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Biomedical subjects

K K Zakzanis

Publications and source records attributed to K K Zakzanis.

At least 19 recordsLinked to original sources

Memory impairment in abstinent MDMA ("Ecstasy") users: a longitudinal investigation.

To examine the neurotoxic potential of continued MDMA ("Ecstasy") use in humans and its functional consequences over the course of 1 year, 15 MDMA users participated in a longitudinal study in which they completed a brief neuropsychological test battery composed mainly of retrospective and prospective memory tasks. Subjects were abstinent for 2 weeks on initial and 1-year testing. Continued use of MDMA was associated with progressive decline in terms of immediate and delayed recall.

Adolescent↗

Posterior cortical atrophy.

BACKGROUND: The term posterior cortical atrophy (PCA) was introduced in 1988 to describe five patients with fairly homogeneous, but otherwise unclassified, symptoms. These patients showed signs of a slowly progressive dementia bearing behavioral and physiologic similarities to Alzheimer's disease, but with notable distinctions. Specifically, PCA is characterized by an early onset of visual agnosia, followed by some or all components of Balint's syndrome, Gerstmann's syndrome, and transcortical sensory aphasia. REVIEW SUMMARY: In this review, the history, epidemiology, pathophysiology, neurobehavioral aspects, assessment (including neurologic and neuropsychologic), differential diagnosis, and treatment recommendations for this disorder are reviewed. CONCLUSIONS: As originally defined, PCA appears to be a clinically homogeneous syndrome. The cluster of symptoms that are common to virtually all examined cases evidences this. Although the behavioral and cognitive properties of the disorder are well established, many aspects of PCA remain unclear. Specifically, available research and understanding of PCA epidemiology and treatment are highly inadequate. In fact, the majority of such information regarding PCA is derived from studies of Alzheimer's disease. To a lesser extent, Pick's disease and Creutzfeldt-Jakob disease research have also provided insight into the underpinnings of PCA. Until PCA is categorically defined as a variant or subgroup of these other neurodegenerative disorders, however, such derivations are merely speculations.

Journal Article↗

Searching the schizophrenic brain for temporal lobe deficits: a systematic review and meta-analysis.

BACKGROUND: Several empirical studies have found temporal lobe impairments in many patients with schizophrenia. The strength and consistency of this evidence, however, has not been evaluated and synthesized quantitatively. Hence, we ask to what extent are temporal cortices really defective in schizophrenia? METHODS: Meta-analytical methods were used to determine the magnitude of evidence in support of structural and physiological temporal-hippocampal system deficits in schizophrenia. We report effect sizes from studies since 1980 that used structural (CT, MRI) and functional (SPECT, PET) neuroimaging methods. RESULTS: Both structural and functional imaging literatures are distinguished by heterogeneity whereby most patients show normative temporal function and structure, a minority shows diminished values and some patients demonstrate augmented function and structure rather than a deficit. CONCLUSIONS: The findings are hard to incorporate within single disease models that propose major involvement of the temporal system in schizophrenia, at least at the degree of resolution obtained with current imaging technology.

Humans↗

Component analysis of verbal fluency in patients with schizophrenia.

OBJECTIVE: Clustering and-switching components of phonemic fluency performance were compared in patients with schizophrenia and healthy normal controls. BACKGROUND: These components were selected to provide evidence for a specific anatomic locus for the breakdown of language processes or for a multiple-disease model of schizophrenia. METHOD: As part of a larger battery of neuropsychological tests, phonemic fluency tests were administered on an individual basis. On separate 60-second trials, participants were instructed to generate words beginning with the letters C, F, and L, excluding proper names and variants of the same word. Three scores were obtained for each participant: (1) number of words generated, excluding errors and repetitions; (2) mean cluster size; and (3) raw number of switches. RESULTS: The patients showed small but significant impairments in clustering and larger impairments in switching relative to normal controls. CONCLUSIONS: This pattern suggests a relatively greater deficit in functioning in the frontal lobe than in the temporal lobe. However, neither measure was able to completely discriminate patients with schizophrenia from controls. Moreover, differences in fluency performance were observed among subtypes of schizophrenia. Taken together, the findings of impaired performance for both aspects of fluency, differences between subtypes, and the failure to completely discriminate patients with schizophrenia from controls indicate that there is not a single marker of the disease, at least among these fluency variables. Instead, the current findings are more supportive of a multiple-disease model of schizophrenia.

Adult↗

The neuropsychological signature of primary progressive aphasia.

An effect size analysis incorporating meta-analytic principles was used to review neuropsychological findings in patients with primary progressive aphasia (PPA). Studies dating back to 1982 were gathered and the neuropsychological test results from a total of 55 patients with PPA and 162 healthy controls were synthesized using effect size analyses. The results indicate that patients with PPA are most deficient on tests of verbal skill, followed by performance on measures of delayed recall, cognitive flexibility and abstraction, memory acquisition, attention/concentration, and, finally, performance skill. A rank-order list of specific neuropsychological tasks and test variables in order of sensitivity to PPA is also provided to aid in the interpretation of the quantitative results and in the differentiation of PPA from other disorders with prominent features of dementia such as Alzheimer's disease.

