Robert E. Hampson and Sam A. Deadwyler 2008.12.23 Jang, HaYoung

1. Neural population recording in behaving animals: constituents of a neural code for behavioral decisions Robert E. Hampson and Sam A. Deadwyler 2008.12.23 Jang, HaYoung

2. Neural population recording • Ultimate purpose of populations of neural ensemble, recording and analysis • What does the ensemble encode? • How does the ensemble encode it? • How do brain structures use that ensemble code? • How neural activity within hippocampal circuits is integrated with behavioral and cognitive events

3. What is hippocampus?

4. Neural Patterns • It has proven more difficult to identify neural patterns that predict behaviors dependent on cognition

5. What constitues a neural code? • Sparse, distributed models (in hippocampus) • Few neurons encode information relevant to the code • Many neurons within a given brain area will be silent or have no correlation to the information • Information encoded by each neuron is novel, with little redundancy across neurons • Dense models (in cortex) • Most neurons within a given region will encode information relevant to the code • A high degree of redundancy between neurons with respect to the information encoded by each neuron • Specific neural correlates exhibit some form of topography or map of the information encoded

6. Single neuron firing in the DNMS task • Delayed-match-to-sample task (DMS) • 표본이 제시되고 나서 파지 기간 후에 그 표본에 대응되는 자극을 선택할 기회가 주어지는, 망각을 검사하는 한 방법 • Delayed-nonmatch-to-sample task(DNMS) • 보상과 자극이 짝지어지는 것을 관찰한 후 보상을 받기 위해 새로운 자극(앞서 제시되지 않은 자극)을 선택하는 것이 요구되는 과제

7. Differential firing patterns during DNMS task

8. Distribution of hippocampal cells • Dense rather than a sparse encoding of the DNMS task by the hippocampus

9. Information content of hippocampal ensembles • Hippocampal code appears to be highly redundant, with individual neurons encoding a specific element of the information

10. Distributed encoding of information in hippocampal emsembles • Hippocampal neurons shares the features of both dense and sparsely distributed models.

11. Summary • Both sparse and dense encoding models • With redundant information encoding among neurons, but dynamic information encoded by the ensemble as a whole that exceeds the information encoded by individual neurons • Hippocampal neural activity has been thoroughly characterized with respect to behavioral performance in the DNMS task