Fat intake at midlife and cognitive impairment later in life: a population-based CAIDE study

OBJECTIVE: To investigate the association of midlife dietary fat intake to cognitive performance, and to the occurrence of clinical mild cognitive impairment (MCI) later in life in a non-demented population. DESIGN: A longitudinal population-based study. SETTING: Populations of Kuopio and Joensuu, Eastern Finland. PARTICIPANTS AND METHODS: Participants of the CAIDE study were derived from random, population-based samples studied at midlife (1972, 1977, 1982 or 1987). After an average follow-up of 21 years, a total of 1449 (72%) individuals aged 65-80 years participated in the re-examination in 1998. Altogether 82 (5.7%) people were diagnosed as having MCI. Dietary information was collected with a structured questionnaire and an interview at midlife. MAIN OUTCOME MEASURES: MCI, global cognitive and executive functions, episodic, semantic and prospective memory and psychomotor speed. RESULTS: Abundant saturated fat (SFA) intake from milk products and spreads at midlife was associated with poorer global cognitive function and prospective memory and with an increased risk of MCI (OR 2.36, 95% CI 1.17-4.74) after adjusting for demographic and vascular factors, other fats and ApoE. On the contrary, high intake of polyunsaturated fatty acids (PUFA) was associated with better semantic memory. Also frequent fish consumption was associated with better global cognitive function and semantic memory. Further, higher PUFA-SFA ratio was associated with better psychomotor speed and executive function. CONCLUSIONS: Our data suggests that dietary fat intake at midlife affects cognitive performance and occurrence of MCI later in life. The impact of dietary interventions needs to be tested in clinical trials.     

Cross-sectional and 35-year longitudinal assessment of salivary cortisol and cognitive functioning: the Vietnam Era twin study of aging

High levels of cortisol, a sign of potential hypothalamic-pituitary-adrenal (HPA) axis dysregulation, have been associated with poor cognitive outcomes in older adults. Most cortisol research has focused on hippocampal-related abilities such as episodic memory; however, the presence of glucocorticoid receptors in the human prefrontal cortex suggests that cortisol regulation is likely to be associated with prefrontally-mediated executive function abilities. We hypothesized that elevated cortisol levels would be associated with poorer frontal-executive function in addition to episodic memory. We assessed cortisol from 15 saliva samples paralleling individual diurnal rhythms across three non-consecutive days in a group of 778 middle-aged twin men ages 51-60. Cognitive domains created from 24 standard measures included: general cognitive ability, verbal and visual-spatial ability, verbal and visual-spatial memory, short-term/immediate memory, working memory, executive function, verbal fluency, abstract reasoning, and psychomotor processing speed. Adjusting for general cognitive ability at age 20, age, race, and multiple health and lifestyle indicators, higher levels of average area-under-the-curve cortisol output across three days were significantly associated with poorer performance in three domains: executive (primarily set-shifting) measures, processing speed, and visual-spatial memory. In a 35-year longitudinal component of the study, we also found that general cognitive ability at age 20 was a significant predictor of midlife cortisol levels. These results possibly support the notion that glucocorticoid exposure is associated with cognitive functions that are mediated by frontal-striatal systems, and is not specific to hippocampal-dependent memory. The results also suggest that the direction of effect is complex.     

Cognitive and Emotional Deficits in Chronic Alcoholics: a Role for the Cerebellum?

It is now widely accepted that in addition to motor coordination, the cerebellum is also involved in the modulation of cognitive and affective processes. Despite alcoholic cerebellar degeneration (ACD) being the most common form of cerebellar disorder, little systematic investigation of cerebellar-mediated cognitive and affective deficits has occurred in chronic alcoholics. Forty-nine chronic alcoholics and 29 healthy control participants underwent testing of cognitive and affective function, along with measurement of cerebellar ataxia using the International Cooperative Ataxia Rating Scale (Trouillas et al., Journal of the Neurological Sciences 145:205–11, 1997). The alcoholic group demonstrated significantly poorer performance as compared to the control group in a number of domains, including visuospatial and language skills, psychomotor speed, new learning and memory, executive functioning, and emotional regulation and affect processing. There were no differences between the alcoholic and control groups in immediate attention and working memory abilities. Years of heavy drinking and total period of abstinence were found to be the best predictors of cognitive and emotional function in the alcoholic group. After accounting for alcohol chronicity, there was still a relationship between the degree of clinical signs of ACD and some areas of cognitive and emotional functioning, including language, executive functioning, processing speed and affect processing. The results suggest that some of the cognitive and affective deficits observed in chronic alcoholics may be mediated, at least in part, by cerebellar dysfunction. These findings add support to the theory of disruption to bidirectional cerebro-cerebellar circuitry underlying cognitive and affective deficits in chronic alcoholics.     

