Effect of Sleep on Motor Learning and Neural Activation Among Individuals with Traumatic Brain Injury

Research Objectives: To examine the effect of a 45-minute nap on motor sequence learning and neural activation compared with a 45-minute period of resting wakefulness among individuals with traumatic brain injury (TBI).

Design: Cross-sectional

Setting: Northeastern Rehabilitation Research Facility

Participants: 23 individuals with a history of TBI between the ages of 21-63 (M=45.1, SD=12.9). Females comprised 13.6 % of the sample.

Interventions: Not Applicable

Main Outcome Measures: E*Prime was used to deliver stimuli and capture the number of correct finger-tapping sequences over 12 learning trials and 6 retest trials after a 45-minute period of either sleep or relaxed wakefulness. A Siemens 3T Skyra MRI scanner was used to collect functional brain data while they completed the tapping sequence. Regressors corresponding to the time period of tapping sequence after the 45-minute Nap or Wake intervention were convolved with a canonical hemodynamic response function. The beta weights associated with the conditions of interest (tap vs non-tap) were entered in random-effects group analysis and corrected for multiple comparisons (z>2.3).

Results: Analysis of covariance demonstrated a significantly greater gain in the number of correct sequences in the Nap group (M=1.8, SD=1.7) compared with the Wake group (M=-.05, SD=2.9), controlling for age and learning capacity across training trials, F(1,18)=5.1, p=0.037. fMRI data revealed that compared with the Wake group, the Nap group had significantly greater activation in primary motor and somatosensory cortex, inferior frontal and temporal gyrus, anterior thalamus, caudate, and anterior cingulate with lesser activation in the posterior thalamus and occipital regions.

Conclusions: The sleep-dependent enhancement of motor sequence learning is consistent with prior research after TBI. The fMRI findings suggest that this effect may be associated with greater activation in the Nap group in regions implicated in memory and procedural learning with less need to rely on networks associated with working memory.

Author(s) Disclosures: Research was funded by the New Jersey Commission on Brain Injury Research. Authors have no conflicts of interest to disclose.