Research Reports - Recovery of episodic memory subprocesses in mild and complicated mild traumatic brain injury at 1 and 12 months post injury
J Clin Exp Neuropsychol. 2016 May 18:1-10. [Epub ahead of print]
Tayim FM(1), Flashman LA(1), Wright MJ(2,)(3,)(4), Roth RM(1), McAllister TW(1).
INTRODUCTION: Episodic memory complaints are commonly reported after traumatic
brain injury (TBI). The contributions of specific memory subprocesses (encoding,
consolidation, and retrieval), however, are not well understood in mild TBI
(mTBI). In the present study, we evaluated subprocesses of episodic memory in
patients with mTBI using the item-specific deficit approach (ISDA), which
analyzes responses on list learning tasks at an item level. We also conducted
exploratory analyses to evaluate the effects of complicated mTBI (comp-mTBI) on
METHOD: We compared episodic verbal memory performance in mTBI (n = 92) at
approximately 1 and 12 months post TBI, as well as in a healthy comparison (HC)
group (n = 40) at equivalent time points. Episodic memory was assessed using the
California Verbal Learning Test-2nd Edition (CVLT-II), and both standard CVLT-II
scores and ISDA indices were evaluated.
RESULTS: Compared to the HC group, the mTBI group showed significantly poorer
encoding and learning across time, as measured by ISDA and CVLT-II. Further
analyses of these mTBI subgroups [(noncomplicated mTBI (NC-mTBI, n = 77) and
comp-mTBI (n = 15)], indicated that it was the comp-mTBI group who continued to
demonstrate poorer encoding ability than the HC group. When the patient groups
were directly compared, the NC-mTBI group improved slightly on the ISDA Encoding
Deficit Index. While the comp-mTBI group worsened slightly over time, their
poorer encoding ability was not likely clinically meaningful.
CONCLUSIONS: These findings indicate that, while the NC-mTBI and HC groups'
performances were comparable by 12 months, a primary, long-term deficit in
encoding of auditory verbal information remained problematic in the comp-mTBI