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Amnesic patients acquired a mirror-reading skill at a rate equivalent to that of matched control subjects and retained it for at least 3 months. The results indicate that the class of preserved learning skills in amnesia is broader than previously reported. Amnesia seems to spare information that is based on rules or procedures, as contrasted with information that is data-based or declarative--"knowing how rather than "knowing that." The results support the hypothesis that such a distinction is honored by the nervous system.

Cardiovascular fitness is thought to offset declines in cognitive performance, but little is known about the cortical mechanisms that underlie these changes in humans. Research using animal models shows that aerobic training increases cortical capillary supplies, the number of synaptic connections, and the development of new neurons. The end result is a brain that is more efficient, plastic, and adaptive, which translates into better performance in aging animals. Here, in two separate experiments, we demonstrate for the first time to our knowledge, in humans that increases in cardiovascular fitness results in increased functioning of key aspects of the attentional network of the brain during a cognitively challenging task. Specifically, highly fit (Study 1) or aerobically trained (Study 2) persons show greater task-related activity in regions of the prefrontal and parietal cortices that are involved in spatial selection and inhibitory functioning, when compared with low-fit (Study 1) or nonaerobic control (Study 2) participants. Additionally, in both studies there exist groupwise differences in activation of the anterior cingulate cortex, which is thought to monitor for conflict in the attentional system, and signal the need for adaptation in the attentional network. These data suggest that increased cardiovascular fitness can affect improvements in the plasticity of the aging human brain, and may serve to reduce both biological and cognitive senescence in humans.S everal approaches to maintaining or improving cognitive performance in older adults have shown promise. It has long been known that older experts in a variety of domains can maintain high levels of performance into their 70s (1, 2). Also, in some cases, older adults have been shown to benefit as much or more than young adults from formal training of different cognitive abilities (3, 4). However, with few exceptions (4), the beneficial effects of these interventions tend to be limited to the tasks used in training. For example, expertise in typing has little or no effect on one's ability to drive a car, and training in visual search paradigms has little effect on working memory performance.Since Spirudiso's seminal study of aging racquet sportsmen (5), there has been increasing interest in the utility of physical exercise as a more global moderator of age-related declines in cognition (6). A recent metaanalysis of the literature examining the effects of cardiovascular fitness training (CFT) on cognitive function has confirmed that CFT can play such a role (7). An analysis of 18 longitudinal fitness training studies demonstrated that regardless of the cognitive task type on which participants were tested, CFT participants showed a significantly greater improvement than control participants.Although, to date, the neural mechanisms underlying cognitive improvements associated with cardiovascular fitness in aging adults have not been well studied in human populations, data collected from animal models suggests some possibilities. For example, aerobic train...

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There is considerable evidence that the hippocampal system contributes both to (1) the temporary maintenance of memories and to (2) the processing of a particular type of memory representation. The findings on amnesia suggest that these two distinguishing features of hippocampal memory processing are orthogonal. Together with anatomical and physiological data, the •neuropsychological findings support a model of cortico-hippocampal interactions in which the temporal and representational properties of hippocampal memory processing are mediated separately. We propose that neocortical association areas maintain shortterm memories for specific items and events prior to hippocampal processing as well as providing the final repositories of long-term memory. The parahippocampal region supports intermediate-term storage of individual items, and the hippocampal formation itself mediates an organization of memories according to relevant relationships among items. Hippocampal-cortical interactions produce (i) strong and persistent memories for events, including their constituent elements and the relationships among them, and (ii) a capacity to express memories flexibly across a wide range of circumstances.It has been known for decades that the hippocampal system plays a prominent role in learning and memory. Only recently has it become clear that only certain properties of memory processing depend on hippocampal system function and that these can be distinguished operationally from other aspects of memory that do not. It has proved difficult, however, to arrive at an understanding of memory rich enough to characterize both the nature of memory that is dependent on the hippocampal system and memory that is independent of this processing, and to tie them to underlying neural mechanisms. The earliest reports of amnesia emphasized the timelimited role of the hippocampal region in memory, focusing on its critical function in "consolidation" processes that bridge between immediate memory and the longterm store (Scoville & Milner 1957). This temporal distinction is most striking: amnesic patients and animals with hippocampal system damage show normal retention at short delays and increasingly impaired retention with longer delays. Recently, some have argued that virtually all aspects of memory processing by the hippocampal system can be attributed to its function as a temporary memory store or buffer (e.g., Rawlins 1985). However, a large body of data indicates that the loss of consolidation or memory-buffer functions cannot account for the full pattern of impaired and spared memory performance observed after hippocampal system damage; some memory capacities are intact in amnesia even across very long temporal intervals, whereas other aspects of memory performance are grossly impaired even over relatively short retention intervals. The buffer hypothesis also fails to account fully for a number of relevant observations on the stable, long-lasting functional correlates of hippocampal neuronal activity (see sect. 5). To accommodate a ...

These findings extend the scope of beneficial effects of aerobic exercise beyond cardiovascular health, and they suggest a strong solid biological basis for the benefits of exercise on the brain health of older adults.

Eye movements were monitored to assess memory for scenes indirectly (implicitly). Two eye movement-based memory phenomena were observed: (a) the repetition effect, a decrease in sampling of previously viewed scenes compared with new scenes, reflecting memory for those scenes, and (b) the relational manipulation effect, an increase in viewing of the regions where manipulations of relations among scene elements had occurred. In normal control subjects, the relational manipulation effect was expressed only in the absence of explicit awareness of the scene manipulations. Thus, memory representations of scenes contain information about relations among elements of the scenes, at least some of which is not accessible to verbal report. But amnesic patients with severe memory impairment failed to show the relational manipulation effect. Their failure to show any demonstrable memory for relations among the constituent elements of scenes suggests that amnesia involves a fundamental deficit in relational (declarative) memory processing.