Biomedical subjects

Ruben C Gur

Publications and source records attributed to Ruben C Gur.

At least 55 records · Page 3Linked to original sources

PubMed2004

Normative data for the symbol cancellation test in young healthy adults.

Mesulam's (1985) symbol cancellation test (SCT) provides a measure of neglect, organizational process, and attention. Although the SCT lends itself to qualitative interpretation, normative data would be helpful for interpreting errors and time to complete this test. SCT normative data are provided for healthy young adults and the contribution of age, education, ethnicity, and gender to SCT performance is examined. Results were as follows: Age was significant (p < .05) and education approached significance (p = .06) as predictors of SCT performance, but percentile ranks revealed an unstable performance pattern across age and education. Thus, normative data for the SCT are provided for the entire sample (n = 136). Conclusions are as follows: Healthy young adults make few errors and complete the SCT in under 2 min, consistent with general findings (Mesulam, 1985). In addition, a relation likely exists between SCT performance and age and education, but a larger sample seems warranted to reliably model the pattern.

Adult↗

PubMed2003

Levels-of-processing effect on word recognition in schizophrenia.

BACKGROUND: Individuals with schizophrenia have difficulty organizing words semantically to facilitate encoding. This is commonly attributed to organizational rather than semantic processing limitations. By requiring participants to classify and encode words on either a shallow (e.g., uppercase/lowercase) or deep level (e.g., concrete/abstract), the levels-of-processing paradigm eliminates the need to generate organizational strategies. METHODS: This paradigm was administered to 30 patients with schizophrenia and 30 healthy comparison subjects to test whether providing a strategy would improve patient performance. RESULTS: Word classification during shallow and deep encoding was slower and less accurate in patients. Patients also responded slowly during recognition testing and maintained a more conservative response bias following deep encoding; however, both groups showed a robust levels-of-processing effect on recognition accuracy, with unimpaired patient performance following both shallow and deep encoding. CONCLUSIONS: This normal levels-of-processing effect in the patient sample suggests that semantic processing is sufficiently intact for patients to benefit from organizational cues. Memory remediation efforts may therefore be most successful if they focus on teaching patients to form organizational strategies during initial encoding.

Adult↗

PubMed2003

Emotion processing in chimeric faces: hemispheric asymmetries in expression and recognition of emotions.

Since the discovery of facial asymmetries in emotional expressions of humans and other primates, hypotheses have related the greater left-hemiface intensity to right-hemispheric dominance in emotion processing. However, the difficulty of creating true frontal views of facial expressions in two-dimensional photographs has confounded efforts to better understand the phenomenon. We have recently described a method for obtaining three-dimensional photographs of posed and evoked emotional expressions and used these stimuli to investigate both intensity of expression and accuracy of recognizing emotion in chimeric faces constructed from only left- or right-side composites. The participant population included 38 (19 male, 19 female) African-American, Caucasian, and Asian adults. They were presented with chimeric composites generated from faces of eight actors and eight actresses showing four emotions: happiness, sadness, anger, and fear, each in posed and evoked conditions. We replicated the finding that emotions are expressed more intensely in the left hemiface for all emotions and conditions, with the exception of evoked anger, which was expressed more intensely in the right hemiface. In contrast, the results indicated that emotional expressions are recognized more efficiently in the right hemiface, indicating that the right hemiface expresses emotions more accurately. The double dissociation between the laterality of expression intensity and that of recognition efficiency supports the notion that the two kinds of processes may have distinct neural substrates. Evoked anger is uniquely expressed more intensely and accurately on the side of the face that projects to the viewer's right hemisphere, dominant in emotion recognition.

Adolescent↗

PubMed2003

Fuzzy cluster analysis of high-field functional MRI data.