Neuropsychological functions in anxiety disorders in population-based samples: evidence of episodic memory dysfunction

Most of the available evidence on neuropsychological functioning in anxiety disorders is based on clinical samples, investigating persons affected by obsessive-compulsive disorder. Knowledge is sparse regarding cognitive functions in other types of anxiety disorders. The aim of this study was to examine whether persons diagnosed with an anxiety disorder show neuropsychological impairments relative to healthy controls in tasks tapping episodic memory, verbal fluency, psychomotor speed, and executive functioning. Population-based samples comprising individuals affected by panic disorder with and without agoraphobia or agoraphobia (n=33), social phobia (n=32), generalised anxiety disorder (n=7), obsessive-compulsive disorder (n=16), and specific phobia (n=24) were compared with healthy controls (n=175) in test performance. Overall, the total anxiety disorder group exhibited significant impairments in episodic memory and executive functioning. Separate analyses on the respective anxiety subgroup indicated that panic disorder with and without agoraphobia, and obsessive-compulsive disorder were related to impairments in both episodic memory and executive functioning. In addition, social phobia was associated with episodic memory dysfunction. Verbal fluency and psychomotor speed were not affected by anxiety. Specific phobia and generalised anxiety disorder did not affect neuropsychological functioning.     

Neuropsychological functions in patients with bipolar I and bipolar II disorder

Objectives:  The literature reports persistent cognitive impairments in patients with bipolar disorder even after prolonged remission. However, a majority of studies have focused only on bipolar I disorder (BP-I), primarily because bipolar II disorder (BP-II) is often underdiagnosed or misdiagnosed. More attention should be paid to the differences between BP-I and BP-II, especially the aspects of neuropsychological functioning. We examined the different neuropsychological functions in BP-I and BP-II patients and compared them with those of healthy controls.
Methods:  The study included 67 patients with interepisode bipolar disorder (BP-I: n = 30; BP-II: n = 37) and 22 healthy controls compared using a battery of neuropsychological tests that assessed memory, psychomotor speed, and certain aspects of frontal executive function.
Results:  The BP-I group performed poorly on verbal memory, psychomotor speed, and executive function compared to the BP-II and control groups. Both bipolar groups performed significantly less well than the control group on measures of working memory and psychomotor speed, while the BP-II group showed an intermediate level of performance in psychomotor speed compared to the BP-I and control groups. There was no difference between the groups on visual memory.
Conclusions:  BP-I was characterized by reduced performance in verbal memory, working memory, psychomotor speed, and executive function, while BP-II patients showed a reduction only in working memory and psychomotor speed. Cognitive impairment existed in both subtypes of bipolar disorder, and was greater in BP-I patients. Rehabilitation interventions should take into account potential cognitive differences between these bipolar subtypes.     

Impairment in associative memory in healthy aging is distinct from that in other types of episodic memory

There is evidence that age related changes in episodic memory are heterogeneous and result from diverse pathologies. To test this, we examined performance of healthy high-functioning younger (N=41, ages 18-60 y) and older (N=58, ages 61-83 y) individuals in tests of associative memory, logical memory and memory in executive and object-recognition domains. We compared their relationships to each other and to other cognitive functions, including, psychomotor speed and verbal and spatial working memory. Older individuals showed significantly greater reduction in an index of the ability to learn new associations (NAL) than for memory in executive and object-recognition domains. Age-related reduction in NAL and in logical memory was of similar severity, but the two measures showed only moderate correlation when age and other cognitive functions were controlled for. NAL shows an age-related pattern of change distinct from memory in executive and object-recognition domains and from logical (item) memory. We propose that in healthy well-functioning individuals, NAL taps processes which support binding of newly learned association in context of accumulating information, a key function of the hippocampus. NAL may thus serve as a selective marker of complex, hippocampus-based, cognitive functions in studies of normal cognitive aging and of its possible relationship to early dementia.     

Cognitive function in late life depression: relationships to depression severity, cerebrovascular risk factors and processing speed.

