Prefrontal cortex and caudate nucleus in conditional associative learning: Dissociated effects of selective brain lesions in rats.

Rats with lesions to prefrontal cortex (PFC) or caudate nucleus (CN) were compared on tests of conditional associative learning (CAL) that placed varying demands on conditional rule learning and working-with-memory operations that are essential for response selection. Damage to either structure impaired performance, but the respective deficits resulted from disruption of different processes. CN lesions produced a consistent learning deficit that was thought to reflect a basic impairment in forming stimulus-response (S-R) associations. The behavior of PFC rats was more variable and depended on task requirements. When S-R learning or response selection was relatively easy, the PFC was not critical. However, when either component was made more difficult, thus requiring the contribution of strategic processes, PFC damage produced profound impairments. In addition to clarifying the roles of the PFC and CN in CAL, the results provide further evidence that multiple brain regions participate in relatively simple behavioral tasks and that their respective contributions can be dissociated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age effects on social cognition: Faces tell a different story.

The authors administered social cognition tasks to younger and older adults to investigate age-related differences in social and emotional processing. Although slower, older adults were as accurate as younger adults in identifying the emotional valence (i.e., positive, negative, or neutral) of facial expressions. However, the age difference in reaction time was largest for negative faces. Older adults were significantly less accurate at identifying specific facial expressions of fear and sadness. No age differences specific to social function were found on tasks of self-reference, identifying emotional words, or theory of mind. Performance on the social tasks in older adults was independent of performance on general cognitive tasks (e.g., working memory) but was related to personality traits and emotional awareness. Older adults also showed more intercorrelations among the social tasks than did the younger adults. These findings suggest that age differences in social cognition are limited to the processing of facial emotion. Nevertheless, with age there appears to be increasing reliance on a common resource to perform social tasks, but one that is not shared with other cognitive domains. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Radial-arm maze behavior by rats with dorsal hippocampal lesions: Effects of cuing.

In 4 experiments with 180 male Wistar and Long-Evans rats, Ss with bilateral dorsal hippocampal lesions were impaired when tested on standard (noncued) versions of the radial-arm maze, but other hippocampal groups performed almost as well as cortical and operated control groups when salient visual cues were added to each arm. Preoperative training on the noncued, but not the cued, maze interfered with the benefits of postoperatively cuing hippocampal groups. Control groups performed equally well under all cuing and training conditions. Procedures that eliminated response sequencing did not affect performance of hippocampal or control groups. Results are interpreted as reflecting hippocampal involvement in mediating spatial cues, but not necessarily along the lines predicted by cognitive map theory. It is suggested that deficits of animals with hippocampal lesions represent 1 manifestation of a general impairment in processing information. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correlation between frontal lobe functions and explicit and implicit stem completion in health elderly.

Investigated the relationship between performance on neuropsychological tests, which were sensitive to medial-temporal and frontal lobe (FL) function, and implicit and explicit stem completion (SC) in a group of healthy elderly Ss (mean age 77.3 yrs). Several SC conditions varying in the size of the search space and the specificity of the cues were included. Across conditions, performance on a FL sensitive test (word fluency) and on medial-temporal tests (California Verbal Learning Test; delayed recall) correlated with explicit SC. The correlations between frontal and medial–temporal test performance and implicit SC were weaker. A relationship was observed between FL functioning and SC when the search space was large and the cues were constrained and when the search space was limited and the cues were relatively unconstrained. The role of the FLs in implicit SC seems to be to detect bias resulting from prior study. This involvement can only be revealed when the interaction between the size of the search space and the retrieval cues (a) makes bias detection necessary and (b) allows it to play a role. The stronger involvement of the FLs in explicit SC likely reflects strategic retrieval processes, and the medial-temporal lobe involvement may be related to verification processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cue-dependent behavior of hippocampally damaged rats in a complex maze.

