Biomedical subjects

C M Mar

Publications and source records attributed to C M Mar.

3 recordsLinked to original sources

PubMed1998

The structure of schizophrenic symptoms: a meta-analytic confirmatory factor analysis.

To quantitatively review all presently available evidence about the interrelations between positive and negative schizophrenic symptoms, we created an aggregate matrix of the intercorrelations among schizophrenic symptoms by combining data from 28 independent samples using meta-analytic procedures (net bivariate dfs ranging from 683 to 1657). Using confirmatory factor analyses, we then statistically compared four theoretically derived models of the structure of schizophrenic symptoms. Although a three-factor model (Liddle, 1987) best fit the data, results suggest that either more factors or different symptoms are required to account well for the latent structure underlying schizophrenic symptomatology. The nature of such augmented approaches, the opportunities and constraints inherent to multifactorial models, and the limitations of current instruments are discussed.

Humans↗

PubMed1996

Behavioural vigilance in schizophrenia. Evidence for hyperattentional processing.

BACKGROUND: Despite 30 years of research, some surprisingly fundamental gaps remain in our understanding of schizophrenic input dysfunctions. METHOD: In a provisional test of a 'hyperattention' hypothesis, schizophrenic patients and control subjects performed a behavioural test that was adapted from a paradigm originally developed for characterising vigilance or sustained attention in animals. On this computerised operant testing procedure, subjects discriminated between signals of various salience and non-signal presentations. Hits and correct rejections resulted in monetary rewards while misses and false alarms entailed monetary costs. RESULTS: Data from in-patients with schizophrenia and age, education and gender-matched controls support hypotheses not only about hyperattentional dysfunctions in schizophrenia with respect to overall signal detectability but also in terms of resistance to the vigilance decrement that normally occurs over trials. CONCLUSIONS: The theoretical importance of impairments of this sort are discussed with respect to the cognitive and perceptual consequences of hypervigilance and 'input dysfunction'.

Adult↗

PubMed1992

Infant temporal contrast sensitivity at low temporal frequencies.

The data on infant temporal contrast sensitivity functions (TCSFs) are scarce and contradictory. Earlier studies suggest that critical flicker frequency (CFF) is adultlike at 2-3 months postnatal (Regal, D. M., 1981 Vision Research, 21, 549-555), while contrast sensitivity at low temporal frequencies remains poor. If both of these findings are true, then infant TCSFs are much flatter than those of adults. In the present study, we have re-investigated 2-month-olds' contrast thresholds at low temporal frequencies. To match the conditions of Regal's CFF study, test fields were embedded in a luminance-matched surround. As in previous studies, low contrast sensitivities were found. Models of infants' flat TCSFs are discussed.

Contrast Sensitivity↗