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J J Sidtis

Publications and source records attributed to J J Sidtis.

At least 19 recordsLinked to original sources
PubMed1995

Principal component analysis and the scaled subprofile model compared to intersubject averaging and statistical parametric mapping: I. "Functional connectivity" of the human motor system studied with [15O]water PET.

Using [15O]water PET and a previously well studied motor activation task, repetitive finger-to-thumb opposition, we compared the spatial activation patterns produced by (1) global normalization and intersubject averaging of paired-image subtractions, (2) the mean differences of ANCOVA-adjusted voxels in Statistical Parametric Mapping, (3) ANCOVA-adjusted voxels followed by principal component analysis (PCA), (4) ANCOVA-adjustment of mean image volumes (mean over subjects at each time point) followed by F-masking and PCA, and (5) PCA with Scaled Subprofile Model pre- and postprocessing. All data analysis techniques identified large positive focal activations in the contralateral sensorimotor cortex and ipsilateral cerebellar cortex, with varying levels of activation in other parts of the motor system, e.g., supplementary motor area, thalamus, putamen; techniques 1-4 also produced extensive negative areas. The activation signal of interest constitutes a very small fraction of the total nonrandom signal in the original dataset, and the exact choice of data preprocessing steps together with a particular analysis procedure have a significant impact on the identification and relative levels of activated regions. The challenge for the future is to identify those preprocessing algorithms and data analysis models that reproducibly optimize the identification and quantification of higher-order sensorimotor and cognitive responses.

Adult↗
PubMed1992

The identification of affective-prosodic stimuli by left- and right-hemisphere-damaged subjects: all errors are not created equal.

Impairments in listening tasks that require subjects to match affective-prosodic speech utterances with appropriate facial expressions have been reported after both left- and right-hemisphere damage. In the present study, both left- and right-hemisphere-damaged patients were found to perform poorly compared to a nondamaged control group on a typical affective-prosodic listening task using four emotional types (happy, sad, angry, surprised). To determine if the two brain-damaged groups were exhibiting a similar pattern of performance with respect to their use of acoustic cues, the 16 stimulus utterances were analyzed acoustically, and the results were incorporated into an analysis of the errors made by the patients. A discriminant function analysis using acoustic cues alone indicated that fundamental frequency (FO) variability, mean FO, and syllable durations most successfully distinguished the four emotional sentence types. A similar analysis that incorporated the misclassifications made by the patients revealed that the left-hemisphere-damaged and right-hemisphere-damaged groups were utilizing these acoustic cues differently. The results of this and other studies suggest that rather than being lateralized to a single cerebral hemisphere in a fashion analogous to language, prosodic processes are made up of multiple skills and functions distributed across cerebral systems.

Adult↗
PubMed1992

Differential effects of congenital versus acquired unilateral brain injury on dichotic listening performance: evidence for sparing and asymmetric crowding.

We assessed dichotic speech and complex-pitch discrimination in nine young patients with unilateral left-hemisphere injury and eight young patients with unilateral right-hemisphere injury incurred in the pre-perinatal (congenital) period. As in adults with acquired unilateral lesions, both congenital lesion groups demonstrated poor performance on stimuli presented to the ear contralateral to the lesion. In overall performance on speech discrimination, however, the left-hemisphere congenital lesion group performed significantly better than the acquired-lesion group did. On complex-pitch discrimination, the right-hemisphere congenital lesion group performed significantly better than did the acquired-lesion group, but both left- and right-hemisphere congenital lesion groups were significantly worse at complex-pitch discrimination than were their age- and gender-matched normal controls. These results indicate that although congenital damage produces a "lesion effect" in dichotic listening similar to that after damage acquired in adulthood, overall function is relatively spared. To the extent that complex-pitch discrimination is affected by congenital damage to either hemisphere but speech discrimination is not, the present results are consistent with an asymmetric form of crowding during reorganization after congenital unilateral brain damage.

Adolescent↗
PubMed1992

Cerebrospinal fluid beta 2-microglobulin in patients with AIDS dementia complex: an expanded series including response to zidovudine treatment.

