Alcohol breaks down interhemispheric inhibition in females but not in males: alcohol and frontal connectivity

Cortical paired associative stimulation shows impaired plasticity of inhibition networks as a function of chronic alcohol use

BACKGROUND

Response inhibition - or the ability to withhold a suboptimal response - relies on the efficacy of fronto-striatal networks, and is impaired in neuropsychiatric disorders including addiction. Cortical paired associative stimulation (cPAS) is a form of transcranial magnetic stimulation (TMS) which can strengthen neuronal connections via spike-timing-dependent plasticity mechanisms. Here, we used cPAS targeting the fronto-striatal inhibitory network to modulate performance on a response inhibition measure in chronic alcohol use.

METHODS

Fifty-five participants (20 patients with a formal alcohol use disorder (AUD) diagnosis (26-74 years, 6[30%] females) and 20 matched healthy controls (HCs) (27-73 years, 6[30%] females) within a larger sample of 35 HCs (23-84 years, 11[31.4%] females) underwent two randomized sessions of cPAS 1-week apart: right inferior frontal cortex stimulation preceding right presupplementary motor area stimulation by either 4 ms (excitation condition) or 100 ms (control condition), and were subsequently administered the Stop Signal Task (SST) in both sessions.

RESULTS

HCs showed decreased stop signal reaction time in the excitation condition (t(19) = -3.01, p = 0.007, [CIs]:-35.6 to -6.42); this facilitatory effect was not observed for AUD (F(1,31) = 9.57, p = 0.004, CIs: -68.64 to -14.11). Individually, rates of SST improvement were substantially higher for healthy (72%) relative to AUD (13.6%) groups (OR: 2.33, p = 0.006, CIs:-3.34 to -0.55).

CONCLUSION

In line with previous findings, cPAS improved response inhibition in healthy adults by strengthening the fronto-striatal network through putative long-term potentiation-like plasticity mechanisms. Furthermore, we identified a possible marker of impaired cortical excitability, and, thus, diminished capacity for cPAS-induced neuroplasticity in AUD with direct implications to a disorder-relevant cognitive process.

Anger and Aggression in Relation to Psychological Resilience and Alcohol Abuse among Health Professionals during the First Pandemic Wave

Mental health problems, behavior changes, and addictive issues have been consistently documented among healthcare workers during the pandemic. The objective of this study was to investigate the levels of anger and aggression in relation to psychological resilience and alcohol abuse among healthcare workers during the first wave of the COVID-19 pandemic. A total of 120 physicians and 123 nurses completed an online survey of the Dimensions of Anger Reactions-5 (DAR-5), the Brief Aggression Questionnaire (BAQ), the Brief Resilience Scale (BRS), and the Alcohol Screening questionnaire CAGE which is an acronym for the focus of the questions (Cutting down, Annoyance by criticism, Guilty feeling, and Eye-openers). Demographic and professional data were also recorded. A total of 53 men and 190 women participated in the study. Almost one-third of the participants had a positive score on the DAR-5 scale and one out of ten respondents presented with current problematic alcohol use. Male participants demonstrated lower scores on the DAR-5 scale compared to females. Individuals with current problematic alcohol use displayed higher scores on the BAQ compared to those without alcohol use disorders. Regression analysis revealed that 16.4% of the variance in the BAQ scores can be attributed to scores on the DAR-5, 5.9% to the BRS scores, 2.1% to the CAGE scores, 1.7% to gender, and 1.2% to years of work experience. Mediation analysis highlighted the role of psychological resilience as a negative mediator in the DAR-5 and BAQ relationship. Professional experience and alcohol abuse emerged as positive and negative risk factors contributing to aggression and psychological resilience. The findings hold practical implications for implementing interventions to strengthen resilience in order to compensate for aggressive tendencies and discourage addictive issues.

Sex, Gender, and Alcohol Use: Implications for Women and Low-Risk Drinking Guidelines

Alcohol use is coming under increasing scrutiny with respect to its health impacts on the body. In this vein, several high-income countries have issued low-risk drinking guidelines in the past decade, aiming to educate the public on safer levels of alcohol use. Research on the sex-specific health effects of alcohol has indicated higher damage with lower amounts of alcohol for females as well as overall sex differences in the pharmacokinetics of alcohol in male and female bodies. Research on gender-related factors, while culturally dependent, indicates increased susceptibility to sexual assault and intimate partner violence as well as more negative gender norms and stereotypes about alcohol use for women. Sex- and gender-specific guidelines have been issued in some countries, suggesting lower amounts of alcohol consumption for women than men; however, in other countries, sex- and gender-blind advice has been issued. This article reports on a synthesis of the evidence on both sex- and gender-related factors affecting safer levels of drinking alcohol with an emphasis on women’s use. We conclude that supporting and expanding the development of sex- and gender-specific low-risk drinking guidelines offers more nuanced and educative information to clinicians and consumers and will particularly benefit women and girls.

