Spatial Memory Deficits and Their Correlations with Clusters of Shrunken Neuronal Soma in the Cortices and Limbic System Following a “Mild’’ Mechanical Impact to the Dorsal Skull in Female Rats

Wudu E Lado,Michael A Persinger

doi:10.4236/jbbs.2012.23038

Abstract

Background: Previous results showed that quantitative changes in behavioural accuracies by rats that sustained a “mild” closed head injury were moderately correlated with the total areas (numbers) of anomalous neuronal soma within regions below the impact. Method: Water maze behavioural measures within one day or two months after a single impact of mechanical force over the right dorsal skull, with or without stunning and with or without subsequent pregnancy, were measured and compared to proportions of anomalous neurons under the impact site. Results: The consequences of the impact accommodated about 20% of the variance in the rats’ scores for less proficient spatial learning and memory. There were significantly more anomalous cells within right hemisphere below the impact site that were correlated with poorer initial maze learning. Maternal experience reduced the numbers of anomalous cells in the right limbic area only. Conclusion: These results suggest weak mechanical impacts produce changes in histomorphology within some neurons that are still evident two months later and that the presence of these anomalous clusters, corresponding to less than 1% of the cross-sectional area and below the resolution of contemporary MRI in human cases, are strongly correlated with specific behavioural impairments.

Highlights

The recent interest in “concussive” injuries from explosive devices or body impacts during sporting events reflects the intrinsic epidemic of these types of injuries
The animals had access to food and tap water ad libitum except when their weights were measured every two days and when they were removed for testing in another room containing a custom-built Morris Water Maze
Weight losses by closed head injuries (CHI) rats compared to controls were apparent for the days after the treatments but were no longer apparent two weeks after the treatment or after weaning of offspring for the maternal study

Summary

Introduction

The recent interest in “concussive” injuries from explosive devices or body impacts during sporting events reflects the intrinsic epidemic of these types of injuries. In addition to behavioural and emotional alterations [3], cognitive domains that include learning and memory are often compromised The magnitude of these cognitive deficits has been considered a function of the severity and location of the cerebral injury. These cognitive alterations strongly influence the individual’s probabilities to return to the premorbid status. Conclusion: These results suggest weak mechanical impacts produce changes in histomorphology within some neurons that are still evident two months later and that the presence of these anomalous clusters, corresponding to less than 1% of the cross-sectional area and below the resolution of contemporary MRI in human cases, are strongly correlated with specific behavioural impairments

Methods

Results

Discussion

Conclusion