THE SIGNIFICANCE OF NEURAL ENSEMBLE CODES DURING BEHAVIOR AND COGNITION

The development of techniques to record from populations of neurons ha s made it possible to ask questions concerning the encoding of task-re levant information in awake, behaving animals. The issue of how groups of neurons within different brain structures register and retrieve re presentations of behaviorally significant events can now be addressed using multineuron-recording techniques. This review examines recent st udies employing simultaneous recording of ten or more individual neuro ns in the mammalian brain. A major issue discussed is whether ensemble information content reconstructed from single-neuron recordings may b e underestimated if compared to ensembles where those same neurons wer e recorded simultaneously. The mechanics of ensemble information encod ing in the hippocampus is illustrated from population statistical anal yses of ensemble activity during performance of a delay task. Detailed descriptions of methods of extracting ensemble information, as well a s cross-correlational analyses, are discussed in the context of emerge nt issues regarding interpretation of ensemble data.