Alcohol, Aggression, and Violence: From Public Health to Neuroscience

Alcohol has been associated with violent crimes and domestic violence across many nations. Various etiological factors were linked to chronic alcohol use and violence including psychiatric comorbidities of perpetrators such as personality disorders, mood disorders, and intermittent explosive disorders. Aggression is the precursor of violence and individuals prone to aggressive behaviors are more likely to commit impulsive violent crimes, especially under the influence of alcohol. Findings from brain studies indicate long-term alcohol consumption induced morphological changes in brain regions involved in self-control, decision-making, and emotional processing. In line with this, the inherent dopaminergic and serotonergic anomalies seen in aggressive individuals increase their susceptibility to commit violent crimes when alcohol present in their system. In relation to this, this article intends to investigate the influence of alcohol on aggression with sociopsychological and neuroscientific perspectives by looking into comorbidity of personality or mood disorders, state of the mind during alcohol consumption, types of beverages, environmental trigger, neurochemical changes, and gender differences that influence individual responses to alcohol intake and susceptibility to intoxicated aggression.

Changes in Affective Behavior and Oxidative Stress after Binge Alcohol in Male and Female Rats

Binge alcohol consumption and alcohol use disorders (AUD) are prevalent, and there is comorbidity with depression and anxiety. Potential underlying mechanisms include neurophysiological, genetic, and metabolic changes resulting from alcohol exposure. Mood and anxiety disorders are more common among women, but whether females are more susceptible to binge-induced oxidative stress and co-occurring anxiety and depression-like behaviors remains unknown. Here, we used a repeated, weekly binge alcohol paradigm in male and female rats to investigate sex differences in despair and anxiety-like behaviors and brain oxidative stress parameters. A single binge alcohol exposure significantly elevated glutathione (GSH) levels in prefrontal cortex (PFC) of both male and female animals. This was accompanied by increased lipid peroxidation in PFC of both sexes. Repeated (once weekly) binge exposure induced changes in anxiety- and depression-like behaviors in both males and females and increased GSH level in the PFC without detectable oxidative damage. Our findings suggest that repeated binge alcohol exposure influences affect regardless of sex and in the absence of membrane damage.

The Influence of Recreational Substance Use in TMS Research

(1) Background: Transcranial magnetic stimulation (TMS) approaches are widely used to study cortical and corticospinal function. However, responses to TMS are subject to significant intra-and inter-individual variability. Acute and chronic exposure to recreational substances alters the excitability of the sensorimotor system and may contribute to the variability in TMS outcome measures. The increasing prevalence of recreational substance use poses a significant challenge for executing TMS studies, but there is a lack of clarity regarding the influence of these substances on sensorimotor function. (2) Methods: The literature investigating the influence of alcohol, nicotine, caffeine and cannabis on TMS outcome measures of corticospinal, intracortical and interhemispheric excitability was reviewed. (3) Results: Both acute and chronic use of recreational substances modulates TMS measures of excitability. Despite the abundance of research in this field, we identify knowledge gaps that should be addressed in future studies to better understand the influence of these substances on TMS outcomes. (4) Conclusions: This review highlights the need for TMS studies to take into consideration the history of participant substance use and to control for acute substance use prior to testing.

Aggression in Women: Behavior, Brain and Hormones

We review the literature on aggression in women with an emphasis on laboratory experimentation and hormonal and brain mechanisms. Women tend to engage in more indirect forms of aggression (e.g., spreading rumors) than other types of aggression. In laboratory studies, women are less aggressive than men, but provocation attenuates this difference. In the real world, women are just as likely to aggress against their romantic partner as men are, but men cause more serious physical and psychological harm. A very small minority of women are also sexually violent. Women are susceptible to alcohol-related aggression, but this type of aggression may be limited to women high in trait aggression. Fear of being harmed is a robust inhibitor of direct aggression in women. There are too few studies and most are underpowered to detect unique neural mechanisms associated with aggression in women. Testosterone shows the same small, positive relationship with aggression in women as in men. The role of cortisol is unclear, although some evidence suggests that women who are high in testosterone and low in cortisol show heightened aggression. Under some circumstances, oxytocin may increase aggression by enhancing reactivity to provocation and simultaneously lowering perceptions of danger that normally inhibit many women from retaliating. There is some evidence that high levels of estradiol and progesterone are associated with low levels of aggression. We highlight that more gender-specific theory-driven hypothesis testing is needed with larger samples of women and aggression paradigms relevant to women.

Sex and gender-related differences in alcohol use and its consequences: Contemporary knowledge and future research considerations

AIMS

To review the contemporary evidence reflecting male/female differences in alcohol use and its consequences along with the biological (sex-related) and psycho-socio-cultural (gender-related) factors associated with those differences.

METHODS

MEDLINE, PubMed, Web of Science, SCOPUS, PsycINFO, and CINAHL databases were searched for relevant publications, which were subsequently screened for the presence/absence of pre-specified criteria for high quality evidence.

