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Konstantine K Zakzanis

Publications and source records attributed to Konstantine K Zakzanis.

13 recordsLinked to original sources
PubMed2006

Memory impairment in now abstinent MDMA users and continued users: a longitudinal follow-up.

The authors further investigated the functional consequences of continued neurotoxicity of (+/-)3,4-methylenedioxymethamphetamine (MDMA) use. Fifteen participants who were previously given a brief neuropsychological battery were tested for a third time 2 years after baseline. At 2 years, seven participants were still using MDMA, whereas eight participants had become abstinent from MDMA since 1-year testing. Current users demonstrated further declines in memory ability; former users improved on several memory measures or remained static in performance.

Adult↗
PubMed2005

An fMRI study of the Trail Making Test.

This study investigated the cerebral correlates of the Trail Making Test (TMT), used commonly as a measure of frontal lobe function. Such work sheds additional light on the known shortcomings of the TMT as a localizing instrument, as indicated, for example, by studies of patients with focal brain lesions. Functional magnetic resonance imaging (fMRI) was used to record brain activity while participants performed the TMT using a custom-built, fiber-optic fMRI-compatible writing device, the "virtual stylus". Unlike in a previous fMRI study that used a verbal adaptation of the TMT, the virtual stylus enabled a closer depiction of the brain regions engaged by the actual paper-and-pencil task. Twelve, right-handed healthy young adults participated. In Part A of the task, participants were required to link in ascending order numbers (1-2-3 ...) that were randomly distributed on a computer screen. In Part B, participants were required to link alternately between numbers and letters (1-A-2-B ...). Although behavioral performance was somewhat less than typically obtained with the TMT due to use of the virtual stylus, distinct left-sided dorsolateral and medial frontal activity was revealed when comparing Part B versus Part A. These findings agree with existing literature showing sensitivity of the TMT to frontal regions in the left hemisphere. However, other activity was also observed (left middle and superior temporal gyrus) reinforcing that the brain-behavior correlations for the TMT are multifaceted and not restricted to the frontal lobe.

Adult↗
PubMed2005

A comparison of donepezil and galantamine in the treatment of cognitive symptoms of Alzheimer's disease: a meta-analysis.

This review was conducted in order to determine the efficacy of donepezil and galantamine in the treatment of cognitive symptoms of Alzheimer's disease, and also to determine whether galantamine was a superior pharmacological intervention. Meta-analytic methods were used to analyse the data from eight empirical studies which met the inclusion criteria specified. By finding the mean effect sizes of the treatment on the outcome measures of cognition, it was determined that neither drug was greatly efficacious. However, this result does not necessarily diminish the practical value of the drug. It was also found that galantamine was no better than donepezil at treating cognitive decline in AD.

Aged↗
PubMed2005

Neurocognitive deficits in cocaine users: a quantitative review of the evidence.

Studies on the neurocognitive effects of cocaine abuse are equivocal with respect to the specific types of deficits observed, although the vast majority of studies indicate that at least some deficits in certain broad functions such as attention, learning and memory, executive functions, and response speed exist. All of these studies based their results on null hypothesis statistical significance testing (NHSST). It is argued that effect size analysis, which provides information about the magnitude of difference, offers a more valid index of cognitive impairments in a population when compared to NHSST. Accordingly, the objective of the current study was to conduct an effect size analysis (or a meta-analysis in cases where the same test measure was utilized in more than one study) to determine the type and the magnitude of the specific cognitive deficits found as a result of cocaine use. Effect sizes were calculated for each test variable across 15 empirical studies that met inclusion criteria. The results from 481 cocaine users and 586 healthy normal controls revealed that cocaine use had the largest effect on several measures of attention (0.40 < d < 1.10). Moderate to large effect sizes (d > 0.50) were also obtained on tests of visual memory and working memory. Minimal effect sizes (d < 0.30) were obtained on tests of verbal fluency and other language functions and sensory-perceptual functions. Tests of executive functioning produced mixed findings and were interpreted in terms of degree rather than nature of impairment. The results are consistent with findings from neuroimaging and neurochemical studies that have found cocaine use to be associated with dysfunctions in the anterior cingulate gyrus and orbitofrontal cortex; these regions are highly implicated in the mediation of attentional and executive functions, respectively. Methodological limitations of the empirical studies included in the analysis are discussed.

