Gesture imitation impaired in schizophrenia patients

By Liam Davenport, medwireNews Reporter

Schizophrenia patients have impaired gesture imitation, especially when the imitation depends on working memory and involves multiple actions, show study results.

Sohee Park, from Vanderbilt University in Nashville, Tennessee, USA, and colleagues comment: "Because imitation is an important means by which we learn new social and nonsocial skills, impaired imitation ability may play a significant role in functional outcome of schizophrenia.

"However, we also found that with repetition, imitation improved even in the patients. This finding underscores the importance of practice and repetition in the learning environment."

The team studied 14 outpatients with schizophrenia and 14 mentally healthy controls matched for age, education, and IQ. The participants were asked to imitate computer-generated hand gestures while wearing a glove with a built-in hand sensor and a lower arm sensor. Single-gesture and multiple-gesture tests were conducted, with the latter designed to examine working memory.

The results, published in Schizophrenia Bulletin, show that, on single-gesture tests, schizophrenia patients made significantly more spatial errors than controls. However, there was no significant interaction with premotor planning time (PMPT), suggesting that improvement in the speed of gesture imitation was not different between groups.

Furthermore, both schizophrenia patients and controls took approximately 1700 ms to imitate the gesture. There were no associations between clinical symptoms or chlorpromazine equivalent dose and imitation errors.

On the multiple-gesture tests, patients and controls produced the same number of gestures. While there were no overall differences in spatial errors between the two groups, more errors were made during the working memory condition, an effect that was significant among schizophrenia patients. There was also a significant learning effect, with a longer PMPT in schizophrenia patients than in controls in the working memory condition.

"This effect may seem odd at first glance but PMPT is not a simple reaction time. It is the interval between the signal to initiate a gesture (tone) and the actual start of the imitation," the team writes. "Therefore, PMPT reflects the time taken to generate the mental representation for imitation."

Finally, there was a significant correlation between Scale for the Assessment of Negative Symptoms total score and increased spatial errors in the working memory condition, and with longer PMPT in the working memory condition.

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