Neural Basis of Sensory Discrimination Learning

描述（由申请人提供）：申请的长期目标是完整描述和理解当学习感官辨别时大脑是如何变化的。首席研究员领导了最近的技术进步，可以让皮质植入物在几个月的时间里从同一个大脑位置取样动作电位反应。这些进展首次为研究在整个学习过程中，大脑中分布式产生的动作电位如何在每天的基础上发生变化提供了机会。我们之前的工作是在整个学习过程中监测动物。在选择目标和避免干扰后的头两天，对任务目标和非目标的动作电位反应都增加了数倍，接受野在空间上拓宽。随着时间的推移，反应性恢复到正常水平，对任务干扰的反应被选择性地抑制。我们的工作假设是，这些可塑性效应只取决于认知奖励关联。在第一项研究中，我们将连续训练植入动物进行检测和识别任务，其中目标分配保持不变，每个任务持续数周。本实验将区分奖励与任务目标刺激的关联和奖励缺失与任务干扰的关联所产生的神经可塑性效应。然后，动物将在目标和干扰物互换的情况下执行相同的任务，以逆转奖励关联。然后，动物将对相同的刺激产生经典的条件反射，这在引入广泛的行为变化的同时保留了奖励关联；初步数据显示，这种转变产生的神经可塑性极小。然后，作为经典条件反射实验，目标和分心物的奖励关联将被逆转。其他研究将测试皮层可塑性的巧合输入模型和奖励关联模型，以确定当它们不一致时哪个优先。最后，研究将测试由这些关联引起的神经可塑性规则如何由大脑的神经调节系统实现的假设。在每项研究中，在行为表现前和行为表现期间，将监测脉冲反应、局部场电位和3b区接受野，以创建输出测量值，与行为数据进行比较。

DESCRIPTION (provided by applicant): The long-term objective of the application is a complete description and understanding of how the brain changes when a sensory discrimination is learned. The Principal Investigator has led recent technological advances that let cortical implants sample action potential responses from the same brain locations over many months. These advances provide the opportunity, for the first time, to study how the distributed generation of action potentials in the brain changes on a daily basis throughout the learning process. Our prior work has monitored animals throughout the learning process. In the first two days after selecting for targets and avoiding distractors, action potential responses to both task targets and non-targets increase several-fold, and receptive fields broaden spatially. With time, responsiveness returns to normal levels, and responses to task distractors become selectively suppressed. Our working hypothesis is that these plasticity effects depend only on cognitive reward associations. In the first study we will serially train implanted animals in detection and discrimination tasks in which the target assignment is kept constant, for several weeks at each task. This experiment will separate neuroplasticity effects that occur through associating rewards with task target stimuli and associating omission of reward with task distractors. Animals will then perform the same task with target and distractor assignments swapped, to reverse reward associations. Then, animals will be classically conditioned to the same stimuli, which preserve reward associations while introducing a broad range of behavioral changes; preliminary data shows minimal neuroplasticity results from this transition. Then, as a classical conditioning experiment, target and distractor reward associations will be reversed. Other studies will test coincident-input models of cortical plasticity against reward association models to determine which takes precedence when they are inconict. And lastly, studies will test hypotheses on how the neuroplasticity rules caused by these associations are implemented by the brain's neuromodulatory systems. Throughout each study, spike responses, local field potentials, and receptive fields in area 3b will be monitored before and during behavioral performance to create output measures to compare with behavioral data. This study proposes basic science investigations into circuitry underlying learning. It will lay the substrate for what is sure to be a very active area in public health in the coming decade. Abnormalities in these neuromodulatory centers, the Nucleus Basalis, Substantia Nigra, and Locus Coeruleus, are thought to be behind an array of neurological and mental disorders such as age-related cognitive decline, Alzheimer's disease, Parkinson's disease, Schizophrenia, General Depression, OCD, and addiction. Understanding how the brain changes when we learn will enable more targeted studies of how learning, and thus neuromodulatory activity, is abnormal in these neurological conditions. However, this is a basic science application, and so direct applicability to public health will depend upon follow-up applied studies.