Temporal Lobe Cortical Electrical Stimulation during the Encoding and Retrieval Phase Reduces False Memories

A recent study found that false memories were reduced by 36% when low frequency repetitive transcranial magnetic stimulation (rTMS) was applied to the left anterior temporal lobe after the encoding (study) phase. Here we were interested in the consequences on a false memory task of brain stimulation throughout the encoding and retrieval task phases. We used transcranial direct current stimulation (tDCS) because it has been shown to be a useful tool to enhance cognition. Specifically, we examined whether tDCS can induce changes in a task assessing false memories. Based on our preliminary results, three conditions of stimulation were chosen: anodal left/cathodal right anterior temporal lobe (ATL) stimulation (“bilateral stimulation”); anodal left ATL stimulation (with a large contralateral cathodal electrode – referred as “unilateral stimulation”) and sham stimulation. Our results showed that false memories were reduced significantly after the two active conditions (unilateral and bilateral stimulation) as compared with sham stimulation. There were no significant changes in veridical memories. Our findings show that false memories are reduced by 73% when anodal tDCS is applied to the anterior temporal lobes throughout the encoding and retrieval stages, suggesting a possible strategy for improving certain aspects of learning

SPECIAL ISSUE ARTICLE ∆ 9-THC REINSTATES BEER- AND SUCROSE-SEEKING BEHAVIOUR IN ABSTINENT RATS: COMPARISON WITH MIDAZOLAM, FOOD DEPRIVATION AND PREDATOR ODOUR

Abstract — Aims: Recent studies suggest that cannabinoid receptor agonists may promote relapse to drug-seeking behaviour after a period of abstinence. In this study, the ability of ∆ 9-tetrahydrocannabinol (THC) to reinstate previously reinforced responding for alcoholic and non-alcoholic beverages was assessed in rats using a novel lick-based paradigm. Methods: Rats were initially given free access to beer (containing 4.5 % ethanol v/v), near-beer (a beverage that looks and tastes like beer but contains <0.5 % ethanol v/v) or isocaloric sucrose in their home cages for 3 weeks. They were then trained to lick at a tube to self-administer the pre-exposed beverage in operant chambers under a VR10 schedule in 30-min sessions daily. After ~3 weeks of such access, the rats underwent an extinction procedure, so that licking at the tube produced no reward. Once responding had ceased, the rats were subjected to various reinstatement tests. Results: In Experiment 1, the cannabinoid receptor agonist ∆ 9-THC (1 mg/kg) significantly reinstated responding, previously reinforced with beer or near-beer. The effect was unlikely to be caused by increased appetite because 24 h food-deprivation had no such effect. Exposure to cat odour in the test chamber failed to reinstate responding for beer or near-beer and caused a complete inhibition of responding. In Experiment 2, ∆ 9-THC (0.3 and 1 but not 3 mg/kg) again reinstated beer-seeking behaviour while the 1 mg/kg dose also reinstated responding in sucrose trained animals. Midazolam (0.15 mg/kg but not 0.5 or 1.5 mg/kg) produced a modest reinstatement of beer-seeking but had no effect on sucrose-seeking behaviour. Conclusions: The finding that ∆ 9-THC ca

Temporal lobe cortical electrical stimulation during the encoding and retrieval phase reduces false memories.

A recent study found that false memories were reduced by 36% when low frequency repetitive transcranial magnetic stimulation (rTMS) was applied to the left anterior temporal lobe after the encoding (study) phase. Here we were interested in the consequences on a false memory task of brain stimulation throughout the encoding and retrieval task phases. We used transcranial direct current stimulation (tDCS) because it has been shown to be a useful tool to enhance cognition. Specifically, we examined whether tDCS can induce changes in a task assessing false memories. Based on our preliminary results, three conditions of stimulation were chosen: anodal left/cathodal right anterior temporal lobe (ATL) stimulation ("bilateral stimulation"); anodal left ATL stimulation (with a large contralateral cathodal electrode--referred as "unilateral stimulation") and sham stimulation. Our results showed that false memories were reduced significantly after the two active conditions (unilateral and bilateral stimulation) as compared with sham stimulation. There were no significant changes in veridical memories. Our findings show that false memories are reduced by 73% when anodal tDCS is applied to the anterior temporal lobes throughout the encoding and retrieval stages, suggesting a possible strategy for improving certain aspects of learning

Mean number of veridical memories during and after stimulation.

<p>Mean number of veridical memories during and after stimulation.</p

Schematic representation of electrode montages.

<p>A represents bilateral stimulation (35 cm² electrodes in the left and right ATL) and B represents unilateral stimulation (35 cm² electrode in the left and 100 cm² electrode in the right ATL).</p

Performance as indexed by number of false memories during sham, unilateral and bilateral stimulation.

<p>Columns represent the mean number of false memories and error bars indicate mean standard error.</p