The effect of ingested alcohol on fusion latency at various viewing distances

Dose-dependent sensorimotor impairment in human ocular tracking after acute low-dose alcohol administration

Key points

Oculomotor behaviours are commonly used to evaluate sensorimotor disruption due to ethanol (EtOH).

The current study demonstrates the dose‐dependent impairment in oculomotor and ocular behaviours across a range of ultra‐low BACs (<0.035%).

Processing of target speed and direction, as well as pursuit eye movements, are significantly impaired at 0.015% BAC, suggesting impaired neural activity within brain regions associated with the visual processing of motion.

Catch‐up saccades during steady visual tracking of the moving target compensate for the reduced vigour of smooth eye movements that occurs with the ingestion of low‐dose alcohol.

Saccade dynamics start to become ‘sluggish’ at as low as 0.035% BAC.

Pupillary light responses appear unaffected at BAC levels up to 0.065%.

Abstract

Changes in oculomotor behaviours are often used as metrics of sensorimotor disruption due to ethanol (EtOH); however, previous studies have focused on deficits at blood‐alcohol concentrations (BACs) above about 0.04%. We investigated the dose dependence of the impairment in oculomotor and ocular behaviours caused by EtOH administration across a range of ultra‐low BACs (≤0.035%). We took repeated measures of oculomotor and ocular performance from sixteen participants, both pre‐ and post‐EtOH administration. To assess the neurological impacts across a wide range of brain areas and pathways, our protocol measured 21 largely independent performance metrics extracted from a range of behavioural responses ranging from ocular tracking of radial step‐ramp stimuli, to eccentric gaze holding, to pupillary responses evoked by light flashes. Our results show significant impairment of pursuit and visual motion processing at 0.015% BAC, reflecting degraded neural processing within extrastriate cortical pathways. However, catch‐up saccades largely compensate for the tracking displacement shortfall caused by low pursuit gain, although there still is significant residual retinal slip and thus degraded dynamic acuity. Furthermore, although saccades are more frequent, their dynamics are more sluggish (i.e. show lower peak velocities) starting at BAC levels as low as 0.035%. Small effects in eccentric gaze holding and no effect in pupillary response dynamics were observed at levels below 0.07%, showing the higher sensitivity of the pursuit response to very low levels of blood alcohol, under the conditions of our study.

Oculomotor behaviours are commonly used to evaluate sensorimotor disruption due to ethanol (EtOH).

The current study demonstrates the dose‐dependent impairment in oculomotor and ocular behaviours across a range of ultra‐low BACs (<0.035%).

Processing of target speed and direction, as well as pursuit eye movements, are significantly impaired at 0.015% BAC, suggesting impaired neural activity within brain regions associated with the visual processing of motion.

Catch‐up saccades during steady visual tracking of the moving target compensate for the reduced vigour of smooth eye movements that occurs with the ingestion of low‐dose alcohol.

Saccade dynamics start to become ‘sluggish’ at as low as 0.035% BAC.

Pupillary light responses appear unaffected at BAC levels up to 0.065%.

Method Standardization for Conducting Innate Color Preference Studies in Different Zebrafish Strains

The zebrafish has a tetrachromatic vision that is able to distinguish ultraviolet (UV) and visible wavelengths. Recently, zebrafish color preferences have gained much attention because of the easy setup of the instrument and its usefulness to screen behavior-linked stimuli. However, several published papers dealing with zebrafish color preferences have contradicting results that underscore the importance of method standardization in this field. Different laboratories may report different results because of variations in light source, color intensity, and other parameters such as age, gender, container size, and strain of fish. In this study, we aim to standardize the color preference test in zebrafish by measuring light source position, light intensity, gender, age, animal size to space ratio, and animal strain. Our results showed that color preferences for zebrafish are affected by light position, age, strain, and social interaction of the fish, but not affected by fish gender. We validated that ethanol can significantly induce color preference alteration in zebrafish which may be related to anxiety and depression. We also explored the potential use of the optimized method to examine color preference ranking and index differences in various zebrafish strains and species, such as the tiger barb and glass catfish. In conclusion, zebrafish color preference screening is a powerful tool for high-throughput neuropharmacological applications and the standardized protocol established in this study provides a useful reference for the zebrafish research community.

Influences of ethanol ingestion on olfactory function in humans

RATIONALE

Although ethanol is known to influence, in humans, psychophysical measures of visual, auditory, and vestibular function, the influence of this drug on the ability to smell is not clear.

OBJECTIVES

To evaluate, in eight men and eight women, the influences of ethanol ingestion on four well-validated measures of olfactory function: an ethanol odor detection threshold test, a phenyl ethyl alcohol odor detection threshold test, a 40-item smell identification test, and an odor discrimination/short-term odor memory test.

