Specific Neuropsychological Deficits in Schizophrenic Patients with Preserved Intellectual Function

Although a wide range of cognitive deficits have been demonstrated in schizophrenia, it is not clear whether specific deficits stand out from general intellectual decline. Separate cases have been made for selective impairments in mnemonic and in executive function but these remain unconfirmed. A common problem in studies of schizophrenia is heterogeneity of deficits and Shallice, Burgess, and Frith (1991) have addressed this by using a single case study approach. The present study used the CANTAB battery of neuropsychological tests to examine cognitive performance in a small group of schizophrenic patients with preserved intellectual function. This test battery allows a componential analysis of performance, and its neurological validation may enable specific neurobiological hypotheses to be addressed. Twelve schizophrenic patients with current IQ greater than 90 and within 10 points of premorbid IQ were assessed on tests of visuospatial memory, spatial working memory, planning, and attentional set-shifting. Their performance was compared to that of 12 matched controls. The patient group, as a whole, was impaired on all tasks but the pattern of impairment varied across individuals. Consistently, severe deficits were seen on tests of delayed matching to sample and attentional set-shifting. These deficits are compared to those seen in patients with unipolar depression, who showed similar deficits in delayed matching to sample but not set-shifting, and are considered in terms of common cognitive mechanisms and possible neural substrates.     

Daytime variation in performance and tiredness/sleepiness ratings in patients with insomnia, narcolepsy, sleep apnea and normal controls

Daytime tiredness or sleepiness and deficits in cognitive performance are common complaints in sleep disordered patients. Till now there are few studies comparing patients from different diagnostic groups of sleep disorders in the same experimental protocol. We studied the time course of cognitive functions and subjective alertness in a parallel group design with four groups of patients [narcolepsy, untreated or treated obstructive sleep apnea (OSA), or psychophysiological insomnia] and a control group of subjects without sleep complaints. Each group consisted of 10 subjects, matched for age and gender. After a night with polysomnography, subjects were studied for 10 h from 08:00 hours to 18:00 hours at 20 min intervals under standardized environmental conditions. Four psychological tests were applied, (1) a critical flicker fusion (CFF) test to measure optical fusion threshold (alertness); (2) a paper-and-pencil visual line tracking test (selective attention); (3) a visual analog scale (VAS) for tiredness/sleepiness; and (4) the Tiredness Symptoms Scale (TSS), a 14 items check list. Each test session lasted for 8 min, followed by a 12 min pause. The level and time course of cognitive performance and self-rating data were analysed with hierarchical linear mixed effects models. Cognitive tests showed decrements in alertness and selective attention in untreated patients with insomnia, narcolepsy, and sleep apnea. Narcoleptic patients and untreated OSA had a lower CFF threshold than controls, and for narcoleptic patients the time course differed from that of all other groups. In the visual tracking test the performance of all groups of patients was worse compared with normal controls. Self-rated tiredness/sleepiness was significantly more pronounced in the three groups of untreated patients than in control subjects.     

Comparison of cognitive functions between first- and multi-episode bipolar affective disorders

BACKGROUND: Cognitive impairment has been commonly found in euthymic patients with bipolar affective disorder (BPAD). Information about onset and course of cognitive deficits is, however, scarce. This study examined the cognitive profile of patients following their first episode of BPAD to determine whether cognitive problems are present at such an early stage. METHODS: Executive functions, memory, IQ, attention-concentration and perceptuomotor function were assessed in 16 euthymic patients with BPAD following their first episodes, and compared with a group of 30 euthymic patients with multiple episodes of BPAD and 20 normal controls. Comparisons were controlled for educational status, current IQ and residual symptoms. RESULTS: First-episode patients were significantly impaired, compared to normal controls, on tests of executive function, sustained attention, perceptuomotor function and IQ. Additionally, their performance was significantly worse than patients with multi-episode BPAD on tests of executive functions, sustained attention and perceptuomotor function. Multi-episode patients had impaired memory, compared to normal controls, and performed poorly on a subtest of executive functions compared to first-episode patients. LIMITATIONS: Sample sizes were small, assessments cross-sectional; all confounds could not be controlled for. CONCLUSIONS: Widespread cognitive disturbances following the first episode of BPAD were found in this study. Whether these disturbances progress following repeated episodes was not entirely clear. Since cognitive impairment can have several adverse consequences for patients of BPAD in terms of disability, quality of life, outcome etc., this must remain a priority area for future research.     