OBJECTIVE: To determine the relationship between cerebrospinal fluid (CSF) beta 2-microglobulin (beta 2M) and severity of AIDS dementia complex (ADC), and between CSF beta 2M and response of ADC to zidovudine. DESIGN: A prospective study. SETTING: Tertiary referral hospital. PATIENTS, PARTICIPANTS: Seventy-eight patients with varying stages of ADC were selected from a subgroup of a cohort of HIV-seropositive patients who are being studied prospectively for the neurological complications of HIV-1 infection. To enter our study, patients had to have an ADC stage of at least 0.5 (equivocal symptoms or abnormal neurological signs in the absence of functional impairment). A control group of 11 HIV-1-seropositive, neurologically normal patients was chosen randomly from the patients followed in the Multicenter AIDS Cohort Study. INTERVENTIONS: Patients were assessed neurologically and neuropsychologically and computed tomography of the brain and CSF studies were performed. MAIN OUTCOME MEASURES: Patients were staged according to severity of ADC on clinical criteria. Neuropsychological test scores were converted to an impairment score. CSF beta 2M was quantified in both serum and CSF of all patients and in 10 patients with pre- and post-zidovudine assessments. RESULTS: There was a high correlation between CSF beta 2M concentration and severity of ADC (P less than 0.0001); treatment with zidovudine significantly reduced these concentrations (P = 0.013). CSF beta 2M concentration was independent of CSF white-cell count and blood-brain barrier impairment. Other CSF changes in the same patients (including blood-brain barrier permeability to albumin, intrathecal synthesis of immunoglobulin G and HIV-1-p24-antigen levels) were less useful as objective correlates of ADC severity and response to zidovudine therapy. CONCLUSIONS: CSF beta 2M may be a valuable marker of ADC severity and response to antiviral therapy.

AIDS Dementia Complex↗
PubMed1991

Quinolinic acid in cerebrospinal fluid and serum in HIV-1 infection: relationship to clinical and neurological status.

Quinolinic acid is an "excitotoxic" metabolite and an agonist of N-methyl-D-aspartate receptors. Of patients infected with human immunodeficiency virus type 1 (HIV-1) who were neurologically normal or exhibited only equivocal and subclinical signs of the acquired immunodeficiency syndrome (AIDS) dementia complex, concentrations of quinolinic acid in cerebrospinal fluid (CSF) were increased twofold in patients in the early stages of disease (Walter Reed stages 1 and 2) and averaged 3.8 times above normal in later-stage patients (Walter Reed stages 4 through 6). However, in patients with either clinically overt AIDS dementia complex, aseptic meningitis, opportunistic infections, or neoplasms, CSF levels were elevated over 20-fold and generally paralleled the severity of cognitive and motor dysfunction. CSF concentrations of quinolinic acid were significantly correlated to the severity of the neuropsychological deficits. After treatment of AIDS dementia complex with zidovudine and treatment of the opportunistic infections with specific antimicrobial therapies, CSF levels of quinolinic acid decreased in parallel with clinical neurological improvement. By analysis of the relationship between levels of quinolinic acid in the CSF and serum and integrity of the blood-brain barrier, as measured by the CSF:serum albumin ratio, it appears that CSF levels of quinolinic acid may be derived predominantly from intracerebral sources and perhaps from the serum. While quinolinic acid may be another "marker" of host- and virus-mediated events in the brain, the established excitotoxic effects of quinolinic acid and the magnitude of the increases in CSF levels of the acid raise the possibility that quinolinic acid plays a direct role in the pathogenesis of brain dysfunction associated with HIV-1 infection.

AIDS Dementia Complex↗
PubMed1991

Abnormal cerebral glucose metabolism in long-term survivors of childhood acute lymphocytic leukemia.

Chemotherapy and radiation treatment of the central nervous system may cause delayed neurotoxicity in children with acute lymphocytic leukemia. We evaluated 12 long-term survivors of childhood leukemia using [18F]fluorodeoxyglucose positron emission tomography, computed tomography scans, clinical neurological examinations, and neuropsychological tests. Regional cerebral metabolic rate for glucose (rCMRGlc) values for white matter were lower in the older long-term survivors (greater than 18 years old) treated with cranial radiation and intrathecal chemotherapy than in normal control subjects or survivors who had been treated with intrathecal chemotherapy alone. The ratio of white matter: cortex rCMRGlc values was lower than control values in the long-term survivors treated with cranial radiation and intrathecal chemotherapy, regardless of age, but not in those treated with intrathecal chemotherapy alone. By contrast, thalamic rCMRGlc values were lower than control values in older survivors regardless of treatment, and the ratio for thalamus:cortex rCMRGlc values was lower in all the treatment groups than in the control subjects. The highest rCMRGlc values were found in the youngest children, indicating an important effect of age on cerebral glucose metabolism. No neuropsychological deficits were identified in patients treated only with intrathecal chemotherapy; however, lower IQ scores were found in the long-term survivors who had been treated with cranial radiation and intrathecal chemotherapy. Treatment of the central nervous system with cranial radiation and intrathecal chemotherapy may cause prolonged alterations in white-matter and thalamic rCMRGlc, which may permit the identification and assessment of neurotoxicity in long-term survivors of acute lymphocytic leukemia by [18F]fluorodeoxyglucose positron emission tomography.

