[Comparison of mental rotation ability for depressive disorder and schizophrenia]

To compare the mechanism of depressive disorder and schizophrenia' mental rotation ability so as to provide specific objective clinical indicators for identifying mental illness.

Thirty depressive disorder (15 males, 15 females), 30 schizophrenia (15 males, 15 females) and 28 healthy participants (14 males, 14 females) were tested to perform mental rotation tasks with the letter F and R graphics. The subjects were required to decide whether the stimulus was a normal or a mirror version of an alphabet letter presented in different views and angular orientations. The mouse left key was pressed for a normal and the mouse right button for a mirror.

(1) Error rate: As compared with the normal control group (normal: 29% ± 10%, mirror: 32% ± 3%), the normal error rate was significantly higher while the mirror error rate significantly lower in depressive disorder (normal: 31% ± 13%, mirror: 22% ± 4%, P < 0.01); the normal error rate was significantly lower while the mirror error rate significantly higher in schizophrenia (normal: 27% ± 9%, mirror: 42% ± 2%, P < 0.01). (2) Normal reaction rate: As compared with the normal control group (50% ± 9%), the normal reaction rate was significantly lower in depressive disorder (38% ± 12%, P < 0.01) and significantly higher in schizophrenia (60% ± 9%, P < 0.01). (3) Response time: As compared with the normal control group (normal (602 ± 25) ms, mirror (606 ± 14) ms), the normal and mirror response durations were both significantly longer in depressive disorder(normal (653 ± 23) ms, mirror (714 ± 13) ms, P < 0.01) while significantly shorter in schizophrenia (normal (571 ± 18) ms, mirror (587 ± 11) ms, P < 0.01).

Normal mental rotation ability is severely impaired in depressive disorder, but its mirror counterpart becomes compensated. In schizophrenia, mirror mental rotation ability is severely impaired, but its normal counterpart becomes compensated. It hints that normal and mirror rotation ability may be interchangeable so as to serve as a state index. The impairment of mental rotation ability impaired can be used as specific objective clinical indicators of identifying mental illness.