Biomedical subjects

R C Gur

Publications and source records attributed to R C Gur.

At least 91 records · Page 5Linked to original sources

PubMed1994

Lateralized increases in cerebral blood flow during performance of verbal and spatial tasks: relationship with performance level.

Physiologic neuroimaging studies have shown lateralized regional increase in brain activity during cognitive tasks, but the hypothesis that such changes are correlated with task performance has not been tested directly. We examined cerebral blood flow (CBF) changes induced by cognitive tasks in relation to performance. CBF was measured with the 133Xenon clearance method in 34 normal right-handed young (age < 30) volunteers during resting baseline and during the performance of a verbal analogies and a spatial line orientation test. Performance measures included "speed" and "power" estimates of both activation tasks. Resting CBF was moderately correlated with performance. The correlations were slightly higher with activated CBF for verbal but not spatial performance. The degree of increase (task-baseline) did not correlate with performance for either task. The highest and topographically specific correlations were obtained between laterality of CBF and verbal performance. Higher left hemispheric activation was correlated with verbal performance, and this correlation was significantly higher in the angular gyrus region. For the spatial task the correlations were with relatively higher right hemispheric activation but without regional specificity. The results underscore the importance of integrating behavioral performance data with physiologic measures in neuroimaging activation studies.

Adolescent↗

PubMed1994

Effects of emotional discrimination tasks on cerebral blood flow: regional activation and its relation to performance.

Facial discrimination tasks were applied as activation probes during physiologic neuroimaging ("neurobehavioral probes"). The stimuli pictured professional actors and actresses, posing degrees of happy and sad emotion. Cortical cerebral blood flow (CBF) was determined using the 133Xenon inhalation method during resting baseline, two emotional (happy from neutral and sad from neutral faces) and one nonemotional discrimination task (age). The three tasks produced CBF increase over baseline, which was greater in the right hemisphere (Task x Hemisphere interaction, p = .0001). There were regionally specific effects (Task x Region x Hemisphere interaction, p = .022). Relative to the age discrimination task, both emotion discrimination tasks were associated with greater right parietal activation. In addition, the happy discrimination task induced greater left frontal activation relative to the sad discrimination task. While overall magnitude of CBF increase did not show regionally specific correlations with performance, laterality did show such specificity. Sad discrimination performance correlated with greater right parietal activation, while performance on the happy discrimination task correlated with left frontal activation. Age discrimination performance correlated with higher activated right temporal CBF. These results support the hypothesis of right hemispheric involvement in facial processing and further suggest regionally specific hemispheric participation in happy and sad emotional discrimination. The study underscores the utility of performance measures for understanding the behavioral significance of activation effects in physiologic neuroimaging studies.

Adult↗

PubMed1994

The stability of tachistoscopic measures of hemispheric specialization.

Two-week test-retest reliabilities were determined for two tachistoscopic tasks, consonant-vowel-consonant trigrams and dot location, in 48 right-handed university students. Both visual field and laterality scores were examined. Analysis of variance showed no significant main effects or interactions of session for either task, indicating stability of mean performance and laterality scores. Likewise, grouping subjects as "high" or "low" by median laterality scores showed concordance across sessions for both tasks. Test-retest correlations were moderately high for all verbal task measures and for visual field scores for the dot location test. However, laterality indices for dot location showed low stability despite comparable within-session reliabilities of laterality scores for the two tasks. These findings suggest stability of group means and subgroups for verbal and dot location tachistoscopic measures. However, the degree to which individual scores are predictable from one session to the next differs between the two tasks.

Adult↗

PubMed1994

Standardized mood induction with happy and sad facial expressions.

