The organization of semantic memory in patients with Alzheimer's disease (AD) was investigated with a triadic comparison task. A multidimensional scaling statistic was used to analyze proximity data and to generate 3-dimensional cognitive maps that were then compared by a discriminant function analysis. The results suggest that the structure of semantic memory in AD patients differs from that of elderly normal controls (NC) in 2 ways. First, AD patients are less consistent in using the attributes (predation, domesticity, and size) of concepts. Second, AD patients focus primarily on concrete perceptual information (size), whereas NC Ss stress abstract conceptual knowledge (domesticity). These results are consistent with the notion that AD is characterized by a breakdown in the structure of semantic knowledge.

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This study explored whether remote blast-related MTBI and/or current Axis I psychopathology contribute to neuropsychological outcomes among OEF/OIF veterans with varied combat histories. OEF/OIF veterans underwent structured interviews to evaluate history of blast-related MTBI and psychopathology and were assigned to MTBI (n 5 18), Axis I (n 5 24), Co-morbid MTBI/Axis I (n 5 34), or post-deployment control (n 5 28) groups. A main effect for Axis I diagnosis on overall neuropsychological performance was identified (F(3,100) 5 4.81; p 5 .004), with large effect sizes noted for the Axis I only (d 5 .98) and Co-morbid MTBI/Axis I (d 5 .95) groups relative to the control group. The latter groups demonstrated primary limitations on measures of learning/memory and processing speed. The MTBI only group demonstrated performances that were not significantly different from the remaining three groups. These findings suggest that a remote history of blast-related MTBI does not contribute to objective cognitive impairment in the late stage of injury. Impairments, when present, are subtle and most likely attributable to PTSD and other psychological conditions. Implications for clinical neuropsychologists and future research are discussed. (JINS, 2012, 18, 845-855)

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