BACKGROUND: A number of studies have examined clinical factors linked to worse neuropsychological performance in late life depression (LLD). To understand the influence of LLD on cognition, it is important to determine if deficits in a number of cognitive domains are relatively independent, or mediated by depression- related deficits in a basic domain such as processing speed. METHODS: Patients who met DSM-IV criteria for major depression (n = 155) were administered a comprehensive neuropsychological battery of tasks grouped into episodic memory, language, working memory, executive function, and processing speed domains. Multiple regression analyses were conducted to determine contributions of predictor variables to cognitive domains. RESULTS: Age, depression severity, education, race and vascular risk factors all made significant and independent contributions to one or more domains of cognitive function, with all five making independent contributions to processing speed. Age of onset made no independent contribution, after accounting for age and vascular risk factors. Of the five cognitive domains investigated, changes in processing speed were found to most fully mediate the influence of predictor variables on all other cognitive domains. CONCLUSIONS: While slowed processing speed appears to be the most core cognitive deficit in LLD, it was closely followed by executive function as a core cognitive deficit. Future research is needed to help clarify mechanisms leading to LLD- related changes in processing speed, including the potential role of white matter abnormalities.     

What is measured with verbal fluency tests in Parkinson’s disease patients at different stages of the disease?

Verbal fluency tests (VFT) are often used to assess executive functioning in Parkinson’s disease (PD). Various cognitive functions may, however, impair performance on VFT. Furthermore, since PD is a progressive neurodegenerative disease, it is also not clear whether deficits on VFT reflect impairments in the same cognitive functions throughout the different disease stages. This study will investigate what is measured with VFT in PD, in particular at different disease stages. Eighty-eight PD patients and 65 healthy participants, matched for age, gender, and education, were included. All were assessed with semantic and phonemic VFT and tests assessing executive functions, memory, and psychomotor speed. Mild and moderate PD patients did not differ in the number of words generated on both VFT. However, mild and moderate PD patients differed significantly with regard to the size of the largest cluster and the number of intra-dimensional shifts on phonemic VFT. Furthermore, at the mild disease stages, psychomotor speed predicted the performance on both VFT; whereas at the moderate stages of the disease, cognitive flexibility and psychomotor speed predicted the performance on both VFT. In conclusion, different cognitive functions underlie the performances of PD patients at different stages of the disease on semantic and phonemic VFT. Impairments in VFT, therefore, do not necessarily represent a specific deficit of executive functioning in patients with PD but should rather be interpreted in the context of disease severity and dysfunctions in other domains of cognition.     

Cognitive function in early Parkinson’s disease: a population‐based study

Background and purpose: The study aims to describe the frequency, pattern and determinants of cognitive function in patients with newly diagnosed Parkinson’s disease (PD); to compare patients with impaired cognition to patients with intact cognition; and to compare to matched healthy controls. Methods: Patients were identified in a longitudinal population based study of idiopathic non‐drug induced parkinsonism. Eighty‐eight newly diagnosed patients with PD and no dementia were included during a four year period. The patients and 30 age‐ and sex‐matched healthy control subjects underwent a comprehensive neuropsychological assessment. Results: Patients performed significantly worse than healthy controls in a majority of neuropsychological tests. Test results in attention, psychomotor function, episodic memory (free recall), executive function and category fluency were significantly lower in the patient group. Comparison with normative data revealed that 30% of the patients had deficits in ≥1 cognitive domain (episodic memory, executive function and verbal function). Seventy per cent of the patients had normal performance. Unified Parkinson's Disease Rating Scale (UPDRS) III sub scores; speech, facial expression, rigidity and bradykinesia were significantly higher, and disease duration shorter amongst the cognitively impaired than amongst the cognitively intact patients. Tremor showed no difference. Education level was an independent predictor of dysfunction in patients with ≥2 cognitive domains affected. Conclusion: Cognitive dysfunction is common in untreated patients in early PD, affecting attention, psychomotor function, episodic memory, executive function and category fluency. Education level was an independent predictor of severe cognitive dysfunction.     