Sex differences in cognitive processing in children treated with CNS prophylaxis for acute lymphoblastic leukemia

Evaluated cognitive processing in 51 children (27 female, 24 male) who had been treated for acute lymphoblastic leukemia (ALL) with CNS prophylaxis (cranial radiation in combination with intrathecal chemotherapy) and were continuously disease-free for 5 to 12 years. The control group comprised 15 children treated for Wilm's tumor. Functions assessed included visuoperceptual skills, generation of organizational strategies, sensitivity to organizational structure, and attention. The ALL group showed performance deficits relative to the solid tumor controls in appreciating the organization inherent in complex visuospatial material and alertness, with females more severely affected than males. Sex differences favoring males on IQ and academic achievement were related to these cognitive processes.     

Neurocognitive Function and Health-Related Quality of Life in Pediatric Korean Survivors of Medulloblastoma

The neurocognitive function and quality of life of 58 Korean survivors of childhood medulloblastoma were assessed after surgery, cranial radiation and chemotherapy. All patients were evaluated with a battery of neurocognitive function tests and the Pediatric Functional Assessment of Cancer Therapy-Brain Tumor Survivors, which consists of self-report questionnaires on quality of life. The mean full-scale intelligence quotient (IQ), verbal IQ, and performance IQ scores were 90.2, 97.1, and 84.16, respectively. The mean memory quotient (MQ) score was 86.78, which was within 1 standard deviation of the average score of 100. Processing speed, attention, and executive function showed mild to moderate deficits. Intelligence, memory, executive function, visuospatial function, and simple motor function were significantly lower in the patients diagnosed before 8 years of age compared with those diagnosed after 8. The cognitive deficits in the patients diagnosed at younger ages might be related to earlier exposure to craniospinal irradiation and chemotherapy. The patient and parent proxy evaluations of attention, fine motor function, and quality of life did not differ. We found significant neurocognitive changes in a wide range of neurocognitive functional domains in Korean survivors of childhood medulloblastoma. Long-term follow-up studies of survivors of childhood medulloblastoma beginning at the time of their first diagnosis are required to better understand the deficits exhibited by survivors of childhood medulloblastoma, so that intervention strategies and treatment refinements that reduce the long-term neurocognitive decline can be developed.     

Altered brain activation during response inhibition in obstructive sleep apnea

This study examined response inhibition during a Go–NoGo task in individuals with obstructive sleep apnea (OSA). Fourteen OSA patients and 14 controls were studied with functional magnetic resonance imaging. Compared to controls, the OSA group showed more false positives (error of commission) during the NoGo trials with decreased brain activation in the left postcentral gyrus, cingulate gyrus and inferior parietal lobe, as well as right insula and putamen. This is consistent with previous findings of impaired performance and decreased brain activation in OSA patients during a working memory task, suggesting that compromised brain function in response to cognitive challenges may underlie some of the cognitive deficits seen in patients with OSA.     

Persistent cognitive dysfunctions in bipolar I disorder and schizophrenic patients: a 3-year follow-up study

BACKGROUND: Neurocognitive impairment has consistently been considered a central and stable feature in schizophrenia. As this possibility has been far less studied in bipolar disorder, we aimed to prospectively investigate the stability and specificity of cognitive performance in bipolar disorder compared to schizophrenia. METHODS: Fifteen DSM-IV bipolar type I patients and 15 schizophrenic patients were assessed twice with a comprehensive neuropsychological battery and the Positive and Negative Syndrome Scale over a 3-year follow-up. The cognitive performance of the groups was compared at baseline and 3 years later as a mean with that of 26 healthy volunteers. Endpoint and baseline assessments were also compared for each patient group in order to evaluate the stability of cognitive impairment. RESULTS: At both time points, bipolar and schizophrenic patients showed significant deficits on most of the cognitive tasks compared to healthy subjects. Overall, the cross-sectional cognitive profile was similar for both patient groups. Moreover, after controlling for age and length of illness, the two groups' cognitive function did not differ over time in any test. With the exception of the Stroop color-word interference task, performance at baseline for each test but neither length of illness nor diagnostic category predicted the endpoint performance. CONCLUSION: This preliminary study suggests that cognitive impairment is also mainly stable over time in bipolar I disorder and thus not specific to schizophrenia.     

