With participation in sport being an increasingly popular interest among individuals of all ages, sport-related injuries are undoubtedly becoming a serious issue. In particular, sport-related concussions (i.e. complex effect on the brain resulting from serious biomechanical force, such as a blow to the head) represent a serious problem, with 15 to 20% of all annual concussions in the United States being attributed to sport participation (Kraus, 1995). Due to the relatively quick return to pre-injury functioning (i.e. 7 to 10 days), concussions are often looked at by the general public as an acute (i.e. temporary) problem. However, research in the area has argued for a number of chronic (i.e. long-lasting) nervous system dysfunctions and cognitive deficits to occur following these injuries. For instance, research using Event-Related Potentials (ERPs) has detected deficits in processes associated with memory, perception and attention following concussions (Broglio, Moore & Hillman, 2011).
Event-Related Potentials are specific patterns of electrical activity which occur across the scalp in response to particular events, and are thought to reflect either automatic processing or higher-order cognitive processing (i.e. requiring explicit activation by the individual) of those events. They are measured using electroencephalography (EEG), which records this electrical activity through various small electrodes placed on the scalp. Although ERPs have been used to demonstrate the long-term effects of concussion on various neurocognitive processes, few previous studies had considered the effect on sensory functioning, particularly visual processing.
The current study by Moore, Broglio & Hillman (2014) was thus interested in using ERPs to determine whether sport-related concussions may lead to chronic impairment in visual processing. In particular, they were interested in visual-evoked potentials (VEPs), electrical signals which represent the automatic (i.e. passive) processing of visual stimuli that affect the parietal-occipital region of the brain. To do so, they compared adults with a history of sport-related concussions on average 6.7 years after their last injury (N=18) to adult controls (with no history of concussion or related symptoms; N=18) on their VEP activity during a pattern-reversal task. In this task, a complex pattern (i.e. a 6×6 checkered box containing black and white squares) is continuously reversed in spatial position—with black squares changing to white squares and vice versa—at a rate of 2 cycles per second. The participant is asked to simply keep both eyes fixated on a point in the center of this pattern. This task is used extensively to measure visual processing, and is associated with a specific VEP component known as the P1. Notably, the P1 is automatic and is thought to represent the functioning of the specific pathway in the brain (i.e. the geniculostriatal pathway) responsible for facilitating visual processing.
The results of this study showed that participants with a history of sport-related concussion showed a lower P1 amplitude, which is argued to reflect the degeneration of neurons (i.e. the dying off of neurons), and suggests that sport-related concussions may in fact impair visual processing. Furthermore, the results showed no significant relationship between the P1 and the time from last injury, number of injuries, or loss of consciousness. These findings suggest that a single sport-related concussion is sufficient to produce long-lasting deficits in visual processing. More generally, the authors suggest that the findings of this study may help to explain the higher-order neurological deficits that have been shown to be characteristic of concussions (e.g. memory and attention deficits). In particular, they argue that these higher-order deficits may simply reflect deficits in lower-level sensory processing, like the automatic visual processing that was looked at in the current study. That is, they argue that individuals who have suffered a concussion may not be capturing sensory information sufficiently, which is ultimately leading to larger-scale deficits in cognitive processes. Importantly, these findings contribute to the knowledge of the specific deficits associated with concussion, including their time-course of development, and thus they have large practical implications for individuals at-risk of concussion injuries (e.g. athletes, military personnel). Furthermore, these findings point to the importance of attending to lower-order sensory functioning (i.e. visual processing) in individuals recovering from such injuries.
References
Broglio, S.P., Moore, R.D., Hillman, C.H. (2011). A history of sport-related concussion on event-related brain potential correlates of cognition. International Journal of Psychophysiology, 82(1), 16–23.
Kraus, J.F. (1995). Epidemiological features of brain injury in childhood: occurrence, children at risk, causes and manner of injury, severity and outcomes. In Broman, S.H., & Michel, M.E., (Eds). Traumatic Head Injury in Children. New York, NY: Oxford University Press, pp 22–39.
Moore, R.D., Broglio, S.P., & Hillman, C.H. (2014). Sport-Related Concussions and Sensory Function in Young Adults. Journal of Athletic Training, 49(1), 36-41.