The transience and nature of cognitive impairments in transient global amnesia: a meta-analysis

Transient global amnesia (TGA) is a clinical syndrome characterized by the sudden onset of severe amnesia without concomitant focal neurological symptoms. This meta-analysis of the cognitive characteristics of TGA addressed two main issues. First, we examined the hypothesis that the acute phase of TGA is associated with changes of anterograde and retrograde episodic long-term memory sparing semantic and short-term memory, while we had no clear prediction for potential reductions of executive functions due to the relative lack of previous studies addressing this issue. Second, we analyzed the time-course of changes in cognitive functions throughout three time intervals--acute (0-24 hours after TGA onset), postacute (24 hours to 5 days), and long-term phase (5-30 days)--to reveal whether there is a fast versus a delayed recovery. The results of the meta-analysis on 152 effect sizes from 25 studies showed that TGA is characterized by an extraordinarily large reduction of anterograde (d* = 1.89) and a somewhat milder reduction of retrograde (d* = 1.28) episodic long-term memory. Moreover, our results indicate the existence of additional, nonamnestic cognitive changes during TGA, because executive functions were also diminished (d* = 0.79). Reductions in both anterograde episodic long-term memory and executive function recover slowly, as slightly poorer performance in these cognitive domains can be found in the postacute phase (d*s = 0.32 and 0.44). All cognitive diminutions resolved within the long-term phase, by this calling into question previous reports of poorer performance of TGA patients relative to comparison subjects weeks or months after the attack.     

Relationship between psychopathology and cognitive functioning in schizophrenia

The purpose of this study was to delineate the relationship between positive, negative, cognitive, depressive, and excitement symptom dimensions of schizophrenia and cognitive functioning. Fifty-eight patients with schizophrenia (DSM-IV criteria) were assessed using the Positive and Negative Syndrome Scale (PANSS) and a battery of neuropsychological tests (executive function/abstraction, verbal and spatial working memory, verbal and nonverbal memory/learning, attention, visuospatial ability, and psychomotor speed). The cognitive symptom dimension correlated with executive functions, attention, verbal memory, and spatial ability. Severity of the negative symptom dimension was related to impairment in the structure of the semantic knowledge system, verbal memory, and auditory attention. In contrast, severity of the positive symptom dimension correlated only with impairment in the structure of the semantic knowledge system, and psychomotor speed. Finally, severity of the depressive and excitement symptom dimension was not associated with cognition. Correlations between symptom dimensions and cognitive measures were at best modest. Severity of cognitive and negative symptoms was mainly correlated with deficits on executive functions, semantic memory, and verbal memory, while positive symptoms only with semantic memory. These correlations were modest, suggesting that psychopathology and cognitive deficits in schizophrenia are caused, at least partially, by distinct pathophysiological processes.     

Older women's cognitive and affective response to moderate drinking

OBJECTIVE: In this paper we investigated the question, how do older women who drink moderate amounts of alcohol differ from those who do not drink on measurements of cognitive function, memory, affect and health? METHODS: The nonprobability sample of female participants (n=182) averaged 75 years of age and had a Mini Mental State Examination scores of 28. The participants were asked to indicate whether they drank alcohol or abstained (yes/no) and if they indicated that they did drink, to describe how many drinks they consumed in a given period of time (day/week/month). RESULTS: None of the participants acknowledged drinking more than 2 drinks a day. Caucasian women had the largest number of moderate drinkers (53% vs 47%), while the majority of African-American and Hispanic women reported not drinking. The moderate drinkers reported less depression, had higher self-reported health, performed better on instrumental everyday tasks, had stronger memory self-efficacy, and used more strategies to improve memory performance. In addition, these women had higher performance on tests of executive function: attention, concentration, psychomotor skills, verbal-associative capacities, and oral fluency. CONCLUSIONS: The circumstances under which people drink are complex and were not evaluated in this study. Therefore, rather than endorsing drinking behavior, these findings suggest that future research might examine why elders make the decision to drink, the circumstances that predispose women to drink (alone/with others), and other qualities that characterize female drinkers over the age of 65.     

