Comparative effects of alcohol, secobarbital, methaqualone, and meprobamate on information processing and memory

Dose effects of secobarbital in a Sternberg memory scanning task

Mean reaction times obtained in a Sternberg memory-scanning task were examined for the effects of secobarbital at two doses (1.47 mg/kg and 2.94 mg/kg) spanning the dose range commonly used in clinical practice. Both doses slowed reaction time significantly, with a more pronounced effect at the higher dose. The discriminability of the probe stimulus interacted with the barbiturate, producing a hyperadditive effect on reaction time, but only at the high dose. There were no other significant interaction effects involving the drug. These data are interpreted as additional support for an hypothesis localizing the effects of secobarbital to stimulus-encoding stages in the reaction process.

Dose effects of methaqualone on stimulus encoding in a memory scanning task

Three task variables, stimulus quality, memory set size and response type, were used in a Sternberg binary classification task to define stimulus encoding, short-term memory scanning, and response selection stages within a serial stage reaction process. Mean reaction times, and the slopes and intercepts of the function relating reaction time to memory set size, were used to test the hypothesis that performance deficits seen at two doses of methaqualone (2.9 mg/kg and 5.9 mg/kg), in the range formerly in common clinical use, were specific to the stimulus encoding stage of the reaction process. Mean reaction times were increased significantly by the methaqualone at both doses, but the effects of the two doses did not differ from one another. The intercept of reaction time as a function of set size showed significant main effects of methaqualone, stimulus quality, and response type, and a significant hyper-additive interaction of methaqualone with stimulus quality. At 2.9 mg/kg, the intercept was increased by methaqualone but only with degraded stimuli. At 5.9 mg/kg, the intercept was increased by methaqualone for both high and low quality stimuli. These results suggested a dose-dependent selective effect of methaqualone on the stimulus encoding stage of the reaction process.

The effects of benzodiazepines on short-term memory and information processing

The effects of flunitrazepam 1 mg, triazolam 0.25 mg, lormetazepam 1 mg and placebo on stages of information processing in a Sternberg memory scanning task were investigated in ten normal volunteers. Overall reaction times for the task were increased 1 h following treatment with triazolam and both 1 h and 10 h following treatment with flunitrazepam. Response latencies were not appreciably altered by lormetazepam or placebo. The effects of flunitrazepam and triazolam were found to be localised in the stimulus encoding and serial comparison stages of the reaction process and not in response-selection organisation.