Apathy is widely reported in patients with neurological disorders or post viral infection but is also seen in otherwise-healthy aged individuals. This study investigated whether aged mice express behavioural and physiological changes indicative of an apathy phenotype. Using measures of motivation to work for reward, we found deficits in the progressive ratio task related to rate of responding. In an effort for reward task, aged mice were less willing to exert effort for high value reward. Aged mice exhibited reduced reward sensitivity and expressed lower measures of anxiety in the novelty supressed feeding test. In a test of cognition (novel object recognition) aged mice showed no impairments but activity was lower in a measure of exploration in a novel environment. Aged mice also showed an attenuated response to restraint stress with lower corticosterone and reduced paraventricular nucleus c-fos activation. Together, these data suggest aged mice show reduced goal-directed behaviour and reduced reward sensitivity and stress reactivity, reflective of emotional blunting and may be a suitable model for pre-clinical apathy research.

中文翻译：

---

老年小鼠的冷漠表型的证据

神经病患者或病毒感染后患者的冷漠感广泛报道，但在其他健康的老年人群中也见到冷漠感。这项研究调查了衰老的小鼠是否表现出指示冷漠表型的行为和生理变化。使用奖励动机的度量，我们发现与响应率相关的累进比率任务存在缺陷。在努力完成奖励任务时，老年小鼠不愿为获得高价值的奖励而付出努力。在新奇抑制喂养试验中，老年小鼠表现出较低的奖赏敏感性，并表现出较低的焦虑程度。在一项认知测试（新物体识别）中，老年小鼠没有出现任何损伤，但在新环境中的探索活动中活性较低。老年小鼠还表现出较低的皮质类固醇对束缚应激的减弱反应以及脑室旁核c-fos活化的降低。总之，这些数据表明，老年小鼠表现出降低了针对目标的行为，降低了奖赏敏感性和压力反应性，反映出情绪低落，可能是临床前冷漠研究的合适模型。