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Matcheri S Keshavan

Publications and source records attributed to Matcheri S Keshavan.

101 records · Page 6Linked to original sources
PubMed2002

Development of the corpus callosum in childhood, adolescence and early adulthood.

The corpus callosum (CC) is the major commissure connecting the cerebral hemispheres and there is evidence of its continuing development into young adulthood [Ann. Neurol. 34 (1993) 71]. Yet, little is known about changes in the size and tissue characteristics of its sub-regions. The sub-regions of the CC (genu, body, isthmus and splenium) are topographically organized to carry interhemispheric fibres representing heteromodal and unimodal cortical brain regions. Studies of the development of each of these sub-regions can therefore provide insights into the time course of brain development. We assessed age-related changes in the size and the signal intensities (SI) of the subregions of the corpus callosum in the Magnetic Resonance Imaging (MRI) scans of a cross-sectional sample of 109 healthy young individuals aged 7-32 years. Age was significantly positively correlated with the size of the callosal sub-regions (with the exception of the isthmus). On the other hand, there was an age-related decrease in SI across all the CC sub-regions. The rates of CC regional size increases appeared to be most pronounced in childhood. By contrast, SI decreases occurred during childhood and adolescence but reached an asymptote during young adulthood. Finally, the observed size and SI changes were similar across CC sub-regions. The observed increases in CC size in conjunction with the decreases in signal intensity reflect continued maturation of the structure from childhood through young adulthood. An increase in axonal size may underlie growth in the size of the CC during childhood. The continued decrease in the CC signal intensity during adolescence may in addition be related to ongoing maturation of the axonal cytoskeleton. CC maturational changes appeared synchronous across sub-regions suggesting parallel maturation of diverse brain regions during childhood and adolescence.

Adolescent↗
PubMed2002

Negative symptom resolution and improvements in specific cognitive deficits after acute treatment in first-episode schizophrenia.

Patients with first-episode schizophrenia show significant cognitive impairments even at this early phase of their illness. Antipsychotic medication improves clinical symptomatology, but the effectiveness of this treatment on neuropsychological deficits remains unclear. We investigated clinical symptom and neuropsychological performance change in 34 unmedicated first-episode psychotic patients (17 males, 17 females) from the time prior to treatment until 33.6+/-11.3 days after treatment initiation at which time patients demonstrated meaningful recovery from psychosis. Twenty-four matched healthy subjects were also studied. Performance in most neuropsychological functions (language skills, attention, nonverbal learning and reasoning, motor speed) remained stable for the group as a whole. However, reduction in negative symptoms was significantly correlated with performance increases in verbal fluency and attention. Higher negative symptom recovery was associated with improvement of cognitive performance to levels approaching those of healthy subjects, whereas low or no negative symptom improvement was associated with stable or decreased cognitive performance. Reduction in positive symptoms was not associated with change in cognitive abilities. These findings suggest a linkage between early, treatment-induced improvements in negative symptoms and reductions in distinct cognitive deficits.

Acute Disease↗
PubMed2002

A preliminary functional magnetic resonance imaging study in offspring of schizophrenic parents.

Studies of high-risk offspring (HR) of schizophrenic patients have found abnormalities in attention, working memory and executive functions, suggesting impaired integrity of the prefrontal cortex and related brain regions. The authors conducted a preliminary high-field (3 T) functional magnetic resonance imaging (fMRI) study to assess performance and activation during a memory-guided saccade (MGS) task, which measures spatial working memory. HR subjects showed significant decreases in fMRI-measured activation in the dorsolateral prefrontal cortex (Brodmann's areas 8 and 9/46) and the inferior parietal cortex (Brodmann's area 40) compared to age- and sex-matched healthy controls (HC). Abnormal functional integrity of prefrontal and parietal regions of the heteromodal association cortical (HAC) regions in subjects at genetic risk for schizophrenia is consistent with findings observed in adults with the illness [Callicott et al., Cereb. Cortex 10 (2000) 1078; Manoach et al., Biol. Psychiatry 48 (2000) 99.]. These abnormalities need to be prospectively investigated in nonpsychotic individuals at risk for schizophrenia in order to determine their predictive value for eventual emergence of schizophrenia or related disorders.

Adolescent↗
PubMed2002

1H MRS brain measures and acute lorazepam administration in healthy human subjects.

The effects of acute lorazepam administration on 1H magnetic resonance spectroscopy (MRS) in vivo brain spectra were examined in the left dorsolateral prefrontal cortex (L-DLPFC) of healthy human subjects. We wanted to examine whether lorazepam administration would result in significant changes in the levels of 1H-MRS metabolites in this brain region. Ten healthy controls underwent a short echo-time 1H-MRS session immediately before, and a second one 1 h after lorazepam administration (2mg/orally). The measured 1H-metabolites included N-acetyl-aspartate, phosphocreatine+creatine, trimethylamines, myo-inositol, glutamate, and glutamine, which were expressed as absolute values and ratios. No significant differences were found after lorazepam administration for any of the measured metabolite levels or ratios (paired t-tests, p >.05). This study demonstrated that lorazepam can potentially be utilized to acutely sedate psychiatric subjects during in vivo 1H-MRS sessions, as it does not appear to produce significant changes in the 1H-MRS spectra in this specific brain region.

Adult↗
PubMed2002

Anatomical MRI study of subgenual prefrontal cortex in bipolar and unipolar subjects.