METHODS

In this double-blind experiment, grape juice alone was administered prior to the olfactory tests on one test occasion, and a grape juice-vodka mixture, designed to produce blood levels of ethanol near the legal level of intoxication, on another. The order of the two drug conditions was counterbalanced, as was the order of the presentation of the olfactory tests.

RESULTS

Ethanol ingestion markedly influenced the detection threshold for ethanol (all 16 subjects exhibited higher thresholds under the ethanol than under the non-ethanol condition) and had a significant, albeit small, influence on odor discrimination performance, as measured by the total number of correct responses independent of delay interval. Women performed significantly better than men on the latter measure. No influences of ethanol on odor identification, the phenyl ethyl alcohol detection threshold, or the delay interval (memory) component of the odor discrimination/memory test were observed.

CONCLUSIONS

Alcohol ingestion markedly and selectively alters olfactory sensitivity to ethanol, perhaps via habituation processes, and may subtly influence some measures of odor discrimination.

Spatial-frequency discrimination, brain lateralisation, and acute intake of alcohol

The effect of alcohol (breath-alcohol level of 0.1%) on perceptual discrimination of low (1.5 cycles deg-1) and high (8 cycles deg-1) spatial frequencies in the left and right visual field was measured in eighteen right-handed males, in a double-blind, balanced placebo design. Discrimination thresholds for briefly (180 ms) presented sinusoidal gratings were determined by two-alternative forced-choice judgments with four interleaving psychophysical staircases providing random trial-to-trial variation of reference spatial frequency and visual field, in addition to a random (+/- 10%) jitter of reference spatial frequency. Alcohol produced overall higher discrimination thresholds but did not alter the visual-field balance: no main effect of visual field was observed, but in both placebo and alcohol conditions spatial frequency interacted with visual field in the direction predicted by the spatial-frequency hypothesis of hemispheric asymmetry in visual-information processing, with left-visual-field/right-hemisphere superiority in discrimination of low spatial frequencies and right-visual-field/left-hemisphere superiority in discrimination of high spatial frequencies.

Differentiation of visibility and alcohol as contributors to twilight road fatalities

Elevated road fatality rates at night involve multiple variables, each of which contributes to an unknown degree. In order to determine the relative contributions of reduced visibility and drivers' consumption of alcohol, we performed two quasi-experiments analyzing data recorded by the U.S. Fatal Accident Reporting System from 1980 through 1990. The results confirmed that both variables play a major role in nighttime road fatalities and revealed new evidence that they contribute differentially to two classes of fatal collisions: Degraded visibility in low illumination is associated primarily with collisions involving pedestrians and pedalcyclists, whereas drivers' consumption of alcohol plays a larger role in other fatal collisions.

Measuring and predicting the effects of alcohol consumption on contrast sensitivity for stationary and moving gratings

Contrast sensitivity was measured for 12 healthy young males while sober, after ingestion of an alcohol placebo, and after ingestion of alcohol (95% grain alcohol; mean estimated blood alcohol level = .088%). Observations were made for both stationary gratings and gratings that traveled through a circular path and required pursuit eye movements. The significant alcohol-related reduction in contrast sensitivity was 2.6 times greater for moving (.29-log-unit reduction) than for stationary gratings (.11-log-unit reduction). The loss in contrast sensitivity for the moving gratings of high spatial frequency (12 cpd) was particularly severe (.37 log unit). Estimated blood alcohol level was correlated with the loss in contrast sensitivity for moving gratings (r = .61), but not with the loss for stationary gratings. Estimated blood alcohol level was strongly correlated with the difference between the loss in contrast sensitivity to moving and stationary gratings (r = .75). These results are consistent with reports that alcohol consumption degrades the ability to make pursuit eye movements. Subjects' perceived intoxication level was not a reliable predictor of any index of visual performance.

Influence of ethanol ingestion on the cornea

The corneal thickness variations on both eyes of thirteen healthy volunteers were measured in absence and presence of ethanol with ultrasound pachymetry. During ethanol ingestion, to a serum ethanol concentration of 0.98 +/- 0.22 g/l, a small and transient, but statistically significant increase of the corneal thickness appeared (3.0 +/- 3.4% right eye - 4.3 +/- 2.9% left eye, p < 0.05). We suggest that ethanol causes a transient depression of the endothelial pump activity. The measured effect on the cornea is too small to cause reduced visual acuity on Snellen chart. However, a resulting loss of contrast sensitivity may have consequences for car driving and safety work.