Adult↗
PubMed2003

A comparison between an interview and a self-report method of insight assessment in chronic schizophrenia.

We examined the relationship between a researcher-rated and a self-report method of insight assessment in patients with schizophrenia. Previous research has established that a moderate correlation exists between several researcher-rated and self-report insight scales. Hence, we wanted to investigate this association using another combination of assessment techniques. Accordingly, 34 patients with chronic schizophrenia were administered the Scale to Assess Unawareness of Mental Disorder (SUMD) and the Birchwood self-report Insight Scale (IS). We found a significantly lower report of insight on the Birchwood IS, regardless of administration order. These findings suggest that inherent bias within the patient-examiner interaction may be responsible for this discrepancy. Overall, a significant positive correlation was observed between total scores on the SUMD and the Birchwood self-report IS. Unexpectedly, there was a remarkable difference in correlation with respect to the order of test administration. The "self-report first" group's scores were strongly correlated, whereas the "researcher-rated first" group's scores showed little relation. These results demonstrate the importance of investigating the effects of administration order, and also question the reliability of other correlational studies between researcher-rated and self-report insight scales that have failed to employ a counterbalanced research design.

Adult↗
PubMed2003

Donepezil in a chronic drug user--a potential treatment?

The objective of the current study was to explore the potential cognitive benefits of an anticholinesterase inhibitor, donepezil, in a former chronic drug user. A neuropsychological test battery composed of the vocabulary and matrix reasoning subtests of the Wechsler adult intelligence scale-III, measures of everyday executive functioning (behavioural assessment of the dysexecutive syndrome [BADS]), and verbal learning and memory tasks (California verbal learning test-II; Rivermead behavioural memory test) was completed at baseline, at 3 months after introducing donepezil, and at 3 months after donepezil was discontinued. After donepezil treatment, substantial improvements were found on tasks of nonverbal fluid reasoning (i.e. matrix reasoning) and other executive functioning tests (i.e. BADS). At entry into the study, poor academic performance and subjective problems with memory and concentration were reported, particularly after amphetamine use (i.e. MDMA and crystal methamphetamine); after donepezil treatment, dramatic increases in memory, concentration and academic achievement were observed. The finding of improvements in tests of executive functioning and in academic performance in this case study, together with the minimal adverse side effects of donepezil, warrants the investigation of controlled studies of cholinergic enhancement in chronic amphetamine and other drug users.

Adult↗
PubMed2003

A meta-analysis of structural and functional brain imaging in dementia of the Alzheimer's type: a neuroimaging profile.

We conducted a quantitative review of the imaging literature using meta-analytic methodology to characterize further the magnitude of hippocampal deficit in probable Alzheimer's disease (AD) and to determine whether other neuroanatomic structures in AD can better discriminate the disease from normal aging. Additionally, we parceled the discriminability of neuroanatomic structures by duration of disease to determine those structures most sensitive to AD in its early and late stages. One hundred twenty-one studies published between 1984 and 2000 met criteria for inclusion in the present analysis. In total, structural (i.e., CT and MRI) and functional (i.e., SPECT and PET) neuroimaging results from 3511 patients with AD, and 1632 normal healthy controls were recorded across meta-analyses. Our results include neuroimaging profiles for both early onset and longer duration patients with AD. In sum, these profiles yield a signature of diagnostic markers in both cortical and subcortical neuroanatomic areas. This signature is consistent with the clinical phenomenology of Alzheimer's dementia and should aid in the positive identification of AD.

Aged↗
PubMed2003

A platform for combining virtual reality experiments with functional magnetic resonance imaging.

How the brain functions during behavioural tasks conducted in virtual reality (VR) remains largely unresolved. This issue is extremely important both in terms of establishing the benefits of VR through basic science, as well as for future optimization of tasks conducted in VR environments. Here, the authors describe their current work to develop a testing platform for conducting VR experiments that can be probed by functional magnetic resonance imaging (fMRI) to measure brain activity. Examples involving human spatial navigation and data glove operation illustrate the technical feasibility of the approach and introduce thought-provoking observations of brain activation patterns. Future research directions for combined use of VR and fMRI are also discussed.