RESULTS

Compared to men, more women are lifetime abstainers, drink less, and are less likely to engage in problem drinking, develop alcohol-related disorders or alcohol withdrawal symptoms. However, women drinking excessively develop more medical problems. Biological (sex-related) factors, including differences in alcohol pharmacokinetics as well as its effect on brain function and the levels of sex hormones may contribute to some of those differences. In addition, differences in alcohol effects on behavior may also be driven by psycho-socio-cultural (gender-related) factors. This is evident by variation in the magnitude of differences in alcohol use between countries, decreasing difference in the rates of alcohol consumption in recent generations and other findings. Evidence indicates that both sex and gender-related factors are interacting with alcohol use in complex manner, which differentially impacts the risk for development of the behavioral or medical problems and alcohol use disorders in men and women.

CONCLUSIONS

Discovery of the mechanisms underlying biological (sex-related) as well as psycho-socio-cultural (gender-related) differences in alcohol use and related disorders is needed for development of personalized recommendations for prevention and treatment of alcohol use disorders and related problems in men and women.

Genders and the concurrent use of cocaine and alcohol: Pharmacological aspects

AIMS

Gender-related differences in the pharmacological effects of addictive drug are an emerging issue. This review examines gender differences in both pharmacokinetic and pharmacodynamic aspects of alcohol and cocaine intake since they cause complex pharmacological interactions, not least the formation of the active metabolite cocaethylene.

METHODS

The MEDLINE database was searched from 1990 to 2014 in order to find articles related to gender differences in alcohol, cocaine and cocaethylene pharmacokinetics and pharmacodynamics.

RESULTS

Besides the well known gender differences in alcohol pharmacokinetics, women appear more susceptible to alcohol-mediated brain damage and seem to suffer more than men the acute effects of alcohol on hepatic and gonadal hormones. No significant gender differences have been found in the pharmacokinetics of cocaine taken alone; yet, in women pharmacological sensitivity to the drug seems to vary in relation to menstrual cycle; moreover, progesterone attenuates subjective effects of cocaine in women. Higher ratings at a subjective measure of mental/physical well-being have been observed in women when given cocaine and alcohol, alone or in combination. Finally, among subjects dependent on both alcohol and cocaine, men only benefit from naltrexone, whereas women used more cocaine during the trial and were less compliant to therapy than men.

CONCLUSIONS

The observed subtle gender differences in the pharmacokinetics and pharmacodynamics of both alcohol and cocaine may have no subtle influence on the natural history of the co-abuse of the two drugs by women.

Motor cortical excitability assessed by transcranial magnetic stimulation in psychiatric disorders: a systematic review

BACKGROUND

Transcranial magnetic stimulation (TMS) is a popular neurostimulation technique suitable for the investigation of inhibitory and facilitatory networks in the human motor system. In the last 20 years, several studies have used TMS to investigate cortical excitability in various psychiatric disorders, leading to a consequent improvement in pathophysiological understanding. However, little is known about the overlap and specificity of these findings across these conditions.

OBJECTIVE

To provide a systematic review of TMS studies (1985-2013) focusing on motor cortical excitability in dementia, schizophrenia, affective disorders (major depression and bipolar), attention deficit hyperactivity disorder (ADHD), obsessive compulsive disorder (OCD), Tourette Syndrome (TS), substance abuse (alcohol, cocaine, cannabis, nicotine) and other disorders (borderline personality disorder, posttraumatic stress disorder (PTSD)).

METHODS

Systematic literature-based review.

RESULTS

Across disorders, patients displayed a general pattern of cortical disinhibition, while the most consistent results of reduced short-interval intracortical inhibition could be found in schizophrenia, OCD and Tourette Syndrome. In dementia, the most frequently reported finding was reduced short-latency afferent inhibition as a marker of cholinergic dysfunction.

CONCLUSIONS

The results of this systematic review indicate a general alteration in motor cortical inhibition in mental illness, rather than disease-specific changes. Changes in motor cortical excitability provide insight that can advance understanding of the pathophysiology underlying various psychiatric disorders. Further investigations are needed to improve the diagnostic application of these parameters.

The corpus callosum: a commissural road to anger and aggression

According to the frontal cortical asymmetry model of motivational direction, anger and aggression are associated with approach motivation and a dominant left frontal hemisphere. Functional interhemispheric connectivity has been proposed as a possible mechanism that could explain the frontal cortical asymmetry of anger and aggression. Reciprocal interactions between the cerebral hemispheres are primarily established by the corpus callosum which is the largest white matter bundle of the human brain. Experimental brain research has now provided evidence for callosal involvement in approach-motivation. In line with the frontal cortical asymmetry model of motivational direction, differences in the direction of interhemispheric signal transfer are proposed to contribute to anger and aggression. It is concluded that the human corpus callosum provides a possible neuroanatomical correlate for frontal cortical asymmetries and that interhemispheric signal transfer plays a role in the emergence of approach-related motivation and behaviour.