Behavioural brain research
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In the present study, we investigated the influence of intra-medial septum (intra-MS) injections of dopamine D1 receptor agents on amnesia induced by intra-CA1 injections of a muscarinic acetylcholine receptor antagonist, scopolamine. This study used a step-through inhibitory (passive) avoidance task to assess memory in adult male Wistar rats. The results showed that in the animals that received post-training intra-MS injections of saline, intra-CA1 administrations of scopolamine (0.75, 1, and 2 μg/rat) decreased inhibitory avoidance (IA) memory consolidation as evidenced by a decrease in step-through latency on the test day, which was suggestive of drug-induced amnesia. ⋯ Intra-MS injections of a dopamine D1 receptor antagonist, SCH23390 (0.5 and 0.75 μg/rat) by itself impaired IA memory consolidation, and also at dose of 0.75 μg/rat increased amnesia induced by intra-CA1 administrations of an ineffective dose of scopolamine (0.5 μg/rat). Post-training intra-MS injections of ineffective doses of SCH23390 (0.1, 0.3 and 0.5 μg/rat) prevented an effective dose of SKF38393 response to the impaired effect of scopolamine. These results suggest that dopamine D1 receptors in the MS via projection neurons to the hippocampus affect impairment of memory consolidation induced by intra-CA injections of scopolamine.
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The fundamental cognitive-control function of inhibitory control over motor behavior has been extensively investigated using the Stop-signal task. The critical behavioral parameter describing stopping efficacy is the Stop-signal response time (SSRT), and correlations with estimates of this parameter are commonly used to establish that other variables (e.g., other behavioral measures or brain activity measures) are closely related to inhibitory motor control. Recently, however, it has been argued that SSRT estimates can be strongly distorted if participants strategically slow down their responses over the course of the experiment, resulting in the SSRT no longer reliably representing response-inhibition efficacy. ⋯ Concerning brain-behavior correlations, only the left anterior insula was found to be significantly correlated with the SSRT within the set of areas tested here. Interestingly, this brain-behavior correlation differed little for the different SSRT-estimation procedures. In sum, the current results highlight that different SSRT-estimation procedures can strongly influence the distribution of SSRT values across subjects, which in turn can ramify into correlational analyses with other parameters.