Brain metabolite composition in relation to cognitive function and dystrophin mutations in boys with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a hereditary X-linked recessive disorder affecting the synthesis of dystrophin, a protein essential for structural stability in muscle. Dystrophin also occurs in the central nervous system, particularly in the neocortex, hippocampus and cerebellum. Quantitative metabolic analysis by localized (1) H MRS was performed in the cerebellum (12 patients and 15 controls) and a temporo-parietal location (eight patients and 15 controls) in patients with DMD and healthy controls to investigate possible metabolic differences. In addition, the site of individual mutations on the dystrophin gene was analyzed and neuropsychological cognitive functions were examined. Cognitive deficits in the patient group were found in line with earlier investigations, mainly concerning verbal short-term memory, visuo-spatial long-term memory and verbal fluency, but also the full-scale IQ. Causal mutations were identified in all patients with DMD. Quantitative MRS showed consistent choline deficits, in both cerebellar white matter and temporo-parietal cortex, as well as small, but significant, metabolic abnormalities for glutamate and total N-acetyl compounds in the temporo-parietal region. Compartment water analysis did not reveal any abnormalities. In healthy subjects, choline levels were age related in the cerebellum. The choline deficit contrasts with earlier findings in DMD, where a surplus of choline was postulated for the cerebellum. In patients, total N-acetyl compounds in the temporo-parietal region were related to verbal IQ and verbal short-term memory. However, choline, the putative main metabolic abnormality, was not found to be associated with cognitive deficits. Furthermore, in contrast with the cognitive performance, the metabolic brain composition did not depend significantly on whether or not gene mutations concerned the expression of the dystrophin isoform Dp140, leading to the conclusion that the effect of the missing Dp140 isoform on cognitive performance is not mediated through the observed metabolite composition, or is caused by local effects beyond the resolution accessible to MRS investigations.     

糖尿病对脑白质病变伴轻度认知功能障碍患者认知功能的影响

目的 探讨糖尿病与脑白质病变(WML)伴轻度认知功能障碍(MCI)患者认知功能减退的关系。方法 2012年1—12月在大坪医院神经内科住院病人中选择257例WML伴MCI患者进行前瞻性研究,随访时间为1年。收集患者血管危险因素(VRFs)及颅脑MRI检查结果,同时行神经心理学测试了解认知功能状态;根据1年内简易精神状态检查量表(MMSE)减少值分为认知功能下降组(≥3分)及无认知功能下降组(≤2分),并比较两组各种危险因素的差异。结果 257例中有246例(95.7%)患者完成了1年的观察随访过程,11例删失者中8例死亡、3例退出观察。246例中,认知功能下降组154例(62.6%),无认知功能下降组92例(37.4%);其中36例在观察期间发生卒中,余210例患者纳入线性回归分析。除受教育水平及血脂异常外,年龄、性别、高血压、糖尿病、短暂性脑缺血发作等各危险因素两组比较差异均有统计学意义 (P值均＜0.05)。糖尿病、基线WML程度及随访期间WML程度的加重与1年内MMSE减少值呈显著的线性关系,且对认知功能减退的影响由大至小依次为基线WML程度(β_j′=0.570)、随访期间WML加重程度(β_j′=0.244)、糖尿病(β_j′=0.171)。结论 糖尿病可使WML伴MCI患者认知功能进一步减退。重度WML伴MCI的糖尿病患者应作为痴呆的高危人群进行早期干预。     

Dietary supplementation of arachidonic and docosahexaenoic acids improves cognitive dysfunction

Age-dependent increase of peroxidation of membrane fatty acids such as arachidonic acid (ARA) and docosahexaenoic acid (DHA) in neurons was reported to cause a decline of the hippocampal long-term potentiation (LTP) and cognitive dysfunction in rodents. Although supplementation of ARA and DHA can improve LTP and cognitive function in rodents, their effects in humans are unknown. The present work was undertaken to study whether ARA and DHA have beneficial effects in human amnesic patients. The subjects were 21 mild cognitive dysfunction (12 MCI-A with supplementation and 9 MIC-P with placebo), 10 organic brain lesions (organic), and 8 Alzheimer's disease (AD). The cognitive functions were evaluated using Japanese version of repeatable battery for assessment of neuropsychological status (RBANS) at two time points: before and 90 days after the supplementation of 240 mg/day ARA and DHA, or 240 mg/day of olive oil, respectively. MCI-A group showed a significant improvement of the immediate memory and attention score. In addition, organic group showed a significant improvement of immediate and delayed memories. However, there were no significant improvements of each score in AD and MCI-P groups. It is suggested from these data that ARA and DHA supplementation can improve the cognitive dysfunction due to organic brain damages or aging.     

