Speed of processing and strategic control of attention after traumatic brain injury.
BACKGROUND
Slowed information processing speed has consistently been documented after traumatic brain injury (TBI). Debate continues as to whether deficits in strategic control are proportionate to, or remain after controlling for, reduced speed of processing. The study aim was to investigate the association of speed of processing and strategic control of attention with working memory, selective attention, response inhibition, and mental flexibility task performance after TBI using traditional and novel clinical measures.


METHODS
Twenty-five individuals with complicated mild to severe TBI (post-traumatic amnesia duration, M = 39.52 days, SD = 38.34; worst Glasgow Coma Scale score, M = 7.33, SD = 4.35; time post-injury, M = 392.64 days, SD = 537.19) and 25 matched healthy controls completed assessment of attentional and executive functioning. Measures included the Symbol Digit Modalities Test (SDMT), the computerized Selective Attention Task (SAT), the Ruff 2&7 Selective Attention Test (2&7), the visual n-back, Digit Span, Hayling Test, and Trail Making Test (TMT).


RESULTS
t tests revealed that individuals with TBI demonstrated reduced processing speed on the SDMT, n-back, SAT, 2&7, Hayling Test, and TMT-A (p ≤ .002 for all). Digit Span performance did not differ between groups. Mixed-model ANOVAs revealed that individuals with TBI demonstrated a disproportionate increase in reaction time with complexity, which was accounted for by speed on the SAT but remained on the Hayling Inhibition Test after controlling for speed in ANCOVAs. Mann-Whitney U tests revealed that individuals with TBI also made more errors on the Hayling Test, missed responses on the n-back and were unable to benefit from the automatic condition of the 2&7.


CONCLUSIONS
While slowed speed of information processing was pervasive across tasks after TBI, residual difficulties in response inhibition remained after controlling for slowness, which suggests impaired strategic control. These findings support targeted intervention for slowed speed of thinking and inhibition following TBI.
a School of Psychological Sciences, Monash University , Clayton , VIC , Australia.|b Monash-Epworth Rehabilitation Research Centre, Epworth HealthCare , Richmond , VIC , Australia.
Alicia Rhian
AR
Dymowski
a School of Psychological Sciences, Monash University , Clayton , VIC , Australia.|b Monash-Epworth Rehabilitation Research Centre, Epworth HealthCare , Richmond , VIC , Australia.
Jacqueline Anne
JA
Owens
a School of Psychological Sciences, Monash University , Clayton , VIC , Australia.|b Monash-Epworth Rehabilitation Research Centre, Epworth HealthCare , Richmond , VIC , Australia.|c Centre of Excellence in Traumatic Brain Injury Rehabilitation, National Trauma Research Institute , Alfred Hospital, Prahran , VIC , Australia.
Jennie Louise
JL
Ponsford
a School of Psychological Sciences, Monash University , Clayton , VIC , Australia.|b Monash-Epworth Rehabilitation Research Centre, Epworth HealthCare , Richmond , VIC , Australia.
Catherine
C
Willmott
D000293:Adolescent; D000328:Adult; D000368:Aged; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000209:etiology*; D001930:Brain Injuries / Q000150:complications*; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology*; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D008606:Mental Processes / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D011597:Psychomotor Performance / Q000502:physiology*; D011932:Reading; D018709:Statistics, Nonparametric; D015599:Trauma Severity Indices; D055815:Young Adult
Attention; Information processing speed; Strategic control; Traumatic brain injury; Working memory