Adult Hippocampal Neurogenesis in Different Taxonomic Groups: Possible Functional Similarities and Striking Controversies.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing cross-species comparative biology and theoretical models without primary empirical data or systematic review methodology.
PubMed 30764477 · doi:10.3390/cells8020125
What was done
This narrative review compared and synthesized literature on adult hippocampal neurogenesis across diverse taxonomic groups, ranging from fish to birds, rodents, primates, and humans. It evaluated proposed cognitive roles, computational models of pattern separation, and the controversy surrounding the presence or absence of adult neurogenesis in primates and humans.
What was found
The abstract reports no numerical metrics or statistical findings. It notes a general cross-species pattern wherein the number of neurogenic zones and the ratio of newly added neurons to existing circuitry decrease with increasing brain complexity. While continuous adult neurogenesis is linked to spatial navigation and cognitive processes in birds and rodents, no literature directly links it to spatial navigation and memory in primates or humans. The authors highlight recent debates suggesting neurogenesis is extremely rare or absent in the adult primate and human hippocampus, contrasting with computational models that assign it a central role in learning, memory, and pattern separation.
Why it matters
The paper contextualizes the evolutionary divergence of adult neurogenesis, emphasizing that functional roles established in rodents and birds cannot be assumed to apply directly to adult humans.
Limits
The abstract describes a narrative review without systematic search criteria or quantitative synthesis. It provides no primary experimental data or specific quantitative measures, and evidence regarding human adult neurogenesis remains conflicting and indirect.
Cited by
- supports Whether adult neurogenesis occurs in the human brain remains an unresolved scientific debate.