title: Persistent neuronal density changes related to the establishment of a motor memory.
abstract: Rats were trained in a lateralized reaching motor task during either an 'early' (22-31 days old) or a 'late' (62-71 days old) postnatal period. The 'late' group showed significant neuronal density reduction in cortical layers II-III of the contralateral motor forelimb representation. The 'early' group evidenced a similar localized contralateral effect that persisted after a subsequent period without training. Furthermore, in this group, a bilateral overall decrease in neuronal density was found throughout the motor cortex. This bilateral experience and age-dependent effect is conceivably related to a critical period of motor cortical development. The localized reduction of neuronal density strongly indicates a morphological expression of the motor engram. Our present study supports the concept that the acquisition and retention of motor learning involves the persistence of structural changes in the brain.
authors.affiliation: Morphology Program, Biomedical Sciences Institute, School of Medicine, University of Chile, Santiago. pmorales@machi.med.uchile.cl
authors.forename: P
authors.initials: P
authors.lastname: Morales
authors.forename: T
authors.initials: T
authors.lastname: Pinto-Hamuy
authors.forename: V
authors.initials: V
authors.lastname: Fernández
authors.forename: E
authors.initials: E
authors.lastname: Díaz
mesh_terms: D000818:Animals; D002452:Cell Count; D003216:Conditioning, Operant / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology; D018737:Hand Strength / Q000502:physiology; D008297:Male; D008568:Memory / Q000502:physiology*; D009044:Motor Cortex / Q000166:cytology* / Q000254:growth & development / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D051381:Rats