Statistical data from: Cholinergic modulation of hippocampally mediated attention and perception

Attention to the relations between visual features modulates hippocampal representations. Moreover, hippocampal damage impairs discrimination of spatial relations. We explore a mechanism by which this might occur: modulation by the acetylcholine system. Acetylcholine enhances afferent input to the hippocampus and suppresses recurrent connections within it. This biases hippocampal processing toward environmental input, and should improve externally-oriented, hippocampally mediated attention and perception. We examined cholinergic modulation on an attention task that recruits the hippocampus. On each trial, participants viewed two images (rooms with paintings). On "similar room" trials, they judged whether the rooms had the same spatial layout from a different perspective. On "similar art" trials, they judged whether the paintings could have been painted by the same artist. On "identical" trials, participants simply had to detect identical paintings or rooms. We predicted that cholinergic modulation would improve performance on the similar room task, given past findings that hippocampal representations predicted, and hippocampal damage impaired, behavior on this task. To test this, nicotine cigarette smokers took part in two sessions: one before which they abstained from nicotine for 12 hours, and one before which they ingested nicotine in the past hour. Individual differences in expired breath carbon monoxide levels — a measure of how recently or how much someone smoked — predicted performance improvements on the similar room task. This finding provides novel support for computational models that propose that acetylcholine enhances externally oriented attentional states in the hippocampus.对视觉特征间关联的注意调控海马体（Hippocampus）表征。此外，海马体损伤会削弱空间关系辨别能力。本研究旨在探究其潜在机制：即乙酰胆碱系统（Acetylcholine system）的调控作用。乙酰胆碱（Acetylcholine）可增强向海马体的传入输入，并抑制海马体内部的循环连接。这会使海马体的信息处理偏向环境输入，从而优化外部导向的、由海马体介导的注意与感知功能。我们针对一项需要调用海马体的注意任务，考察了胆碱能（Cholinergic）调控的效果。在每一轮试次中，被试会观看两张带有画作的房间图像。在“相似房间”试次中，被试需判断两个房间从不同视角观察时是否拥有相同的空间布局；在“相似画作”试次中，被试需判断两幅画作是否可能出自同一位艺术家之手；在“完全相同”试次中，被试仅需识别完全一致的画作或房间。基于过往研究发现：海马体表征可预测该任务的行为表现，而海马体损伤会损害该任务的行为成绩，我们预测胆碱能调控能够提升“相似房间”任务的完成表现。为验证这一假设，我们招募了尼古丁卷烟吸烟者参与两个实验阶段：一个阶段要求被试在实验前12小时内戒除尼古丁，另一个阶段则要求被试在实验前1小时内摄入尼古丁。呼出气一氧化碳水平（用于衡量被试近期吸烟时长与吸烟量的指标）的个体差异，可预测“相似房间”任务的成绩提升幅度。本研究结果为相关计算模型提供了新的实证支持：这些模型提出，乙酰胆碱可增强海马体中的外部导向注意状态。