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Semantic hyperpriming in schizophrenia. An artefact of general slowing of reaction time?
- Laurent Lecardeur, Sonia Dollfus, and Emmanuel Stip (9 April 2008)
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Laurent Lecardeur, Ph.D., psychologist, postdoctoral trainee Centre de Recherche Fernand-Seguin, Montréal (Québec) H1N 3V2, Canada, Sonia Dollfus, and Emmanuel Stip
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lecardeur{at}cyceron.fr Laurent Lecardeur, et al.
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Semantic hyperpriming in schizophrenia. An artefact of general slowing of reaction time? Impairment of memory is one of the principal cognitive symptoms of schizophrenia. We read with interest the article by Pomarol-Clotet et al (1)who reported on a relevant meta-analysis in which they evaluated the results of studies on semantic priming (SP) in schizophrenia. The SP is a component of long term implicit memory. They argued that hyperpriming (HP) (i.e. greater semantic priming in patients than healthy controls) could be an artefact of a general slowing in schizophrenia. As a consequence, these authors aimed to consider general slowing as a moderator variable in their statistical analysis. The measure of general slowing that they choose, corresponded to the difference in response time between controls and patients, when prime and target are unrelated. In our opinion, this measure is not the most suitable to account for, rather it reflects other cognitive processes. Subjects need to inhibit the prime so as to be able to process the target, since prime and target do not share any semantic relationship. Consequently, response time in an unrelated condition could be rather the expression of an accurate inhibitory process, than of a general slowing as proposed by the authors. Some arguments support this view. First, we evaluated slowing in a simple reaction task in two different studies (2;3). Values were included as covariates in the analyses of covariance of priming effects. Despite confirming general slowing, there was evidence of significant increased priming in schizophrenic patients compared to controls. Consequently, HP can be demonstrated even if general slowing is taken into account and controlled. Second, we demonstrated that the time required to inhibit an unrelated prime was significantly enhanced in schizophrenic patients compared to healthy controls. General slowing was also controlled. Consequently, we demonstrated that the increased priming effect in patients compared to controls was mainly induced by increased time required to inhibit unrelated prime. Our results support the impairment of inhibitory process of semantically unrelated information in schizophrenic patients. In their meta-analysis, Pomarol-Clotet et al suggested that “the greater the slowing the greater the amount of priming”. Given our results, an alternative explanation has to be considered. We suggest that HP of schizophrenic patients could reflect decreased abilities to inhibit irrelevant information, such as semantically unrelated information. Reference List (1) Pomarol-Clotet E, Oh TM, Laws KR, McKenna PJ. Semantic priming in schizophrenia: systematic review and meta-analysis. Br J Psychiatry 2008 Feb;192(2):92-7. (2) Lecardeur L, Giffard B, Laisney M, Brazo P, Delamillieure P, Eustache F, et al. Semantic hyperpriming in schizophrenic patients: Increased facilitation or impaired inhibition in semantic association processing? Schizophr Res 2007 Jan;89(1-3):243-50. (3) Lecardeur L, Brazo P, Dollfus S, Giffard B, Laisney M, Eustache F, et al. Does hyperpriming reveal impaired spreading of activation in schizophrenia? Schizophr Res 2007 Dec;97(1-3):289-91. Corresponding author: Laurent Lecardeur Centre de Recherche Fernand-Seguin Montréal (Québec) H1N 3V2, Canada Telephone: 0 514 251 4015 Fax: 0 514 251 2617 Other authors: Sonia Dollfus Centre Esquirol, CHU de Caen Centre d’Imagerie – Neurosciences et d’Application aux PathologieS – UMR 6232 14074 Caen, France Emmanuel Stip Centre de Recherche Fernand-Seguin Hôpital Louis-H. Lafontaine Montréal (Québec) H1N 3V2, Canada Declaration of interest: None |
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