Learning Enhances the Survival of New Neurons beyond the Time when the Hippocampus Is Required for Memory

By B. Leuner, Sabrina Mendolia‐Loffredo, Y. Kozorovitskiy, Deanna Samburg, E. Gould, T. Shors. 2004

312 citations recorded by the source corpus.

Trace memories are formed when a stimulus event becomes associated with another event that occurs later in time and is discontinuous with the first event. The formation of trace memories enhances the survival of newly generated neurons in the dentate gyrus of the adult hippocampus (Gould et al., 1999a). Here we tested whether the acquisition of trace memories early during training is sufficient to enhance cell survival. We also examined whether the new neurons affected by trace memory formation persist indefinitely or only as long as the hippocampus is necessary for the expression of those memories. Groups of adult rats were injected with bromodeoxyuridine (BrdU), a marker of dividing cells, and trained 1 week later with paired stimuli using a trace eyeblink conditioning task or exposed to the same number of unpaired stimuli. Cell survival was assessed after different numbers of training trials and survival periods after training. Overall cell survival was not enhanced by exposure to 200 trials of paired stimuli during trace conditioning. However, there was a positive correlation between performance of individual animals and cell survival. In addition, exposure to 800 trials of paired stimuli during trace conditioning increased the number of BrdU-labeled cells 60 d after training. The vast majority of these cells were neurons and coexpressed the neuronal markers class IIIβ-tubulin or neuronal nuclei. These data suggest that individual differences in associative learning predict whether new neurons will survive and that once affected, these neurons remain for months and beyond the time when they are required for the retention of trace memories.

Subfields: Cognitive Neuroscience, Developmental Neuroscience, Neurology

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Citations in the corpus

New neurons and new memories: how does adult hippocampal neurogenesis affect learning and memory? (2010, background): “For example, learning of hippocampus-dependent tasks but not hippocampus-independent tasks increases the number of adult-born DGCs at around 1 week of ag”
Antidepressants increase neural progenitor cells in the human hippocampus (2009, methodology): “In rodents, stress decreases neurogenesis while antidepressants (Dranovsky and Hen 2006), environmental enrichment, exercise (Kempermann et al, 1998; van Praag et al, 1999) and learning (Leuner et al, 2004) stimulate neurogenesis.”
Adult-born hippocampal neurons are more numerous, faster-maturing and more involved in behavior in rats than in mice (2009, background): “Environmental factors such as housing enrichment, learning, and stress can all affect the survival rate of young granule cells (Kempermann et al., 1997b; Leuner et al., 2004; Snyder et al., 2009b).”
Stress and adult neurogenesis (2006, background): “, 2004) and training on learning paradigms (Leuner et al., 2004) appear to increase circulating glucocorticoid levels.”
Inhibition of neurogenesis interferes with hippocampus‐dependent memory function (2006, background): “Gould and her colleagues (Gould et al., 1999; Leuner et al., 2004) found that training adult rats on two hippocampus-dependent tasks—trace conditioning and spatial maze learning— resulted in a dramatic increase in the number of newly generated neurons in the dentate gyrus (DG) of the hippocampus…”
Adult neurogenesis: from precursors to network and physiology. (2005, background): “after acquisition of associative learning (309).”
Structural Plasticity and Hippocampal Function (2010, background): “This effect persists until the new neurons are at least two months old (Leuner et al. 2004).”
Experience-Specific Functional Modification of the Dentate Gyrus through Adult Neurogenesis: A Critical Period during an Immature Stage (2007, methodology): “A similar question has been addressed using a hippocampus-dependent learning task, trace eye-blink conditioning (Leuner et al., 2004).”
Temporal Discontiguity Is neither Necessary nor Sufficient for Learning-Induced Effects on Adult Neurogenesis (2006, background): “The timing of BrdU injection, training, and perfusion was similar to those of our previous studies, which reported increases in numbers of BrdU-labeled cells after training with trace eyeblink conditioning (Gould et al., 1999; Leuner et al., 2004).”
Long-Term Potentiation Enhances Neurogenesis in the Adult Dentate Gyrus (2006, background): “Interestingly, this long-lasting effect parallels that recently found after learning (Leuner et al., 2004).”