New hippocampal neurons are not obligatory for memory formation; cyclin D2 knockout mice with no adult brain neurogenesis show learning.
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.
Jaholkowski
Piotr
P
Laboratory of Molecular Neurobiology, Nencki Institute, Warsaw, Poland.
Kiryk
Anna
A
Jedynak
Paulina
P
Ben Abdallah
Nada M
NM
Knapska
Ewelina
E
Kowalczyk
Anna
A
Piechal
Agnieszka
A
Blecharz-Klin
Kamilla
K
Figiel
Izabela
I
Lioudyno
Victoria
V
Widy-Tyszkiewicz
Ewa
E
Wilczynski
Grzegorz M
GM
Lipp
Hans-Peter
HP
Kaczmarek
Leszek
L
Filipkowski
Robert K
RK
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
C486196:Ccnd2 protein, mouse; D056742:Cyclin D2; D016213:Cyclins; D000089622:Doublecortin Domain Proteins; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides; D001973:Bromodeoxyuridine