Functional magnetic resonance imaging (fMRI) based on blood-oxygen level dependent (BOLD) contrast today is an established brain research method and quickly gains acceptance for complementary clinical diagnosis. However, neither the basic mechanisms like coupling between neuronal activation and haemodynamic response are known exactly, nor can the various artifacts be predicted or controlled. Thus, modeling functional signal changes is non-trivial and exploratory data analysis (EDA) may be rather useful. In particular, identification and separation of artifacts as well as quantification of expected, i.e. stimulus correlated, and novel information on brain activity is important for both, new insights in neuroscience and future developments in functional MRI of the human brain. After an introduction on fuzzy clustering and very high-field fMRI we present several examples where fuzzy cluster analysis (FCA) of fMRI time series helps to identify and locally separate various artifacts. We also present and discuss applications and limitations of fuzzy cluster analysis in very high-field functional MRI: differentiate temporal patterns in MRI using (a) a test object with static and dynamic parts, (b) artifacts due to gross head motion artifacts. Using a synthetic fMRI data set we quantitatively examine the influences of relevant FCA parameters on clustering results in terms of receiver-operator characteristics (ROC) and compare them with a commonly used model-based correlation analysis (CA) approach. The application of FCA in analyzing in vivo fMRI data is shown for (a) a motor paradigm, (b) data from multi-echo imaging, and (c) a fMRI study using mental rotation of three-dimensional cubes. We found that differentiation of true "neural" from false "vascular" activation is possible based on echo time dependence and specific activation levels, as well as based on their signal time-course. Exploratory data analysis methods in general and fuzzy cluster analysis in particular may help to identify artifacts and add novel and unexpected information valuable for interpretation, classification and characterization of functional MRI data which can be used to design new data acquisition schemes, stimulus presentations, neuro(physio)logical paradigms, as well as to improve quantitative biophysical models.

Artifacts↗

PubMed2003

Neurocognitive performance and clinical changes in olanzapine-treated patients with schizophrenia.

Diffuse cognitive impairment characterizes patients with schizophrenia throughout the course of illness. The deficits persist despite clinical improvement associated with neuroleptic intervention and are related to outcome. It is unclear whether treatment with atypical agents is associated with improved cognition that relates to symptoms and outcome. Using a set of computerized neurocognitive measures, we evaluated whether the effects of olanzapine are greater than practice effects for specific neurocognitive domains that could provide targets for large-scale randomized studies. We enrolled 19 patients with schizophrenia before initiation of treatment with olanzapine and 16 of them were examined at 6 weeks and 6 months of follow-up. They were compared to 34 healthy participants who enrolled, 24 of whom were evaluated longitudinally. Improvement exceeding practice effects was observed in patients for abstraction and spatial memory and the latter correlated with clinical improvement in negative symptoms. These results suggest that some effects of olanzapine may impact both symptoms and cognitive performance.

Adolescent↗

PubMed2003

Facial emotion recognition in schizophrenia: intensity effects and error pattern.

OBJECTIVE: The authors used color photographs of emotional and neutral expressions to investigate recognition patterns of five universal emotions in schizophrenia. METHOD: Twenty-eight stable outpatients with schizophrenia (19 men and nine women) and 61 healthy subjects (29 men and 32 women) completed an emotion discrimination test that presented mild and extreme intensities of happy, sad, angry, fearful, disgusted, and neutral faces, balanced for gender and ethnicity. Analyses evaluated accuracy of identifying emotions as a function of intensity, diagnosis, and gender of poser and rater. RESULTS: Patients performed worse than comparison subjects on recognition of all emotions and neutral faces combined, including mild and extreme expressions. For specific emotions, patients performed worse on recognition of fearful, disgusted, and neutral expressions. For all emotions except disgust, recognition of extreme intensity was better than recognition of mild intensity. However, patients showed less benefit from increased intensity for all emotions combined, and the difference was most pronounced for fear. Thus, patients were more impaired than healthy comparison subjects in identifying high-intensity expressions, even though this was an easier task than identifying low-intensity expressions. In the comparison of patterns of errors, patients and healthy subjects differed only in misattributions of neutral expressions; patients overattributed disgusted expressions and underattributed happy expressions. CONCLUSIONS: Patients with schizophrenia were impaired in overall emotion recognition, particularly fear and disgust, and did not benefit from increased emotional intensity. Error patterns indicate that patients misidentified neutral cues as negatively valenced.

Adult↗

PubMed2003

Working memory deficit as a core neuropsychological dysfunction in schizophrenia.

