ABSTRACT
Alcohol-related falls are recognized as a major contributor to the occurrence of traumatic brain injury. The control of upright standing balance is complex and composes of contributions from several partly independent mechanisms such as appropriate information from multiple sensory systems and correct feedback and feed forward movement control. Analysis of multisegmented body movement offers a rarely used option for detecting the fine motor problems associated with alcohol intoxication. The study aims were to investigate whether (1) alcohol intoxication at 0.06 and 0.10% blood alcohol concentration (BAC) affected the body movements under unperturbed and perturbed standing; and (2) alcohol affected the ability for sensorimotor adaptation. Body movements were recorded in 25 participants (13 women and 12 men, mean age 25.1 years) at five locations (ankle, knee, hip, shoulder, and head) during quiet standing and during balance perturbations from pseudorandom pulses of calf muscle vibration over 200s with eyes closed or open. Tests were performed at 0.00, 0.06, and 0.10% BAC. The study revealed several significant findings: (1) an alcohol dose-specific effect; (2) a direction-specific stability decrease from alcohol intoxication; (3) a movement pattern change related to the level of alcohol intoxication during unperturbed standing and perturbed standing; (4) a sensorimotor adaptation deterioration with increased alcohol intoxication; and (5) that vision provided a weaker contribution to postural control during alcohol intoxication. Hence, alcohol intoxication at 0.06 and 0.10% BAC causes a complex multifaceted deterioration of human postural control.
Subject(s)
Alcoholic Intoxication/physiopathology , Central Nervous System Depressants/pharmacology , Ethanol/pharmacology , Gait Disorders, Neurologic/physiopathology , Postural Balance/drug effects , Adaptation, Physiological/drug effects , Adaptation, Physiological/physiology , Adult , Alcoholic Intoxication/complications , Ankle , Biomechanical Phenomena , Breath Tests , Central Nervous System Depressants/blood , Ethanol/blood , Female , Gait Disorders, Neurologic/etiology , Head , Hip , Humans , Knee , Leg , Male , Movement/physiology , Muscle, Skeletal , Posture/physiology , Proprioception/physiology , Psychomotor Performance/physiology , Shoulder , VibrationABSTRACT
OBJECTIVE: The visual system is vital during critical activities such as driving. Studying how alcohol compromises the visual system physiologically is therefore important for safety reasons. The objective of the study was to investigate alcohol-related impairments in visual tasks performed under controlled breath alcohol concentrations (BAC) to determine dose-dependent effects. METHODS: Alcohol's effects on smooth pursuit and saccadic eye movements at 0.06% and 0.10% BAC were examined whilst recording alcohol levels by real-time measurements using a high precision breath analyzer. Oculomotor performance was recorded from 25 subjects by electronystagmography comprising measurements of smooth pursuit gain, saccade velocity, saccade accuracy and two novel parameters further describing oculomotor performance. RESULTS: Alcohol deteriorated accuracy of smooth pursuit movements (p<0.001) and saccadic velocities (p<0.01) at 0.06% BAC. At 0.10% BAC, smooth pursuit gains (p<0.01), saccade accuracies and saccade latencies (p<0.01) were also affected. The ratio between saccade velocity and saccade amplitude decreased significantly under alcohol intoxication (p<0.01). Self-perceptions of drunkenness correlated well with changes in smooth pursuit accuracy, but poorly with other oculomotor measures. CONCLUSIONS: Several of the smooth pursuit and saccade functions were altered dose-dependently by alcohol and small changes in BAC substantially changed the effects observed. Additionally, alcohol altered the relationship between saccade velocity and saccade amplitude, diminishing the capacity for saccades to reach high peak velocities. SIGNIFICANCE: The alcohol-induced oculomotor deficits, which were found already at 0.06% BAC by our more sensitive analysis methods, may have safety implications for tasks that rely on visual motor control and visual feedback.
Subject(s)
Alcoholic Intoxication/complications , Alcohols/blood , Eye Movements/physiology , Ocular Motility Disorders/blood , Ocular Motility Disorders/etiology , Perception/physiology , Adult , Alcoholic Intoxication/blood , Analysis of Variance , Circadian Rhythm/physiology , Electromyography/methods , Female , Humans , Male , Pain Measurement , Photic Stimulation/methods , Reaction Time/physiology , Young AdultABSTRACT
Alcohol intoxication affects the vestibular system and balance control in many ways. We have investigated how acute, moderate (blood alcohol concentrations of 0.06+/-0.01%), and high (0.10+/-0.02%) alcohol intoxication affects the ability to perceive the visual horizontal and vertical and the visual field dependence measured with the rod and frame tests in 24 healthy participants. Alcohol ingestion impaired the ability to use gravitational vestibular cues when determining the visual vertical and horizontal, and caused increased visual field dependence. With conflicting gravitational and visual information, alcohol seems to promote a reweighting in balance control from a vestibular to a more visual dependency. Furthermore, the results indicate that alcohol intoxication at these levels start instigating a decompensation of minute subclinical vestibular asymmetries.
