients with major depression treated at seven facilities in the New York City metropolitan area. Of 751 patients referred for ECT with a provisional diagnosis of a depressive disorder, 347 patients were eligible and participated in at least one post-ECT outcome evaluation. The primary outcome measures, Modified Mini-Mental State exam scores, delayed recall scores from the Buschke Selective Reminding Test, and retrograde amnesia scores from the Columbia University Autobiographical Memory Interview–SF (AMI–SF), were evaluated shortly following the ECT course and 6 months later. A substantial number of secondary cognitive measures were also administered. The seven sites differed significantly in cognitive outcomes both immediately and 6 months following ECT, even when controlling for patient characteristics. Electrical waveform and electrode placement had marked cognitive effects. Sine wave stimulation resulted in pronounced slowing of reaction time, both immediately and 6 months following ECT. Bilateral (BL) ECT resulted in more severe and persisting retrograde amnesia than right unilateral ECT. Advancing age, lower premorbid intellectual function, and female gender were associated with greater cognitive deficits. Thus, adverse cognitive effects were detected 6 months following the acute treatment course. Cognitive outcomes varied across treatment facilities and differences in ECT technique largely accounted for these differences. Sine wave stimulation and BL electrode placement resulted in more severe and persistent deficits.

Catechol-O-Methyltransferase (COMT) Genotypes and Working Memory: Associations with Differing Cognitive Operations

BACKGROUND Catechol-O-methyltransferase (COMT) is a strong candidate gene for schizophrenia and cognitive functions disrupted in this disorder. This report examines the relation of COMT genotypes to performance on a battery of working memory tests differing in the cognitive operations to be performed on the material. METHODS A large sample of 402 healthy adults were tested on four working memory tests: Spatial Delayed Response (SDR), Word Serial Position Test (WSPT), N-back, and Letter-Number Sequencing. A subsample (n = 246) was tested on the Wisconsin Card Sorting Test (WCST). A saliva swab was used to obtain DNA from all participants. RESULTS Letter-Number Sequencing, which requires both storage and manipulation of information, was the only working memory test that showed expected differences among COMT genotypes, with the met/met group showing the best performance and the val/val group the poorest performance. As in previous studies, the met/met group also performed better than the val/val group on the WCST. CONCLUSIONS COMT genotypes were not associated with performance on tests measuring simple storage, maintenance of temporal order or updating of information in working memory. Genotype differences in Letter-Number Sequencing and WCST suggest that higher-order components of processing (e.g., mental manipulation) are more closely related to this gene.

A brain imaging (single photon emission computerized tomography) study of semantic and affective processing in psychopaths

Psychopaths have been described as human predators who use charm, intimidation, and violence to control others and to satisfy their own needs. Underlying their propensity to violate social norms and expectations is a profound lack of empathy, guilt, or remorse, affective processes that have long resisted scientific investigation. Using brain imaging technology we found that psychopaths differed from nonpsychopaths in the pattern of relative cerebral blood flow during processing of emotional words. The results were consistent with the hypothesis that there are anomalies in the way psychopaths process semantic and affective information.

Blunted Serotonergic Responsivity in Depressed Inpatients

We found a 38% lower maximal prolactin response to an oral challenge dose of 60 mg of dl-fenfluramine relative to placebo in younger (<30 years) depressed inpatients compared with the response in age-matched healthy controls (p <. 03). Severity of depression did not correlate with prolactin response. Prolactin responses in older depressed patients (⩾30 years) did not differ from older controls. Younger depressed patients differed from older depressed patients in terms of earlier age of onset of first lifetime episode of major depression, greater degree of suicidal intent during a recent suicide attempt, double the level of hopelessness on admission to hospital, and a higher rate of comorbid borderline personality disorder. A blunted prolactin response to fenfluramine may be interpreted as evidence for reduced serotonergic function in younger depressed patients and may underlie their observed greater suicidality and hopelessness.

Correlates of trait impulsiveness in performance measures and neuropsychological tests

Performance measures of impulsiveness offer great promise for assessing this trait in clinical and experimental studies. However, little is known about their relative superiority or inferiority to standard cognitive performance measures as correlates of this trait. In this study, 58 healthy volunteers completed a self-rating of impulsiveness (Barratt Impulsiveness Scale) and a battery of neuropsychological tests. The test battery included measures of reaction time, attention, memory, fluency, and executive function, as well as two performance measures of impulsiveness--Time Estimation and a Go-No Go task. Self-ratings correlated moderately with a number of these test scores, but many correlations became non-significant after adjustment for age and education. Correlations with the Go-No Go task, verbal fluency, executive function measures (Trails B), and tasks requiring decision-making against time (Choice Reaction Time, Reaction Time to Paired Words and Paired Faces Memory Tasks, and response bias on the Continuous Performance Test) remained significant. Performance on the Go-No Go task was the strongest correlate of self-rated impulsiveness. The findings suggest that once general demographic or ability factors are accounted for, specialized performance tasks requiring decision-making and response organization under time pressure provide the most effective means of assessing this behavioral trait.