Brain morphology links systemic inflammation to cognitive function in midlife adults

Background: Inflammation is linked to cognitive decline in midlife, but the neural basis for this link is unclear. One possibility is that inflammation associates with adverse changes in brain morphology, which accelerates cognitive aging and later dementia risk. Clear evidence is lacking, however, regarding whether inflammation relates to cognition in midlife via changes in brain morphology. Accordingly, the current study examines whether associations of inflammation with cognitive function are mediated by variation in cortical gray matter volume among midlife adults. Methods: Plasma levels of interleukin (IL)-6 and C-reactive protein (CRP), relatively stable markers of peripheral systemic inflammation, were assessed in 408 community volunteers aged 30–54 years. All participants underwent structural neuroimaging to assess global and regional brain morphology and completed neuropsychological tests sensitive to early changes in cognitive function. Measurements of brain morphology (regional tissue volumes and cortical thickness and surface area) were derived using Freesurfer. Results: Higher peripheral inflammation was associated with poorer spatial reasoning, short term memory, verbal proficiency, learning and memory, and executive function, as well as lower cortical gray and white matter volumes, hippocampal volume and cortical surface area. Mediation models with age, sex and intracranial volume as covariates showed cortical gray matter volume to partially mediate the association of inflammation with cognitive performance. Exploratory analyses of body mass suggested that adiposity may be a source of the inflammation linking brain morphology to cognition. Conclusions: Inflammation and adiposity might relate to cognitive decline via influences on brain morphology.     

White matter hyperintensities are related to physical disability and poor motor function

OBJECTIVE: To determine the impact of white matter hyperintensities (WMHs) on physical health and cognitive function in 60-64 year old individuals residing in the community. METHODS: A subsample of 478 persons aged 60-64 from a larger community sample underwent brain magnetic resonance imaging (MRI) scans. WMHs on T2 weighted FLAIR (fluid attenuated inversion recovery) MRI scans were assessed using an automated procedure. Subjects were assessed for global cognitive function, episodic memory, working memory (digit span), information processing speed (Symbol Digit Modalities Test; SDMT), fine motor dexterity (Purdue Pegboard), and grip strength, and completed the Physical Component Summary of the Short Form Health Survey (SF-12). Regression analyses were used to examine the effect of WMHs on physical and cognitive function. RESULTS: Deep and periventricular WMHs were present in all subjects, with women having slightly more lesions than men. WMHs were significantly associated with poorer reported physical health on the SF-12 scale, after adjusting for depression, cognitive function, and brain atrophy. WMHs were also related to lower scores on the Purdue Pegboard test, grip strength, choice reaction time, and SDMT, but not on tests of episodic memory, working memory, general intellectual function, and global cognitive function. On regression analyses, the Purdue Pegboard test and grip strength were related to physical disability. CONCLUSION: WMHs are common, albeit mild, in middle adult life. They are associated with physical disability, possibly through reduced speed, fine motor coordination, and muscular strength. They are also related to slowed information processing speed but not other cognitive functions.     

Detection and staging of early clinical dementia

In order to find neuropsychological indicators for detection and staging of dementia, groups of very mild, mild, and moderate dementia were compared to healthy aged individuals in neuropsychological tests tapping various cognitive and finger-motor functions. Results showed that the groups differed significantly in all cognitive tests, but not in the finger-motor tests. A stepwise disriminant analysis indicated that detection of very mild dementia was best accomplished by three tests assessing episodic memory, semantic memory, and visuospatial functioning. Staging of dementia was best accomplished by means of only one canonical function based on tests tapping episodic memory, semantic memory, visuospatial functions, and psychomotor speed. These results indicate that the pattern of dysfunction is similar for different levels of dementia, suggesting that similar cognitive functions may be involved in detection and staging of dementia.     

Neuropsychological performance and seizure-related risk factors in patients with temporal lobe epilepsy: a retrospective cross-sectional study

The aim of this study was to identify the neuropsychological features in patients with temporal lobe epilepsy (TLE) and their correlation with seizure-related variables. For this purpose, we carried out a retrospective analysis of data from 65 patients with TLE who had undergone a comprehensive neuropsychological assessment. The results suggest that the majority of patients with TLE were impaired in more than one cognitive domain, and among these patients, the mean proportions with defective semantic memory, language, motor/psychomotor speed, verbal episodic memory, and executive function were > 50% each. Moreover, age at seizure onset was the strongest predictor of general intellectual impairment, and number of antiepileptic drugs and seizure frequency could significantly predict deficits in verbal memory, language, and psychomotor speed. However, epilepsy duration was a less potent predictor of cognitive deficit than has been reported in cross-sectional studies.     

