Spatial learning of the water maze: Progression of brain circuits mapped with cytochrome oxidase histochemistry

The progression of brain circuits involved in spatial learning tasks is still a matter of debate. In addition, the participation of individual regions at different stages of spatial learning remains a controversial issue. In order to address these questions, we used quantitative cytochrome oxidase histochemistry as a metabolic brain mapping method applied to rats (Rattus norvegicus) trained in a water maze for 1, 3 or 5 days of training. Sustained changes throughout training were found in the lateral septal nucleus and anteroventral thalamic nucleus. As compared to naïve or habituation groups, rats with 1 day of training in the spatial learning task showed involvement of the lateral mammillary nucleus, basolateral amygdala and anterodorsal thalamic nucleus. By 5 days of training, there were mean changes in the hippocampal CA3 field and the prefrontal cortex. The regions involved and their pattern of network interactions changed progressively over days of training. At 1-day there was an open serial network of pairwise correlations. At 3-days there was a more closed reciprocal network of intercorrelations. At 5-days there were three separate parallel networks. In addition, brain-behavior correlations showed that CA1 and CA3 hippocampal fields together with the parietal cortex are related to the mastery of the spatial learning task. The present study extends previous findings on the progressive contribution of neural networks to spatial learning.     

认知与情绪过程的脑诱发电位研究——情绪的适应性假说

本研究观测了30名女性被试在月经周期中的不同激素时相对图像刺激的情绪价值的主观评估和脑诱发电位反应。调节刺激的情绪价值的五类幻灯片分别为普通人像、婴儿像、皮肤病人像、男模特儿像和女模特儿像。实验发现只有脑诱发电位的P3成份随刺激的情绪价值和激素的时相而变化。被评为喜爱与不喜爱的图像(婴儿像和皮肤病人像)所诱发的P3波在幅度上均明显高于中性图像(普通人像)所致的P3反应。在高孕激素时相,对婴儿像和男模特儿像的P3反应高于在低孕激素时相对同类刺激的P3反应。高孕激素时相还伴有对各类图像性感程度评估值的降低。对各类图像喜爱程度的评估则随雌激素水平的上升而增高。上述实验结果表明,P3波敏感于刺激的情绪价值并反映了认知与情绪过程中受生理状态调节的适应性变化。     

Brain c-Fos immunocytochemistry and cytochrome oxidase histochemistry after a fear conditioning task

The involvement of the basolateral and the medial amygdala in fear conditioning was evaluated using different markers of neuronal activation. The method described here is a combination of cytochrome oxidase (CO) histochemistry and c-Fos immunocytochemistry on fresh frozen brain sections. Freezing behavior was used as an index of auditory and contextual fear conditioning. As expected, freezing scores were significantly higher in rats exposed to tone-shock pairings in a distinctive environment (conditioned; COND), as compared to rats that did not receive any shocks (UNCD). CO labeling was increased in the basolateral and medial amygdala of the COND group. Conversely, c-Fos expression in the basolateral and medial amygdala was lower in the COND group as compared to the UNCD group. Furthermore, c-Fos expression was particularly high in the medial amygdala of the UNCD group. The data provided by both techniques indicate that these amygdalar nuclei could play different roles on auditory and contextual fear conditioning.