Commentary on Laws: What are we Trying to Explain?

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  • This article was downloaded by: [University of California SantaCruz]On: 18 November 2014, At: 09:06Publisher: RoutledgeInforma Ltd Registered in England and Wales Registered Number:1072954 Registered office: Mortimer House, 37-41 MortimerStreet, London W1T 3JH, UK

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    Commentary on Laws:What are we Trying toExplain?Chris FrithPublished online: 09 Sep 2010.

    To cite this article: Chris Frith (1999) Commentary on Laws: Whatare we Trying to Explain?, Cognitive Neuropsychiatry, 4:1, 31-32, DOI:10.1080/135468099396034

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  • Commentary on Laws: What are we Trying to Explain?

    Chris Frith

    Institute of Neurology, University College London, UK

    Keith Laws provides us with a useful review of the many studies of executive

    function in schizophrenia. He makes a number of good points. First, not all

    patients with schizophrenia perform badly on frontal lobe tests. Second, in those

    patients that do perform badly there is usually evidence of a more general

    intellectual impairment. Third, poor performance on tests of executive function

    does not necessarily mean executive impairments or frontal lobe damage. All

    sensible and informed people would agree with these points. Laws is much less

    clear about the implications of these conclusions for future studies of executive

    function in schizophrenia.

    First I would suggest that we should not expect to find a characteristic

    neuropsychology associated with schizophrenia. Schizophrenia is a diagnostic

    category including patients who show a wide range of signs and symptoms

    which fluctuate over time. Although it is still possible that there is a specific

    biological marker associated with this disease I do not think that we should

    expect to find a specific psychological marker. In contrast, it is reasonable to

    expect to find psychological markers for particular signs and symptoms.

    Executive dysfunction (and general intellectual impairment) tends to correlate

    with severity of negative signs or disorganisation, but not with severity of

    hallucinations and delusions (e.g. Johnstone & Frith, 1996) . This relationship

    would be more compelling if it could be demonstrated in longitudinal studies; if

    the negative signs resolve does the intellectual functioning return to premorbid

    levels?

    From this symptom-based perspective we would not expect to find a general

    nonspecific executive problem. Negative signs (poverty of speech, flattening of

    affect) are associated with a general failure to initiate action, whereas

    disorganisation (incoherent speech, incongruity of affect) is associated with

    failure to inhibit inappropriate action. Both these problems could arise from an

    impaired executive system, but these signs occur independently of each in cross-

    sectional studies of schizophrenia (e.g. Johnstone & Frith, 1996). There is

    currently much interest in fractionating the executive system using both lesion

    studies and brain imaging. I would expect to see different kinds of executive

    problem associated with different aspects of schizophrenia.

    The success of attempts to fractionate the executive system will depend to a

    considerable extent on our ability to develop more specific models of executive

    function. This will, in turn, lead to the development of novel test procedures.

    The current standard frontal tests used by neuropsychologists tend to be crude

    and underspecified in terms of the cognitive processes which they engage.

    Results with laboratory tests suggest that schizophrenic patients are only

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  • impaired on certain executive processes (e.g. Hutton et al., 1998) . A particularly

    elegant example, also quoted by Laws, is the study by Elliott, McKenna,

    Robbins, & Sahakian (1995) demonstrating that patients with negative features

    showed marked response perseveration, but having no difficulty in switching

    attention to a previously irrelevant stimulus dimension. Progress in our

    understanding of the signs and symptoms of schizophrenia will require studies

    of executive processes which are conducted at this level of detail.

    REFERENCESElliott, R., McKenna, P.J., Robbins, T.W., & Sahakian, B.J. (1995). Neuropsychological evidence

    for frontostriatal dysfunction in schizophrenia. Psychological Medicine, 25, 619630.

    Hutton, S.B., Puri, B.K., Duncan, L.-J., Robbins, T.W ., Barnes, T.R.E., & Joyce, E.M. (1998).

    Executive function in first episode schizophrenia. Psychological Medicine, 28, 463474.

    Johnstone, E.C., & Frith, C.D. (1996). Validation of three dimensions of schizophrenic symptoms in

    a large unselected sample of patients. Psychological Medicine, 26, 669679.

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