Delayed nonmatch-to-sample performance in HIV-seropositive and HIV-seronegative polydrug abusers

Working memory (WM) deficits are common in HIV-seropositive (HIV+) individuals and can be amplified by manipulating a variety of task parameters, such as increasing memory load or information complexity. The authors investigated the role of timing in HIV-associated WM defects by varying the amount of time required to maintain information online while holding memory load and information complexity constant. The authors studied 50 HIV+ and 35 HIV-seronegative (HIV-) polydrug abusers abstinent at testing and well-matched on demographic variables. The HIV- group outperformed the HIV+ group across all stimulus-response time delays. HIV-associated WM defects are not critically dependent on the amount of time stimulus representations must be maintained and might be attributed to impaired encoding or retrieval of stimulus representations.     

Test-retest reliability of the Temperament and Character Inventory in patients with opiate dependence

We examined the test-retest reliability of the Temperament and Character Inventory (TCI) in a clinical sample of 29 inpatients with opiate dependence disorder (DSM-IV). The previously validated French translation of the TCI was administered at baseline and again four weeks later. Intraclass correlation coefficients (ICCs) were used to estimate stability of the TCI over time for the 15 patients who completed the study. For all ICCs, the TCI showed satisfactory to excellent stability across all factors (ICC= 0.66-0.82). Stability was lower for the two temperamental traits of 'persistence' (ICC=0.51) and 'reward dependence' (ICC=0.63), possibly reflecting both clinical instability and measurement errors. These results highlighted the overall stability of the TCI in patients with opiate dependence and provided evidence for the usefulness of this questionnaire, which was originally designed to explore genetic and environmental factors underlying normal and abnormal personality dimensions. Further studies are required to confirm these results on larger clinical samples.     

Association of gephyrin with synaptic and extrasynaptic GABAA receptors varies during development in cultured hippocampal neurons

Several studies have reported extrasynaptic clusters of GABAA receptors in hippocampal neurons. Yet their functional relevance as well as their evolution in relation with gephyrin during synaptogenesis remain unknown. We have analyzed the expression pattern of the main proteins of the GABAergic synapses during synaptogenesis in cultured hippocampal neurons. We found that GABAergic terminals, characterized by VIAAT and GAD-65 expression, differentiated 3 to 7 days after the glutamatergic endings. At the postsynaptic side, the GABAAR- beta3 subunit was first diffuse and then clustered when GABAergic terminals differentiated and gephyrin formed large clusters. Colocalization of these proteins was high and increased with development. At later stages, GABAAR beta3 clusters colocalized with gephyrin at synaptic but also at extrasynaptic sites. GABAAR gamma2 subunits were directly expressed as clusters which were first extrasynaptic and not associated with gephyrin. Subsequently, the GABAAR gamma2 subunits associated with gephyrin at synaptic and/or extrasynaptic sites. Our data indicate that formation of GABAAR gamma2 subunit clusters is gephyrin independent.