The feasibility of applying ecologically valid and socially relevant emotional stimuli in a standardized fashion to obtain reliable mood changes in healthy subjects was examined. The stimuli consisted of happy and sad facial expressions varying in intensity. Two mood-induction procedures (happy and sad, each consisting of 40 slides) were administered to 24 young healthy subjects, who were instructed to look at each slide (self-paced) and try to feel the happy or sad mood expressed by the person in the picture. On an emotional self-rating scale, subjects rated themselves as relatively happier during the happy mood-induction condition and as relatively sadder during the sad mood-induction condition. Conversely, they reported that they were less happy during the sad mood-induction condition and less sad during the happy mood-induction condition. The effects were generalized to positive and negative affect as measured by the Positive and Negative Affect Scale. The intraindividual variability in the effect was very small. In a retest study after 1 month, the mood-induction effects showed good stability over time. The results encourage the use of this mood-induction procedure as a neurobehavioral probe in physiologic neuroimaging studies for investigating the neural substrates of emotional experience.

Adult↗

PubMed1994

Differential effects of mood on cortical cerebral blood flow: a 133xenon clearance study.

Studies of healthy and clinical populations have suggested valence-specific cortical and subcortical neural systems regulating emotions. In a study of 12 normal volunteers, the 133xenon clearance method for measuring regional cerebral blood flow (CBF) was used to study the effects of experimentally controlled mood states on regional brain activity within superficial cortex. CBF was measured with 254 detectors and bolus infusion during a happy mood induction task, a sad mood induction task, a sex differentiation task, and a resting baseline condition. CBF increased during sad and decreased during happy mood induction, relative to the activated (sex differentiation) and the nonactivated (resting) nonemotional control conditions. Increased CBF during sad mood induction was correlated with greater negative mood changes. Conversely, increased CBF was associated with a stronger subjective experience of positive affect during happy mood induction. This suggests that cortical arousal may serve to intensify the conscious experience of emotion. Heart rate accelerated during happy and sad mood induction and during sex differentiation relative to a pretask baseline condition. Some regional specificity of effects was also observed. The occipital temporal region showed higher overall CBF during sad mood induction than during happy mood induction. The only region that showed specific lateralized changes in CBF which differentiated sad from happy states was the frontal pole, with left CBF being higher during sad and lower during happy mood induction relative to right CBF. For sad mood induction, there were significant regional differences among correlations between CBF and self-ratings. These were attributable to higher negative correlations (i.e., higher CBF correlates with negative self-rating) in midtemporal, occipital temporal, and postcentral regions. These correlations did not vary across the 15 regions for happy mood induction. For sad mood induction, heart rate correlated positively with CBF increase and with negative affect. Correlations were opposite for happy mood induction. The results suggest high cortical and autonomic arousal during negative/sad mood and low cortical and high autonomic arousal during positive/happy mood. They underscore the value of integrating emotional experience with physiologic measures in neuroimaging activation studies.

Adult↗

PubMed1994

Magnetic resonance imaging in schizophrenia: relationship with clinical measures.

Relationships were examined between clinical features of schizophrenia and cerebrospinal fluid (CSF) volume in brain obtained by magnetic resonance imaging (MRI) in a sample of 59 patients. The volumes of the cerebral hemispheres and CSF were measured with a computer program designed to separate reliably neural tissue from CSF. The CSF to cranial volume ratios were related to history, symptom profile and outcome functioning. Earlier age of onset was associated with higher sulcal CSF ratio, r = -0.40. The anatomic measures were unrelated to symptom severity. However, patient subtypes differed in the laterality of measures. Higher left hemispheric ratios were seen in patients with severe negative symptoms, and left predominance of ventricular relative to sulcal ratios was associated with the presence of hallucinations and delusions. The results suggest that while higher CSF is related to earlier age of onset, the clinical symptoms are more related to its lateralization. This is consistent with the hypothesis that schizophrenia is a lateralized brain disease.

Adolescent↗

PubMed1994

Clinical subtypes of schizophrenia: differences in brain and CSF volume.

