Contribution of peripheral input to length discrimination during use of a precision grip.

This study examined the ability of 63 subjects to discriminate a length difference, using a precision grip with the thumb and the index finger. To assess the relative contribution of different peripheral inputs associated with the discriminative ability of precision grip, three tasks were performed under each of three conditions-normal conditions; when vibratory stimuli were delivered to the forearm muscles; and when a local anesthetic was administered to the index finger. Under the first and second conditions, the length difference detected most frequently was 2.0 mm; in the third task, it was 3.0 mm. When a 100-Hz vibratory stimulus was applied to the forearm muscles, no difference in the threshold for length discrimination was observed for three of seven subjects. After injection of lidocaine into the metacarpophalangeal joint of the index finger, the threshold for length discrimination was significantly different for five of seven subjects. The detected length difference ranged from 1.0 to 4.0 mm. The authors question whether a single peripheral input is likely to make a major contribution to the complex perception that is used for discrimination tasks.

[A case report of volatile solvent psychosis].

A case (male, 27 years old) with chronic thinner intoxication, whose mental condition was reexamined in accord with a court order, is reported. He had been sniffing thinner from age 12 to 27. Since the age of 17, he experienced visual and auditory hallucinations without sniffing thinner. He had no family history of schizophrenia. The psychiatric examination revealed that he had positive symptoms of schizophrenia, especially the first rank symptoms, such as auditory hallucinations (i.e. voices commenting and voices arguing), experience of influence (withdrawal of thought, thought insertion and influence of thought) and delusional perception, but did not show negative symptoms (i.e. blunting thought). Furthermore, he could maintain good emotional contact with others. Hallucinations, which appeared in acute intoxication with thinner, were second rank symptoms, different from those observed in the sober period when he was not under the influence of the thinner. Judging from above facts it was difficult to diagnose this case as schizophrenia or the flashback phenomenon of thinner dependence. Although the disease concept of volatile solvent psychosis has not been clearly established, this case may suggest that the first rank symptoms are important manifestations of volatile solvent psychosis.