SLEEP LOSS IMPAIRS SHORT AND NOVEL LANGUAGE TASKS HAVING A PREFRONTALFOCUS

Most cognitive tests administered during sleep loss are well rehearsed to remove practice effects. This can introduce tedium and a loss of n ovelty, which may be the key to the test's subsequent sensitivity to s leep loss, and why it may need only a few minutes administration befor e sleep loss effects are apparent. There is little evidence to show th at any of these tests are actually affected by sleep loss if given de novo, without practice, but using a non-sleep deprived control group. Although the sleep deprivation literature advocates that short, novel and stimulating tests would not be expected to be sensitive to sleep l oss, recent sleep loss findings using neuropsychological tests focussi ng on the prefrontal cortex, indicate that such tests may challenge th is maxim. Twenty healthy young adults were randomly assigned to two gr oups: nil sleep deprivation (control), and 36h continuous sleep depriv ation (SD). Two, novel, interesting and short (6 min) language tests, known (by brain imaging) to have predominantly a PFC focus, were given , once, towards the end of SD: (i) the Haylings test - which measures the capacity to inhibit strong associations in favour of novel respons es, and (ii) a variant of the word fluency test - innovation in a verb -to-noun association. Subjects were exhorted to do their best. Compare d with control subjects both tasks were significantly impaired by SD. As a check on the effects on the Haylings test, a repeat study was und ertaken with 30 more subjects randomly divided as before. The outcome was similar. Linguistically, sleep loss appears to interfere with nove l responses and the ability to suppress routine answers.