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Lynn D Selemon

Publications and source records attributed to Lynn D Selemon.

5 recordsLinked to original sources
PubMed2003

Regional specificity in the neuropathologic substrates of schizophrenia: a morphometric analysis of Broca's area 44 and area 9.

BACKGROUND: Numerous recent studies of postmortem schizophrenic brains have reported the presence of structural abnormalities in the dorsolateral prefrontal cortex (dlPFC) that are consistent with a reduction of neuropil. Ventrolateral prefrontal areas have been studied less extensively, and therefore it is not clear whether these cortices exhibit pathologic abnormalities of the same type and magnitude. Because thought disturbances in schizophrenic patients involve language processing, we have performed a morphometric analysis of Broca's area in the ventral frontal lobe. METHODS: Neuronal and glial density and somal size were assessed via stereologic cell counting in postmortem samples of Broca's area 44 in 9 schizophrenic patients and 14 normal controls. Cell density was reexamined in dorsolateral prefrontal area 9 as an internal control. RESULTS: We did not detect abnormalities in overall or laminar neuronal density, glial density, cortical thickness, or somal size in area 44 of schizophrenic patients. In contrast, neuronal density in area 9 exhibited a 12% increase in the schizophrenic cohort, replicating previous findings. In addition, there was a significant effect of disease on laminar neuronal density in area 9, with neuronal density tending to be higher (7%-29%) in all layers. CONCLUSIONS: The absence of significant cytoarchitectonic abnormalities in Broca's area in the same brains in which the dlPFC exhibited an increase in neuronal density suggests that the neuropil deficit is a regionally specific pathologic finding in schizophrenia and indicates that the dlPFC is a particularly vulnerable target of the disease process.

Adult↗
PubMed2002

Craniofacial dysmorphogenesis in fetally irradiated nonhuman primates: implications for the neurodevelopmental hypothesis of schizophrenia.

BACKGROUND: Craniofacial abnormalities arising from gestational disturbances have been documented in some schizophrenic patients. Reduction of thalamic neurons, a key feature of the neuropathology of schizophrenia, could also have a prenatal origin via disruption of thalamic neurogenesis. This study investigates whether craniofacial dysmorphology and thalamic neuron loss might be associated manifestations of a disruption in embryonic development. METHODS: Thalamic neurons were deleted by exposing fetal macaques to x-rays during thalamic genesis (E33-42). Another group of macaques was irradiated after thalamic genesis (E70-81). Body, head, and facial measurements were obtained from the early irradiated (EX), late irradiated (LX), and control animals at adulthood. RESULTS: Head width, distance between outer eye edges, and ear width were smaller in EX macaques compared with control animals. The LX macaques exhibited only reduced ear width compared with control animals. CONCLUSIONS: These findings indicate that certain features of thalamic neuropathology and craniofacial dysmorphogenesis observed in schizophrenic patients may have a common etiology.

Animals↗
PubMed2002

Abnormalities of thalamic volume and shape detected in fetally irradiated rhesus monkeys with high dimensional brain mapping.

BACKGROUND: Prior research has indicated neuroanatomical abnormalities of the thalamus in schizophrenia. To study the possible pathogenesis, an animal model of neurodevelopmental thalamic damage has been developed by applying low-dose radiation to rhesus monkeys in early gestation. Irradiated monkeys sacrificed as infants demonstrate neuronal losses in specific thalamic nuclei and decreases in cortical neuropil. METHODS: Magnetic resonance scans were collected in adult Rhesus monkeys exposed to irradiation during thalamic neurogenesis (E33-42), after thalamic neurogenesis (E70-81), and in nonirradiated control animals. High dimensional brain mapping was used to compare thalamic volumes and shape characteristics in the three groups of animals. RESULTS: Animals exposed to irradiation at E33-42 showed a significant bilateral loss of thalamic volumes (> 20%) compared with controls and with animals irradiated at E70-81 when total brain volume was used as a covariate in the analysis. Thalamic volume loss was associated with a nonuniform deformation of thalamic shape. CONCLUSIONS: A first-trimester, neurodevelopmental insult in the nonhuman primate during thalamic neurogenesis produces a complex pattern of thalamic volume loss and shape deformation in adulthood. Low-dose irradiation of the fetal primate may be useful for modeling key features of the pathology described in schizophrenic patients.

Animals↗
PubMed2002

Smaller frontal gray matter volume in postmortem schizophrenic brains.

OBJECTIVE: The prefrontal cortex exhibits prominent functional, biochemical, and anatomic abnormalities in schizophrenic patients. However, smaller than normal volume of the frontal lobe has not been found in previous postmortem studies of schizophrenic subjects, and magnetic resonance imaging (MRI) scans of schizophrenic subjects have not consistently revealed frontal volumetric deficits. The variability in MRI findings may be related partly to difficulty in defining the posterior border of the frontal lobe. In this study, precise measurements of frontal lobe volume from postmortem brains were derived by defining the posterior border according to the brain atlas of Talairach and Tournoux and by applying stereologic methods to estimate gray and white matter volumes. METHOD: Whole, or nearly whole, formalin-fixed left hemispheres from 14 schizophrenic and 19 normal comparison subjects were analyzed. Total cortical gray and white matter volumes, as well as frontal cortical gray and white matter volumes, were measured by using the Cavalieri method. RESULTS: Only frontal gray matter volume was significantly smaller in the schizophrenic subjects than in the comparison subjects (12% difference). The differences between groups in total gray and white matter volumes and frontal white matter volume (6%-8% smaller in the schizophrenic subjects than in the comparison subjects) did not reach statistical significance. CONCLUSIONS: The smaller frontal gray matter volume observed in schizophrenic brains suggests that pathology of the frontal lobe may be more severe than that of the three posterior lobes and may account for the prominence of prefrontal dysfunction associated with schizophrenia.

Adult↗