Side-bias in alcohol and heroin addicts

Crossed Eye/Hand Laterality and Left-Eyedness Predict a Positive 24-Month Outcome in Alcohol-Dependent Patients

BACKGROUND

Available predictors of hospital readmission following withdrawal in alcohol-dependent patients are limited. However, such parameters are needed to optimize individualized treatment strategies. This study investigated whether crossed eye/hand laterality, eyedness, and handedness may predict outcomes in alcohol dependence.

METHODS

The prospective study included 200 early-abstinent alcohol-dependent inpatients (n[males] = 113, n[females] = 87) and 240 control subjects (n[males] = 133, n[females] = 107). We assessed eyedness and handedness using the hole-in-the-card and Shimizu tests and documented alcohol-related readmissions over 12 and 24 months.

RESULTS

Crossed eye/hand laterality and left-eyedness were associated with a reduced risk for alcohol-related readmission (12-month: odds ratios [OR] = 0.41, p = 0.008, OR = 0.42, p = 0.004; 24-month: OR = 0.57, p = 0.097, OR = 0.47, p = 0.016), fewer median readmissions (12-month: 0 vs. 1, p = 0.005, 0 vs. 1, p = 0.005; 24-month: 1 vs. 2, p = 0.014, 1 vs. 2, p = 0.006), and more mean days to the first readmission (12-month: 270 vs. 209, p = 0.007, 269 vs. 207, p = 0.003; 24-month: 462 vs. 335, p = 0.039, 461 vs. 323, p = 0.005). They also interacted with treatment and alcohol drinking history to predict the outcome. In sex-specific analyses, most of these effects remained significant in males but not in females. Handedness alone did not significantly predict outcome. Moreover, the laterality markers did not significantly differ between alcohol-dependent patients and control subjects.

CONCLUSIONS

Determining crossed eye/hand laterality and eyedness may help to individualize relapse prevention in the future. Both are easily accessible predictors of alcohol-related readmission following inpatient withdrawal treatment.

Epigenetic regulation of lateralized fetal spinal gene expression underlies hemispheric asymmetries

Lateralization is a fundamental principle of nervous system organization but its molecular determinants are mostly unknown. In humans, asymmetric gene expression in the fetal cortex has been suggested as the molecular basis of handedness. However, human fetuses already show considerable asymmetries in arm movements before the motor cortex is functionally linked to the spinal cord, making it more likely that spinal gene expression asymmetries form the molecular basis of handedness. We analyzed genome-wide mRNA expression and DNA methylation in cervical and anterior thoracal spinal cord segments of five human fetuses and show development-dependent gene expression asymmetries. These gene expression asymmetries were epigenetically regulated by miRNA expression asymmetries in the TGF-β signaling pathway and lateralized methylation of CpG islands. Our findings suggest that molecular mechanisms for epigenetic regulation within the spinal cord constitute the starting point for handedness, implying a fundamental shift in our understanding of the ontogenesis of hemispheric asymmetries in humans.

DOI:http://dx.doi.org/10.7554/eLife.22784.001

Left-handedness is statistically linked to lifetime experimentation with illicit drugs

Handedness has been linked to an enhanced risk of alcohol abuse, while less is known about other drugs. A convenience sample of 1004 male and female Italian participants (females=58%) from the general community (18 to 65 years old: average age = 30; standard deviation = 10, median = 25) was asked about: handedness (preference in writing); lifetime use of alcohol, tobacco, and illicit drugs; levels of psychological distress, as measured by the General Health Questionnaire (GHQ); and levels of delusion proneness, as measured by the Peters et al. Delusions Inventory (PDI). Overall, 92 individuals (9.2%) were classified as left-handed, with no significant difference reported among genders. Lifetime use of illicit drugs, primarily cannabis, was reported by 20% of the sample. In a multiple logistic regression analysis, after taking into account sex, age, and caseness on GHQ and PDI, left-handed people in the sample were statistically more likely to report lifetime experimentation with heroin, ecstasy/amphetamine, and, marginally, hallucinogens, but not alcohol or tobacco. Different mechanisms might contribute to an explanation of greater lifetime experimentation with some illicit drugs among left-handed people as compared to right-handed people. However, replications with clinical samples are necessary before any definitive statements can be made.

Detour behavior changes associated with prenatal morphine exposure in 11-day-old chicks

The central nervous system exhibits remarkable plasticity in early life. Prenatal morphine exposure may induce adverse behavioral effects on the neonate and the developing offspring. In the present study, we investigated the effect of prenatal morphine exposure (daily from embryonic days 12-16, 20mg/kg) on 11-day-old chicks using two forms of spatial paradigms: one trial detour behavior task in which animals must bypass an obstacle to reach the desired goal without any training and detour learning task which required several trials of training to reach the detour criterion. The results showed that, on the condition that chicks could successfully detour in the first trial, morphine exposed chicks exhibited longer detour latency to finish the task, coupled by a preference for turning right versus turning left. In contrast, no significant difference in learning and memory was found in detour learning task between morphine exposed chicks and saline chicks. These findings suggest specific behavioral changes associated with prenatal exposure to opioids during mid to late gestation, also raise attention to the possible health hazard from pregnancy drug use in everyday life.

Neurocognitive characterizations of Russian heroin addicts without a significant history of other drug use

Research on the neurocognitive characteristics of heroin addiction is sparse and studies that do exist include polydrug abusers; thus, they are unable to distinguish neurocognitive effects of heroin from those of other drugs. To identify neurocognitive correlates specific to heroin addiction, the present study was conducted in St. Petersburg, Russia where individuals typically abuse and/or become addicted to only one substance, generally alcohol or heroin. Heroin addicts were recruited from an inpatient treatment facility in St. Petersburg. Three comparison groups included alcoholics, addicts who used both alcohol and heroin, and non-abusers. Psychiatric, background, and drug history evaluations were administered after detoxification to screen for exclusion criteria and characterize the sample. Executive Cognitive Functions (ECF) that largely activate areas of the prefrontal cortex and its circuitry measured include complex visual pattern recognition (Paired Associates Learning), working memory (Delayed Matching to Sample), problem solving (Stockings of Cambridge), executive decision making (Cambridge Decision Making Task), cognitive flexibility (Stroop Color-Word Task) and response shifting (Stop Change Task). In many respects, the heroin addicts were similar to alcohol and alcohol+heroin dependent groups in neurocognitive deficits relative to controls. The primary finding was that heroin addicts exhibited significantly more disadvantageous decision making and longer deliberation times while making risky decisions than the other groups. Because the nature and degree of recovery from drug abuse are likely a function of the type or pattern of neurocognitive impairment, differential drug effects must be considered.

Laterality and accident proneness: A study of locomotive drivers

This study attempted to find the association between four measures of laterality (handedness, footedness, eyedness, and earedness) and accident proneness in locomotive drivers. The Sidedness Bias Schedule was administered to a sample of 80 locomotive drivers to ascertain their preferential bias. Their accident records were also available. Positive correlations were mostly found between the measures of hand, foot, ear, and eye dominance. Analyses suggested that there was a higher accident rate among left-handers and left-footers, with multiple regression unable to determine whether handedness or footedness was related more strongly to accident proneness. However, it was clear that accident rate was primarily associated with direction of lateralisation, and not with degree of lateralisation. Drivers with left-handedness were more likely to be involved in accidents, and it is possible that that may be related to the design of the locomotive cabs.