Cognitive features in euthymic bipolar patients in old age

Objectives:  Studies of cognition in bipolar disorder (BD) have reported impairments in processing speed, working memory, episodic memory, and executive function, but they have primarily focused on young and middle-aged adults. In such studies, the severity of cognitive deficits increases with the duration of illness. Therefore, one would expect more pronounced deficits in patients with longstanding BD. The first aim of the present study was to determine the pattern and the magnitude of cognitive impairment in older euthymic BD patients. The second aim was to explore the interrelationship between these cognitive deficits and determine whether they reflect a single core impairment or the co-occurrence of independent cognitive deficits.
Methods:  Twenty-two euthymic elderly BD patients and 22 controls, matched for gender, age, and education, underwent a comprehensive neuropsychological assessment.
Results:  Compared to controls, BD patients had significantly reduced performance in processing speed, working memory, verbal fluency, and episodic memory, but not in executive function. Hierarchical regression analyses showed that verbal fluency and working memory impairments were fully mediated by changes in processing speed. This was not the case for the episodic memory dysfunction.
Conclusion:  The cognitive profile in older euthymic BD cases is similar to the one described in younger BD cohorts. Our results further suggest that impaired processing speed plays a major role in the cognitive changes observed in BD patients except for deficits in episodic memory, thus providing strong evidence that processing speed and episodic memory are two core deficits in elderly BD patients.     

Neuropsychological performance and seizure-related risk factors in patients with temporal lobe epilepsy: A retrospective cross-sectional study

The aim of this study was to identify the neuropsychological features in patients with temporal lobe epilepsy (TLE) and their correlation with seizure-related variables. For this purpose, we carried out a retrospective analysis of data from 65 patients with TLE who had undergone a comprehensive neuropsychological assessment. The results suggest that the majority of patients with TLE were impaired in more than one cognitive domain, and among these patients, the mean proportions with defective semantic memory, language, motor/psychomotor speed, verbal episodic memory, and executive function were > 50% each. Moreover, age at seizure onset was the strongest predictor of general intellectual impairment, and number of antiepileptic drugs and seizure frequency could significantly predict deficits in verbal memory, language, and psychomotor speed. However, epilepsy duration was a less potent predictor of cognitive deficit than has been reported in cross-sectional studies.     

Cognitive function in early HIV infection

This study aimed to examine cognitive function in acute/early HIV infection over the subsequent 2 years. Fifty-six HIV+ subjects and 21 seronegative participants of the Chicago Early HIV Infection Study were evaluated using a comprehensive neuropsychological assessment at study enrollment and at 2-year follow-up. Cognitive performance measures were compared in the groups using t tests and mixed-effect models. Patterns of relationship with clinical measures were determined between cognitive function and clinical status markers using Spearman’s correlations. At the initial timepoint, the HIV group demonstrated significantly weaker performance on measures of verbal memory, visual memory, psychomotor speed, motor speed, and executive function. A similar pattern was found when cognitive function was examined at follow-up and across both timepoints. The HIV subjects had generally weaker performance on psychomotor speed, executive function, motor speed, visual memory, and verbal memory. The rate of decline in cognitive function across the 2-year follow-up period did not differ between groups. Correlations between clinical status markers and cognitive function at both timepoints showed weaker performance associated with increased disease burden. Neurocognitive difficulty in chronic HIV infection may have very early onset and reflect consequences of initial brain viral invasion and neuroinflammation during the intense, uncontrolled viremia of acute HIV infection. Further characterization of the changes occurring in initial stages of infection and the risk and protective factors for cognitive function could inform new strategies for neuroprotection.     

What is measured by verbal fluency tests in schizophrenia?

INTRODUCTION: Schizophrenia patients perform below the norm on verbal fluency tests. The causes for this are unknown, but defective memory, executive functioning and psychomotor speed may play a role. METHOD: We examined 50 patients with schizophrenia and related disorders, and 25 healthy controls with a cognitive test battery containing tests for verbal memory, executive functioning and psychomotor speed, and a categorical fluency test. RESULTS: Patients obtained significantly lower test results than the controls on most cognitive measures including the verbal fluency test. During the fluency test, they formed as many clusters, and switched as often between clusters as the controls did, but they generated fewer words per cluster. Interestingly, in the control group, fluency performance was predicted by memory and executive functioning, but not by psychomotor speed. In patients, verbal fluency was predicted by psychomotor speed, but not by memory or executive functioning. DISCUSSION: We conclude that psychomotor speed could be a crucial factor in cognition, and its influence on cognitive test performance should be considered in schizophrenia research. Furthermore, these data illustrate the importance of qualitative analysis of cognitive impairments in schizophrenia patients, as traditional cognitive tests often only provide quantitative information.