Neuropsychological function and suicidal behavior: attention control, memory and executive dysfunction in suicide attempt

BACKGROUND Executive dysfunction, distinct from other cognitive deficits in depression, has been associated with suicidal behavior. However, this dysfunction is not found consistently across samples. METHOD Medication-free subjects with DSM-IV major depressive episode (major depressive disorder and bipolar type I disorder) and a past history of suicidal behavior (n = 72) were compared to medication-free depressed subjects with no history of suicidal behavior (n = 80) and healthy volunteers (n = 56) on a battery of tests assessing neuropsychological functions typically affected by depression (motor and psychomotor speed, attention, memory) and executive functions reportedly impaired in suicide attempters (abstract/contingent learning, working memory, language fluency, impulse control). RESULTS All of the depressed subjects performed worse than healthy volunteers on motor, psychomotor and language fluency tasks. Past suicide attempters, in turn, performed worse than depressed non-attempters on attention and memory/working memory tasks [a computerized Stroop task, the Buschke Selective Reminding Task (SRT), the Benton Visual Retention Test (VRT) and an N-back task] but not on other executive function measures, including a task associated with ventral prefrontal function (Object Alternation). Deficits were not accounted for by current suicidal ideation or the lethality of past attempts. A small subsample of those using a violent method in their most lethal attempt showed a pattern of poor executive performance. CONCLUSIONS Deficits in specific components of attention control, memory and working memory were associated with suicidal behavior in a sample where non-violent attempt predominated. Broader executive dysfunction in depression may be associated with specific forms of suicidal behavior, rather than suicidal behavior per se.

Attention Deficit in Depressed Suicide Attempters

Attention is typically impaired in depression and may play a role in risk for suicidal behavior. In this study, 66 non-patients, 83 depressed subjects with no past history of suicide attempt, 53 depressed subjects with one or more low lethality suicide attempts, and 42 depressed subjects with at least one high lethality attempt were compared on two computerized measures of attention, a continuous performance test (CPT) and a Stroop task. All subjects were medication free at the time of assessment. Attention was impaired in all depressed subjects but worse in those with a past history of suicidal behavior. CPT performance did not differ among the groups, but Stroop interference was significantly poorer in all depressed subjects relative to non-patients, and poorer still in high lethality suicide attempters relative to all other groups. Interference scores correlated modestly with subjective depression, functional level, suicide ideation, number of past suicide attempts, and lethality of past attempts. Depression-related impairments of attention, especially susceptibility to interference, are accentuated in those with a past history of suicidal behavior. Fundamental deficits in attentional control may play a role in risk for suicidal behavior, and may contribute to a variety of cognitive deficits in suicidal patients. Brain regions subserving attentional control, which overlap considerably with regions implicated in affective disorders, may be a useful target for studies seeking to characterize neuropsychological factors associated with suicidal behavior.

Aggressiveness, not impulsiveness or hostility, distinguishes suicide attempters with major depression

BACKGROUND Impulsiveness, hostility and aggressiveness are traits associated with suicidal behavior, but also with borderline personality disorder (BPD). The presence of large numbers of BPD subjects in past attempter samples may distort the relative importance of each of these traits to predicting suicidal behavior, and lead to prospective, biological and genetic models that systematically misclassify certain subpopulations of suicidal individuals. METHOD Two hundred and seventy-five subjects with major depressive disorder (MDD), including 87 with co-morbid BPD (69 past suicide attempters, 18 non-attempters) and 188 without BPD (76 attempters, 112 non-attempters) completed standard impulsiveness, hostility and aggressiveness ratings. Differences between past suicide attempters and non-attempters were examined with the sample stratified by BPD status. RESULTS As expected, BPD subjects scored significantly higher than non-BPD subjects on all three trait measures. Stratifying by BPD status, however, eliminated attempter/non-attempter differences in impulsiveness and hostility in both patient subgroups. Past suicide attempters in each of the two subgroups of patients were only distinguished by higher levels of aggressiveness. CONCLUSIONS Once BPD is accounted for, a history of aggressive behavior appears to be the distinguishing trait characteristic of suicide attempters with major depression, rather than global personality dimensions such as impulsiveness or hostility. Aggressiveness, and not these related traits, may be the ideal target for behavioral, genetic and biological research on suicidal behavior, as well as for the clinical assessment of suicide risk.

DRD2 C957T polymorphism interacts with the COMT Val158Met polymorphism in human working memory ability

The C957T polymorphism in the dopamine D2 receptor (DRD2) gene and the Val158Met polymorphism in the Catechol-O-Methyl-Transferase (COMT) gene affect dopamine transmission and have been found to be associated with schizophrenia. Since DRD2 in mice and the COMT gene in humans modulate working memory, we examined the relationship and possible interaction of both polymorphisms to working memory performance in 188 healthy adults. Subjects having the DRD2 C/C allele showed the poorest performance in a word serial position test. Moreover, the effect of the C957T genotype was strengthened when interaction with the COMT Val158Met polymorphism was included in the analysis. We propose that an interaction of the DRD2 C957T and COMT Val158Met may be involved in the generation of some working memory deficits in schizophrenia.