Beneficial effects of thiamine on recognition memory and P300 in abstinent cocaine-dependent patients

Amphetamine and the Smart Drug 3,4-Methylenedioxypyrovalerone (MDPV) Induce Generalization of Fear Memory in Rats

Human studies have consistently shown that drugs of abuse affect memory function. The psychostimulants amphetamine and the "bath salt" 3,4-methylenedioxypyrovalerone (MDPV) increase brain monoamine levels through a similar, yet not identical, mechanism of action. Findings indicate that amphetamine enhances the consolidation of memory for emotional experiences, but still MDPV effects on memory function are underinvestigated. Here, we tested the effects induced by these two drugs on generalization of fear memory and their relative neurobiological underpinnings. To this aim, we used a modified version of the classical inhibitory avoidance task, termed inhibitory avoidance discrimination task. According to such procedure, adult male Sprague-Dawley rats were first exposed to one inhibitory avoidance apparatus and, with a 1-min delay, to a second apparatus where they received an inescapable footshock. Forty-eight hours later, retention latencies were tested, in a randomized order, in the two training apparatuses as well as in a novel contextually modified apparatus to assess both strength and generalization of memory. Our results indicated that both amphetamine and MDPV induced generalization of fear memory, whereas only amphetamine enhanced memory strength. Co-administration of the β-adrenoceptor antagonist propranolol prevented the effects of both amphetamine and MDPV on the strength and generalization of memory. The dopaminergic receptor blocker cis-flupenthixol selectively reversed the amphetamine effect on memory generalization. These findings indicate that amphetamine and MDPV induce generalization of fear memory through different modulations of noradrenergic and dopaminergic neurotransmission.

CSD/BEM localization of P300 sources in adolescents "at-risk": evidence of frontal cortex dysfunction in conduct disorder

BACKGROUND

Longitudinal studies have demonstrated that childhood conduct disorder is a significant risk factor for a wide range of adult psychiatric disorders. The present study attempted to identify neurophysiologic differences that might underlie this risk factor.

METHODS

The study examined 158 subjects, aged 14 to 20 years. Each subject was assigned to one of four groups defined by the factorial combination of the subject's gender and the relative number (-/+) of conduct problems exhibited before age 15. Event-related electroencephalographic potentials were recorded from each subject while he or she performed a memory scanning task. Each trial consisted of the brief presentation of either two or four consonant letters, a 2-sec memorization period, and a single "probe" letter. The subject was instructed to mentally compare the probe with the memory set and execute a discriminative (match vs. mismatch) key-press response.

RESULTS

Analyses of P300 event-related potentials elicited by the probe stimuli revealed a significant interaction between probe stimulus membership and conduct problems: the P300 difference between trials with matching versus mismatching probes was significantly greater in the control (CP-) group than in the CP+ group. Current source density analyses, utilizing a realistic head-shape boundary element model, revealed that CP- subjects exhibited a robust activation of the left prefrontal cortex on matching versus mismatching trials. Among CP+ subjects, the degree of prefrontal cortex activation was not significant.

CONCLUSIONS

The P300 results are consistent with those reported from previous studies of adolescents with conduct problems. Our study is unique in implementing current source density-boundary element method techniques for modeling P300 sources in "at-risk" adolescents. These techniques lend greater anatomical precision to the conclusion that conduct problems are associated with a specific dysfunction of the frontal brain.