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Biomedical subjects

J H Callicott

Publications and source records attributed to J H Callicott.

32 records · Page 2Linked to original sources
PubMed1997

Abnormal functional lateralization of the sensorimotor cortex in patients with schizophrenia.

Previous neuroimaging studies have suggested that patients with schizophrenia fail to recruit appropriate focal patterns of cortical responses to cognitive tasks. We investigated whether patients with schizophrenia show a normal focal response to a simple motor task. Seven strongly right-handed patients with schizophrenia and seven strongly right-handed normal subjects performed motor tasks of increasing complexity. Patients were unable to recruit as focal a response even to a simple, automatic sequential finger movement task. They showed greater ipsilateral activation in the primary sensorimotor and lateral premotor regions and had a significantly lower laterality quotient than normal subjects. These phenomena increased with the complexity of the task. These results demonstrate a functional disturbance in the cortical motor circuitry of patients with schizophrenia.

Adult↗
PubMed1990

Neonatal progeroid syndrome: more than one disease?

We report on an infant with the neonatal progeroid syndrome whose clinical course and autopsy findings indicate that this may be a heterogeneous phenotype. The infant had intrauterine growth retardation, absence of subcutaneous fat, and a wizened, aged face, all apparently characteristic of the condition, but also had congenital heart defects and urinary reflux not reported in previous cases. An elevated maternal serum alpha fetoprotein was noted at 16 weeks of gestation and late-onset growth retardation appeared after 31 weeks. Autopsy findings showed normal cerebral myelination, in contrast to findings of sudanophilic leukodystrophy in the one patient with the syndrome previously examined at autopsy. These findings suggest that the neonatal progeroid syndrome may be a phenotype and have more than one cause.

Abnormalities, Multiple↗
PubMed1982

Amyloid tumor of the breast.

A 55-year-old woman had a solitary mammary amyloid tumor without evidence of a systemic, amyloid-related illness. The tumor produced a palpable, firm mass suspicious for carcinoma. Microscopically, amyloid was found in a periductal and perivascular location. It was seen in the fat as well. A prominent giant cell reaction and chronic inflammatory infiltrate were present.

Amyloid↗
PubMedDate not supplied

Physiological characteristics of capacity constraints in working memory as revealed by functional MRI.

A fundamental characteristic of working memory is that its capacity to handle information is limited. While there have been many brain mapping studies of working memory, the physiological basis of its capacity limitation has not been explained. We identified characteristics of working memory capacity using functional magnetic resonance imaging (fMRI) in healthy subjects. Working memory capacity was studied using a parametric 'n-back' working memory task involving increasing cognitive load and ultimately decreasing task performance. Loci within dorsolateral prefrontal cortex (DLPFC) evinced exclusively an 'inverted-U' shaped neurophysiological response from lowest to highest load, consistent with a capacity-constrained response. Regions outside of DLPFC, in contrast, were more heterogeneous in response and often showed early plateau or continuously increasing responses, which did not reflect capacity constraints. However, sporadic loci, including in the premotor cortex, thalamus and superior parietal lobule, also demonstrated putative capacity-constrained responses, perhaps arising as an upstream effect of DLPFC limitations or as part of a broader network-wide capacity limitation. These results demonstrate that regionally specific nodes within the working memory network are capacity-constrained in the physiological domain, providing a missing link in current explorations of the capacity characteristics of working memory.

Adolescent↗