Relative memory deficits in recurrent versus first-episode major depression on a word-list learning task.

Although memory deficits are associated with major depressive disorder, few studies have identified which patient characteristics predict impairment. Because recurrent depression appears related to more severe cerebral dysfunction, the present study tested whether recurrent depressed individuals have worse memory function than first-episode depressed individuals. Two groups of young-adult, nonpsychotic, depressed inpatients (20 single episode [SE] and 46 recurrent episode [RE]) were administered the California Verbal Learning Test within a broader battery of neuropsychological tests. The groups were equivalent in age, education, estimated IQ, severity of depression, and demographic composition. The RE group demonstrated memory deficits relative to both the SE group and published norms, but no other significant difference was found across the battery. Data indicate that abnormal memory performance is associated with recurrent depression, whereas memory deficits are not prominent in first-episode depressed individuals.     

Heterogeneity in cognitive functioning among patients with bipolar disorder

BACKGROUND: Nowadays it is not clear if in bipolar disorders (BD) cognitive impairments are heterogeneous and if so which are the variables that determine it. METHODS: Fifty patients with BD and thirty healthy controls were clinically evaluated including measures of obstetric complications history. All subjects completed an extensive neuropsychological battery selected to asses premorbid IQ and different cognitive domains. RESULTS: Compared with standardized norms, 38% of patients had none cognitive domain affected, while 40% had 1 to 2, and 22% had 3 to 5. Patients with cognitive functioning within normal limits had higher psychosocial functioning and premorbid IQ, and lower history of obstetric complications. LIMITATIONS: The small sample size could limit the generalizability of the results; since these data should be taken as preliminaries. CONCLUSIONS: The extension and severity of cognitive impairments may be heterogeneous in patients with BD, and it might contribute to explain the variability in functional outcome. Bipolar patients with low premorbid IQ and history of obstetric complications may represent a subgroup with lower cognitive performance and psychosocial functioning.     

Periodic limb movements and sleep apnoea

This study investigated the relationship of Periodic Leg Movements (PLMs) to the severity of Obstructive Sleep Apnoea (OSA) in 52 patients. In addition the prevalence of PLMs in OSA was compared with two other patient populations: narcolepsy and idiopathic PLM disorder (n = 38). All patients were between 20 and 50 years in age and were compared with a control group of 88 asymptotic paid volunteers aged between 20 and 50. PLMs were scored when tibialis anterior EMG activity lasted 0.5-5.0 s with an amplitude of at least half that of pre-sleep voluntary ankle dorsiflexion and when they were part of 4 or more consecutive events separated by 20-90 s. The prevalence of PLMs in OSA was 27.6%, which was similar to the prevalence in our normal controls of 20.5%. However, in the OSA group the majority of the PLMs occurred in the mild OSA patients (40.7%). This was similar to the prevalence of PLMs in narcoleptics (50%). The prevalence of PLMs in moderate OSA, was 24.5%; similar to that of normal controls. In severe OSA, PLMs were also low (12.5%). There is an inverse relationship between PLMs and the severity of OSA. The greater number of arousals and awakenings associated with respiratory irregularities seen in the severe OSA group produced an equivocal manifestation of PLMs.     

