Neurogenesis in the adult is involved in the formation of trace memories

Abstract

The vertebrate brain continues to produce new neurons throughout life. In the rat hippocampus, several thousand are produced each day, many of which die within weeks. Associative learning can enhance their survival; however, until now it was unknown whether new neurons are involved in memory formation. Here we show that a substantial reduction in the number of newly generated neurons in the adult rat impairs hippocampal-dependent trace conditioning, a task in which an animal must associate stimuli that are separated in time. A similar reduction did not affect learning when the same stimuli are not separated in time, a task that is hippocampal-independent. The reduction in neurogenesis did not induce death of mature hippocampal neurons or permanently alter neurophysiological properties of the CA1 region, such as long-term potentiation. Moreover, recovery of cell production was associated with the ability to acquire trace memories. These results indicate that newly generated neurons in the adult are not only affected by the formation of a hippocampal-dependent memory, but also participate in it.

Regulation of Adult Neurogenesis by Antidepressant Treatment

“…More definitive evidence for a functional role of adult neurogenesis has been reported in a recent study. In this paper Shors and Gould demonstrate that inhibition of neurogenesis by administration of a chemical cell cycle inhibitor blocks hippocampal-dependent learning (Shors et al 2001). Although there is concern about the specificity of chemical inhibitors like the one used in this study, the results provide the first direct evidence that new neurons contribute to the function of adult hippocampus.…”

“…In addition, pCREB is colocalized with polysialic acidneural cell adhesion molecular (PSA-NCAM), a marker of neurons that are maturing and/or undergoing morphogenic remodeling. Colocalization of pCREB and PSA-NCAM in BrdU-positive newborn cells is observed only during a critical period of cell maturation (one to three weeks) when the neurogenesis is required for hippocampal-dependent learning (Shors et al 2001). This suggests that pCREB may play a role in determining the functional fate of maturing neurons in adult hippocampus.…”

“…The expression of phospho-CREB, as well as PSA-NCAM during the 1 to 3-week time frame of neurogenesis, is particularly interesting in light of the recent study from Shors and Gould on neurogenesis and hippocampal-dependent learning (Shors et al 2001). They found that there was a critical period of neuronal maturation of approximately two weeks that was required for neurogenesis-dependent learning.…”

Isoflurane Anesthesia Induced Persistent, Progressive Memory Impairment, Caused a Loss of Neural Stem Cells, and Reduced Neurogenesis in Young, but Not Adult, Rodents

“…Evidence indicates that new neurons produced in the hippocampus have a functional role in cognitive processes such as learning and memory (Aimone et al, 2006;Kempermann et al, 1997;Shors et al, 2001). In our study, a stronger reduction in neurogenesis was correlated with more pronounced memory impairment.…”

Manipulation of Neural Precursors in situ Induction of Neurogenesis in the Neocortex of Adult Mice

“…Non-specifically inhibiting hippocampal neurogenesis using a systemic mitotic toxin impairs trace conditioning in a manner not seen in relevant controls, suggesting a role for newly born neurons in the formation of memories (Shors et al 2001). These results, though correlative so far, suggest that adult-born hippocampal neurons integrate functionally into the adult mammalian brain.…”