The alcohol facilitation effect on memory: a dose-response study

The relationship between ethanol-induced locomotor activation and narcosis in long-sleep and short-sleep mice

Mice selectively bred for marked response to hypnotic doses of ethanol (long-sleep, LS) respond to subhypnotic doses of ethanol (ETOH) with less stimulation of locomotor activity than their short-sleep (SS) counterparts. This assessment was made by comparing ETOH-induced alterations in locomotor activity to an untreated baseline within individual subjects, and to a saline-treated control group. A correlational study, using the same method in F2 generation hybrids of the LS and SS lines, produced a negative correlation (-.36) between locomotor stimulant effects of a subhypnotic dose of ETOH and length of loss of the righting reflex following a hypnotic dose. This relationship also appeared in a factor analysis of baseline locomotor activity, ETOH-stimulated activity, and depressant response variables. The genetic selection for LS and SS mice appears to have differentiated loci that influence more than one type of behavioral response to ETOH, an example of pleiotropism.

Retrograde enhancement by alcohol of delayed free recall performance

Two experiments are reported in which retrograde enhancement of human memory by alcohol was observed. In both studies male undergraduate volunteers performed an immediate free recall task before and after consuming either alcohol (0.66 abs alc/kg) or placebo. About two hours later, many words as they could delayed free recall was tested when subjects were asked to write down as many words as they could remember from the free recall trials in the session. Subjects given alcohol recalled significantly more words from lists heard before drinking than subjects given placebo; this effect appeared more pronounced for words from the primacy portion of the lists. The possibility that this retrograde enhancement effect is due to alcohol's effects on brain reward systems is raised.

Apomorphine effects on behavioral response to ethanol in mice selectively bred for differential sensitivity to ethanol

Two lines of mice selectively bred for differences in response to a hypnotic dose of ethanol were administered apomorphine alone or in combination with ethanol. When administered by itself, apomorphine produced similar dose-dependent depression of locomotor activity and increases in stereotypy in the two lines. Doses of apomorphine (0.5 microM/kg and 2 microM/kg) thought to bind only presynaptic dopamine receptors blocked the slight locomotor activation to 1.5 g/kg ethanol in the ethanol-sensitive Long-Sleep (LS) mice; in the ethanol-insensitive Short-Sleep (SS) mice which show marked activation to all subhypnotic doses of ethanol, these doses of apomorphine only attenuated the activation. A higher apomorphine dose (8 microM/kg) antagonized the locomotor depressant effects of 2.0 and 2.5 g/kg of ethanol in LS mice but did not alter the shape of the SS ethanol dose response curve for locomotor activity. Apomorphine (2 and 8 microM/kg) potentiated ethanol-induced loss of the righting reflex in LS mice in a dose dependent fashion, but did not alter this soporific effect of ethanol in SS mice. These findings extend the data base suggesting a role for dopamine both in the mechanism(s) differentiating the LS and SS mice and the stimulant and intoxicating properties of ethanol.

Diazepam and memory: retrograde facilitation produced by interference reduction

Although diazepam (Valium) reduces learning and memory of information presented after administration (anterograde amnesia), in some cases it improves retention of predrug information (retrograde facilitation). Three experiments examined the magnitude and the conditions for producing retrograde facilitation and tested three hypotheses about the cause of memory enhancement. Differential effort and enhanced consolidation explanations were rejected in favor of a reduced interference interpretation. Improvement in predrug memory occurs because poor postdrug learning reduces the amount of new information available to interfere with prior learning.