Attention and executive functions in remitted major depression patients

BACKGROUND: Although deficits in attention and executive functions in patients with Major Depressive Disorder (MDD) are well confirmed [Veiel, H.O.F., 1997. A preliminary profile of neuropsychological deficits associated with major depression. Journal of Clinical and Experimental Neuropsychology 19, 587-603.]. The database regarding the relationship between impairments and the duration of disease or the number of episodes is inconsistent. Furthermore, the role of long-term cognitive impairments in MDD during remitted state is not well understood [Elliott, R., 2002. The neuropsychological profile in primary depression. Taylor and Francis, London, pp. 273-293.]. There is consequently a lack of studies accounting for different courses of illness in the euthymic state and considering the influence of possible attentional deficits on executive performance. METHODS: 40 euthymic patients with MDD diagnosis according to DSM-IV (20 patients with 1-2 episodes and 20 severe depressives with at least three episodes) as well as 20 healthy controls matched for education and age were administered three tests for attention (attentional shift, Stroop task, sustained attention) and three for executive functions (BADS, word fluency, memory span). The methods selected were theory based with regard to an involvement of frontal-subcortical networks in MDD, attention, and executive functions, respectively. RESULTS: Euthymic patients with MDD showed deficits in all tests related to attentional and executive functions compared to healthy controls. The patient groups did not differ with regard to attentional performance. Executive functions in severe depressives were more impaired than in mild depressives. LIMITATIONS: Differing performances of the patient groups in the subtests of the executive test battery (BADS) can only be interpreted to a limited extent. CONCLUSIONS: The results support the assumption that deficits in attention and executive functions in MDD show an increase in trait character and executive function during chronic course. Implications for differential diagnosis and cognitive psychotherapy are discussed.     

Bipolar I and bipolar II disorder: cognition and emotion processing

BACKGROUND: Cognitive impairment may be part of the endophenotype of bipolar disorder (BP), but little is known about patterns and severity of impairment in BP subgroups and their relation to depression. The same applies to deficits in emotion processing known to be present in BP. METHOD: To explore the relationship between depression and impairment in cognition and emotion processing and the differences between BP subgroups, we assessed 36 (25 BP I and 11 BP II) patients using a cognitive battery and a facial emotion recognition task. RESULTS: BP patients were impaired compared to published norms on memory, naming and executive measures (Binomial Single Proportion tests, p<0.05). Cognitive performance was largely unrelated to depression ratings. Surprise recognition was the only emotion processing impairment in BP patients compared to controls (patients' recognition score 75% v. controls' 89%, p=0.024). Patients with higher depression ratings were more impaired in recognizing expressions of anger (t23=2.21, p=0.037). BP II patients were more impaired than BP I patients in IQ, memory and executive measures (Mann-Whitney tests, p<0.05). Depression severity or exposure to medication or electroconvulsive therapy (ECT) did not explain these differences. CONCLUSIONS: We confirm cognitive impairment and an isolated facial emotion processing deficit in BP patients and suggest that these deficits are largely unrelated to depressive symptoms. Our study also provides evidence that cognitive deficits are more severe and pervasive in BP II patients, suggesting that recurrent depressive episodes, rather than mania, may have a more detrimental and lasting effect on cognition.     

Relationship Between Obstructive Sleep Apnea Severity and Brain Activation During a Sustained Attention Task

Study Objectives:

The objectives of this study were to (1) characterize cognitive and cerebral correlates of attention and response speed in patients with obstructive sleep apnea (OSA) and (2) assess the association of performance and brain activation with measures of OSA severity.

Design:

Patients with OSA and controls were compared on performance and brain activation during a sustained attention task. The association of reaction time and brain activation with apnea-hypopnea index, nocturnal hypoxia, and arousals was assessed.

Setting:

Functional magnetic resonance imaging was conducted while participants performed a Go–No-Go task. The ‘Go’ trials of the Go–No-Go task were used to index attention processing.

Participants:

Fourteen patients with OSA and 14 normal control subjects with equivalent age, body mass index, blood pressure, and education.

Interventions:

N/A.

Measurements and Results:

Patients with OSA showed decreased brain activation in cingulate, frontal, and parietal regions typically involved in attention tasks, compared with control subjects. Within the patients with OSA, increasing arousal index, but not desaturation index, was associated with slower mean reaction time and with decreased brain activation in areas involved in arousal and attention, response selection, motor response, and decision making. The apnea-hypopnea index, by itself, was not associated with changes in cerebral response.

Conclusions:

Patients with OSA showed decreased brain activation compared with control subjects during an attention task. The association of arousal index (but not hypoxia) with slow reaction times and brain activation suggests that alertness and reaction times show greater correlations with measures of sleep disruption than with measures of hypoxia.

Citation:

Ayalon L; Ancoli-Israel S; Aka AA; McKenna BS; Drummond SPA. Relationship between obstructive sleep apnea severity and brain activation during a sustained attention task. SLEEP 2009;32(3):373–381.     