Aphasia↗

Schizophrenia and the frontal brain: a quantitative review.

Structural and physiological frontal brain system deficits in patients with schizophrenia are reviewed quantitatively. We report effect sizes from studies since 1980 that used structural (CT, MRI), and functional (PET) neuroimaging methods. We found both literatures to be distinguished by heterogeneity whereby most patients show normative frontal function and structure, a minority shows diminished values and some patients demonstrate augmented function and structure rather than deficit. The average magnitude of difference between patients and controls is generally too modest to support the idea that frontal brain dysfunction is a necessary component of schizophrenia. This modesty is most apparent in average effects obtained for frontal brain volume (M = -.36), left frontal brain volume (M = -.16), frontal resting metabolism, and blood flow (M = -.64). Effect sizes of this magnitude imply that schizophrenia and control distributions overlap by as much as 88% and no less than about 60% on frontal brain measures. It is only when behavioral measures are employed as activation tasks during frontal blood flow and metabolism studies, that average effect sizes rise in magnitude to indicate patient-control distribution overlaps that are less than 50%. Overall, the findings are hard to incorporate within single disease models that propose major involvement of the frontal system, at least at the degree of resolution obtained with current imaging technology.

Adult↗

A neuropsychological comparison of demented and nondemented patients with Parkinson's disease.

The strength and sensitivity of neuropsychological test findings in patients with Parkinson's disease (PD) was reviewed using meta-analytic principles to provide a basis of comparison of deficits in nondemented and demented patients with PD. The review revealed significant relationships among duration of disease, physical disability, and cognitive impairment in nondemented patients, and qualitative and quantitative differences in the pattern of neuropsychological test impairments between nondemented and demented patients with PD. The disparate profiles of neuropsychological impairment in nondemented and demented patients may indeed reflect disease progression in keeping with the significant clinical correlations in nondemented patients. That is, as the duration of the disease endures, it appears that performance on tasks of delayed recall deteriorates first, followed by performance on measures of manual dexterity, cognitive flexibility, and abstraction.

Adult↗

Dopamine D2 densities and the schizophrenic brain.

Meta-analytic methods were used to test the D2 dopamine density hypothesis in schizophrenia. Post-mortem as well as in-vivo (i.e., PET and SPECT) neuroimaging studies that met criteria for inclusion into the meta-analysis were gathered from 1980 to 1996. The mean effect size across studies corresponds to an effect size of 1.47 (d). Although large, the effect size obtained does not meet heuristic benchmark criteria that would suggest D2 density increases to be a marker for schizophrenia. That is, roughly 30% of patients with schizophrenia could not be discriminated from normal healthy controls. Based on the findings, it is argued that D2 density receptor increases in patients with schizophrenia, although a reliable finding in many patients (i.e., approximately 70%), is not a specific or consistent marker for schizophrenia.

Animals↗

Neuropsychological correlates of positive vs. negative schizophrenic symptomatology.

This study attempts to further the validity of the subtype hypothesis in schizophrenia by testing the relationship of neuropsychological functions in schizophrenics with predominantly positive vs. negative symptoms. The Brief Psychiatric Rating Scale (BPRS) was used to parse schizophrenics into positive and negative symptom groups, while a neuropsychological test battery was administered to both types of patients. The results indicate that positive schizophrenic symptomatology is related to frontal executive tasks, whereas negative schizophrenic symptomatology is related to mental tracking tasks that require motoric and dexterous manipulation. However, the absence of non-overlapping symptomatic and neuropsychological functioning groups raises the possibility that a three or more factor model may be more reasonable for reflecting the variety of symptom and neuropsychological patterns in patients, rather than the two-type positive vs. negative dichotomy. The results further the hypothesis that schizophrenia is not a single disease entity.

Adult↗

Structural and functional meta-analytic evidence for fronto-subcortical system deficit in progressive supranuclear palsy.

Meta-analytic methods were used to determine the most sensitive indexes to fronto-subcortical deficit in progressive supranuclear palsy (PSP) and to further characterize the neurocognitive and related features of PSP that can provide a basis of comparison to other disorders with prominent subcortical brain lesions. Studies dating back to 1984 were gathered and calibrated to compare the neuropsychological, neuroimaging, and neurophysiological test results from 229 patients with PSP, and 357 healthy controls. The tests most sensitive to fronto-subcortical deficit in PSP were mostly neuropsychological measures that include such tests as the Stroop Task, Trail Making Test Part A, and Purdue pegboard performance. We conclude that although neuropsychological measures may be most sensitive to deficits in PSP, they are also less specific and valid indicators of fronto-subcortical brain system integrity.

