Adam C. Raikes

Chronic sleep restriction differentially affects implicit biases toward food among men and women: preliminary evidence

Chronic sleep restriction and obesity are two major public health concerns. This study investigated how chronic sleep restriction changes implicit attitudes towards low‐ and high‐calorie foods. In a randomized, counterbalanced cross‐over design, 17 participants (eight females, nine males) underwent two laboratory testing sessions where they were either sleep‐restricted for 3 weeks (i.e. underwent three weekly cycles of 5 nights of 4 h of sleep followed by 2 nights of 8 h of sleep opportunity) or received 3 weeks of control sleep (i.e. 8 h of sleep opportunity per night for 3 weeks). There was evidence for a significant sleep condition x sex interaction (F(1, 20) = 4.60, P = 0.04). After chronic sleep restriction, men showed a trend towards a significant decrease in their implicit attitudes favouring low‐calorie foods (P = 0.08), whereas women did not show a significant change (P = 0.16). Men may be at increased risk of weight gain when sleep‐deprived due to a reduced bias towards low‐calorie foods.

Evidence of Actigraphic and Subjective Sleep Disruption Following Mild Traumatic Brain Injury

OBJECTIVE/BACKGROUNDnMild traumatic brain injuries (mTBI) are frequently associated with long-term, self-reported sleep disruption. Objective corroboration of these self-reports is sparse and limited by small sample sizes. The purpose of this study was to report on actigraphically-measured sleep outcomes in individuals with and without a history of recent mTBI in two U.S. cities (Boston, MA and Tucson, AZ).nnnPATIENTS/METHODSnFifty-eight individuals with a recent (within 18 months) mTBI and 35 individuals with no prior mTBI history were recruited for one of four studies across two sites. Participants completed a minimum of one week of actigraphy. Additionally, mTBI participants self-reported daytime sleepiness, sleep disruption, and functional sleep-related outcomes.nnnRESULTSnIn Boston, mTBI participants obtained less average sleep with shorter sleep onset latencies (SOL) than healthy individuals. In Tucson, mTBI participants had greater SOL and less night-to-night SOL variability compared to healthy individuals. Across mTBI participants, SOL was shorter and night-to-night SOL variability was greater in Boston than Tucson. Sleep efficiency (SE) variability was greater in Tucson than Boston across both groups. Only SOL variability was significantly associated with daytime sleepiness (rxa0=xa00.274) in the mTBI group after controlling for location.nnnCONCLUSIONnSleep quality, SOL and SE variability, are likely affected by mTBIs. Between-group differences in each site existed but went in opposite directions. These findings suggest the possibility of multiple, rather than a singular, profiles of sleep disruption following mTBI. Precision medicine models are warranted to determine whether multiple sleep disruption profiles do indeed exist following mTBI and the predisposing conditions that contribute to an individuals experience of sleep disruption.

Chronic sleep restriction affects the association between implicit bias and explicit social decision making

Objectives: Previous work suggests that sleep restriction (SR) reduces cognitive control and may increase negative implicit biases. Here we investigated whether SR might influence decision making on a social‐evaluative task where individuals had to make judgments of threat based on facial photographs. Furthermore, we investigated the effect of changes in negative implicit biases as a result of sleep restriction on this decision‐making task. Design: Fourteen healthy adults underwent two 3‐week counterbalanced in‐laboratory stays (chronic SR and control sleep [CS] conditions). Participants completed the Arab Muslim Names implicit association test (a measure of implicit bias/attitudes toward Arab Muslims) and the Karolinska Airport Task (a measure of explicit decision making). The Karolinska Airport Task requires participants to judge the potential dangerousness of individuals based on facial photographs. Results: After SR, participants were more likely to deem individuals with less positive and more negative facial features as dangerous than after CS. In addition, after SR, those participants showing higher negative implicit bias toward Arab Muslims tended to consider as more dangerous individuals with more quintessentially untrustworthy facial features (r = 0.76, P = .007), whereas this relationship was nonsignificant after CS (r = 0.33, P = .28). Conclusions: These findings show not only that SR may increase implicit biases against a particular minority group but that SR also modifies how individuals make explicit decisions about anothers trustworthiness based on facial features. These findings may have important implications for many occupations where workers who are routinely restricted of sleep are also responsible for making judgments about other peoples trustworthiness (eg, police, security, military personnel).

The Relationship Between General Intelligence and Cortical Structure in Healthy Individuals

Considerable work in recent years has examined the relationship between cortical thickness (CT) and general intelligence (IQ) in healthy individuals. It is not known whether specific IQ variables (i.e., perceptual reasoning [PIQ], verbal comprehension IQ [VIQ], and full-scale IQ [FSIQ]) are associated with multiple cortical measures (i.e., CT, cortical volume (CV), cortical surface area (CSA) and cortical gyrification (CG)) within the same individuals. Here we examined the association between these neuroimaging metrics and IQ in 56 healthy adults. At a cluster-forming threshold (CFT) of pu202f<u202f0.05, we observed significant positive relationships between CT and all three IQ variables in regions within the posterior frontal and superior parietal lobes. Regions within the temporal and posterior frontal lobes exhibited positive relationships between CV and two IQ variables (PIQ and FSIQ) and regions within the inferior parietal lobe exhibited positive relationships between CV and PIQ. Additionally, CV was positively associated with VIQ in the left insula and with FSIQ within the inferior frontal gyrus. At a more stringent CFT (pu202f<u202f0.01), the CT-PIQ, CT-VIQ, CT-FSIQ, and CV-PIQ relationships remained significant within the posterior frontal lobe, as did the CV-PIQ relationship within the temporal and inferior parietal lobes. We did not observe statistically significant relationships between IQ and either CSA or CG. Our findings suggest that the neural basis of IQ extends beyond previously observed relationships with fronto-parietal regions. We also conclude that CT and CV may be more useful metrics than CSA or CG in the study of intellectual abilities.

