Impaired perceptual discrimination of complex objects in older adults at risk for dementia.

Tau pathology accumulates in the perirhinal cortex (PRC) of the medial temporal lobe (MTL) during the earliest stages of the Alzheimer's disease (AD), appearing decades before clinical diagnosis. Here, we leveraged perceptual discrimination tasks that target PRC function to detect subtle cognitive impairment even in nominally healthy older adults. Older adults who did not have a clinical diagnosis or subjective memory complaints were categorized into "at-risk" (score <26; n = 15) and "healthy" (score ≥26; n = 23) groups based on their performance on the Montreal Cognitive Assessment. The task included two conditions known to recruit the PRC: faces and complex objects (greebles). A scene condition, known to recruit the hippocampus, and a size control condition that does not rely on the MTL were also included. Individuals in the at-risk group were less accurate than those in the healthy group for discriminating greebles. Performance on either the face or size control condition did not predict group status above and beyond that of the greeble condition. Visual discrimination tasks that are sensitive to PRC function may detect early cognitive decline associated with AD.

Differential impairment of positive and negative schizotypy in list-method and item-method directed forgetting.

Schizophrenia is characterized by cognitive impairment and this impairment is expected to occur, albeit to a lesser degree, in people putatively at risk for schizophrenia. Two experiments assessed the relationship between directed forgetting (DF) and schizotypy, which is a multidimensional construct that reflects the expression of the underlying vulnerability for schizophrenia. Experiment 1 involved item-method DF and Experiment 2 involves list-method DF study. The schizotypy dimensions exhibited differential patterns of impairment across the 2 methods that suggest different underlying processes. Positive schizotypy showed impairment in item-method DF that was driven by reduced ability to forget forget-cued items, whereas performance on remember-cued items was unaffected in positive schizotypy. Despite the deficit in item-method DF, positive schizotypy participants showed preserved performance in list-method DF. The opposite pattern was found in negative schizotypy participants, who showed impairment in list-method DF, despite preserved performance in item-method DF. Negative schizotypy was previously associated with deficits in context processing and, consistent with context-change account of list-method DF, showed deficits in list-method DF task. Positive schizotypy is characterized by deficits in inhibitory control and, consistent with inhibitory account of item-method DF, showed deficits in item-method DF task. Collectively, these results (a) suggest that different DF methods involve different underlying mechanisms, (b) support the context-account of list-method DF and an inhibitory account of item-method DF, and (c) support the multidimensional model of schizotypy by showing differential impairment in positive and negative schizotypy across the 2 DF tasks. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Examination of relational memory in multidimensional schizotypy.

We report the first study to examine the association of positive, negative, and disorganized schizotypy with relational memory. Relational memory refers to memory for relations among multiple elements of an experience, and this form of episodic memory is different from memory for individual elements themselves. Using a cornerstone task from the neurocognitive literature that is designed specifically to assess relational memory, we found that negative schizotypy, but not positive or disorganized schizotypy, is associated with impaired relational memory performance. The deficit was observed both in poorer accuracy and slower response time. The results demonstrate the importance of examining schizotypy as a multidimensional construct, and indicate that using a total schizotypy score both obscures the nature of the association with various dimensions of schizotypy and also explains only half of the variance accounted for by taking into consideration the multidimensionality of schizotypy. These results add to previous findings that negative schizotypy is associated with a wide array of episodic memory deficits linked to impairment in retrieval and processing of contextual information.