Stimulant and depressant properties of sedative-hypnotics in mice selectively bred for differential sensitivity to ethanol

A genetic analysis of sedative-hypnotic response in selectively bred Long-Sleep (LS) and Short-Sleep (SS) mice showed LS mice to be more depressed by acetaldehyde, ethanol (ETOH), and t-butanol, but less sensitive to pentobarbital. Intermediate inheritance was shown by the two reciprocal F1 hybrids for the alcohols, but dominance to the LS genotype occurred for the aldehyde and the barbiturate. At several subhypnotic doses of ETOH in two experiments, LS mice showed less locomotor stimulation and greater disruption of coordination than the SS mice. The two reciprocal F1 hybrids did not differ from one another and had dose-response curves intermediate to the two parental lines. Study of the effects of t-butanol on locomotor activity revealed a pattern of line differences similar to that for ETOH. The genetic selection for LS and SS mice appears to have differentiated loci that pleiotropically influence a variety of behavioral responses to alcohols.

Sequence of alcohol presentation is important in the potentiation of long-term events

Animal and human studies have demonstrated that, depending upon the sequence of alcohol presentation, long-term memory of events can either be enhanced or diminished. In the present study a similar phenomenon is demonstrated in the neuronal excitability of slices of hippocampus from guinea pig brains. Alcohol given after, but not before, 3 days of pentylenetetrazol (PTZ) administration to the intact animal produced kindling equivalent to 5 days of PTZ given by itself. This effect appears to be independent of the known withdrawal effects of alcohol and lasts for at least 14 days after the alcohol and PTZ administration have been discontinued.

Behavioral and physiological effects of ethanol in high-risk and control children: a pilot study

Blood and breath acetaldehyde levels were measured following ethanol ingestion (0.5 ml/kg) in 11 boys familially at risk for alcoholism and 11 age-matched controls. No significant differences were found between groups for acetaldehyde, objective, or subjective measures of intoxication. Previous reports of acetaldehyde as a marker of risk for alcoholism were not confirmed. Baseline behavioral state predicted response to alcohol. Children tended to have a subjective response in a direction opposite from the baseline mood state.

Alcohol enhancement of human memory: tests of consolidation and interference hypotheses

Two hypotheses about the phenomenon of alcohol-enhanced human memory were investigated. Whereas a consolidation account of this phenomenon indicates that continued processing of a target memory is facilitated by alcohol, an interference account states that the alcohol main effect is to impair the acquisition of potentially interfering new memories. No support was found for the consolidation view in an experiment manipulating (1) the length of time items preceded drug administration, (2) the amount of postpresentation processing each item received, and (3) the type of memory test employed. In line with expectations derived from interference theory, retention was substantially improved only for recall and not for tests of recognition memory.

Alcohol and proactive interference: a test of response eccentricity theory of alcohol's psychological effects

A theory is offered which proposes that alcohol induces eccentricity in the neurophysiological mechanism by which responses are selected for emission by the nervous system. Hence, in a specific stimulus situation, normally high probability responses decrease in frequency, while lower probability responses increase in frequency. From this postulate, the prediction is derived that in a verbal paired-associate learning task administered over two days, alcohol will decrease proactive interference from first-day learning (high probability associate) and result in enhanced acquisition of second day items. This paper reports two experimental tests of the prediction, each of which employs four subject groups tested over two days. Experiment 1 (n = 24) provides tentative support while ruling out some potential confounds. With these confounds eliminated, Experiment 2 (n = 40) confirms the prediction in a more direct test. A variety of possible alternative explanations for the counter-intuitive finding of improved cognitive performance under alcohol are evaluated against the theory proposed, as are other recent theories which address the variable behavioral effects of alcohol. Finally, the new data gathered on the effects of imagery instructions on proactive interference are considered.

Effects of dietary substances in children

Five studies on behavioral effects of dietary substances (alcohol, caffeine, and sugar) in children are reviewed to evaluate methodology. Pharmacokinetic and dose response data are essential in understanding age differences in behavioral response. For pediatric populations, objective behavioral data including speech rate, attention span, reaction time and motor activity are more sensitive than subjective reports of mood change. A variety of cognitive and behavioral tasks failed to show "excitatory" effects of sugar in a supposedly vulnerable population. Randomized double blind trials are essential as the children's behavior changed systematically over the course of the study independent of the substance administered.