Abnormal CNV in chronic heavy drinkers

Hypotension with neurovascular changes and cognitive dysfunction: An epidemiological, pathobiological, and treatment review

ABSTRACT

Hypotension is a leading cause of age-related cognitive impairment. The available literature evidences that vascular factors are associated with dementia and that hypotension alters cerebral perfusion flow and can aggravate the neurodegeneration of Alzheimer's disease (AD). Despite the discovery of biomarkers and the recent progress made in neurovascular biology, epidemiology, and brain imaging, some key issues remain largely unresolved: the potential mechanisms underlying the neural deterioration observed in AD, the effect of cerebrovascular alterations on cognitive deficits, and the positive effects of hypotension treatment on cognition. Therefore, further well-designed studies are needed to unravel the potential association between hypotension and cognitive dysfunction and reveal the potential benefits of hypotension treatment for AD patients. Here, we review the current epidemiological, pathobiological, and treatment-related literature on neurovascular changes and hypotension-related cognitive dysfunction and highlight the unsettled but imminent issues that warrant future research endeavors.

Dysfunctional preparatory processes in hazardous drinkers: An ERP study

Alcohol drinking is associated with impaired cognitive and motor performance. This electrophysiological study examined the differences in the preparatory processes preceding motor imagery (visual and kinesthetic) and execution between hazardous drinkers and non-hazardous drinking controls. Twenty-two hazardous drinkers and 22 non-hazardous drinking controls were recruited to participate in the study. They were required to produce a 3-key response sequence physically or mentally 3 s after the appearance of a corresponding cue. Here we showed significantly smaller amplitudes of both early and late negative contingent variation in hazardous drinkers compared to controls. In addition, the early negative contingent variation preceding motor execution was greater than those in the motor imagery conditions in both groups. Results of this study suggest impairments of attentional control and motor preparation in hazardous drinkers. Preparatory processes of motor execution and motor imagery mainly differ from each other in voluntary attention orientation, but not in motor preparation.

Contingent negative variation in acute trauma patients: A prospective exploratory study

It is still unclear why some individuals completely recover after an acute trauma and others develop a long-lasting post-traumatic stress disorder (PTSD). This study investigates whether the contingent negative variation (CNV) - a slow negative event-related potential - may be associated with the occurrence of PTSD after acute trauma. CNV (auditory 2-stimulus reaction time paradigm) was recorded within one month as well as 6 months after an acute trauma (dangerous or grave physical injuries, witnessing of attempted suicide or murder, robbery, extortion, accidents, heavy illness, death or loss of an important person, hostage-taking) in 39 otherwise healthy adults and compared with CNV recordings in 38 healthy control subjects without potentially traumatizing experience in their history. According to their subsequent clinical course, these subjects were divided into two groups: participants who recovered completely 1 month after the trauma (PTSD- group, n = 31), and those who began to experience PTSD (PTSD+ group, n = 8). Patients from both trauma groups were characterized by a significantly longer reaction time immediately after the trauma. The PTSD+ group demonstrated lower amplitudes of the late CNV component immediately and six months after the trauma compared with the PTSD- and the control group. Whether the lower CNV amplitudes in patients who develop PTSD after the acute trauma, which is already present in the first days after the trauma, may be related to a higher risk for development of PTSD in these subjects, this has to be clarified in further prospective studies.

Interactions between autonomic cardiovascular regulation and cortical activity: a CNV study

The study investigated interactions between autonomic cardiovascular regulation and cortical activity. In 54 healthy subjects, baroreflex sensitivity (BRS) and respiratory sinus arrhythmia (RSA) were assessed at resting conditions. As an EEG indicator of cortical excitability, the contingent negative variation (CNV) was induced using a constant foreperiod reaction time task. At bivariate level, only RSA showed a moderate positive correlation with the CNV recorded at frontal electrodes. However, when common variance of BRS and RSA was controlled for in multiple regression analysis, an inverse association between BRS and the frontal CNV also arose. The inverse association between BRS and the CNV is discussed as reflecting bottom-up modulation of cortical excitability by baroreceptor afferents. The positive correlation between RSA and the CNV may relate to the interplay between prefrontal processing and cardiac vagal tone.

