Disruption of Eye Movements by Ethanol Intoxication Affects Perception of Depth From Motion Parallax

Impaired face symmetry detection under alcohol, but no 'beer goggles' effect

BACKGROUND

The 'beer goggles' phenomenon describes sexual attraction to individuals when alcohol intoxicated whom we would not desire when sober. One possible explanation of the effect is that alcohol impairs the detection of facial asymmetry, thus lowering the drinker's threshold for physical attraction.

AIMS

We therefore tested the hypotheses that higher breath alcohol drinkers would award more generous ratings of attractiveness to asymmetrical faces, and be poorer at discriminating bilateral facial asymmetry than less intoxicated counterparts.

METHODS

Ninety-nine male and female bar patrons rated 18 individual faces for attractiveness and symmetry. Each type of rating was given twice, once per face with an enhanced asymmetry and once again for each face in its natural form. Participants then judged which of two same-face versions (one normal, the other perfectly symmetrised) was more attractive and, in the final task, more symmetrical.

RESULTS

Alcohol had no influence on attractiveness judgements but higher blood alcohol concentrations were associated with higher symmetry ratings. Furthermore, as predicted, heavily intoxicated individuals were less able to distinguish natural from perfectly symmetrised face versions than more sober drinkers.

CONCLUSIONS

Findings therefore suggest alcohol impairs face asymmetry detection, but it seems that this perceptual distortion does not contribute to the 'beer goggles' phenomenon.

Changes in Visual Performance under the Effects of Moderate-High Alcohol Consumption: The Influence of Biological Sex

The purpose of this study was to analyze the changes in visual functions under the effects of moderate-high breath alcohol concentrations (BrACs), and the influence of biological sex on visual deterioration, considering different factors. A total of 37 healthy habitual alcohol users were enrolled in the experiment. The participants underwent a baseline session and a second session after an intake of 450 mL of red wine, so that all of them reached a BrAC above 0.25 mg/L. Visual performance was assessed by measuring the contrast sensitivity function, the halo perception, the stereopsis, and finally the retinal image quality. A Visual Deterioration Score (VDS) was calculated using the deterioration of these visual variables. All visual functions analyzed were significantly impaired following alcohol consumption (p < 0.05). The VDS was associated with the BrAC (ρ = -0.476). The VDS was also significantly higher in females, with the BrAC having a significant effect on the variability of the VDS in males and females (p < 0.05). However, the body mass index showed no significant effect (p > 0.05). Visual functions were significantly impaired under the influence of alcohol, and this deterioration was greater in females. The deterioration depends on the BrAC reached, being the primary thing responsible for the differences observed between males and females.

Visuoperceptive Impairments in Severe Alcohol Use Disorder: A Critical Review of Behavioral Studies

The present literature review is aimed at offering a comprehensive and critical view of behavioral data collected during the past seventy years concerning visuoperception in severe alcohol use disorders (AUD). To pave the way for a renewal of research and clinical approaches in this very little understood field, this paper (1) provides a critical review of previous behavioral studies exploring visuoperceptive processing in severe AUD, (2) identifies the alcohol-related parameters and demographic factors that influence the deficits, and (3) addresses the limitations of this literature and their implications for current clinical strategies. By doing so, this review highlights the presence of visuoperceptive deficits but also shows how the lack of in-depth studies exploring the visual system in this clinical population results in the current absence of integration of these deficits in the dominant models of vision. Given the predominance of vision in everyday life, we stress the need to better delineate the extent, the specificity, and the actual implications of the deficits for severe AUD.

Alcohol myopia and the distracting effects of hair in face recognition

BACKGROUND

According to alcohol myopia theory, alcohol reduces cognitive resources and restricts the drinker's attention to only the more prominent aspects of a visual scene. As human hairstyles are often salient and serve as important facial recognition cues, we consider whether alcohol restricts attention to this region of faces upon initial viewing.

AIMS

Participants with higher breath alcohol concentrations just prior to encoding a series of unfamiliar faces were expected to be poorer than more sober counterparts at recognising the internal but not external features of those faces at test.

METHODS

Drinkers in a nearby bar (n=76) were breathalysed and then shown a sequence of 21 full face photos. After a filled five-minute retention interval they completed a facial recognition task requiring them to identify the full, internal or external region of each of these among a sequence of 21 previously unseen (part or whole) faces.

RESULTS

As predicted, higher breath concentrations were associated with poorer discrimination of internal but not external face regions.

CONCLUSIONS

Our findings suggest that alcohol restricts unfamiliar face encoding by narrowing the scope of attention to the exterior region of unfamiliar faces. This has important implications for drunk eyewitness accuracy, though further investigation is needed to see if the effect is mediated by gender, hair length and face feature distinctiveness.

