Negative neuroplasticity in chronic traumatic brain injury and implications for neurorehabilitation

Abstract

Based on growing findings of brain volume loss and deleterious white matter alterations during the chronic stages of injury, researchers posit that moderate-severe traumatic brain injury (TBI) may act to "age" the brain by reducing reserve capacity and inducing neurodegeneration. Evidence that these changes correlate with poorer cognitive and functional outcomes corroborates this progressive characterization of chronic TBI. Borrowing from a framework developed to explain cognitive aging (Mahncke et al., Progress in Brain Research, 157, 81-109, 2006a; Mahncke et al., Proceedings of the National Academy of Sciences of the United States of America, 103(33), 12523-12528, 2006b), we suggest here that environmental factors (specifically environmental impoverishment and cognitive disuse) contribute to a downward spiral of negative neuroplastic change that may modulate the brain changes described above. In this context, we review new literature supporting the original aging framework, and its extrapolation to chronic TBI. We conclude that negative neuroplasticity may be one of the mechanisms underlying cognitive and neural decline in chronic TBI, but that there are a number of points of intervention that would permit mitigation of this decline and better long-term clinical outcomes.

Fig. 1

Depiction of framework in context of TBI, showing neurodegeneration in chronic TBI secondary to negative learning/neuroplasticity. Figure adapted from Mahncke et al. (2006a), employing elements of the International Classification of Functioning, Disability and Health framework (World Health Organization 2013). Arrows between boxes (and within the “Changes in Brain Structure/Function” box) indicate postulated direction of causal influence, with solid arrows indicating direct influence and dashed arrow indicating modulator variables. In this adapted framework, various behavioural impairments caused by TBI result in deleterious changes in functioning and participation. As a result, negative learning creates negative neuroplastic brain changes resulting in neurodegeneration, which feed back to worsen behavioural impairments. Environmental and personal factors are posited to modulate the impact of changes in functioning on participation