Time estimation in a case of Tourette's syndrome: Effect of antipsychotic medications

Perceptual inference, accuracy, and precision in temporal reproduction in schizophrenia

Accumulating evidence suggests that deficits in perceptual inference account for symptoms of schizophrenia. One manifestation of perceptual inference is the central bias, i.e., the tendency to put emphasis on prior experiences over actual events in perceiving incoming sensory stimuli. Using an interval reproduction task, this study aimed to determine whether patients with schizophrenia show a stronger central bias than participants without schizophrenia. In the interval reproduction task, participants were shown a cross on a screen. The cross was replaced with a Gaussian patch for a predetermined time interval, and participants were required to reproduce the interval duration by pressing and releasing the space key. We manipulated the uncertainty of prior information using different interval distributions. We found no difference in the influence of prior information on interval reproduction between patients and controls. However, patients with SZ showed a stronger central bias than healthy participants in the intermediate interval range (approximately 450 ms to 900 ms). It is possible that the patients in SZ have non-uniform deficits associated with interval range or uncertainty of prior information in perceptual inference. Further, the severity of avolition and alogia was correlated with the strength of central bias in SZ. This study provides some insights into the mechanisms underlying the association between schizophrenic symptoms and perceptual inference.

Time estimation in a case of Tourette's syndrome: Effect of antipsychotic medications

Aims

Dopamine (DA) hyperactivity causes overestimation of time, whereas DA hypoactivity produces its underestimation. DA activity also provides neurochemical substrates pertinent to several psychiatric conditions, such as schizophrenia and Tourette's syndrome. The overestimation of time sometimes exists in patients with Tourette's syndrome, but no reports have addressed time perception in relation to antipsychotic medications which typically act as DA receptor antagonists. We herein report a case of Tourette's syndrome, in which time estimation was differentially affected by risperidone (a DA antagonist) and aripiprazole (a DA partial agonist).

Case

A 27‐year‐old man who suffered from verbal and motor tics was treated with risperidone. His tic symptoms disappeared; however, he began to experience a strange feeling that “time is going too fast.” For example, “people walk more quickly compared to a normal pace.” These complaints were thought to represent underestimation of time. Then, risperidone was switched to oral aripiprazole to optimize DA transmissions, which resulted in the amelioration of these subjective feelings.

Conclusion

Our observations indicate that the underestimation of time may occur in patients with Tourette's syndrome who receive antipsychotic drugs with high DA D₂ receptor blocking potency. This may support the concept that the estimation of time is influenced by DA activity.

Estimation of time in patients with Tourette's syndrome is affected by actions of antipsychotic drugs on dopamine type 2 receptors.