Diffusion Tensor Imaging (DTI) Correlates of Self-Reported Sleep Quality and Depression Following Mild Traumatic Brain Injury

Background: Mild traumatic brain injuries (mTBIs) are a significant social, sport, and military health issue. In spite of advances in the clinical management of these injuries, the underlying pathophysiology is not well-understood. There is a critical need to advance objective biomarkers, allowing the identification and tracking of the long-term evolution of changes resulting from mTBI. Diffusion-weighted imaging (DWI) allows for the assessment of white-matter properties in the brain and shows promise as a suitable biomarker of mTBI pathophysiology. Methods: 34 individuals within a year of an mTBI (age: 24.4 ± 7.4) and 18 individuals with no history of mTBI (age: 23.2 ± 3.4) participated in this study. Participants completed self-report measures related to functional outcomes, psychological health, post-injury symptoms, and sleep, and underwent a neuroimaging session that included DWI. Whole-brain white matter was skeletonized using tract-based spatial statistics (TBSS) and compared between groups as well as correlated within-group with the self-report measures. Results: There were no statistically significant anatomical differences between the two groups. After controlling for time since injury, fractional anisotropy (FA) demonstrated a negative correlation with sleep quality scores (higher FA was associated with better sleep quality) and increasing depressive symptoms in the mTBI participants. Conversely, mean (MD) and radial diffusivity (RD) demonstrated positive correlations with sleep quality scores (higher RD was associated with worse sleep quality) and increasing depressive symptoms. These correlations were observed bilaterally in the internal capsule (anterior and posterior limbs), corona radiata (anterior and superior), fornix, and superior fronto-occipital fasciculi. Conclusion: The results of this study indicate that the clinical presentation of mTBI, particularly with respect to depression and sleep, is associated with reduced white-matter integrity in multiple areas of the brain, even after controlling for time since injury. These areas are generally associated not only with sleep and emotion regulation but also cognition. Consequently, the onset of depression and sleep dysfunction as well as cognitive impairments following mTBI may be closely related to each other and to white-matter integrity throughout the brain.

Elevated aggression and reduced white matter integrity in mild traumatic brain injury: A DTI study

Mild traumatic brain injury (mTBI) remains the most commonly reported head injury in the United States, and is associated with a wide range of post-concussive symptoms including physical, cognitive and affective impairments. Elevated aggression has been documented in mTBI; however, the neural mechanisms associated with aggression at the chronic stage of recovery remain poorly understood. In the present study, we investigated the association between white matter integrity and aggression in mTBI using diffusion tensor imaging (DTI). Twenty-six age-matched adults participated in the study, including 16 healthy controls (HCs) and 10 individuals in the chronic stage of recovery (either 6-months or 12 months post-mTBI). Psychological measures of aggression included the Buss-Perry Aggression Questionnaire and the Personality Assessment Inventory (PAI). Axonal pathways implicated in affective processing were studied, including the corpus callosum, anterior thalamic radiation, cingulum and uncinate fasciculus, and measures of white matter integrity included fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD). We found that adults with mTBI in the chronic stage of recovery had higher levels aggression. Individuals with mTBI also had greater RD in the corpus callosum compared to HCs, indicating reduced fiber integrity. Furthermore, we observed a significant association between reduced white matter integrity in the corpus callosum and greater aggression. Our findings provide additional evidence for underlying neuroanatomical mechanisms of aggression, although future research will be necessary to characterize the specific relationship between aggression and the white matter pathways we identified.

Potential for the development of light therapies in mild traumatic brain injury

Light affects almost all aspects of human physiological functioning, including circadian rhythms, sleep–wake regulation, alertness, cognition and mood. We review the existing relevant literature on the effects of various wavelengths of light on these major domains, particularly as they pertain to recovery from mild traumatic brain injuries. Evidence suggests that light, particularly in the blue wavelengths, has powerful alerting, cognitive and circadian phase shifting properties that could be useful for treatment. Other wavelengths, such as red and green may also have important effects that, if targeted appropriately, might also be useful for facilitating recovery. Despite the known effects of light, more research is needed. We recommend a personalized medicine approach to the use of light therapy as an adjunctive treatment for patients recovering from mild traumatic brain injury.

Concussion history is negatively associated with visual-motor force complexity: evidence for persistent effects on visual-motor integration

ABSTRACT Objectives: Long-term monitoring of concussion recovery requires time- and cost-effective methods. Physiologic complexity may be useful in evaluating visual-motor integration following concussion. The purpose of this study was to quantify the extent to which prior number of concussions influenced visual-motor tracking force complexity. Methods: Thirty-five individuals with a self-reported concussion history (age: 20.92 ± 1.98) and 15 without (age: 20.92 ± 2.21) performed an isometric visual-motor tracking task, using index finger force to trace a straight line across a computer screen. Finger force root mean square error (RMSE), multi-scale complexity, and average power from 0 to 12 Hertz (Hz) were calculated. Individual multiple regressions were fit to these outcomes. Results: Force complexity decreased linearly with an increasing number of concussions (R2 = 0.101). Males had more complex force overall (R2 = 0.219) and greater 4–8 Hz average power (R2 = 0.193). The 8–12 Hz average power decreased significantly for individuals with prior loss of consciousness (LOC) and increasing numbers of concussions (R2 = 0.143). Conclusion: Individuals exhibited linear decreases in visual-motor tracking force complexity with increasing numbers of concussions, influenced by both gender and a history of LOC. These findings indicate cumulative changes in the ways in which previously concussed individuals process and integrate visual information to guide behaviour.