The relationship of neuropsychological measures of frontal lobe function to age differences in false recall was assessed using the Deese/Roediger-McDermott associative false memory paradigm (Deese, 1959;Roediger & McDermott, 1995). As other studies have found, older adults were less likely to correctly recall studied items and more likely to falsely recall highly related but nonpresented items than were younger adults. When older adults were divided based on a composite measure of frontal lobe functioning, this age difference was found only for low frontal lobe functioning individuals. High frontal lobe functioning older adults and young adults had equivalent levels of false recall, as well as equivalent levels of veridical recall. These results suggest that age differences in memory may be due to declines in frontal lobe function. More important, our findings indicate that declines in veridical recall and increases in false recall are not an inevitable consequence of aging.

Measures of explicit rule-based category learning are commonly used in neuropsychological evaluation of individuals with Parkinson's disease (PD) and the pattern of PD performance on these measures tends to be highly varied. We review the neuropsychological literature to clarify the manner in which PD affects the component processes of rule-based category learning and work to identify and resolve discrepancies within this literature. In particular, we address the manner in which PD and its common treatments affect the processes of rule generation, maintenance, shifting and selection. We then integrate the neuropsychological research with relevant neuroimaging and computational modeling evidence to clarify the neurobiological impact of PD on each process. Current evidence indicates that neurochemical changes associated with PD primarily disrupt rule shifting, and may disturb feedback-mediated learning processes that guide rule selection. Although surgical and pharmacological therapies remediate this deficit, it appears that the same treatments may contribute to impaired rule generation, maintenance and selection processes. These data emphasize the importance of distinguishing between the impact of PD and its common treatments when considering the neuropsychological profile of the disease. Keywords PARKINSON'S DISEASE; STRIATUM; CATEGORY LEARNING; DOPAMINE; EXECUTIVE FUNCTIONAs a fundamental aspect of human cognition, categorization enables appropriate responses to a variety of familiar and novel stimuli. The same categorization processes that govern decisions of dire importance, such as whether or not the street sign ahead signals a road hazard, also govern more mundane behaviors such as filing papers or sorting laundry. The ubiquitous nature Correspondence concerning this article should be addressed to: Amanda Price, Department of Psychology, Elizabethtown College, Elizabethtown, PA 17022, E-mail: HUpricea@etown.eduU, (717)475-9789. 2 We use the general abbreviation PD when discussing research that did not specifically examine the impact of PD medication. When addressing research that specifically examined the impact of medication, we distinguish between PD patients on and off medication. 3 The present discussion focuses specifically on rule shifting within category learning tasks and does not address the substantial literature related to task switching. Task switching differs from rule shifting in that it does not emphasize learning and involves changing stimulusresponse mappings. In addition, task switching is more consistently affected by DA withdrawal than rule shifting, which suggests the two processes are sufficiently different to not be discussed as relying on the same mechanisms. of categorization has led to extensive examination of the cognitive and, more recently, neurobiological processes underlying its performance. NIH Public AccessMuch work in the area of categorization has focused on the processes underlying the acquisition of new categories and it is generally accepted that multiple learni...

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Cyanobacteria and similar organisms produced most of the oxygen found in Earth's atmosphere, which implies that early photosynthetic organisms would have lived in an atmosphere that was rich in CO2 and poor in O2. We investigated the tolerance of several cyanobacteria to very high (>20 kPa) concentrations of atmospheric CO2. Cultures of Synechococcus PCC7942, Synechocystis PCC7942, Plectonema boryanum, and Anabaena sp. were grown in liquid culture sparged with CO2-enriched air. All four strains grew when transferred from ambient CO2 to 20 kPa partial pressure of CO2 (pCO2), but none of them tolerated direct transfer to 40 kPa pCO2. Synechococcus and Anabaena survived 101 kPa (100%) pCO2 when pressure was gradually increased by 15 kPa per day, and Plectonema actively grew under these conditions. All four strains grew in an anoxic atmosphere of 5 kPa pCO2 in N2. Strains that were sensitive to high CO2 were also sensitive to low initial pH (pH 5-6). However, low pH in itself was not sufficient to prevent growth. Although mechanisms of damage and survival are still under investigation, we have shown that modern cyanobacteria can survive under Earth's primordial conditions and that cyanobacteria-like organisms could have flourished under conditions on early Mars, which probably had an atmosphere similar to early Earth's.

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To better characterize the neuropsychological mechanisms of implicit and verbalizable category learning, the author studied weather prediction task (WPT) and information integration task (IIT) performance in patients with Parkinson's disease (PD) and healthy older and younger adults. Both older adults and patients with PD were impaired on the WPT, but only patients were impaired on the IIT, suggesting the 2 tasks rely on dissociable systems. Whereas the IIT appeared to rely on implicit processes, results suggest WPT classification depends on explicit processes. Awareness of underlying structure, hypothesis testing ability, and working memory capacity were all related to accuracy on the WPT but not the IIT. The variability commonly noted in WPT performance may reflect individual differences in hypothesis testing ability.

Novice clinicians should be supported by educators and nurse managers to note when their intuitions are likely to be valid. Our findings emphasize the integrated nature of intuition and analysis in clinical decision-making.