When alcohol narrows the field of focal attention

The aim of this study was to measure the extent to which alcohol intoxication restricts the scope of attention in the visual field. A group of intoxicated ( n = 31; mean BAC ≈ .08%) and placebo control ( n = 31; mean BAC ≈ .00%) participants were required to correctly identify visual probes while performing two verbal categorization tasks: one designed to widen the scope of visual attention on to each stimulus word, the other to narrow attention on to the central letter of each word. Response times to surprise probes interpolated between categorization trials were measured and these catch trials could appear in any of the stimulus word letter positions. As predicted by alcohol myopia theory (AMT), which assumes that the drug narrows focal attention, intoxicated participants made slower responses than the sober controls to probes displayed in non-central letter positions, although right-field probe reaction times (RTs) were slower than those for left-field targets. This response asymmetry and the wider theoretical implications of these findings are discussed.

Some effects of alcohol and eye movements on cross-race face learning

This study examines the impact of acute alcohol intoxication on visual scanning in cross-race face learning. The eye movements of a group of white British participants were recorded as they encoded a series of own-and different-race faces, under alcohol and placebo conditions. Intoxication reduced the rate and extent of visual scanning during face encoding, reorienting the focus of foveal attention away from the eyes and towards the nose. Differences in encoding eye movements also varied between own-and different-race face conditions as a function of alcohol. Fixations to both face types were less frequent and more lingering following intoxication, but in the placebo condition this was only the case for different-race faces. While reducing visual scanning, however, alcohol had no adverse effect on memory, only encoding restrictions associated with sober different-race face processing led to poorer recognition. These results support perceptual expertise accounts of own-race face processing, but suggest the adverse effects of alcohol on face learning published previously are not caused by foveal encoding restrictions. The implications of these findings for alcohol myopia theory are discussed.

The behavior and social communication of honey bees (Apis mellifera carnica Poll.) under the influence of alcohol

In this study, the effects of ethanol on honey bee social communication and behavior within the hive were studied to further investigate the usefulness of honey bees as an ethanol-abuse model. Control (1.5 M sucrose) and experimental (1.5 M sucrose, 2.5% w/v ethanol) solutions were directly administered to individual forager bees via proboscis contact with glass capillary tubes. The duration, frequency, and proportion of time spent performing social and nonsocial behaviors were the dependent variables of interest. No differences in the relative frequency or proportion of time spent performing the target behaviors were observed. However, ethanol consumption significantly decreased bouts of walking, resting, and the duration of trophallactic (i.e., food-exchange) encounters. The results of this study suggest that a low dose of ethanol is sufficient to disrupt both social and nonsocial behaviors in honey bees. In view of these results, future behavioral-genetic investigations of honey bee social behavior are encouraged.

MT neurons combine visual motion with a smooth eye movement signal to code depth-sign from motion parallax

The capacity to perceive depth is critical for an observer to interact with his or her surroundings. During observer movement, information about depth can be extracted from the resulting patterns of image motion on the retina (motion parallax). Without extraretinal signals related to observer movement, however, depth-sign (near versus far) from motion parallax can be ambiguous. We previously demonstrated that MT neurons combine visual motion with extraretinal signals to code depth-sign from motion parallax in the absence of other depth cues. In that study, head translations were always accompanied by compensatory tracking eye movements, allowing at least two potential sources of extraretinal input. We now show that smooth eye movement signals provide the critical extraretinal input to MT neurons for computing depth-sign from motion parallax. Our findings demonstrate a powerful modulation of MT activity by eye movements, as predicted by human studies of depth perception from motion parallax.

Effectiveness of mandatory alcohol testing programs in reducing alcohol involvement in fatal motor carrier crashes

Mandatory alcohol testing programs for motor carrier drivers were implemented in the United States in 1995 and have not been adequately evaluated. Using data from the Fatality Analysis Reporting System during 1982-2006, the authors assessed the effectiveness of mandatory alcohol testing programs in reducing alcohol involvement in fatal motor carrier crashes. The study sample consisted of 69,295 motor carrier drivers and 83,436 non-motor-carrier drivers who were involved in 66,138 fatal multivehicle crashes. Overall, 2.7% of the motor carrier drivers and 19.4% of the non-motor-carrier drivers had positive blood alcohol concentrations. During the study period, the prevalence of alcohol involvement in fatal crashes decreased by 80% among motor carrier drivers and 41% among non-motor-carrier drivers. With adjustment for driver age, sex, history of driving while intoxicated, and survival status, implementation of the mandatory alcohol testing programs was found to be associated with a 23% reduced risk of alcohol involvement in fatal crashes by motor carrier drivers (odds ratio = 0.77, 95% confidence interval: 0.62, 0.94). Results from this study indicate that mandatory alcohol testing programs may have contributed to a significant reduction in alcohol involvement in fatal motor carrier crashes.