Adolescent↗
PubMed1991

Absolute quantitation in neurological PET: do we need it?

This article addresses the question posed in the title by examining the effects of parameters traditionally associated with improved absolute quantitation, on the analysis of 12 acquired immune deficiency syndrome dementia complex (ADC) patients compared to a normal control group. Results are discussed within the framework of the subprofile scaling model (SSM) for analyzing patterns of regional covariation. It is demonstrated that the ability to extract measures of group discrimination and disease progression are unaffected by (1) limited improvements in image resolution, (2) the use of transmission scan smoothing, (3) the application of a scatter deconvolution correction, and (4) converting region-of-interest measurements of counts per voxel to measurements of regional CMRglc. This "robustness" of the SSM approach is partly due to the extraction of disease-related subject weights, independent of any subject's global scaling effects. It is argued that other analysis techniques that initially reduce intersubject variation (e.g., using regional ratios or normalizing by global metabolic rates before applying traditional multivariate procedures) lack analytic features that may be important to identify multidimensional, disease-related image patterns. Based on the ADC patient data, it is concluded that measures of group discrimination and disease progression will not necessarily benefit from the organization of parameters traditionally associated with improved absolute quantitation.

AIDS Dementia Complex↗
PubMed1991

AIDS dementia complex and HIV-1 infection: a view from the clinic.

The AIDS dementia complex (ADC) is a clinical syndrome which characteristically presents as a "subcortical dementia" with cognitive, motor and behavioral changes. While the pathogenesis remains puzzling in a number of critical aspects, ADC likely relates in a fundamental way to HIV-1, itself, rather than to a secondary, opportunistic condition. This review focuses on some of the clinical information which bears on the pathogenesis of this syndrome and its relation to HIV-1 infection. This information derives from studies of the clinical character of ADC, its epidemiology and natural history, cerebrospinal fluid analysis, neuroimaging results, clinical correlates of pathological findings and its response to antiviral therapy.

AIDS Dementia Complex↗
PubMed1991

The metabolic landscape of cortico-basal ganglionic degeneration: regional asymmetries studied with positron emission tomography.

Regional metabolic rate for glucose (rCMRGlc) was estimated using [18F]fluorodeoxyglucose (FDG) and positron emission tomography (PET) in five patients (four men, one woman; mean age 68; mean disease duration 2.4 years) with clinical findings consistent with the syndrome of cortico-basal ganglionic degeneration (CBGD). Left-right rCMRGlc asymmetry, (L-R)/(L + R) x 100, was calculated for 13 grey matter regions and compared with regional metabolic data from 18 normal volunteers and nine patients with asymmetrical Parkinson's disease (PD). In the CBGD group mean metabolic asymmetry values in the thalamus, inferior parietal lobule and hippocampus were greater than those measured in normal control subjects and patients with asymmetrical PD (p less than 0.02). Parietal lobe asymmetry of 5% or more was evident in all CBGD patients, whereas in PD patients and normal controls, all regional asymmetry measures were less than 5% in absolute value. Measures of frontal, parietal and hemispheric metabolic asymmetry were found to be positively correlated with asymmetries in thalamic rCMRGlc (p less than 0.05). The presence of cortico-thalamic metabolic asymmetry is consistent with the focal neuropathological changes reported in CBGD brains. Our findings suggest that metabolic asymmetries detected with FDG/PET may support a diagnosis of CBGD in life.

Aged↗
PubMed1991

Pursuit eye movement dysfunction in HIV-1 seropositive individuals.

Studies of smooth pursuit eye movements were conducted in 30 ambulatory drug-free HIV-1 seropositive patients who did not yet manifest marked clinical signs of the AIDS Dementia Complex. Seropositive patients demonstrated disturbances in pursuit eye movements that were correlated with extent of immunosuppression, with impairments on neuropsychological tests of fine motor control/speed, and with independent clinical staging of the AIDS Dementia Complex. The results provide quantitative evidence that oculomotor disturbances are present in HIV-1 seropositive individuals before the manifestation of marked AIDS Dementia Complex. For this reason, and because more severe eye movement impairments have been observed in patients with AIDS, quantitative eye movement studies may provide a useful neurobehavioral procedure for characterizing and monitoring progression of CNS involvement associated with HIV-1 infection from early in its course.

Adult↗
PubMed1990

The metabolic anatomy of Parkinson's disease: complementary [18F]fluorodeoxyglucose and [18F]fluorodopa positron emission tomographic studies.