OBJECTIVE: Investigations of the relation of clinical features of schizophrenia to neuroanatomic measures have produced inconclusive results. The purpose of this study was to examine measures of whole-brain volume in men and women and relate them to clinical subtypes of schizophrenia. METHOD: Magnetic resonance imaging measures of cranial, brain, and ventricular and sulcal CSF volume were examined in 81 patients with schizophrenia (50 men and 31 women), divided into subgroups based on their symptom profiles, and 81 demographically matched healthy comparison subjects. RESULTS: The men had higher cranial and brain volumes than the women. The patients had smaller cranial and brain volumes than the comparison subjects; they also had higher ventricular CSF volumes and thus higher ventricle-brain ratios (VBRs). Ratio elevations were larger for the female than for the male schizophrenic patients. The patients with predominantly negative symptoms of schizophrenia had higher VBRs and sulcal CSF-brains ratios than the comparison subjects, although the component volumes did not differ. The patients with predominantly Schneiderian symptoms had higher VBRs than the comparison subjects but showed reduced cranial and brain volumes. The paranoid patients had normal VBRs, reduced sulcal CSF-brain ratios, and lower cranial and sulcal CSF volumes. CONCLUSIONS: The results suggest two patterns of neuroanatomic whole-brain abnormalities that differ in severity according to the relative prominence of negative, Schneiderian, and paranoid symptoms. These patterns may reflect differential involvement of dysgenic and atrophic pathophysiological processes. Sex moderates abnormalities in the neuroanatomic features of schizophrenia.

Adolescent↗

PubMed1994

MMPI characteristics in adults diagnosed with ADD: a preliminary report.

Characterization of Attention Deficit Disorder (ADD) in adults has been hampered by an absence of well-defined clinical profiles on objective personality measures. A sample of 22 ADD adults completed personality testing (MMPI) in conjunction with cognitive assessment. A sample of 30 normal controls and 20 patients diagnosed with schizophrenia, who had completed the MMPI as part of a larger research protocol, were utilized as comparison groups. Validity and clinical scales revealed multiple elevations in the ADD group which were similar in nature but not to the same degree as elevations observed in the schizophrenia group. Harris-Lingoes subscales identified the sources of clinical scale elevations indicating a pattern of specific and nonspecific symptomatology which differentiated the three groups. The results may aid in identifying ADD in adults.

Adult↗

PubMed1994

Sex differences in aging of the human frontal and temporal lobes.

This study investigated effects of age and sex on regional brain structure in humans, focusing on the frontal and temporal lobes. Hemispheric volumes were obtained from magnetic resonance images (MRIs) of 96 young (53 men, 43 women; aged 18-40 years) and 34 older (17 men, 17 women; aged 41-80) healthy volunteers. Images (5 mm axial spin-echo, repetition time of 3000 msec and echo times of 30 and 80 msec) were resliced along the anterior commissure-posterior commissure (AC-PC) axis to standardize for difference in head tilt, and imported into a computer program where borders of the frontal and temporal lobes were delineated. The program calculated regional brain volumes based on slice data from which CSF was segmented out. An age x sex x hemisphere x region interaction indicated that age-related reductions in brain volume were sexually dimorphic, lateralized, and region specific. Greater decrements in brain volume occurred with age in the frontal lobe than in the temporal lobe. Age-related reductions in both regions were greater in men than in women, demonstrating that sexual dimorphisms in human neuroanatomy are not fixed, but continue to change throughout adulthood. The possibility that gonadal hormones play a role in the promotion and/or prevention of neural atrophy with aging is discussed.

Adolescent↗

PubMed1993

Effects of hypnosis on regional cerebral blood flow during ischemic pain with and without suggested hypnotic analgesia.

