A Rapid Form of Offline Consolidation in Skill Learning.

The brain strengthens memories through consolidation, defined as resistance to interference (stabilization) or performance improvements between the end of a practice session and the beginning of the next (offline gains) [1]. Typically, consolidation has been measured hours or days after the completion of training [2], but the same concept may apply to periods of rest that occur interspersed in a series of practice bouts within the same session. Here, we took an unprecedented close look at the within-seconds time course of early human procedural learning over alternating short periods of practice and rest that constitute a typical online training session. We found that performance did not markedly change over short periods of practice. On the other hand, performance improvements in between practice periods, when subjects were at rest, were significant and accounted for early procedural learning. These offline improvements were more prominent in early training trials when the learning curve was steep and no performance decrements during preceding practice periods were present. At the neural level, simultaneous magnetoencephalographic recordings showed an anatomically defined signature of this phenomenon. Beta-band brain oscillatory activity in a predominantly contralateral frontoparietal network predicted rest-period performance improvements. Consistent with its role in sensorimotor engagement [3], modulation of beta activity may reflect replay of task processes during rest periods. We report a rapid form of offline consolidation that substantially contributes to early skill learning and may extend the concept of consolidation to a time scale in the order of seconds, rather than the hours or days traditionally accepted.

Sensorimotor Oscillatory Phase-Power Interaction Gates Resting Human Corticospinal Output.

Oscillatory activity within sensorimotor networks is characterized by time-varying changes in phase and power. The influence of interactions between sensorimotor oscillatory phase and power on human motor function, like corticospinal output, is unknown. We addressed this gap in knowledge by delivering transcranial magnetic stimulation (TMS) to the human motor cortex during electroencephalography recordings in 20 healthy participants. Motor evoked potentials, a measure of corticospinal excitability, were categorized offline based on the mu (8-12 Hz) and beta (13-30 Hz) oscillatory phase and power at the time of TMS. Phase-dependency of corticospinal excitability was evaluated across a continuous range of power levels using trial-by-trial linear mixed-effects models. For mu, there was no effect of PHASE or POWER (P > 0.51), but a significant PHASE × POWER interaction (P = 0.002). The direction of phase-dependency reversed with changing mu power levels: corticospinal output was higher during mu troughs versus peaks when mu power was high while the opposite was true when mu power was low. A similar PHASE × POWER interaction was not present for beta oscillations (P > 0.11). We conclude that the interaction between sensorimotor oscillatory phase and power gates human corticospinal output to an extent unexplained by sensorimotor oscillatory phase or power alone.

Race and Ethnicity Do Not Clinically Associate with Quality of Life Among Patients with Chronic Severe Pain in a Federally Qualified Health Center.

Objective: Previous research suggests that race/ethnicity predicts health-related quality of life (HRQL) in chronic pain populations but has not examined this in community settings. This study evaluated this association in 522 community-dwelling patients with chronic pain treated at a Federally Qualified Health Center (FQHC). Design: Cross-sectional secondary analysis. Setting: Six practice sites of an FQHC in New York. Subjects: One hundred forty-two non-Hispanic blacks, 121 non-Hispanic whites, 219 Hispanics, and 40 classified as "other" with severe chronic pain. Methods: Patients with chronic severe pain (three or more months with worst pain ≥ 4/10 or T-score > 60.5 on the Patient-Reported Outcomes Measurement Information System pain interference tool) were interviewed as part of a clinical trial. Race/ethnicity and other potential predictors of HRQL were assessed. Results: Mean age was 53.0 years, and 70.1% were women; 62.8% earned less than $10,000 per year, and 22.8% were Spanish-speaking with low acculturation. Mean worst pain during the past week was 8.6/10, and 39.6% used opioids. In multivariate analyses, race/ethnicity was not significantly associated with mental HRQL. Hispanics had significantly lower physical HRQL than non-Hispanic whites or blacks, but this difference was not clinically meaningful (mean T-scores = 33.9 [Hispanics], 35.8 [non-Hispanic whites], and 35.6 [non-Hispanic blacks]). Mental HRQL was predicted by depression, anxiety, pain disability, income, and physical HRQL; physical HRQL was predicted by race/ethnicity, anxiety, pain disability, age, care satisfaction, and mental HRQL. Conclusions: Race/ethnicity does not explain important variation in HRQL reported by diverse patients with chronic pain. Psychological distress, pain disability, age, and socioeconomic status predicted this health outcome. Future studies may clarify modifiers of these associations to guide treatment in FQHC populations.