OBJECTIVE: This study tested the hypothesis that impaired working memory is a core deficit underlying multiple neuropsychological deficits in schizophrenia patients. METHOD: The subjects were 27 men with stable chronic schizophrenia treated with atypical antipsychotics and 38 normal participants. They were assessed with a battery of neuropsychological tests. Verbal working memory was measured with the WAIS digit span tests, and the Dot Test was used to test spatial working memory. RESULTS: In the patients, verbal working memory showed significant correlations with visual retention, visual orientation, simple motor function, visuomotor coordination, and executive function but not with memory for objects, memory for faces, recognition of facial emotions, or attention. Spatial working memory showed significant correlations with visual retention, visual orientation, memory for objects, memory for faces, and simple motor function but not attention, executive function, or visuomotor coordination. In the comparison group, no correlations between working memory and other neuropsychological functions were found. CONCLUSIONS: These findings support the hypothesis that working memory is a core deficit in schizophrenia. The authors postulate that the lower capacity for verbal and spatial "on-line storage" is rate limiting in the performance of other cognitive functions. Executive functions rely critically on the phonetic loop, complex visual functions such as object and face memory rely on the spatial on-line storage system (visuospatial scratch pad), while other functions such as visual orientation depend critically on both capacities.

Adult↗

PubMed2002

The orbitofrontal cortex in methamphetamine addiction: involvement in fear.

We used Tellegen's Multidimensional Personality Questionnaire (MPQ) harm avoidance (fear) scale and the constraint superfactor as personality measures of inhibitory control and examined their association with glucose metabolism in the orbitofrontal gyrus at rest in 14 recently abstinent methamphetamine-dependent subjects and 22 comparison subjects. Higher MPQ scores were associated with higher relative orbitofrontal gyrus metabolism in the methamphetamine-dependent subjects. There was a tendency towards a negative association for the comparison subjects (test of coincidence of regression lines for the two subject groups: F = 3.3, df = 2,32; = 0.051). These results suggest that the role of the orbitofrontal cortex in inhibitory control can be manifested in stable personality predispositions and further implicate this region in the core characteristics of drug addiction.

Adult↗

PubMed2002

Development of an abbreviated schizophrenia quality of life scale using a new method.

The goal of the study was to develop and apply a predictive model approach to reduce the number of items collected for scales that yield a total summary score. A parsimonious subset of items from the 21-item Quality of Life Scale (QLS) that can accurately predict the total scale score was sought and evaluated in 198 patients with schizophrenia, using a statistical modeling approach. Two additional data sets were used for model validation: the subset of 101 patients used in the model construction who had the QLS administered approximately 1 year later and a new sample of 37 patients. Using only seven QLS items as predictors, the correlation was 0.9831 between the predicted and true QLS totals. Applying the model based for these seven QLS items, the correlations from the first and second validation data sets were 0.9791 and 0.9637, respectively. The study demonstrates that a small subset of items of the QLS predicts the entire 21-item scale with high accuracy. Two validation samples have confirmed the finding. This reduces the effort associated with scale administration and is likely to increase the assessment of an important functional domain. Such models can guide efforts for item reduction in other rating instruments.

Adolescent↗

PubMed2002

Perception of happy and sad facial expressions in chronic schizophrenia: evidence for two evaluative systems.

BACKGROUND: Persons suffering from schizophrenia have impaired perception of emotional expressions, but it is not clear whether this is part of a generalized deficit in cognitive function. AIM: To test for existence of emotion-specific deficits by studying the effects of valence on recognition of facial emotional expressions. METHODS: 24 male subjects suffering from chronic schizophrenia were examined with two tests of perception of emotion: the Penn Emotion Acuity Test (PEAT 40) and the Emotion Differentiation Task (EMODIFF). Clinical state was assessed with the Scale for the Assessment of Negative Symptoms (SANS) and Scale for the Assessment of Positive Symptoms (SAPS), visual memory with the Benton Visual Retention Test (BVRT) and motor function with the finger tapping test. RESULTS: Identification of happy facial expressions showed significant negative correlation with age, cumulated time in hospital and length of current hospitalization; positive correlations were found with visual retention and finger tapping scores. Identification of sad facial expressions showed significant correlation only with cumulated time in hospital while identification of neutral facial expressions showed no significant correlations. Discrimination between degrees of happy but not sad facial expression showed a positive correlation with negative symptoms. CONCLUSION: Perception of happy and sad emotion relates differently to significant illness parameters. This differentiability supports the existence of an emotion-specific deficit in perception of emotions in schizophrenia and of separate channels for processing positive and negative emotions.

Adult↗

PubMed2002

A method for obtaining 3-dimensional facial expressions and its standardization for use in neurocognitive studies.

