The nature of the relationship of psychomotor slowing with negative symptomatology in schizophrenia.

INTRODUCTION: Psychomotor slowing is an important feature of schizophrenia and the relation with negative symptoms is not fully understood. This study aims, first, to investigate the association between negative symptoms and psychomotor slowing. Second, we want to investigate whether fine motor slowing reflects clinically observable gross motor slowing. METHODS: In 53 stabilised adult patients with schizophrenia, negative symptoms were assessed using the Positive and Negative Syndrome Scale negative subscale (PANSS-N) with two calculated factors entering the analysis: an expressivity factor and a volitional factor. Psychomotor slowing was assessed by using a modified version of the Salpêtrière Retardation Rating Scale, the Finger Tapping Test, and a writing task measuring fine psychomotor slowing. RESULTS: Negative symptomatology is associated with difficulties in the initiation of fine motor movements, r=.334, p<.05, whilst planning and execution are not. The volitional factor, r=-.407, p=.005, but not the expressivity factor, r=.060, p=.689, is significantly associated with psychomotor slowing. No associations between fine and clinically observable gross psychomotor functioning were found. CONCLUSIONS: These findings indicate that higher values of negative symptomatology-more specifically the volitional deficit cluster-affect motor initiation, indicating a heterogeneity in the PANSS-N factorial structure, and that gross and fine psychomotor functioning are affected independently.

Longitudinal evaluation of the psychomotor syndrome in schizophrenia.

Little is known about the longitudinal course of psychomotor signs and symptoms after illness onset in schizophrenia. Therefore, a 1-year follow-up study was conducted in which patients with schizophrenia were assessed three times with an extensive battery of psychomotor rating scales and tests. The syndromic structure of psychomotor symptoms was also studied. In accordance with a neurodevelopmental view on schizophrenia, psychomotor functioning was found to remain stable or improve slightly. Prospective studies with longer follow-up periods are needed to rule out the possibility of neurodegeneration in subgroups of patients and to evaluate possible covariation in the course of psychomotor symptoms.

Increased orienting to unexpected action outcomes in schizophrenia.

Although some recent research has indicated reduced performance monitoring in patients with schizophrenia, the literature on this topic shows some remarkable inconsistencies. While most studies suggest diminished error signals following error responses, some studies reported normal post-error slowing, while others reported reduced post-error slowing. Here we review these studies and highlight the most important discrepancies. Furthermore, we argue that overall error rates are a mostly neglected issue that can at least partly explain these discrepancies. It has been reported previously that post-error slowing depends on the error rates. Participants or patients that make more errors are likely to show decreased post-error slowing. Therefore, when a group of patients is compared to a group of controls, it is extremely important to match error rates. For this purpose, we developed a procedure where we matched individuals' error rates. In a task where subjects had to press a response key corresponding to one of four colors we manipulated the difficulty on an individual basis by varying the discriminability between the colors. Schizophrenic patients and a group of controls were tested with this procedure showing that differences in accuracy disappear. Interestingly, we can see that in patients, the color values that were needed to reach similar levels of accuracy correlate with the Positive and Negative Syndrome Scale (PANSS) scale, with higher PANSS requiring more color. Most important, we found that schizophrenic patients have increased rather than decreased post-error slowing when the inter-trial interval (ITI) is short. This result can be interpreted within the framework of the orienting account, as it has been demonstrated previously that schizophrenic patients show increased distractibility.