Schizophrenia in Children and Adolescents by Helmut Remschmidt

Author:Helmut Remschmidt
Language: eng
Format: mobi, pdf
Tags: Psychopathology, Mental Health, Pediatrics, Psychology, Medical, General, Child & Adolescent, Psychiatry
ISBN: 9780521794282
Publisher: Cambridge University Press
Published: 2000-11-22T22:00:00+00:00

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Neurobehavioral perspective

Fig. 7.5. Partial report span of apprehension task from Asarnow and Sherman (1984) from Child Development.

upper quadrants than when it was in the lower quadrants. This result suggests

that both the schizophrenic and older normal children consistently began their

serial search in the upper quadrants, and that their iconic image of the stimulus

display faded before they could adequately process the lower quadrants.

In Experiment III, subjects were administered the full-report version of the

Span of Apprehension task, which required them to report as many letters as

they could from the display. Compared to the partial-report Span task, the

full-report task makes greater demands on iconic memory (a large capacity

visual memory store that holds information for 200–400 milliseconds) and

immediate memory, but fewer demands on serial search and processing re-

sources. Schizophrenic children were able to report as many letters as mental

age-matched normal children on the full-report task, suggesting that impair-

ments on the partial report version are not attributable to a deficiency in iconic

memory.

150

R. F. Asarnow and C. Karatekin

In a follow-up study, we tested whether the impairment of schizophrenic

children on the partial-report Span task is due to a delay in initiation of search

or to a slow rate of serial search (Karatekin & Asarnow, 1998a). These

hypotheses were tested within the framework of a Treisman’s feature integra-

tion theory, which provides a model for the role of attention in visual search.

We administered subjects two search tasks from Treisman and Souther (1985)

that use the same stimuli but differ in their attentional requirements. According

to feature integration theory, one task requires attention to be distributed over

the whole display (parallel search), whereas the other requires attention to be

focused (serial search). This distinction has been supported by behavioral,

electrophysiological, and other neurobiological evidence (e.g., Luck and Hill-

yard 1990). To estimate rate of search, we recorded items searched per unit

time. To estimate the duration of initiation of search, we took advantage of the

fact that the basic oculomotor system is intact in schizophrenia and recorded

time to make the first saccade on each trial. If schizophrenic children were slow

to initiate their search, they should also be slow to start making a saccade. To

test the specificity of findings, we compared schizophrenic children to age-

matched children with Attention-Deficit/Hyperactivity Disorder (ADHD) and

to chronological age-matched normal children. Results showed (i) delayed

initiation of search in ADHD, but not in schizophrenic children; and (ii) a clear

dissociation between intact parallel search rates and slowed serial search rates

in both clinical groups. These results narrowed down the source of the search

impairment in schizophrenia to a slow rate of serial search.

Next, we investigated deployment of visual attention under less constrained

conditions in the same children by recording their eye movements to thematic

pictures (Karatekin and Asarnow, 1998a). For each picture, the children were

asked three questions varying in amount of structure. We determined if

schizophrenic children would stare or scan too extensively and if their scan

patterns would be differentially affected by the questions. The key measures

were time spent viewing relevant and irrelevant regions, fixation duration, and

distance between fixations. ADHD children had slightly shorter fixations than

normal children on the question requiring the most detailed analysis (e.

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