Apparent diffusion coefficient changes in human brain during sleep - Does it inform on the existence of a glymphatic system?

The role of sleep in brain physiology is poorly understood. Recently rodent studies have shown that the glymphatic system clears waste products from brain more efficiently during sleep compared to wakefulness due to the expansion of the interstitial fluid space facilitating entry of cerebrospinal fluid (CSF) into the brain. Here, we studied water diffusivity in the brain during sleep and awake conditions, hypothesizing that an increase in water diffusivity during sleep would occur concomitantly with an expansion of CSF volume - an effect that we predicted based on preclinical findings would be most prominent in cerebellum. We used MRI to measure slow and fast components of the apparent diffusion coefficient (ADC) of water in the brain in 50 healthy participants, in 30 of whom we compared awake versus sleep conditions and in 20 of whom we compared rested-wakefulness versus wakefulness following one night of sleep-deprivation. Sleep compared to wakefulness was associated with increases in slow-ADC in cerebellum and left temporal pole and with decreases in fast-ADC in thalamus, insula, parahippocampus and striatal regions, and the density of sleep arousals was inversely associated with ADC changes. The CSF volume was also increased during sleep and was associated with sleep-induced changes in ADCs in cerebellum. There were no differences in ADCs with wakefulness following sleep deprivation compared to rested-wakefulness. Although we hypothesized increases in ADC with sleep, our findings uncovered both increases in slow ADC (mostly in cerebellum) as well as decreases in fast ADC, which could reflect the distinct biological significance of fast- and slow-ADC values in relation to sleep. While preliminary, our findings suggest a more complex sleep-related glymphatic function in the human brain compared to rodents. On the other hand, our findings of sleep-induced changes in CSF volume provide preliminary evidence that is consistent with a glymphatic transport process in the human brain.

Emotion Recognition Biases in Alcohol Use Disorder.

BACKGROUND: Alcohol use disorder (AUD) has been associated with impairments in cognitive and emotional function, including difficulty identifying emotional facial expressions. However, it is unclear whether these deficits are associated with alcohol consumption or related anxious and depressive symptoms. METHODS: We compared the recognition of emotional faces expressing happiness, surprise, sadness, fear, anger, and disgust in 19 AUD participants and 19 healthy volunteers using the Cambridge Neuropsychological Test Automated Battery Emotion Recognition Task. We analyzed group differences in response latency, accuracy, and misidentification patterns (as defined by the tendency to mislabel facial expressions as exhibiting specific emotions). To assess whether misidentification patterns were associated with drinking severity, we also examined associations with alcohol consumption over the past 90 days. RESULTS: There were no differences in response latency or accuracy between groups. However, there were group differences in misidentification patterns. While controls tended to misidentify emotional expressions as happy, those with AUD tended to misidentify expressions as angry or disgusted. In AUD participants, the degree to which individuals were biased toward anger or disgust was positively correlated with the number of drinks they consumed in the past 90 days but was not associated with depression or anxiety scores. CONCLUSIONS: Our findings suggest that individuals with AUD have a bias toward misidentifying emotional facial expressions as hostile, which is not mediated by associated mood changes. This provides further evidence of disrupted social cognition in AUD.

Impact of sugar on the body, brain, and behavior.

Sugar is highly palatable and rewarding, both in its taste and nutritive input. Excessive sugar consumption, however, may trigger neuroadaptations in the reward system that decouple eating behavior from caloric needs and leads to compulsive overeating. Excessive sugar intake is in turn associated with adverse health conditions, including obesity, metabolic syndrome, and inflammatory diseases. This review aims to use recent evidence to connect sugar's impact on the body, brain, and behavior to elucidate how and why sugar consumption has been implicated in addictive behaviors and poor health outcomes.