Biomedical subjects

Julia A Nunn

Publications and source records attributed to Julia A Nunn.

3 recordsLinked to original sources

PubMed2003

Executive function assessed by memory updating and random generation in schizotypal individuals.

Individuals scoring high (N=32) and low (N=27) on the unusual experiences (UnEx) scale of the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE) were selected from a large sample (N=265) of normal volunteer undergraduates. The high- and low-UnEx groups were compared on two tasks, random generation and memory updating, which target executive functions that inhibit prepotent responses and update current information. The groups differed only on the R measure of random generation that assesses inequality in the relative frequencies of response alternatives, a result attributed to superstitious behaviour rather than to executive deficit. The results suggest that the executive impairments previously observed in high schizotypal individuals using the Wisconsin Card Sorting Test and other measures are selective rather than global.

Adult↗

PubMed2002

Perceptual organization deficits in psychotic patients.

It has been proposed that a characteristic of schizophrenic processing is an abnormality of top-down processing. The relationship between impaired top-down processing and symptoms of reality distortion was investigated using a 'degraded interference' task. In this task, fragmented stimuli (Stroop words, control words and crosses) are presented on a computer screen, and the extent to which they are visually integrated is inferred by their interfering properties. It was predicted that psychotic individuals would fail to show an interference effect with degraded Stroop stimuli. This predicts the absence of a delay in reaction time in the experimental condition, which therefore cannot be attributed to a generalized deficit. A sample of inpatients experiencing positive symptoms was compared to a healthy control group. The results provided support for a deficiency in top-down processing, with the psychotic group failing to show the significant degraded interference effect found in the healthy controls. Degraded interference was associated with low verbal IQ, but with no other symptomatic or demographic variables.

Adult↗

PubMed2002

Novelty-related activation within the medial temporal lobes.

Functional magnetic resonance imaging (fMRI) was used to examine whether (1) verbal associative encoding activates the medial temporal lobes (MTL) and related regions more than non-associative encoding, (2) verbal associative novelty is related to enhanced MTL activation, and (3) verbal item novelty is related to enhanced MTL activation and, if so, whether these activations are in different or overlapping sites. No increase in MTL activation was found during verbal associative encoding relative to non-associative encoding, although associative encoding was related to a relative increase in activation in the posterior cingulate cortex. In contrast, verbal associative novelty was found to activate the MTL and posterior cingulate cortex. Verbal item novelty did not significantly activate any brain region. The verbal associative novelty-related effect occurred despite subjects having little awareness of associative novelty. The verbal associative novelty-related activation in the MTL may be related either to unconscious novelty detection or to a priming effect at encoding. We argue that if the priming explanation is correct then this may account for our failure to observe an associative encoding MTL activation.

Adult↗