Brain↗
PubMed2003

A data glove with tactile feedback for FMRI of virtual reality experiments.

Virtual reality (VR) technology is increasingly recognized as a useful tool for the assessment and rehabilitation of neurologic and psychiatric disorders. The hope that VR can accurately mimic real-life events is also of great interest in basic neuroscience, to identify the brain activity that underlies complex behavior by combining VR with techniques such as functional magnetic resonance imaging (fMRI). Toward these applications, in this study we designed and validated an fMRI-compatible data glove with a built-in vibratory stimulus device for tactile feedback during VR experiments. A simple VR-fMRI experiment was performed at 3.0 Tesla on four young healthy adults involving touching a virtual object with and without tactile feedback. The usefulness of the data glove was subsequently assessed using a series of questionnaires, behavioral performance, and the resulting activation images. Questionnaire scores indicated positive opinions with respect to the data glove, the tactile feedback, and the experimental paradigm. All subjects felt comfortable in the scanner during the VR experiment and were able to perform all aspects of the tasks successfully and with reasonable accuracy. In addition, activation maps showed the anticipated modulations in motor, somatosensory, and parietal cortex. These results support that tactile feedback enhances the realism of virtual hand-object interactions, and that the tactile data glove is suitable for use in other VR-fMRI research applications (e.g., VR physical therapy for stroke recovery).

Adult↗
PubMed2003

Neuropsychological differentiation of late-onset schizophrenia and dementia of the Alzheimer's type.

Late-onset schizophrenia and dementia of the Alzheimer's type (DAT) often present with some pathological and behavioral commonalities. Specifically, both illnesses may involve varying degrees of delusional manifestation, apathy, lateral/third-ventricular enlargement, reduced frontal lobe activity, and hippocampal atrophy. Moreover, patients with either disease have shown comparable cognitive impairment on standardized neuropsychological tests. As such, a differential diagnosis of the 2 disorders on the basis of such testing can prove to be difficult. This study evaluated the neuropsychological test results of 32 patients with late-onset schizophrenia and 32 patients with DAT to distinguish the tests that best differentiate the 2 disorders. Results indicate that the Wechsler Adult Intelligence Scale-Revised Similarities subtest and the California Verbal Learning Test (both short- and long-delay free recall) correspond to sensitive diagnostic neuropsychological measures. This investigation was preliminary in nature, and should aid in the development of a definitive differential profile.

Age of Onset↗
PubMed2002

Attentional processes in abstinent methylenedioxymethamphetamine (ecstasy) users.

In recent years, methylenedioxymethamphetamine (MDMA or ecstasy) has gained great popularity among young adults. Although human research in abstinent users has focused primarily on memory function, little attention has been given to other neuropsychological functions that may have some bearing on memory performance, such as attention. Hence, the purpose of this study was to examine the effects of MDMA on attentional processes. Accordingly, 24 MDMA users and 30 matched normal controls were tested on the Wechsler Abbreviated Scale of Intelligence (WASI) and the Test of Everyday Attention (TEA). We found MDMA users to show generally no significant difference on attention tasks compared with controls with the exception of a single TEA subtest. More interestingly, we found some preliminary evidence to indicate that dosage, in terms of the number of tablets used, may be related to impairment on specific component attentional tasks. This finding brings to light the important relationship between poor attentional processes and drug-taking behaviors and their reciprocal relationship.

Adult↗
PubMed2002

A shrinking span of temporal continuity in dementia of the Alzheimer's type.

OBJECTIVE: To examine the integrity of memory function in terms of temporal continuity in a way that would engage a patient in everyday behavior, such as informal conversation, but still allow memory function to be quantified. BACKGROUND: This bedside task allowed the measurement of the duration of continuous, conscious experience of the present and was therefore termed "span of temporal continuity." METHOD: We tracked span of temporal continuity in a patient we believed was in the very early stages of Alzheimer's disease longitudinally. RESULTS: We found a progressively smaller span in which this patient experiences continuity in keeping with disease duration. CONCLUSION: In terms of span of temporal continuity in our single subject, we were able to document a progressively smaller span in which VB experiences continuity before any telling neuropsychologic deficits. Hence, our measure might serve to better identify and characterize dementia of the Alzheimer's type in its incipient stages.

Aged↗