Author:

Abstract:

Traumatic brain injury (TBI) has been recognized as a major health issue and has received more and more attention in recent years. TBI has devastating acute effects and seems to initiate long-term neurodegeneration. Concussion, or mild traumatic brain injury (mTBI) is the mildest form for TBI and results in transient cognitive malfunction. The aim of this study was to investigate the nature and extent of the behavioural changes after mild traumatic brain injury (mTBI). Thirty-four female mice were included in the study. Animals received a single mild closed-head impact injury or sham surgery. We examined spatial learning acquisition, retention and reversal in a Morris water maze and assessed search strategies during task performance. Additionally, we investigated changes in conditioned learning in a contextual fear-conditioning paradigm. Results show marked but temporary deficits in spatial long-term memory. These deficits were accompanied by a relapse to less effective search strategies affecting performance after a training pause of 72 hours. Apart from cognitive deficits, results support a sub-acute, transient increase in freezing response after fear conditioning, being indicative of a stronger affective reaction to aversive stimuli after mTBI. Our findings provide further evidence that even exposure to a single-impact mTBI is sufficient to trigger marked cognitive impairments that manifest as temporary deficits in long-term memory during the early phase of spatial learning in the water maze accompanied by a decrease of spatial search strategies. In addition, mTBI results in an increased anxiety-like behaviour in response to an aversive stimulus.