Cognitive performance in treatment-naïve active alcoholics

BACKGROUND

Most studies reporting cognitive deficits in chronic alcoholics have relied on treatment samples (predominantly men) from inpatient or outpatient treatment facilities. However, the majority of chronic alcoholics have never been in treatment and there is increasing evidence that treated and non-treatment-seeking alcoholic samples come from different populations with regard to alcohol use and other factors related to the severity of disease. Accordingly, in the present study, we assessed a broad range of cognitive functions in 55 treatment-naïve alcohol-dependent (TNAD) individuals and 55 nonalcoholic controls (NAC) matched for age and education. In addition, a goal of the present study was to assess potential differential effects of alcohol dependence on cognitive performance in TNAD men and women.

METHODS

Comprehensive neuropsychological assessment was conducted on TNAD and NAC. The following 9 performance domains, each consisting of multiple measures, were examined: attention, auditory working memory, verbal processing, abstraction/cognitive flexibility, psychomotor function, immediate memory, delayed memory, reaction time, and spatial processing.

RESULTS

Analysis revealed no cognitive deficits in TNAD, relative to NAC, in any of the 9 cognitive domains. TNAD performed better than NAC in the attention domain. In addition, while men performed better than women in the spatial domain, there were no TNAD versus NAC group by gender interactions for any domain.

CONCLUSIONS

Our results extend findings that TNAD show minimal behavioral effects of chronic heavy alcohol use and are consistent with the contention that TNAD are relatively cognitively intact. Differences between our findings and those often reported for alcoholics recruited from treatment settings may be understood in terms of differences in alcohol use, along with genetic, psychiatric, and nutritional factors. In addition, the lack of differential effects of alcohol dependence on male and female cognitive performance in our study suggests that TNAD men and women do not differ in the severity of cerebral consequences of alcohol dependence.

Chronic alcoholism: insights from neurophysiology

INTRODUCTION

Increasing knowledge of the anatomical structures and cellular processes underlying psychiatric disorders may help bridge the gap between clinical signs and basic physiological processes. Accordingly, considerable insight has been gained in recent years into a common psychiatric condition, i.e., chronic alcoholism.

MATERIAL AND METHODS

We reviewed various physiological parameters that are altered in chronic alcoholic patients compared to healthy individuals--continuous electroencephalogram, oculomotor measures, cognitive event-related potentials and event-related oscillations--to identify links between these physiological parameters, altered cognitive processes and specific clinical symptoms.

RESULTS

Alcoholic patients display: (1) high beta and theta power in the resting electroencephalogram, suggesting hyperarousal of their central nervous system; (2) abnormalities in smooth pursuit eye movements, in saccadic inhibition during antisaccade tasks, and in prepulse inhibition, suggesting disturbed attention modulation and abnormal patterns of prefrontal activation that may stem from the same prefrontal "inhibitory" cortical dysfunction; (3) decreased amplitude for cognitive event-related potentials situated along the continuum of information-processing, suggesting that alcoholism is associated with neurophysiological deficits at the level of the sensory cortex and not only disturbances involving associative cortices and limbic structures; and (4) decreased theta, gamma and delta oscillations, suggesting cognitive disinhibition at a functional level.

DISCUSSION

The heterogeneity of alcoholic disorders in terms of symptomatology, course and outcome is the result of various pathophysiological processes that physiological parameters may help to define. These alterations may be related to precise cognitive processes that could be easily monitored neurophysiologically in order to create more homogeneous subgroups of alcoholic individuals.

