Delayed voluntary physical exercise restores when and where object recognition memory after traumatic brain injury

Physical exercise has been associated with improved cognition and may even reduce memory deficits after brain injuries. The aims of this work were to: 1) assess whether voluntary physical exercise can reduce the deficits associated with traumatic brain injury (TBI) in two different components of episodic-like memory based on object recognition, temporal order memory (when), and object location memory (where); and 2) determine whether changes in levels of brain-derived neurotrophic factor (BDNF) in the hippocampus and prefrontal cortex, as well as alterations in hippocampal cytokines, insulin-like growth factor-1 (IGF-1) and vascular endothelial growth factor (VEGF), may influence the effects exercise has on either or both tasks. The rats were distributed into a sham group, a TBI group that remained sedentary (TBI-sed), and a TBI group that had access to a running wheel for a 25-day period from post-injury day 11 (TBI-exe). The rats were sacrificed after the where memory task, at post-injury day 37. Physical exercise restored the when and where memories, which had been impaired by the TBI, and increased the concentration of BDNF in the hippocampus, but not the prefrontal cortex. Neither TBI nor exercise were found to significantly affect hippocampal cytokines, IGF-1 or VEGF at this time post-injury. BDNF levels showed significant positive correlations with exercise, and with when (but not where) memory. These results indicate that post-injury physical exercise restores when and where object recognition memory tasks after TBI, and that increased BDNF seems to be involved in this effect, particularly with regard to when memory.

Automated summary

Physical exercise can reduce memory deficits after traumatic brain injury, particularly in episodic-like memory tasks related to object recognition. This effect is associated with increased levels of BDNF in the hippocampus and the restoration of temporal order memory.