This study attempted to replicate previous findings of decreased gray matter content in the subgenual prefrontal cortex (SGPFC) in mood disorder patients. Eighteen DSM-IV unipolar patients, 27 DSM-IV bipolar patients, and 38 healthy controls were studied. A 1.5T GE Signa Imaging System with Signa 5.4.3 software was used. The semi-automated software MedX (Sensor Systems, Sterling, VA) was utilized for the anatomical measures of SGPFC volumes. There were no significant differences in SGPFC volumes in familial and non-familial unipolar and bipolar patients compared with healthy controls, nor between drug-free and lithium-treated bipolar patients (ANOVA, p >.05). In vivo abnormalities in the volumes of SGPFC were not identified in mildly depressed or euthymic unipolar or bipolar mood disorder outpatients, either familial or non-familial.

Adult↗
PubMed2002

Cavum septi pellucidi in first-episode patients and young relatives at risk for schizophrenia.

Studies on schizophrenia (SZ) have documented an increased presence of cavum septi pellucidi (CSP) in individuals suffering from the illness. Moreover, the presence of CSP has been cited in support of the early neurodevelopmental hypothesis in SZ. Our objective was to assess the magnetic resonance imaging (MRI) scans of first-episode patients and healthy controls to evaluate the frequency of CSP. The presence and the size of CSP were visually assessed on the MRI scans of 40 first-episode SZ patients, 19 nonpsychotic child and high-risk adolescent offspring of patients with SZ or schizoaffective disorder, and 59 controls. Our analysis revealed an absence of statistically significant differences in the occurrence of CSP between SZ patients, high-risk subjects, and controls. Even when the analysis was restricted to large CSP, no differences were found. Furthermore, no association between CSP and sex or handedness was observed. The absence of CSP abnormalities in first-episode SZ subjects might indicate that SZ is not characterized by developmentally mediated alterations in CSP. Also, family history of SZ might not increase likelihood for CSP.

Journal Article↗
PubMed2002

Physical and neurologic examinations in neuropsychiatry.

The direct physical examination of psychiatric patients is underutilized by clinicians and underinvestigated by researchers. Both clinicians and researchers thus bypass important information. The authors review the literature on physical and neurologic examinations, with attention to aspects of these examinations that might specifically enhance the understanding of the psychiatric patient. Coverage includes the "minor" physical anomalies and "soft" neurologic signs. Findings related to the psychiatric conditions themselves are given precedence over findings of general medical importance. Some of the available physical and neurologic examination schedules are reviewed. A unified examination protocol is presented, incorporating physical and neurologic examinations pertinent to both general medical and specifically psychiatric assessment.

Humans↗
PubMedDate not supplied

MRI investigation of temporal lobe structures in bipolar patients.

Previous anatomical MRI studies have suggested abnormalities in amygdala volumes in bipolar disorder, whereas hippocampus, temporal lobe (TL), and superior temporal gyri (STG) measures have been reported to be normal. This study further investigated the existence of anatomical abnormalities in these brain structures in bipolar subjects, to attempt to replicate previously reported findings. Twenty-four DSM-IV bipolar patients (mean age+/-S.D.=35+/-10 years) and 36 healthy controls (mean age+/-S.D.=37+/-10 years) were studied. 3D SPGR images were obtained with a 1.5T-GE Signa magnet (TR=25 ms, TE=5 ms, FOV=24 cm, slice-thickness=1.5 mm, matrix-size=256 x 192). Volumetric measurements of TL, hippocampus, amygdala, and STG were performed blindly, with a semi-automated software. Bipolar patients had significantly larger left amygdala volumes compared with controls (mean volumes+/-S.D.=2.57+/-0.69 vs. 2.17+/-0.58 ml, respectively; ANCOVA, age, gender, ICV as covariates; F=4.42, df=1/55, P=0.04). The volumes of the other temporal lobe structures did not differ significantly between the two groups (ANCOVA, age, gender, and ICV as covariates, P>0.05). Our findings of enlarged left amygdala in bipolar patients are in agreement with prior MRI studies, suggesting that abnormalities in this brain structure may be implicated in pathophysiology of the illness. Longitudinal studies in high-risk offspring and first-episode patients will be needed to examine whether such abnormalities precede the appearance of symptoms, or whether they may appear subsequently as a result of illness course.

Adult↗
PubMedDate not supplied

Sex differences in brain maturation in maltreatment-related pediatric posttraumatic stress disorder.

BACKGROUND: Recent investigations suggested that pediatric posttraumatic stress disorder (PTSD) is associated with adverse brain development. However, sex differences are poorly understood. METHODS: In this study, 61 medically healthy children and adolescents (31 males and 30 females) with chronic PTSD secondary to abuse, who had similar trauma and mental health histories, and 122 healthy controls (62 males and 60 females) underwent comprehensive psychiatric assessments and an anatomical MRI brain scan. RESULTS: When gender groups were analyzed separately, findings of larger prefrontal lobe CSF volumes and smaller midsagittal area of the corpus callosum subregion 7 (splenium) were seen in both boys and girls with maltreatment-related PTSD compared to their gender-matched comparison subjects. Subjects with PTSD did not show the normal age related increases in the area of the total corpus callosum and its region 7 (splenium) compared to non-maltreated subjects; however, this finding was more prominent in males with PTSD. Significant sex by group effects demonstrated smaller cerebral volumes and corpus callosum regions 1 (rostrum) and 6 (isthmus) in PTSD males and greater lateral ventricular volume increases in maltreated males with PTSD than maltreated females with PTSD. CONCLUSIONS: These data suggest that there are sex differences in the brain maturation of boys and girls with maltreatment-related PTSD. Longitudinal MRI brain investigations of childhood PTSD and the relationship of gender to psychosocial outcomes are warranted.

Adolescent↗