RESUMEN
In order to assess the impact of chronic alcohol misuse on basic visual functions, we investigated motion perception, visual short-term memory, and visual divided attention in recently detoxified patients and matched controls by means of visual psychophysical tasks. Subjects were tested twice within the first 3 weeks of detoxification in order to assess the potential recovery of visual performance. Patients demonstrated significant impairments in visual perception of coherent motion for slow, but not faster, speeds, and in speed discrimination as assessed by random dot kinematograms. Visual short-term memory tested with a delayed vernier discrimination task, on the other hand, was not significantly affected in patients. When processing hierarchical letters, a divided attention task, detoxified patients showed neither impairments in overall attentional capacity nor attentional allocation, but slightly enhanced interference of global information on local target processing. The results of the visual divided attention task contradict the predictions of the 'right hemisphere' hypothesis of alcoholism: global target information - mediated by the right hemisphere - was not only accessible to detoxified patients, but seemed to exert an even greater influence on local processing during early detoxification, than in matched controls. Limited recovery within the first 3 weeks was seen only in visual speed discrimination. Recently detoxified patients revealed deficits similar to intoxicated social drinkers in identical tests of visual perception of motion, but not visual short-term memory.
Asunto(s)
Alcoholismo/fisiopatología , Atención/fisiología , Memoria a Corto Plazo/fisiología , Percepción de Movimiento/fisiología , Tiempo de Reacción/fisiología , Templanza , Adulto , Alcoholismo/psicología , Análisis de Varianza , Discriminación en Psicología/fisiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estimulación Luminosa/métodos , Templanza/psicologíaRESUMEN
RATIONALE: Alcohol is known to affect most parameters of visually guided saccades, but it is unclear whether intoxicated subjects are able to utilize temporal or spatial pre-cues to compensate for their alcohol-related slowing of saccades. OBJECTIVES: We examined the effects of both temporal and spatial predictability on gain, latency, and peak velocity in sober and intoxicated subjects, e.g. by employing a temporal gap condition. METHODS: Saccades were recorded with subjects once sober and once intoxicated (0.8 g ethanol per kg body weight). Unpredictable and predictable target locations alternated in both the classical (no gap) and temporal gap condition (extinction of fixation point 200 ms before target onset). RESULTS: The gain was only slightly affected by alcohol, but increased for predictable target locations. After alcohol consumption, latencies increased, even in the gap condition and for predictable targets. However, intoxicated subjects took relatively more benefit from the gap than sober subjects did. In addition, they showed a "pretrial effect", i.e. their latencies depended on the condition for the previous saccade. For predictable target locations, latencies decreased and peak velocities increased both in sober and intoxicated subjects. Thus, intoxicated subjects were able to utilize both the spatial predictability and the temporal gap to speed up their saccades. CONCLUSIONS: These results lead to suggest that as far as the saccadic system is concerned alcohol predominantly affects the function of the superior colliculus (SC) and/or the oculomotor regions in the brain stem, either directly or indirectly. On the other hand, cortical areas assumed to mediate prediction and the gap effect seem to be less affected by alcohol intoxication.
Asunto(s)
Etanol/toxicidad , Movimientos Sacádicos/efectos de los fármacos , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Tiempo de Reacción/efectos de los fármacosRESUMEN
1. The authors examined the effect of acute alcohol consumption on a set of visual tasks: visual short term memory, depth perception, and attention. 2. In a repeated measurement design, thirteen subjects performed the tasks once sober and once intoxicated with 0.8 g/kg body weight pure ethanol in orange juice (33% alcohol). Subjects underwent a neuropsychological (Benton test) and a psychophysical test (vernier discrimination) both assessing visual short term memory, the test d2 as a measure of attention and concentration, and a psychophysical depth perception task. 3. Subjects demonstrated significant alcohol-related impairments in depth perception and in visual short term memory as assessed by the vernier discrimination task. However, the neuropsychological Benton test and test d2 failed to reveal alcohol-related changes in performance-probably due to superimposed learning effects. Performance was neither correlated with blood alcohol levels (BAL) nor perceived intoxication. Even though the current BAL was known to the subjects, only half of them demonstrated a close correlation between BAL and perceived intoxication.