Abstract
Time processing critically relies on the mesencephalic dopamine system and striato-prefrontal projections and has thus been suggested to play a key role in schizophrenia. Previous studies have provided evidence for an acceleration of the internal clock in schizophrenia that may be linked to dopaminergic pathology. The present study aimed to assess the relationship between altered time processing in schizophrenia and symptom manifestation in 22 patients and 22 controls. Subjects were required to estimate the time needed for a visual stimulus to complete a horizontal movement towards a target position on trials of varying cognitive demand. It was hypothesized that patients – compared to controls – would be less accurate at estimating the movement time, and that this effect would be modulated by symptom manifestation and task difficulty. In line with the notion of an accelerated internal clock due to dopaminergic dysregulation, particularly patients with severe positive symptoms were expected to underestimate movement time. However, if altered time perception in schizophrenia was better explained in terms of cognitive deficits, patients with severe negative symptoms should be specifically impaired, while generally, task performance should correlate with measures of processing speed and cognitive flexibility. Patients underestimated movement time on more demanding trials, although there was no link to disease-related cognitive dysfunction. Task performance was modulated by symptom manifestation. Impaired estimation of movement time was significantly correlated with PANSS positive symptom scores, with higher positive symptom scores associated with stronger underestimation of movement time. The present data thus support the notion of a deficit in anticipatory and predictive mechanisms in schizophrenia that is modulated both by symptom manifestation and by cognitive demand.
Highlights
If altered time processing in schizophrenia is better explained in terms of cognitive deficits, patients – and those with severe negative symptoms - should be impaired on more cognitively demanding trials, while generally, task performance should correlate with measures of processing speed and cognitive flexibility
Cognitive flexibility as assessed by the Trail Making Test (TMT) difference score was significantly lower in patients compared to controls (U = 114.00, p = .003)
The present study investigated the relationship between altered time perception on the AMT in schizophrenia and symptom manifestation in 22 patients and 22 controls
Summary
Participants Twenty-two adult individuals (15 male, 7 female; mean age = 35.6868.73 years) meeting the Diagnostic and Statistical Manual IV (DSM-IV) [40] criteria for schizophrenia and 22 nonpsychiatric control participants (15 male, 7 female; mean age = 32.6867.61 years) were recruited for participation. Exclusion criteria for all participants comprised self-reported neurological diseases, left-handedness, and a history of substance abuse, head injury resulting in episodes of unconsciousness or head surgery. Psychiatric disorders other than schizophrenia led to exclusion from the study, as did a personal or family history of schizophrenia in the control group. All control participants were screened with a German version of the Mini International Interview (M.I.N.I.) [42] in order to exclude the presence of any psychiatric Axis I disorder. All participants had normal or corrected-to-normal vision and hearing acuity
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