Hippocampal lesions and transfer behavior in the rat.
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Analysis of Variance↗
Biomedical subjects
G Winocur
Publications and source records attributed to G Winocur.
Conditional learning in aged rats: evidence of hippocampal and prefrontal cortex impairment.
Groups of normal old rats and young adult rats were administered a test of conditional discrimination learning in which different visual stimuli were associated with responses to different levers. Initially, rats were tested in a zero-delay condition in which they selected their responses in the presence of the conditional stimuli. They were later tested at 5- and 15-s delays between stimulus presentation and the appearance of the levers. Old rats were impaired in learning the basic conditional discrimination, a test thought to be sensitive to frontal lobe dysfunction. Age differences increased with the length of the interval, revealing a time-dependent memory loss that was attributed to impaired hippocampal function.
Aging↗
A neuropsychological analysis of memory loss with age.
This paper reports a series of experiments that assessed learning and memory performance in aged rats from a neuropsychological perspective. Relative to young adults, old rats displayed rapid rates of forgetting, increased susceptibility to interference, and poor long-term recall of specific experiences. There were no age differences on tests of short-term memory. In general, the performance of aged rats paralleled that of young rats with restricted lesions to the hippocampus, thereby supporting the conclusion that normal memory loss with age is related to progressive hippocampal dysfunction.
Aging↗
Glucose treatment attenuates spatial learning and memory deficits of aged rats on tests of hippocampal function.
Groups of old and young rats were administered three tests of spatial learning and memory that are known to be sensitive to hippocampal dysfunction: the radial arm maze (RAM), spatial non-matching-to-sample (SNMTS), and a spatial vs. local cue-preference task. Old rats performed worse than young rats on the RAM and SNMTS tasks; on the cue-preference task, young rats were biased to use spatial cues, whereas old rats exhibited strong preferences for distinct, local cues. Peripheral injections of glucose (100 mg/kg) improved performance by old rats on the RAM and SNMTS, which correlated with measures of glucose metabolism. Glucose treatment did not affect old rats performance on the cue-preference task. There was evidence that glucose-treatment improved performance of young rats in the RAM test, but not the other tests. The results extend the range of tasks on which glucose-induced cognitive enhancement has been demonstrated in aged rats, and provides further evidence that memory loss resulting from hippocampal dysfunction is especially amenable to glucose treatment.
Aging↗
Environmental influences on cognitive decline in aged rats.
Two experiments are reported in which young and old rats, housed in an impoverished (IE), enriched (EE), or standard (SE), environment, were tested on a series of complex, blind-alley mazes. In Experiment 1, 3-months exposure to IE exacerbated age differences in maze performance, relative to the differences between young and old rats in EE and SE. Old rats in the EE and SE conditions did not differ from each other. In Experiment 2, rats were raised for an additional 3 months in either IE or EE before further maze testing. The main findings were that the maze performance of old rats, transferred from IE to EE, improved significantly, whereas the performance of old rats, transferred from SE or EE to IE, declined. These results indicated that the deleterious effects of an impoverished environment on learning and memory are, at least partly, reversible, and that experience in a stimulating environment can protect old rats from the adverse effects of relocation to a deprived environment. Taken together, the results highlight the impact of environmental influences on cognitive function in old age, and emphasize the need to consider nonbiological factors in understanding the process of cognitive aging.
Aging↗
Functional interactions between the medial temporal lobes and posterior neocortex related to episodic memory retrieval.
We applied structural equation modeling to positron emission tomography data in humans to examine functional interactions between the right medial temporal lobe (MTL) and selected right neocortical regions in relation to visual recognition memory. Using a priori knowledge about anatomical connections between these regions as a guiding constraint, we modeled the pattern of interactions [i.e. covariances in regional cerebral blood flow (rCBF)] associated with episodic memory retrieval of spatial location and compared it with the pattern for retrieval of object identity. We also compared these patterns with those associated with perceptual matching of spatial location and object identity. Although displaying no difference in average rCBF across tasks, the right MTL showed domain-specific qualitative differences in interactions with posterior dorsal (parieto-occipital sulcus, supramarginal gyrus) and ventral regions (fusiform gyrus, superior temporal sulcus) but not with a prefrontal region. MTL interactions involving dorsal regions were positive in the spatial retrieval task but negative for object retrieval. Interactions involving ventral regions showed the reverse pattern. No comparable changes were observed during perceptual matching. Using control models, we demonstrated the neuroanatomical specificity of these results. Our results provide support for the notion that the nature of interactions between the MTL and posterior neocortex depends on the domain of information to-be-recovered.
Brain Mapping↗