Facial expressions of emotion are increasingly being used in neuroscience as probes for functional imaging and as stimuli for studying hemispheric specialization for face and emotion processing. Available facial stimuli are 2-dimensional and therefore, their orientation is fixed and poorly suited for examining asymmetries, they are often obtained under poorly specified conditions, usually posed, lack ethnic diversity, and are of restricted age range. We describe a method for accurately acquiring and reconstructing the geometry of the human face and for display of this reconstruction in a 3-dimensional format. We applied the method in a sample of 70 actors and 69 actresses expressing happiness, sadness, anger, fear and disgust, as well as neutral expressions. Each emotion was expressed under three levels of intensity and under both posed and evoked conditions. Resulting images are of high technical quality and are accurately identified by raters. The stimuli can be downloaded in digital form as 'movies' where angle and orientation can be manipulated for inclusion in functional imaging probes or in tests that can be administered as measures of individual differences in facial emotion processing. The database of emotional expressions can also be used as a standard for comparison with clinical populations.

Adolescent↗

PubMed2002

Brain activation during facial emotion processing.

Functional neuroimaging studies have helped identify neural systems involved in cognitive processing and more recently have indicated limbic activation to emotional stimuli. Some functional magnetic resonance imaging (fMRI) studies have reported increased amygdala response during exposure to emotional stimuli while others have not shown such activation. The present study was designed to test the hypothesis that activation of the amygdala is related to the relevance of the emotional valence of stimuli. Healthy young participants (7 men, 7 women) were studied in a high-field (4 tesla) scanner using blood oxygenation-level dependent (BOLD) signal changes in a blocked "box car" design. They viewed facial displays of happiness, sadness, anger, fear, and disgust as well as neutral faces obtained from professional actors and actresses of diverse ethnicity and age. Their task alternated between emotion discrimination (indicating whether the emotion was positive or negative) and age discrimination (indicating whether the poser was older or younger than 30). Blocks contained the same proportion of emotional and neutral faces. Limbic response was greater during the emotion than during the age discrimination conditions. The response was most pronounced in the amygdala, but was also present in the hippocampus and circumscribed voxels in other limbic regions. These results support the central role of the amygdala in emotion processing, and indicate its sensitivity to the task relevance of the emotional display.

Adult↗

PubMed2002

Ethical considerations for neuropsychologists as functional magnetic imagers.

This discussion highlights ethical and practical issues potential neuropsychologist-imagers should consider in conducting functional magnetic resonance imaging (fMRI). While fMRI is not currently approved for clinical use, research is ongoing which has implications for clinical practice, from refining brain-behavior relationships, to assisting with diagnosis and treatment decisions. To protect the welfare of cognitively impaired populations requires special care with respect to MR risks and informed consent. Competent functional imaging requires an understanding of the strengths, limitations, and appropriate domain of applications of the measure.

Aged↗

PubMed2002

Neuropsychological profiles delineate distinct profiles of schizophrenia, an interaction between memory and executive function, and uneven distribution of clinical subtypes.

Neuropsychological performance in 151 patients with schizophrenia was examined using cluster analysis to identify neurocognitive subtypes. Hierarchical and iterative partitioning methods identified four clusters using an extended neuropsychological battery. Consistent with previous findings two extreme clusters were characterized by near normative performance and profound global dysfunction, respectively. The two remaining neurocognitive clusters displayed moderate-severe dysfunction and were differentiated by unique patterns of abstraction and flexibility, attention, spatial memory, and sensory-perception. Analysis of variance revealed an interaction between global memory and executive function for clusters III and IV. Although limited cluster differences were found relative to clinical and historical data, the distribution of previously defined clinical subtypes was uneven among neurocognitive clusters. Paranoid patients were significantly more likely to be classified into cluster II and disproportionately absent from clusters I and IV. Patients with negative and disorganized clinical subtypes comprised a disproportionate component of clusters I and IV but were less likely to be classified in cluster II. This suggests greater correspondence than previously postulated between systems responsible for clinical symptomatology and those moderating neurocognitive dysfunction.

Adult↗

PubMed2002

Sex differences in temporo-limbic and frontal brain volumes of healthy adults.

