Information processing

What is information processing in schizophrenia? 

Information processing involves a number of cognitive functions, including perception, attention, memory and decision making, as well as the speed at which these cognitive functions are executed. Any impairment in information processing can reflect impairments in these other cognitive domains. Information processing can be assessed using various tests. The Wechsler Adult Intelligence Scale (WAIS) digit symbol coding test presents participants with paired numbers and symbols and when shown several numbers, participants must write down the missing corresponding symbols as quickly as possible. The Wisconsin Card Sorting Task (WCST) requires an ability to shift cognitive sets; participants are asked to match stimulus cards, with feedback provided as to whether the match was correct or incorrect based on a colour, quantity, or design rule that changes during the task. The Trail Making Test (TMT) requires participants to connect, in order, letters and/or numbers as quickly as possible. The Stroop Colour Word Test (SCWT), presents colour names printed in an ink congruent to the colour name (e.g. blue), or incongruent to the colour name (e.g. blue). Participants are asked to either read the word or name the ink colour. Category fluency is an oral test that requires participants to name as many items in a category (e.g. furniture items) as they can in one minute.

What is the evidence for information processing?

Compared to people without schizophrenia, high quality evidence shows a large effect of poorer information processing in people with first-episode or chronic schizophrenia. Moderate to high quality evidence found no differences in initial thinking time, but more subsequent thinking time on the SOC task.

Moderate to high quality evidence also found a large effect of slower processing speed in people at high risk who converted to psychosis compared to controls, and a small effect in non-converters compared to controls. There was slower processing speed in people with first-episode psychosis than in people at clinical high-risk of psychosis.

Compared to people with affective psychoses (including bipolar disorder and schizoaffective disorder), moderate to high quality evidence found small effects of poorer information processing on the TMT and WCST tasks.

Moderate to high quality evidence found a medium-sized association between better information processing and better community functioning, and weak associations between better information processing and better emotion processing and less severe symptoms. High quality evidence found a small impairment in speed of processing in smokers vs. non-smokers with schizophrenia. Moderate to high quality evidence suggests better speed of processing in people with schizophrenia with any substance use disorder compared with people with schizophrenia without any substance use disorder.

There were greater improvements in processing speed in people taking second-generation antipsychotics than in people taking first-generation antipsychotics. People taking olanzapine, clozapine or risperidone showed improvements in processing speed after treatment, while people taking quetiapine or haloperidol showed no improvement.

March 2022

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Last updated at: 11:24 am, 29th March 2022
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