Friday, October 22, 2010

Research bytes: The nose knows: More research on olfactory (Go) abilities

Nguyen, A. D., Shenton, M. E., & Levitt, J. J. (2010). Olfactory Dysfunction in Schizophrenia: A Review of Neuroanatomy and Psychophysiological Measurements. Harvard Review of Psychiatry, 18(5), 279-292.

Olfactory processing is thought to be mediated via the frontal and temporolimbic brain regions, both of which, as well as olfactory dysfunction, are implicated in schizophrenia. Likewise, several empirical studies of olfactory dysfunction—in particular, olfactory deficits in identification, odor detection threshold sensitivity, and odor memory, along with associated brain structural changes—have been conducted to illuminate the pathophysiology of schizophrenia. These anomalies have been investigated, more recently, as possible biological markers of that disabling illness. This article summarizes recent research on neuroimaging changes associated with olfactory impairments in schizophrenia patients and on related functional changes in psychophysiological measurements (e.g., odor identification, odor discrimination, odor detection threshold, and odor memory). The possible role of these changes as biological markers of the disorder will be discussed, as will potentially productive directions for future research.

Clear, A. M., Konikel, K. E., Nomi, J. S., & McCabe, D. P. (2010). Odor recognition without identification. Memory & Cognition, 38(4), 452-460.

Odors are notoriously difficult to identify, yet an odor can often lead to a sense of recognition, despite an inability to identify it. In the present study, we examined this phenomenon using the recognition-without-identification paradigm. Participants studied either odor names alone or odor names that were accompanied by scratch-and-sniff stickers containing their corresponding scents. At test, the participants were presented with blank scratch-and-sniff stickers, half of which corresponded to items that were studied and half of which did not. The participants attempted to identify each test odor, as well as to rate the likelihood that it corresponded to a studied item. In addition, the participants indicated whether they were in a tip-of-the-tongue (TOT) state for a given odor's name. Odor recognition without identification was found, but only when the participants had actually smelled the test odor at study; it was not found when the participants only studied odor names and were then tested with odors, suggesting that this effect is an episode-specific, perceptually driven phenomenon. Despite this difference, an overall TOT-attribution effect, whereby recognition ratings were higher during TOT states than during non-TOT states, was shown across conditions.

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