Nonstereotyped Responding in Positive Schizotypy after a Single Dose of Levodopa

Abstract

Stereotyped behavior and left-sided orientation biases, associated with the dopamine (DA) system, were observed in populations of the schizophrenia spectrum disorders. We investigated whether heightened DA concentrations influence both side biases and stereotyped responding in a visuo-motor computer task, in which 90, 180, and 2701 rotated objects had to be brought into a target position. To account for the role of the schizophrenia spectrum, task performance was also analyzed as a function of healthy participants' high or low magical ideation (MI), a positive schizotypal feature. The first 36 participants (20 women) remained substance free. In a second sample, 20 men received levodopa and 20 men a placebo in a double-blind procedure. Results showed that high MI scorers responded more stereotyped than low MI scorers, without being specifically biased towards the left side. Rotation preferences toward one or the other side made high MI scorers less flexible for objects efficiently to be rotated into the opposite direction. This inflexibility may reflect impaired left hemisphere functioning. Unexpectedly, in the levodopa group, high MI scorers performed superior to low MI scorers. Since DA actions appear to follow an inverted U-shape function, the 'low' performing high MI scorers profited from the enhanced DA availability. Our observation in the levodopa group points to a dissociation between schizotypy and schizophrenia: while cognitive improvement in schizophrenia can occur after treatment with atypical neuroleptic agents, in our positive schizotypal participants a DA agonist resulted in improved task performance. This dissociation may point to protective neurochemical mechanisms preventing healthy schizotypes from developing full-blown psychotic symptoms.

Dopamine, Paranormal Belief, and the Detection of Meaningful Stimuli

“…The lower sensitivity in the levodopa than placebo group was dependent on participantsʼ paranormal belief. Links between the emergence of paranormal belief and the DA system have been suggested (Brugger & Graves, 1997a) and tested (Mohr et al, 2004;Kumari et al, 1999). Here, contrary to our expectation, a reduced sensitivity in the levodopa as compared to the placebo group was only evident in the skeptics.…”

“…Immediately after behavioral testing, a second sample was drawn. Blood plasma was separated by centrifugation, and the samples were immediately frozen at −80°C for later high-pressure liquid chromatography for electrochemical detection (see Mohr, Landis, Sandor, Fathi, & Brugger, 2004 for further details). No levodopa was detected in the placebo group.…”

High estradiol levels improve false memory rates and meta-memory in highly schizotypal women

“…Indeed, behavioural evidence suggests that schizotypy (and schizotypal personality disorder) is associated with aberrant dopamine function (e.g. Mohr et al, 2004;McClure et al, 2010). Mohr et al (2004) demonstrated that levodopa (a dopamine agonist) improved visuo-motor performance exclusively in participants with high 'positive' schizotypy (i.e.…”

“…Mohr et al, 2004;McClure et al, 2010). Mohr et al (2004) demonstrated that levodopa (a dopamine agonist) improved visuo-motor performance exclusively in participants with high 'positive' schizotypy (i.e. magical ideation); low schizotypy participants showed a slight performance deterioration with levodopa.…”

“…Subsequently, Mohr et al (2004) suggest that high schizotypy is associated with a relative hyperdopaminergia, and a better ability to adapt to higher dopamine levels. If high levels of cognitive disorganisation are associated with relative hyperdopaminergia, this might also explain the improvement in false positive error rates shown by participants high in schizotypy with high estradiol levels, while low schizotypy participants showed a slight (non-significant) impairment.…”