We studied the metabolic anatomy of typical Parkinson's disease (PD) using [18F]fluorodeoxyglucose (FDG) and [18F]fluorodopa (FDOPA) and positron emission tomography (PET). Fourteen PD patients (mean age 49 years) had FDG/PET scans, of which 11 were scanned with both FDOPA and FDG. After the injection of FDOPA, brain uptake and arterial plasma radioactivity were monitored for 2 h. Striatal FDOPA uptake was analyzed with regard to a two-compartment model, and target-to-background ratios (TBRs) and TBR-versus-time slopes were also calculated. Regional patterns of metabolic covariation were extracted from FDG/PET data using the Scaled Subprofile Model (SSM). SSM pattern weights, FDOPA uptake constants (Ki), TBRs, and TBR slopes were correlated with clinical measures for bradykinesia, rigidity, tremor, gait disturbance, left-right asymmetry, dementia, and overall disease severity. In PD patients, rate constants for FDOPA uptake correlated with individual measures of bradykinesia (p = 0.001) and gait disability (p less than 0.05). SSM analysis revealed a distinct pattern of regional metabolic asymmetries, which correlated with motor asymmetries (p less than 0.001) and left-right differences in Ki (p less than 0.01). Our data suggest that in PD patients, FDG/PET and FDOPA/PET may provide unique and complementary information about underlying disease processes.

Adult↗
PubMed1990

The effects of precocious adrenarche on cognition and hemispheric specialization.

Cognitive skills were assessed in 13 females with a history of precocious adrenarche (PA). They were of average intelligence. In terms of lateralized cognitive skills, PA had no effect on verbal fluency. The spatial abilities of females with a history of PA, who had reached gonarche (were fully pubertal), were inferior to those of females tested in the midst of PA and to population controls. The physiologic/hormonal changes associated with normal adrenarche may curtail further specialization of the right hemisphere, resulting in a relative spatial deficit among females in general, who as a group reach adrenarche earlier than males. This spatial performance deficit is exaggerated in females with PA.

Adolescent↗
PubMed1990

Transient ischemic attacks presenting with a loss of pitch perception.

It has been suggested that the non-dominant hemisphere is specialized for receptive and expressive music and prosody. The present report describes a patient who experienced a series of non-dominant hemisphere transient ischemic attacks (TIA's) which included an inability to perceive intonation during one episode, and a failure to perceive melody during another. The perceptual losses during these TIA's are consistent with experimental results which suggest that the non-dominant hemisphere is specialized for complex-pitch processing. In some instances, amusia, dysprosody, and aprosodia reflect a common functional deficit.

Cerebrovascular Disorders↗
PubMed1990

Specific motor abilities associated with speech fluency in Down's syndrome.

Eight adult male stutterers with Down's syndrome (DS) were compared with a matched group of fluent speakers with DS on verbal and manual motor production tasks at two levels of complexity. The simpler tasks involved diadochokinetic rate (syllable repetition) and finger tapping; the more complex tasks involved the imitation of sentences and placing pegs in the grooved pegboard. On both verbal and manual tasks, stutterers were faster on the simpler but slower on the more complex tasks than were the fluent speakers. The findings suggest that stutterers with DS have a different motor organization than fluent speakers with DS.

Adult↗
PubMed1990

Evaluation of the AIDS dementia complex in clinical trials.

The AIDS dementia complex (ADC) is one of the most common and important causes of morbidity associated with infection by human immunodeficiency virus type 1 (HIV-1). The evaluation of ADC in clinical trials is significant not only because of the clinical impact of this syndrome, but also because of the value of measuring its cardinal features as an index of drug efficacy and because of its emerging role as a major clinical end point. The objectives of therapy include both prevention of ADC in the presymptomatic patient and alleviation of established disease. At present, the pathogenesis of ADC is incompletely understood in several critical aspects, particularly the processes underlying the clinical manifestations of central nervous system (CNS) HIV-1 infection and, further, how such processes are related to systemic disease. Consequently, it is not yet clear to what extent, or in which patients, it is necessary to achieve "therapeutic" drug levels within the CNS. Nevertheless, the assessment of ADC prevention and treatment relies principally on the complementary approach of neurological examination for diagnosis and neuropsychological testing for quantitative serial measurement of treatment effects. Additionally, surrogate markers in cerebrospinal fluid (CSF) may hold promise for objective, rapid assessment of treatment response and dose adjustment. Other measurements, including more routine CSF analysis, neuroimaging, and neurophysiological assessments, are used principally for differential diagnosis rather than for monitoring ADC status. Accumulating experience with available antiviral agents suggests that ADC can be effectively prevented and treated, at least for some period of time, and that assessment of this condition is indeed a valuable approach for measuring antiviral therapy.

AIDS Dementia Complex↗