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Magnetic resonance spectroscopy (MRS) is an important tool for studying the effects of nutrition on brain health. MRS can be used to measure the concentrations of metabolites which are related to cognitive performance and sensitive to diet. These measurements can provide information about metabolic efficiency, plasma membrane stability, antioxidant status, and neurotransmitter availability. MRS can therefore be used to elucidate the biochemical mechanisms by which diet influences cognition, and to characterize the effects of nutritional interventions targeted to improve cognition. [ABSTRACT FROM PUBLISHER]

Recent evidence suggests that astrocytes convert glucose to lactate, which is released from the astrocytes and supports learning and memory. This report takes a multiple memory perspective to test the role of astrocytes in cognition using real-time lactate measurements during learning and memory. Extracellular lactate levels in the hippocampus or striatum were determined with lactate biosensors while rats were learning place (hippocampus-sensitive) or response (striatum-sensitive) versions of T-mazes. In the first experiment, rats were trained on the place and response tasks to locate a food reward. Extracellular lactate levels in the hippocampus increased beyond those of feeding controls during place training but not during response training. However, striatal lactate levels did not increase beyond those of controls when rats were trained on either the place or the response version of the maze. Because food ingestion itself increased blood glucose and brain lactate levels, the contribution of feeding may have confounded the brain lactate measures. Therefore, we conducted a second similar experiment using water as the reward. A very different pattern of lactate responses to training emerged when water was used as the task reward. First, provision of water itself did not result in large increases in either brain or blood lactate levels. Moreover, extracellular lactate levels increased in the striatum during response but not place learning, whereas extracellular lactate levels in the hippocampus did not differ across tasks. The findings from the two experiments suggest that the relative engagement of the hippocampus and striatum dissociates not only by task but also by reward type. The divergent lactate responses of the hippocampus and striatum in place and response tasks under different reward conditions may reflect ethological constraints tied to foraging for food and water. [ABSTRACT FROM AUTHOR]

• Astrocytes produce lactate from glycogen to support learning and memory. • Astrocytic changes in glycogen content are evident soon after training. • Astrocytic changes in glycogen content also emerge long after spatial training. • These glial changes may prepare the brain for future learning based on the past. • Thus, long-lasting brain changes in response to experience include astrocytes. Long-lasting biological changes reflecting past experience have been studied in and typically attributed to neurons in the brain. Astrocytes, which are also present in large number in the brain, have recently been found to contribute critically to learning and memory processing. In the brain, glycogen is primarily found in astrocytes and is metabolized to lactate, which can be released from astrocytes. Here we report that astrocytes themselves have intrinsic neurochemical plasticity that alters the availability and provision of metabolic substrates long after an experience. Rats were trained to find food on one of two versions of a 4-arm maze: a hippocampus-sensitive place task and a striatum-sensitive response task. Remarkably, hippocampal glycogen content increased while striatal levels decreased during the 30 days after rats were trained to find food in the place version, but not the response version, of the maze tasks. A long-term consequence of the durable changes in glycogen stores was seen in task-by-site differences in extracellular lactate responses activated by testing on a working memory task administered 30 days after initial training, the time when differences in glycogen content were most robust. These results suggest that astrocytic plasticity initiated by a single experience may augment future availability of energy reserves, perhaps priming brain areas to process learning of subsequent experiences more effectively. [ABSTRACT FROM AUTHOR]

While compelling evidence indicates that poorer aerobic fitness relates to impairments in retrieving information from hippocampal-dependent memory, there is a paucity of research on how aerobic fitness relates to the acquisition of such relational information. Accordingly, the present investigation examined the association between aerobic fitness and the rate of encoding spatial relational memory-assessed using a maximal oxygen consumption test and a spatial configuration task-in a sample of 152 college-aged adults. The findings from this investigation revealed no association between aerobic fitness and the acquisition of spatial relational memory. These findings have implications for how aerobic fitness is characterized with regard to memory, such that aerobic fitness does not appear to relate to the rate of learning spatial-relational information; however, given previously reported evidence, aerobic fitness may be associated with a greater ability to recall relational information from memory. [ABSTRACT FROM AUTHOR]

ABSTRACT This article reviews evidence showing that neurochemical modulators can regulate the relative participation of the hippocampus and striatum in learning and memory tasks. For example, relative release of acetylcholine increases in the hippocampus and striatum reflects the relative engagement of these brain systems during learning of place and response tasks. Acetylcholine release is regulated in part by available brain glucose levels, which themselves are dynamically modified during learning. Recent findings suggest that glucose acts through astrocytes to deliver lactate to neurons. Brain glycogen is contained in astrocytes and provides a capacity to deliver energy substrates to neurons when needed, a need that can be generated by training on tasks that target hippocampal and striatal processing mechanisms. These results integrate an increase in blood glucose after epinephrine release from the adrenal medulla with provision of brain energy substrates, including lactate released from astrocytes. Together, the availability of peripheral and central energy substrates regulate the processing of learning and memory within and across multiple neural systems. Dysfunctions of the physiological steps that modulate memory-from hormones to neurotransmitters to metabolic substrates-may contribute importantly to some of the cognitive impairments seen during normal aging and during neurodegenerative diseases. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT One of the now classic tenets of neuroscience is that the brain retains a substantial amount of structural and functional plasticity throughout adulthood and old age. Enriching experiences that stimulate physical and mental activity produce robust changes in subsequent behaviors, including learning and memory, that tap a wide range of neural systems. In this article, we review evidence for cognitive priming with physical and mental exercise through a memory systems lens and present brain-derived neurotrophic factor (BDNF) signaling as one candidate neural mechanism for experience-dependent modulation of learning and memory. We highlight our recent findings showing that priming with voluntary exercise or with spontaneous alternation, a working memory task, enhances new learning of hippocampus-sensitive place, or striatum-sensitive response tasks. Blocking BDNF signaling with infusions of a BDNF receptor inhibitor into hippocampus or striatum just before training on place or response tasks, respectively, abrogated the benefits of priming regardless of the type of priming experience. These results suggest that enhanced BDNF signaling during learning may itself produce the cognitive benefits afforded by prior physical or mental activity. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]