Aged↗

Neurocognitive deficit in schizophrenia: a quantitative review of the evidence.

The neurocognitive literature on test performance in schizophrenia is reviewed quantitatively. The authors report 22 mean effect sizes from 204 studies to index schizophrenia versus control differences in global and selective verbal memory, nonverbal memory, bilateral and unilateral motor performance, visual and auditory attention, general intelligence, spatial ability, executive function, language, and interhemispheric tactile-transfer test performance. Moderate to large raw effect sizes (d > .60) were obtained for all 22 neurocognitive test variables, and none of the associated confidence intervals included zero. The results indicate that schizophrenia is characterized by a broadly based cognitive impairment, with varying degrees of deficit in all ability domains measured by standard clinical tests.

Attention↗

Quantitative evidence for neuroanatomic and neuropsychological markers in dementia of the Alzheimer's type.

Meta-analytic methods were used to determine the sensitivity of neuropsychological, structural, and physiological measures to temporal-hippocampal system function in dementia of the Alzheimer's type. Effect sizes are reported for the California Verbal Learning Test, the Wechsler Memory Scale-Revised, structural (i.e., magnetic resonance imaging [MRI]), and functional (i.e., positron emission tomography [PET], single photon emission computed tomography [SPECT]) neuroimaging methods. Overall, effect sizes from MRI studies are larger than those obtained from SPECT and PET, respectively, but not as large as those obtained from the neuropsychological measures. On the basis of this finding, the neuropsychological and gross pathologic similarities between Alzheimer's disease, other dementing conditions, and mixed dementias, warrants the coupling of neuropsychological evaluation for its sensitivity with neuroimaging visualization for its specificity in improving diagnostic and differential accuracy.

Aged↗

Brain is related to behavior (p<.05).

This article demonstrates that sole reliance on tests of statistical significance in the analysis and interpretation of neuropsychological data that is grounded in quasi-experimentation can systematically confound the conclusions drawn from our neuropsychological research regarding brain-behavior relations. The conclusion of this article is that we must accompany the statistical significance test with more appropriate statistics--namely, point-estimate effect sizes along with interval estimation and meta-analysis for the analysis of data from multiple studies. The argument for this conclusion is demonstrated from the re-analysis of published neuropsychological test findings. It is recommended on the basis of this review that the consumer of neuropsychological reports will be better served if due consideration is given to the magnitude of effect in brain-behavior statistical analyses.

Data Interpretation, Statistical↗

The subcortical dementia of Huntington's disease.

An effect size analysis incorporating meta-analytic principles was used to review neuropsychological findings in patients with Huntington's disease (HD). Studies dating back to 1980 were gathered and the neuropsychological test results from a total of 760 patients with HD, and 943 healthy controls were synthesized using effect size analyses. The results indicate that patients with HD are most deficient on tests of delayed recall, followed by performance on measures of memory acquisition, cognitive flexibility and abstraction, manual dexterity, attention/concentration, performance skill, and, finally, verbal skill. However, patients with HD display core deficits in fronto-subcortical circuits that give rise to a multitude of cognitive deficits. A rank-order list of specific neuropsychological tasks and test variables in order of sensitivity to HD is also provided to aid in the interpretation of the quantitative results.

Adult↗

Further parameters of insight and neuropsychological deficit in schizophrenia and other chronic mental disease.

Evidence has begun to accumulate which suggests that lack of awareness of illness in schizophrenia is related to and possibly the result of a cognitive deficit involving prefrontal cerebral dysfunction. This study further explores this relationship along with other domains of self-awareness in chronic schizophrenics and other subjects with serious mental disorders. One hundred eight schizophrenics and 21 bipolar subjects from three separate sites in Britain, Germany, and Canada were administered the Wisconsin Card Sorting Test and three measures of self-awareness. Lack of illness awareness and other domains of self-knowledge were significantly more related to poorer neuropsychological performance in schizophrenia patients than in the other subjects. The results support the hypothesis that lack of illness awareness is related to defective frontal lobe functioning as indexed by neuropsychological measures.

Activities of Daily Living↗

On the nature and pattern of neurocognitive function in major depressive disorder.

An effect size analysis of neurocognitive function in patients with major depressive disorder using meta-analytic principles was conducted. The results from 726 patients with depression and 795 healthy normal controls revealed that depression had the largest effect on measures of encoding and retrieval from episodic memory. Intermediate effect sizes were recorded on tests of psychomotor speed and tests that require sustained attention. Minimal effect sizes were found on tests of semantic memory, primary memory, and working memory. Moreover, major depressive disorder is accompanied by dysfunction of effortful encoding of information along with an accompanying inefficiency of retrieving poorly encoded information from declarative memory.

Cognition Disorders↗