Impaired stimulus-outcome but preserved stimulus-response shifting in young substance-dependent individuals

Substance dependency has been related to an impairment in executive functions and to a dysfunction of the frontal cortex. In this study we developed two experimental tasks, which are physically identical, to analyze whether substance-dependent individuals are impaired in shifting response patterns (stimulus response links) or preferences (stimulus outcome links). To increase the specificity of the dependent variable, we also used two control tasks to analyze for unspecific performance deficits. We included 35 young subjects with polysubstance abuse (International Classification of Diseases, F19.2 ICD 10 diagnosis, mean age of 22 years, maximum age < 27 years) and 18 normal controls, but for a first step focused on only 22 patients and 15 age-matched controls, because we excluded all patients with an IQ below 100. The results show that the substance-dependent individuals are selectively impaired in shifting object preference (stimulus-outcome links) and not in shifting response patterns. They moreover show a higher general impulsivity as reflected in their faster responses than controls on all tasks except the stimulus-outcome task. In a second step we replicated these results by analyzing the original groups of 35 patients and 18 controls. We argue that substance-dependent subjects show an impairment only on specific executive tasks, and these tasks concern stimulus-outcome link shifting, which has been associated with the functioning of the orbitofrontal cortex, not of the lateral prefrontal cortex.

Mismatch negativity impairment associated with alcohol consumption in chronic alcoholics: A scalp current density study

Previous studies, based on amplitude and latency measurements of auditory event-related brain potentials, yielded inconclusive results about the status of mismatch negativity (MMN) in chronic alcoholics. The present study explores scalp current density (SCD) dynamics during MMN latency range in alcoholics, and correlates electrical SCD results with clinical data of the patients. SCD was computed from 30 electrodes in 16 abstinent chronic alcoholics and 16 healthy control volunteers in a paradigm on MMN elicited by duration changes. Reduced activity was observed in left frontal and right anterior and posterior temporal areas during MMN in alcoholics. Alcohol consumption correlated negatively with SCD intensity in these regions. Delayed activation was observed in the left posterior temporal area in the patients. Alcohol abstinence duration correlated positively with SCD intensity in this region. These results point to an impairment of automatic brain processing mechanisms associated with auditory change detection in chronic alcoholism. The present results suggest a reorganization of the computational neurodynamics of automatic auditory change detection linked to the amount of alcohol consumed in abstinent chronic alcoholics.

Dissociation between cortical activation and cognitive performance under pharmacological blood pressure elevation in chronic hypotension

The present study explored the impact of pharmacological blood pressure elevation on cortical activation and reaction time in chronic hypotension. Effects of the sympathomimetic etilefrine were investigated in 50 hypotensive persons based on a randomized, placebo-controlled double blind design. As an indicator of cortical excitability, the contingent negative variation (CNV), induced by a constant foreperiod reaction time task, was assessed at frontal (F3, Fz, F4) and central (C3, Cz, C4) scalp sites. Etilefrine provoked a decrease in the frontal and central CNV. In contrast, shorter reaction times were observed following drug administration. The degree of pharmacologically induced blood pressure elevation was correlated to CNV attrition as well as to performance enhancement. Inhibitory effects of baroreceptor activation on cortical excitability and enhanced cerebral blood flow are considered to be involved in mediating the effects of blood pressure elevation on cerebral functioning. Implications for the treatment of chronic hypotension are discussed.

Reduced brain perfusion and cognitive performance due to constitutional hypotension

This review article includes a systematic evaluation of the empirical data concerning deficits in mental ability, brain perfusion, and cerebral functioning due to chronically low blood pressure. A number of studies have provided strong evidence for reduced cognitive performance in hypotension, particularly in the domains of attention and memory. EEG studies have demonstrated that the hypotension-related poorer mental ability is also reflected in diminished cortical activity. Contrary to convention, more recent research has suggested a deficient regulation of cerebral blood flow in persons with low blood pressure. In addition to reduced tonic brain perfusion, studies demonstrated insufficient adjustment of blood flow to cognitive requirements. Altogether, these findings suggest that more attention should be allocated to chronic hypotension in both research and clinical practice.