Sex differences have been observed in neurobehavioral measures and in neuroanatomic studies. Men and women differ in emotion processing, including perception, experience and expression, most notably reflected in greater male aggression. We examine temporo-limbic and prefrontal structures volumetrically in a large well-characterized sample of healthy adults, applying morphometric methods across cerebral regions that regulate emotions. Quantitative magnetic resonance imaging (MRI) was performed in 116 healthy adults, 57 men and 59 women, age range 18-49 years. We used reliable methods of region of interest identification to examine sex differences in volume of temporo-limbic and frontal regions. An automated tissue segmentation procedure was used to obtain separate measurements for gray and white matter. After correcting for cranial volume, men and women had identical volumes of amygdala and hippocampus, as well as dorsal prefrontal cortex. However, women had larger orbital frontal cortices than men, resulting in highly significant difference in the ratio of orbital gray to amygdala volume (P = 0.002). The larger volume of cortex devoted to emotional modulation may relate to behavioral evidence for sex differences in emotion processing.

Adolescent↗

PubMed2002

An fMRI study of facial emotion processing in patients with schizophrenia.

OBJECTIVE: Emotion processing deficits are notable in schizophrenia. The authors evaluated cerebral blood flow response in schizophrenia patients during facial emotion processing to test the hypothesis of diminished limbic activation related to emotional relevance of facial stimuli. METHOD: Fourteen patients with schizophrenia and 14 matched comparison subjects viewed facial displays of happiness, sadness, anger, fear, and disgust as well as neutral faces. Functional magnetic resonance imaging was used to measure blood-oxygen-level-dependent signal changes as the subjects alternated between tasks of discriminating emotional valence (positive versus negative) and age (over 30 versus under 30) of the faces with an interleaved crosshair reference condition. RESULTS: The groups did not differ in performance on either task. For both tasks, healthy participants showed activation in the fusiform gyrus, occipital lobe, and inferior frontal cortex relative to the resting baseline condition. The increase was greater in the amygdala and hippocampus during the emotional valence discrimination task than during the age discrimination task. In the patients with schizophrenia, minimal focal response was observed for all tasks relative to the resting baseline condition. Contrasting patients and comparison subjects on the emotional valence discrimination task revealed voxels in the left amygdala and bilateral hippocampus in which the comparison subjects had significantly greater activation. CONCLUSIONS: Failure to activate limbic regions during emotional valence discrimination may explain emotion processing deficits in patients with schizophrenia. While the lack of limbic recruitment did not significantly impair simple valence discrimination performance in this clinically stable group, it may impact performance of more demanding tasks.

Affect↗

PubMed2002

Working memory for complex figures: an fMRI comparison of letter and fractal n-back tasks.

n-back letter and fractal tasks were administered to 11 participants during functional magnetic resonance imaging to test process specificity theories of prefrontal cortex (PFC) function and assess task validity. Tasks were matched on accuracy, but fractal n-back responses were slower and more conservative. Maintenance (1-back minus 0-back) activated inferior parietal and dorsolateral PFC, with additional activation in right ventrolateral PFC during letter n-back and left lingual gyrus during fractal n-back. Maintenance plus manipulation (2-back minus 0-back) activated inferior parietal, Broca's area, insula, and dorsolateral and ventral PFC, with greater right dorsolateral PFC activation for letter n-back. Manipulation only (2-back minus 1-back) produced additional and equivalent dorsolateral PFC and anterior cingulate activation in both tasks. Results support fractal n-back validity and indicate substantial overlap in working memory functions of dorsal and ventral PFC.

Adult↗

PubMed2002

Memory-delineated subtypes of schizophrenia: relationship to clinical, neuroanatomical, and neurophysiological measures.

Memory performance was examined in patients with schizophrenia to determine whether subgroups conforming to cortical and subcortical dementias could be identified and, if so, whether subgroups differed on clinical, neuroanatomical, and neurophysiological measures. A cluster analysis of California Verbal Learning Test performance classified patients into 3 subgroups. Two groups exhibited memory deficits consistent with the cortical-subcortical distinction, whereas 1 group was unimpaired. Cortical patients tended to be male, and they had earlier illness onset, reduced temporal lobe gray matter, and hypometabolism. Subcortical patients had ventricular enlargement and more negative symptoms. Unimpaired patients had fewer negative symptoms and dorsal medial prefrontal hypermetabolism. The authors conclude that categorizing patients on the basis of memory deficits may yield neurobiologically meaningful disease subtypes.

Adult↗