The effect of acute ethanol challenge on global visuospatial attention: exaggeration of leftward bias in line bisection

Acute alcohol challenge has been associated with a selective impairment of right hemisphere function. A hallmark of visuospatial neglect syndrome is that patients with right hemisphere lesions misbisect horizontal lines far rightward of veridical centre. Neurologically intact participants misbisect lines with a systematic leftward bias (pseudoneglect). Neuroimaging studies in neurologically intact participants reveal predominant right hemisphere activation during performance of line bisection tasks. The current study assessed whether acute alcohol challenge alters global visuospatial attention. Participants (N=18; 10 male; strongly right-handed; mean age 23 years) engaged in a forced-choice tachistoscopic line bisection task in both ethanol challenge (mean BAC=.077) and no ethanol control conditions. Mean leftward bisection error in the control condition was -0.238 degrees visual angle (1.05% line length), and leftward bisection error significantly increased (p=.001) under ethanol challenge (-0.333 degrees visual angle, 1.47% line length). Mean bisection precision in the control condition was 0.358 degrees visual angle (1.58% line length); bisection precision significantly deteriorated (p=.008) under ethanol challenge (0.489 degrees, 2.17% line length). Decreased bisection precision indicates that ethanol disrupts the fidelity of visuospatial performance. The exaggerated leftward bisection error implies that ethanol may exert a differential effect on left versus right hemispheric function with respect to the control of global visuospatial attention.

Concordant eye movement and motion parallax asymmetries in esotropia

The role of eye movements in the perception of depth from motion was investigated in esotropia. Elevated motion parallax thresholds have been shown in strabismus [Thompson, A. M., & Nawrot, M. (1999). Abnormal depth perception from motion parallax in amblyopic observers. Vision Research, 39, 1407-1413] suggesting a global deficit in depth perception involving both stereopsis and motion. However, this motion parallax deficit in strabismus might be better explained by the role that eye movements play in motion parallax [Nawrot, M., & Joyce, L. (2006). The pursuit theory of motion parallax. Vision Research, 46, 4709-4725]. Esotropia is associated with asymmetric pursuit and optokinetic response eye movements [Demer, J. L., & von Noorden, G. K. (1988). Optokinetic asymmetry in esotropia. Journal of Pediatric Ophthalmology and Strabismus, 25, 286-292; Schor, C. M., & Levi, D. M. (1980). Disturbances of small-field horizontal and vertical optokinetic nystagmus in amblyopia. Investigative Ophthalmology and Visual Science, 19, 851-864; Tychsen, L., & Lisberger, S. G. (1986). Maldevelopment of visual motion processing in humans who had strabismus with onset in infancy. The Journal of Neuroscience, 6, 2495-2508; [Westall, C. A., Eizenman, M., Kraft, S. P., Panton, C. M., Chatterjee, S., & Sigesmund, D. (1998). Cortical binocularity and monocular optokinetic asymmetry in early-onset esotropia. Investigative Ophthalmology and Visual Science, 39, 1352-1360.]. The first experiment demonstrates that the motion parallax deficit in esotropia mirrors the pursuit eye movement asymmetry: in the direction of normal pursuit, esotropic observers had normal depth from motion parallax. A second set of experiments, conducted in normal observers, demonstrates that this motion parallax deficit is not a secondary problem due to the retinal slip created by inadequate pursuit. These results underscore the role of pursuit eye movements in the perception of depth from motion parallax.

Differential effects of alcohol on working memory: distinguishing multiple processes

The authors assessed effects of alcohol consumption on different types of working memory (WM) tasks in an attempt to characterize the nature of alcohol effects on cognition. The WM tasks varied in 2 properties of materials to be retained in a 2-stimulus comparison procedure. Conditions included (a) spatial arrays of colors, (b) temporal sequences of colors, (c) spatial arrays of spoken digits, and (d) temporal sequences of spoken digits. Alcohol consumption impaired memory for auditory and visual sequences but not memory for simultaneous arrays of auditory or visual stimuli. These results suggest that processes needed to encode and maintain stimulus sequences, such as rehearsal, are more sensitive to alcohol intoxication than other WM mechanisms needed to maintain multiple concurrent items, such as focusing attention on them. These findings help to resolve disparate findings from prior research on alcohol's effect on WM and on divided attention. The results suggest that moderate doses of alcohol impair WM by affecting certain mnemonic strategies and executive processes rather than by shrinking the basic holding capacity of WM.

The pursuit theory of motion parallax

Although motion parallax is closely associated with observer head movement, the underlying neural mechanism appears to rely on a pursuit-like eye movement signal to disambiguate perceived depth sign from the ambiguous retinal motion information [Naji, J. J., & Freeman, T. C. A. (2004). Perceiving depth order during pursuit eye movement. Vision Research, 44, 3025-3034; Nawrot, M. (2003). Eye movements provide the extra-retinal signal required for the perception of depth from motion parallax. Vision Research, 43, 1553-1562]. Here, we outline the evidence for a pursuit signal in motion parallax and propose a simple neural network model for how the pursuit theory of motion parallax might function within the visual system. The first experiment demonstrates the crucial role that an extra-retinal pursuit signal plays in the unambiguous perception of depth from motion parallax. The second experiment demonstrates that identical head movements can generate opposite depth percepts, and even ambiguous percepts, when the pursuit signal is altered. The pursuit theory of motion parallax provides a parsimonious explanation for all of these observations.