Conditional Responding is Impaired in Chronic Alcoholics

Bechara (2003) describes a model for disturbances in executive functions related to addiction. This model involves deficits in decision-making and in suppressing pre-potent representations or response patterns. We tested this model in 29 individuals with long-term heavy alcohol dependency and compared their performance with that of 20 control subjects. Only individuals without memory impairment, with normal intelligence and normal visual response times were included. We examined word fluency, object alternation, spatial stimulus-response incompatibility, extra-dimensional shift learning and decision-making using the Gambling task. We subtracted the performance in a control condition from that of the executive condition, in order to focus specifically on the executive component of each task. Only the object alternation and incompatibility tasks revealed significant differences between the group of alcoholics and the control group. Moreover, response times in the object alternation task correlated with duration of alcohol dependency. The results do not argue in favor of a specific deficit in decision-making or in shifting between relevant representations. We conclude that long-term alcohol abuse leads to an impairment in conditional responding, provided the response depends on former reactions or the inhibition of pre-potent response patterns.

Reduced cortical activity due to chronic low blood pressure: an EEG study

Alterations in cortical activation processes due to chronic low blood pressure were investigated. In 40 hypotensive subjects and 40 normotensive controls, the contingent negative variation (CNV), induced by a constant foreperiod reaction time task, was assessed at nine scalp sites (F3, Fz, F4, C3, Cz, C4, P3, Pz, P4). Additionally, spontaneous EEG was recorded at resting conditions. In hypotensives, a reduced amplitude of both the early and the late component of the CNV were found at Cz. At Fz the early CNV was reduced. Hypotensives exhibited longer reaction times, and the reaction time was negatively correlated with the CNV amplitude. Resting alpha power correlated negatively with blood pressure. The findings can be related to cognitive deficits due to hypotension found in earlier studies. The effects of hypotension on cortical activity are discussed to be mediated by afferents from the cardiovascular system to the prefrontal cortex as well as by reduced cerebral blood flow.

Quantitative trait locus-specific genotype x alcoholism interaction on linkage for evoked electroencephalogram oscillations

We explored the evidence for a quantitative trait locus (QTL)-specific genotype × alcoholism interaction for an evoked electroencephalogram theta band oscillation (ERP) phenotype on a region of chromosome 7 in participants of the US Collaborative Study on the Genetics of Alcoholism. Among 901 participants with both genotype and phenotype data available, we performed variance component linkage analysis (SOLAR version 2.1.2) in the full sample and stratified by DSM-III-R and Feighner-definite alcoholism categories. The heritability of the ERP phenotype after adjusting for age and sex effects in the combined sample and in the alcoholism classification sub-groups ranged from 40% to 66%. Linkage on chromosome 7 was identified at 158 cM (LOD = 3.8) in the full sample and at 108 in the non-alcoholic subgroup (LOD = 3.1). Further, we detected QTL-specific genotype × alcoholism interaction at these loci. This work demonstrates the importance of considering the complexity of common complex traits in our search for genes that predispose to alcoholism.

Effects of Chronic Alcohol Consumption in a Visual Attention Task and an Auditory Oddball Task: An Event-Related Potential Study

BACKGROUND

In alcohol-dependent individuals changes in brain functioning, as measured with Event Related Potentials (ERP) have been reported.

METHODS

In the present study a visual attention and an auditory oddball task were used to investigate possible differences between light, moderate, and heavy social drinkers and excessive drinkers. It was hypothesized that with increasing alcohol intake an increasing number of ERP components elicited in the visual attention task and the auditory oddball task would show diminished amplitudes.

RESULTS

No differences were found between light, moderate, and heavy social drinkers. A trend for a smaller P3 amplitude in the visual attention task was found when comparing the alcohol-dependent participants with the light social drinkers. It is argued that this difference might be an effect of alcohol dependence and/or a reflection of possible unknown or undetected family history of alcohol-related disturbances.

CONCLUSIONS

In the current study, even at rather large amounts of regular alcohol intake, no evidence was found for any toxic effect of social alcohol use neither in a visual attention task nor in an auditory oddball task.