Department of Psychology, University of Connecticut, Storrs, Connecticut 06269, USA.
J Neurosci. 2013 Apr 3;33(14):6212-24. doi: 10.1523/JNEUROSCI.2915-12.2013.
Hippocampal theta oscillations are postulated to support mnemonic processes in humans and rodents. Theta oscillations facilitate encoding and spatial navigation, but to date, it has been difficult to dissociate the effects of volitional movement from the cognitive demands of a task. Therefore, we examined whether volitional movement or cognitive demands exerted a greater modulating factor over theta oscillations during decision-making. Given the anatomical, electrophysiological, and functional dissociations along the dorsal-ventral axis, theta oscillations were simultaneously recorded in the dorsal and ventral hippocampus in rats trained to switch between place and motor-response strategies. Stark differences in theta characteristics were found between the dorsal and ventral hippocampus in frequency, power, and coherence. Theta power increased in the dorsal, but decreased in the ventral hippocampus, during the decision-making epoch. Interestingly, the relationship between running speed and theta power was uncoupled during the decision-making epoch, a phenomenon limited to the dorsal hippocampus. Theta frequency increased in both the dorsal and ventral hippocampus during the decision epoch, although this effect was greater in the dorsal hippocampus. Despite these differences, ventral hippocampal theta was responsive to the navigation task; theta frequency, power, and coherence were all affected by cognitive demands. Theta coherence increased within the dorsal hippocampus during the decision-making epoch on all three tasks. However, coherence selectively increased throughout the hippocampus (dorsal to ventral) on the task with new hippocampal learning. Interestingly, most results were consistent across tasks, regardless of hippocampal-dependent learning. These data indicate increased integration and cooperation throughout the hippocampus during information processing.
海马体θ 振荡被认为在人类和啮齿动物中支持记忆过程。θ 振荡促进编码和空间导航,但迄今为止,很难将自主运动的影响与任务的认知需求区分开来。因此,我们研究了在做决策时,是自主运动还是认知需求对θ 振荡产生更大的调节作用。鉴于沿着背腹轴的解剖学、电生理学和功能分离,在接受训练以在位置和运动反应策略之间切换的大鼠中,同时在背侧和腹侧海马体中记录θ 振荡。在频率、功率和相干性方面,背侧和腹侧海马体的θ 振荡特征存在明显差异。在决策时期,θ 功率在背侧增加,但在腹侧减少。有趣的是,在决策时期,跑步速度和θ 功率之间的关系被解除,这种现象仅限于背侧海马体。在决策时期,θ 频率在背侧和腹侧海马体中均增加,尽管在背侧海马体中这种效应更大。尽管存在这些差异,但腹侧海马体的θ 振荡对导航任务有反应;θ 频率、功率和相干性都受到认知需求的影响。在所有三个任务中,在决策时期,背侧海马体中的θ 相干性增加。然而,在具有新海马体学习的任务中,相干性选择性地在整个海马体(从背侧向腹侧)增加。有趣的是,无论是否有海马体依赖性学习,大多数结果在所有任务中都是一致的。这些数据表明,在信息处理过程中,整个海马体的整合和协作增加。