The Spatial Signal in the Learning of an Auditory Decision

Every day we make behavioral decisions based on our environment, in which the transformation of sensory information to motor command through learning and experience is essential. The behavior and neuronal mechanisms underlying the establishment of association between single sensory modality and motor decision are widely studied. However, many of decisions are made based on combined information from multiple sensory modalities. A few cross-modality studies showed that multiple sensory information significantly influenced the behavioral decisions that differs from single modality both in human and animals. Therefore, examining the behavior and neuronal mechanisms underlying how we learn to associate multiple sensory information to one motor decision will substantially advance our knowledge in sensory-cued decision making. Recent works including our own study have demonstrated that corticostriatal activity drives animal’s decision in an auditory frequency-discrimination task, and the plasticity pattern of these corticostriatal synapses encodes the learned associated between auditory cue and rewarded action. In the task, the animals learned to go to corresponding ports for reward based on different frequencies of the tones in the auditory cues. Interestingly, in these studies the navigation process between the end of auditory cues and the time that animals reached reward ports is largely ignored. In addition to the learning of auditory discrimination, the proper navigation to the ports is obviously an important learning part in this task. Therefore, we modified the task with a prolonged path between initiation port and reward port for better navigation analysis, and propose to examine how processes of spatial information and auditory information are coordinated during task learning. Hippocampus serves as an essential circuit unit to process spatial information. Our preliminary results indicated that the intact activity of hippocampal tri-synaptic circuit is required for learning this auditory task. To understand the functional role of hippocampal spatial coding for animal learning the auditory task, in aim I we will examine the role of spatial encoding in the learning of an auditory discrimination task. To understand how spatial information and auditory information processes are combined and coordinated during the task learning, in aim II we will dissect the circuit mechanism underlying the spatial coding in the learning of the auditory task.