Heterozygous fragile X female: historical, physical, cognitive, and cytogenetic features

Historical, physical, cognitive, and cytogenetic data were documented in 105 heterozygous fragile X [fra(X)] females and 90 controls in a prospective fashion. For comparisons, we divided heterozygotes and controls into those with cognitive impairment (IQ less than 85) and normal IQ (IQ greater than or equal to 85). The only finding that was significantly more frequent in impaired heterozygotes compared with impaired controls chi 2 analysis was shyness. Features that were more frequent in normal IQ heterozygotes compared with normal controls were voluntary thumb dislocation and hyperextensible metacarpal-phalangeal (MP) joints. Comparisons among heterozygotes demonstrated more math problems, hand biting, strabismus, high-arched palate, hyperextensible finger joints, and flat feet in impaired heterozygotes than in normal heterozygotes. Premature menopause was present in 8 of 61 normal heterozygotes and in none of the impaired heterozygotes. A multiple regression analysis demonstrated a significant inverse correlation between the percent fragility and IQ for the heterozygotes as a group. However, no correlation existed between IQ and fragility when the percent fragility was 2% or greater. However, a higher percentage of fragility was positively correlated with the total number of physical findings present.     

Do cognitive complaints in euthymic bipolar patients reflect objective cognitive impairment?

BACKGROUND: In clinical practice, bipolar patients complain of cognitive deficits such as attentional or memory disturbances. The main aim of this study was to determine whether subjective cognitive complaints were associated with objective neuropsychological impairments. METHOD: Sixty euthymic bipolar patients were assessed through a neuropsychological battery. A structured clinical interview was used to determine subjective cognitive complaints in patients. Thirty healthy controls were also included in the study in order to compare the neuropsychological performance among groups. RESULTS: Bipolar patients with a higher number of episodes, especially the number of mixed episodes, longer duration of the illness and the onset of the illness at an earlier age showed more subjective complaints. Furthermore, bipolar patients with subjective complaints showed lower scores in several cognitive measures related to attention, memory and executive function compared with the control group. Nevertheless, patients without complaints also performed less well than controls in some neuropsychological measures. CONCLUSION: Bipolar patients who were aware of cognitive deficits were more chronic, had presented more previous episodes, especially mixed type, and their illness had started at an earlier age compared with patients who did not complain about cognitive problems. Moreover, patients with good cognitive insight also had a poorer social and occupational functioning as well as a poorer neuropsychological performance. However, the bipolar group without complaints also obtained lower scores in several tests compared with healthy controls. Cognitive status of bipolar patients should be routinely assessed, regardless of the patients awareness about their cognitive deficits.     

Neuropsychological impairment after hemorrhagic stroke in basal ganglia.

We aimed to determine the severity and pattern of cognitive dysfunction in patients with basal ganglia (BG) hemorrhage within the first 6 months after stroke and to identify its clinical correlates. The study samples consisted of 30 patients with BG hemorrhage and 37 healthy controls. A comprehensive neuropsychological battery including tests of attention, memory, language, visuospatial function, and executive function was administered to all participants. Relative to healthy controls, BG patients performed significantly worse across different cognitive domains after controlling for age, sex, and education. 96.7% of patients displayed defective performance on at least three neuropsychological tests. Discriminant function analysis showed that visuospatial function and memory were the best predictors of group membership (patient/control), with an overall classification rate of 95.5%. Only side of stroke and admission Glasgow Coma Scale (GCS) score correlated significantly with some of the cognitive domains. The widespread pattern of cognitive deficits seen in BG patients provides evidence for the substantial involvement of the BG in many neuronal pathways connecting cortical and subcortical brain areas responsible for various cognitive functions.     

Beyond memory impairment: cognitive changes in Alzheimer's disease.

In addition to memory impairment, deficits in other cognitive processes are common in the advanced stages of Alzheimer's disease (AD). The diagnosis of AD does not consider the relative prevalence of deficits in cognitive areas other than memory. We report on the prevalence of aphasia, apraxia, and other cognitive changes in individuals from a large representative sample of elderly Canadians. The proportion of these symptoms and the relevant neuropsychological test performance were compared in a group of 749 people over 65 years in age with AD and a control group of 563 people without cognitive impairment. Agnosia was less common in both groups than were deficits in complex visuomotor tasks, abstract thinking, aphasia, and constructional defects. The occurrence of all symptoms increased, and levels of performance on relevant neuropsychological tests decreased, with severity of Alzheimer disease. The tests did not, however, distinguish between possible and probable AD. Both these diagnostic groups showed similar levels of performance, which suggests that this distinction is not clinically meaningful.