Using 133Xe regional cerebral blood flow (CBF) imaging, two male groups having high and low hypnotic susceptibility were compared in waking and after hypnotic induction, while at rest and while experiencing ischemic pain to both arms under two conditions: attend to pain and suggested analgesia. Differences between low and highly-hypnotizable persons were observed during all hypnosis conditions: only highly-hypnotizable persons showed a significant increase in overall CBF, suggesting that hypnosis requires cognitive effort. As anticipated, ischemic pain produced CBF increases in the somatosensory region. Of major theoretical interest is a highly-significant bilateral CBF activation of the orbito-frontal cortex in the highly-hypnotizable group only during hypnotic analgesia. During hypnotic analgesia, highly-hypnotizable persons showed CBF increase over the somatosensory cortex, while low-hypnotizable persons showed decreases. Research is supportive of a neuropsychophysiological model of hypnosis (Crawford, 1991; Crawford and Gruzelier, 1992) and suggests that hypnotic analgesia involves the supervisory, attentional control system of the far-frontal cortex in a topographically specific inhibitory feedback circuit that cooperates in the regulation of thalamocortical activities.

Adult↗

PubMed1993

Reliability of regional cerebral blood flow activation to cognitive tasks in elderly normal subjects.

The assessment of cerebral blood flow (CBF) using noninvasive 133Xe techniques provides an indirect measurement of cortical metabolic activity. The utility of this method in longitudinal clinical studies depends on the stability and reproducibility of resting and activated flow measures. We evaluated CBF in a sample of 16 elderly normal subjects (aged 54-73 years) at rest and during task performance in two sessions separated by an average of 9 weeks. Resting global CBF was lower in the second session, a finding consistent with the known effects of habituation previously reported. Regionally specific activated CBF did not change with repeated measurements. The results provide evidence that the 133Xe technique is reliable and of potential utility in evaluating the effect of the natural course of brain disease, as well as the effects of therapeutic interventions on brain activity.

Aged↗

PubMed1993

Asymmetrical visual deprivation: a technique to differentially influence lateral hemispheric function.

This article describes a contact-lens method to sustain asymmetry in visual deprivation and the use of this method to test the general hypothesis that asymmetry in input deprivation can shift activation balance in the integrated brain, differentially influencing lateral hemispheric function. Effects of asymmetrical visual deprivation were as predicted on lateral asymmetry of EEG theta, producing more theta over the deprived hemisphere. Cross-modal influence of such visual deprivation was found in the perception of pleasantness of odors. An interaction was found between side of visual deprivation and performance on verbal reasoning and spatial orientation tasks. A line-bisection test of visual attention was not sensitive to the effects. Fatigue as rated on the Profile of Mood States was greatest when the left hemisphere was deprived.

Adolescent↗

PubMed1993

Effects of memory processing on regional brain activation: cerebral blood flow in normal subjects.

The role of the temporal lobe in memory has been implicated in lesion studies, which have also suggested the hypothesis of greater left hemispheric involvement in verbal, and right hemispheric involvement in facial memory. We tested these hypotheses in a sample of 27 normal right-handed subjects using the 133Xenon clearance method for measuring cerebral blood flow (CBF). The CBF was measured during resting baseline, word recognition, and face recognition conditions in counterbalanced order. CBF increased during recognition compared to baseline, and for the midtemporal lobe this increase was asymmetric to the left hemisphere for words and to the right for faces. While overall CBF levels and task related increases in CBF were uncorrelated either with performance or with delta performance (excess performance relative to basal memory abilities), laterality of task-related CBF correlated with both performance indices, showing regional specificity of correlations. This neurobehavioral probe paradigm can be applied in the study of neural substrates of normal and disturbed memory.

Adult↗

PubMed1992

Neurobehavioral probes for physiologic neuroimaging studies.

The potential of physiologic neuroimaging for contributing to the understanding of behavior and the psychopathologic condition is being enhanced by increased application of "neurobehavioral probes," tasks performed during measurement. Thus far, little attention has been paid to the psychometric properties of such tasks as reliability, difficulty, and construct validity. We propose steps for applying such probes, considering issues in defining the behavior and task selection. Few available neuropsychometric tasks meet criteria for optimal use in neuroimaging studies, and a procedure is outlined for developing new probes. Highlighted are issues encountered during the phases of conceptualization, assembly and screening of items, task construction, and the psychometric validation. A set of language tasks illustrates the process. The procedure may enhance efficiency of acquiring knowledge in this area where the magnitude of potential may be matched by the costs and complexity of research.

