Effects of Subconcussive Head Trauma on the Default Mode Network of the Brain

Address correspondence to: Brian Johnson, PhD, Center for Sport Concussion Research, Department of Kinesiology, The Pennsylvania State University, 19 Recreation Building, University Park, PA 16802, E-mail: [email protected]

Introduction

There is growing concern in the neuroscience community regarding the immediate and long-lasting effects from sports-related traumatic brain injury,¹ especially the effects these may have on the risks for developing neurodegenerative diseases.² Much of the research focused on sports-related traumatic brain injuries has been centered on concussions, while little attention has been placed on subconcussive impacts. However, subconcussive blows, which are below the threshold to cause or elicit any signs of a concussion,³ should not be overlooked as insignificant. Both animal and human research have shown that subconcussive blows can cause damage to the central nervous system and pathophysiological changes in the brain despite not evoking any apparent acute behavioral changes.^4-6 These recent studies have identified that injury does not only come from full-blown concussive episodes but also from the repetitive nature of subconcussive blows.⁷ Similar to concussions, subconcussive impacts have the potential to transfer a high degree of linear and rotational acceleration forces to the brain⁸ and can cause pathophysiological changes in the brain.⁶ Yet unlike concussions, this type of repetitive head trauma in contact sports goes undiagnosed or unmanaged^9,10 leading to a large number of these insults accumulated over the course of a season, let alone a career.^9,10 Post-mortem studies have identified that repeated subconcussive impacts may have an accumulative effect,³ and it is thought they accelerate the cognitive aging process, leading to altered...