title: New hippocampal neurons are not obligatory for memory formation; cyclin D2 knockout mice with no adult brain neurogenesis show learning.
abstract: The role of adult brain neurogenesis (generating new neurons) in learning and memory appears to be quite firmly established in spite of some criticism and lack of understanding of what the new neurons serve the brain for. Also, the few experiments showing that blocking adult neurogenesis causes learning deficits used irradiation and various drugs known for their side effects and the results obtained vary greatly. We used a novel approach, cyclin D2 knockout mice (D2 KO mice), specifically lacking adult brain neurogenesis to verify its importance in learning and memory. D2 KO mice and their wild-type siblings were tested in several behavioral paradigms, including those in which the role of adult neurogenesis has been postulated. D2 KO mice showed no impairment in sensorimotor tests, with only sensory impairment in an olfaction-dependent task. However, D2 KO mice showed proper procedural learning as well as learning in context (including remote memory), cue, and trace fear conditioning, Morris water maze, novel object recognition test, and in a multifunctional behavioral system-IntelliCages. D2 KO mice also demonstrated correct reversal learning. Our results suggest that adult brain neurogenesis is not obligatory in learning, including the kinds of learning where the role of adult neurogenesis has previously been strongly suggested.
authors: Laboratory of Molecular Neurobiology, Nencki Institute, Warsaw, Poland.
authors: Piotr
authors: P
authors: Jaholkowski
authors: Anna
authors: A
authors: Kiryk
authors: Paulina
authors: P
authors: Jedynak
authors: Nada M
authors: NM
authors: Ben Abdallah
authors: Ewelina
authors: E
authors: Knapska
authors: Anna
authors: A
authors: Kowalczyk
authors: Agnieszka
authors: A
authors: Piechal
authors: Kamilla
authors: K
authors: Blecharz-Klin
authors: Izabela
authors: I
authors: Figiel
authors: Victoria
authors: V
authors: Lioudyno
authors: Ewa
authors: E
authors: Widy-Tyszkiewicz
authors: Grzegorz M
authors: GM
authors: Wilczynski
authors: Hans-Peter
authors: HP
authors: Lipp
authors: Leszek
authors: L
authors: Kaczmarek
authors: Robert K
authors: RK
authors: Filipkowski
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001007:Anxiety / Q000235:genetics; D001973:Bromodeoxyuridine / Q000378:metabolism; D003214:Conditioning, Classical / Q000502:physiology; D003216:Conditioning, Operant / Q000502:physiology; D056742:Cyclin D2; D016213:Cyclins / Q000172:deficiency*; D000089622:Doublecortin Domain Proteins; D005106:Exploratory Behavior / Q000502:physiology; D005239:Fear / Q000502:physiology; D006624:Hippocampus / Q000166:cytology*; D008124:Locomotion / Q000235:genetics; D018782:Maze Learning / Q000502:physiology; D008568:Memory / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D055495:Neurogenesis / Q000235:genetics*; D009474:Neurons / Q000502:physiology*; D009479:Neuropeptides / Q000378:metabolism; D000857:Olfaction Disorders / Q000235:genetics; D011597:Psychomotor Performance / Q000502:physiology
chemical_list: C486196:Ccnd2 protein, mouse; D056742:Cyclin D2; D016213:Cyclins; D000089622:Doublecortin Domain Proteins; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides; D001973:Bromodeoxyuridine