Some persons with schizophrenia can remember complex sounds, such as intricate bird songs, but not simple words, providing yet more evidence about the complex nature of the mental illness, a study by Yale researchers has found.
"This gives you a sense of what patients with schizophrenia are up against when such a core aspect of normal cognitive operations is impaired," said Bruce Wexler, M.D., associate professor of psychiatry at Yale School of Medicine. "It shows how profound the effects of the illness can be."
The study published in the January issue of the journal Schizophrenia Research was based on tests performed with 23 outpatients with schizophrenia and 15 people with no mental illness. Those in the study listened to brief recordings of three intricate bird songs and, after a pause, listened to one of the three songs and were asked to recall where it appeared in the sequence. The same exercise was performed using familiar sounds like a dog barking or a telephone ringing. In this second test subjects could attach verbal labels to each stimulus and use those labels when trying to remember the sequence of sounds.
The ability to use verbal labels made the memory test much easier for the healthy subjects, raising performance from 69 percent to 93 percent. In contrast, the performance of the patients was little improved by the use of the verbal labels, going only from 61 percent to 63 percent. Two of the patients even scored as well or better than all of the healthy controls on the bird song test, yet performed worse than all of the control subjects on the verbal memory test.
"It is not clear whether the proposed disability in activating verbal labels to sensory input is part of a more general deficit in retrieval from long term memory or is a deficit specific to language related processes," Wexler said. "In either case, its impact on cognitive function would be profound, as the use of internal language mechanisms to enhance cognition is an essential aspect of a wide range of normal human brain functions."
He said the current study is one more step along the path of further specifying cognitive deficits among patients with schizophrenia.
Co-authors on the study were Nelson Donegan and Sharif Jacob, both at Yale, and Alexander Stevens of the Oregon Health Sciences University.
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