In Exp. I, rats with hippocampal lesions were severely impaired in learning a fixed response sequence in a complex maze. Following subsequent manipulations, it was found that hippocampally damaged rats could learn the sequence as well as cortical and operated control Ss in the presence of highly conspicuous cues. Performance of hippocampally damaged Ss, unlike that of the control groups, deteriorated following removal of the cue used in original learning. In Exp. V, Ss with medial thalamic lesions also exhibited maze-learning impairment, but they benefited less than the hippocampal groups from an enhancement of cue conditions. The hippocampus is discussed in terms of its importance in processing relevant stimulus cues and in the organization of appropriate response strategies. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual cues and release from proactive inhibition in young and old people.

Three experiments examined whether elderly people perform similarly to Korsakoff amnesics on tests of release from proactive inhibition (PI). In Exp I, with 20 18–36 yr old undergraduates, 20 64–77 yr old university alumni, 20 employed 21–43 yr olds, and 21 institutionalized but healthy 71–92 yr olds, only the latter Ss failed to release from PI, like Korsakoff amnesics, whereas all the other groups of Ss showed the normal release from PI. Exp II, with 12 institutionalized 64–90 yr olds and 12 25–47 yr old controls, showed that release from PI could be induced in institutionalized elderly, as in Korsakoff amnesics, by salient environmental cues that coincided with the category shift. Exp III, with 13 67–89 yr old institutionalized Ss and 12 22–42 yr old controls, demonstrated that even in the absence of a category shift, salient environmental cues could lead to smaller, but noticeable, release from PI in institutionalized elderly, but not in young controls. The similarity in performance between the institutionalized elderly and Korsakoff amnesics suggested that it results from a common neurological deficit. (French abstract) (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term memory loss in senescent rats: Neuropsychological analysis of interference and context effects.

Four experiments were reported in which normal, senescent (25–27 months) and young adult (6 months) rats were tested for recall of a passive avoidance response 1 hr or several weeks after conditioning. There were no age differences at the 1-hr test, but a decrement was observed in old rats tested under standard conditions after long delays. The age-related impairment was exaggerated when additional approach training was administered in an identical apparatus between avoidance conditioning and testing. When the approach training was administered in an apparatus that contrasted markedly from the original, no age differences were observed. It was concluded that increased susceptibility to interference and contextual factors contributed to rapid forgetting in old rats, a pattern very similar to that observed previously in young adult rats with selective lesions to the hippocampus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dual-wavelength adaptive optical systems

A method for decomposition of phase difference error between measurements of atmospheric turbulence-induced phase distortion at two different wavelengths is described. Calculations are made of the phase difference errors in the first five Zernike radial modes for both ground-to-ground and ground-to-space transmission of laser radiation. It is found that the phase difference error compared with the uncorrected wavefront phase error is relatively insignificant in the first (tilt) Zernike mode but increases in significance with the order of the Zernike mode. Relative phase difference error is also found to depend on transmitted and received wavelengths, aperture diameter, propagation path, and strength of turbulence.     

The Relation Between Brain Activity During Memory Tasks and Years of Education in Young and Older Adults.

Higher education is associated with less age-related decline in cognitive function, but the mechanism of this protective effect is unknown. The authors examined the effect of age on the relation between education and brain activity by correlating years of education with activity measured using functional MRI during memory tasks in young and older adults. In young adults, education was negatively correlated with frontal activity, whereas in older adults, education was positively correlated with frontal activity. Medial temporal activity was associated with more education in young adults but less education in older adults. This suggests that the frontal cortex is engaged by older adults, particularly by the highly educated, as an alternative network that may be engaged to aid cognitive function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory impairment in obese Zucker rats: An investigation of cognitive function in an animal model of insulin resistance and obesity.

The genetically obese Zucker rat is a widely investigated model of pathological changes associated with type 2 diabetes. To assess cognitive function, obese and lean Zucker rats were tested on a variable-interval delayed alternation test of learning and memory. There were no group differences in learning the alternation rule or at short intervals, but obese rats were impaired at longer intervals where performance is hippocampus dependent. Plasma membrane association of the insulin sensitive glucose transporter, GLUT4, was reduced in the hippocampus of obese rats in the absence of changes in total GLUT4 and insulin receptor expression. These results parallel those of human studies in pointing to the susceptibility of the hippocampus and related structures to the adverse environment of diabetes mellitus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)