State-dependent effects of marihuana on human memory

State-Dependent Memory: Neurobiological Advances and Prospects for Translation to Dissociative Amnesia

In susceptible individuals, overwhelming traumatic stress often results in severe abnormalities of memory processing, manifested either as the uncontrollable emergence of memories (flashbacks) or as an inability to remember events (dissociative amnesia, DA) that are usually, but not necessarily, related to the stressful experience. These memory abnormalities are often the source of debilitating psychopathologies such as anxiety, depression and social dysfunction. The question of why memory for some traumatic experiences is compromised while other comparably traumatic experiences are remembered perfectly well, both within and across individuals, has puzzled clinicians for decades. In this article, we present clinical, cognitive, and neurobiological perspectives on memory research relevant to DA. In particular, we examine the role of state dependent memory (wherein memories are difficult to recall unless the conditions at encoding and recall are similar), and discuss how advances in the neurobiology of state-dependent memory (SDM) gleaned from animal studies might be translated to humans.

Hashish extract impairs retention of defeat-induced submissive behavior in mice

The effects of hashish extract on adaptive behavior of male mice were studied in a paradigm which allows the investigation of learning mechanisms in a social context. Mice of the C3H strain, which were not submissive in a confrontation with a nonaggressive DBA mouse on day 1, were defeated on day 2 over 3 min by aggressive, isolated DBA mice, and showed conditioned submissive behavior upon mere contact with a nonaggressive DBA mouse on day 3. A hashish extract containing 38.6-39.4% delta 9-tetrahydrocannabinol (delta 9-THC), 11.6-12.0% cannabinol and 47.7-48.5% cannabidiol was administered orally in all experiments. Hashish extract given 90 min before defeat on day 2, in dosages corresponding to 1, 5, and 10 mg delta 9-THC/kg, impaired retention of defensive upright, defensive sideways and immobility on day 3 (experiment 1). Experiment 2 showed that the drug (5, and 10 mg delta 9-THC/kg) had no antinociceptive potency in mice and did not modify defeat-induced analgesia. Experiment 3, with drug (5 mg delta 9-THC/kg) or solvent administration on day 2 and day 3, showed that the retention deficit was neither due to state-dependent learning, nor to impaired retrieval. It is suggested that hashish extract administered before learning may interfere with memory processing.

State-dependent learning in children receiving methylphenidate

Methylphenidate state-dependent learning was investigated using a paired-associate learning task of 16 pairs of pictures. Subjects were 15 children for whom methylphenidate was currently being prescribed. Each child was seen for two learning sessions and two testing sessions. Learning took place under placebo and under the child's regular dosage of methylphenidate. During retention testing all combinations of learning drug-state and testing drug-state were observed for each child. Data were analyzed using contrast variables which took into account the repeated-measures nature of the design. The results indicated that there was a trend in the direction of state-dependence in the whole sample. Significant symmetrical state-dependent effects were obtained in those subjects whose original learning was facilitated by methylphenidate.

Effect of diazepam and chlorpromazine on memory functions in man

The effect of a single oral dose of diazepam 10 mg or chlorpromazine 25 mg on memory in man was examined in a double-blind study, each drug being crossed-over against placebo, with 20 subjects for each drug. Kahn's Test for Symbol Arrangement and a paired association-learning task were used for assessment of acquisition, storage and retrieval, and state-dependency effects. A flicker-fusion test, two coordination tests, and a choice reaction task were used to evaluate alertness in the subjects. Diazepam significantly impaired acquisition, but slightly facilitated recall. Reaction time was shortened after acute diazepam treatment and coordination was impaired after two weeks treatment with diazepam. Acute treatment with chlorpromazine did not change memory or psychomotor performance.

Separation of DNA-dependent DNA polymerase activities in Micrococcus radiodurans

DNA polymerase activities in Micrococcus radiodurans were separated into two fractions after purification more than 2000 fold. They differ in pH optimum and residual activities in the absence of a full deoxyribonucleoside triphosphates complement. NAD partly inhibited one of the activities. Both activities were eluted as a single peak on gel filtration and sedimented at the same rate on glycerol gradient centrifugation. Molecular weight 140000 was calculated from Stokes radius and sedimentation constant. Deoxyribonuclease activity was detected on one of the polymerase activities which preferentially degraded double-stranded DNA. Priming activity of nicked DNA was reduced by gamma-irradiation. These results have been related to the possible rolls in repair synthesis in vivo or DNA synthesis in permeable cells of M. radiodurans.

A test of state dependency effects in marihuana intoxication for the learning of psychomotor tasks

Cannabis cigarettes calibrated to deliver 7 mg delta9-THC were administered to experienced cannabis users and to novices in a 2 x 2 state-dependency learning design using psychomotor tasks. Subjects given four training sessions under marihuana performed no better on the fifth (test) session with the drug than those subjects who had trained in the non-drug condition and were tested in the drug condition. Cannabis-induced impairment in the performance of these tasks is such that prior training in the non-drug condition appears to confer no advantage to the subject. There was no evidence of state-dependency effects in psychomotor performance between drug and non-drug conditions.

A rapid rise in cell variants during the senescence of populations of human fibroblasts

An attempt has been made to measure the frequency of mutations throughout the lifespan of human fibroblast strain MRC-5. A novel procedure has been used which involves staining individual cells for high levels of glucose-6-phosphate dehydrogenase. Evidence is presented that this phenotype is due to mutation. The frequency of variants was scored from passage 16 until the final phase of senescence (passage 60). There is an exponential increase of stained cells throughout this period. The results are in agreement with the general error theory, which proposes that aging is due to a breakdown in the fidelity of information transfer between macromolecules.