Behavior↗

PubMed1992

Facial emotion discrimination: I. Task construction and behavioral findings in normal subjects.

Facial discrimination tasks (age, happy-neutral, and sad-neutral) were developed to address the need for activation tasks that engage emotional processing and can be used during physiologic neuroimaging ("neurobehavioral probes"). The stimuli pictured professional actors and actresses who had been screened for asymmetric features. In experiment I, same-sex stimuli were used to examine the performance of normal subjects (24 men, 15 women) on the three tasks. Performance was better during the emotion-discrimination tasks than during the age-discrimination task, and males had higher sensitivity scores for the detection of sad emotion. However, experiment II showed that the sex of the stimulus interacts with the sex of the subject. Compared with female subjects, male subjects (n = 10) were selectively less sensitive to sad emotion in female faces. Female subjects (n = 10) were more sensitive overall to emotional expression in male faces than in female faces. Thus, men and women differed in performance depending on the sex of the facial stimulus.

Adult↗

PubMed1992

Facial emotion discrimination: II. Behavioral findings in depression.

The facial discrimination tasks described in part I (Erwin et al., 1992) were administered to a sample of 14 patients with depression and 14 normal controls matched for sex (12 women, 2 men) and balanced for age and sociodemographic characteristics. Patients performed more poorly on measures of sensitivity for happy discrimination and specificity for sad discrimination, and had a higher negative bias across tasks. Severity of negative affect was correlated with poorer performance for patients. The results suggest that depression is associated with an impaired ability to recognize facial displays of emotion.

Adult↗

PubMed1992

Facial emotion discrimination: III. Behavioral findings in schizophrenia.

Emotional discrimination was studied in patients with schizophrenia (n = 20) and matched controls. Performance of the emotion-discrimination tasks in the schizophrenic patients was impaired, relative to their performance of an age-discrimination task. Performance patterns in the patient group could also be reliably distinguished from those of normal controls. The impairment was associated with the severity of both emotional and nonemotional symptoms specific to schizophrenia, but not with the severity of nonspecific symptoms. The deficit associated with schizophrenia is more marked than that reported for depression (Gur et al., 1992), particularly for the emotion-discrimination tasks, and showed no difference between "happy" discrimination and "sad" discrimination. The main difficulty in patients with schizophrenia is the assignment of emotional valence to neutral faces. The magnitude of the deficit underscores the salience of emotional impairment in schizophrenia, and its relation to cognitive dysfunction in this disorder merits further scrutiny.

Adolescent↗

PubMed1992

Information processing in the separated hemispheres of callosotomy patients: does the analytic-holistic dichotomy hold?

The characterization of the left and right cerebral hemispheres as analytic and holistic, respectively, was evaluated with callosotomy patients. This distinction was operationalized by reference to the work of Garner, Kemler Nelson, and their colleagues on separable (analytic) and integral (holistic) dimensions of cognition. In one experiment, patients were asked to make similarity judgments when faced with triads of stimuli such that one pair matched on a criterial attribute (analytic) and another pair showed a family resemblance (holistic). The right hemisphere showed a stronger bias to judge on the basis of the criterial attribute. In a second experiment, each hemisphere was engaged separately in a concept formation task. Depending on the exemplars in a particular set, analytic or holistic processing was seen in either hemisphere. However, the left hemisphere was more likely to engage in analytic processing. The results suggest that both hemispheres are capable of either type of processing and may use either mode, depending on the nature of the task and stimulus material. Thus, the analytic/holistic distinction may not provide a simple, generalizable description of information processing differences between the two hemispheres.

Adult↗