Article

Executive control deficits are deleterious and enduring consequences
of moderate-severe traumatic brain injury (TBI) that disrupt everyday
functioning. Clinically, such impairments can manifest as behavioural
inconsistency, measurable experimentally by the degree of variability across
trials of a reaction time (RT) task (also known as intraindividual variability
[IIV]). Growing research on cognition after TBI points to cognitive deterioration
in the chronic stages postinjury. OBJECTIVE: To examine the longitudinal recovery
of RT characteristics (IIV and more detailed ex-Gaussian components, as well as
the number of impulsively quick responses) following moderate-severe TBI.
METHODS: Seventy moderate-severe TBI patients were assessed at 2, 5, 12, and 24+
months postinjury on a go/no-go RT task. RT indices (ex-Gaussian parameters mu
and sigma [mean and variability of the normal distribution component], and tau
[extremely slow responses]; mean, intraindividual coefficient of variation [ICV],
and intraindividual standard deviation [ISD]) were analyzed with
repeated-measures multivariate analysis of variance. RESULTS: ICV, ISD, and
ex-Gaussian tau significantly decreased (ie, improved) over time in the first
year of injury, but worsened from 1 to 2+ years, as did the frequency of
extremely fast responses. These quadratic patterns were accentuated by age and
shown primarily in tau (extremely slow) and extremely fast (impulsive) responses.
CONCLUSIONS: The pattern of early recovery followed by decline in executive
control function is consistent with growing evidence that moderate-severe TBI is
a progressive and degenerative disorder. Given the responsiveness to treatment of
executive control deficits, elucidating the trajectory and underpinnings of
inconsistent behavioral responding may reveal novel prognostic and clinical
management opportunities.

Langue : ANGLAIS