ABSTRACT

Experimental studies of neural activity in vivo have historically focused on the spiking of single neurons. Single-neuron recordings have revealed a great deal about how the ring of individual neurons is modulated by sensory stimuli. However, any one neuron functions only as part of a much larger population whose combined activity underlies an animal’s processing of information. Characterizing the structure of neuronal population activity, and its relationship to sensory stimuli, is a key step toward understanding how information is processed in the brain. Over the last decade or so, technological advances, such as the development of tetrodes, silicon microelectrode arrays, spike-sorting techniques, and two-photon calcium imaging, have allowed for recording the activity of up to hundreds of neurons simultaneously in vivo. An understanding of how neuronal populations come together to process information together is thus now coming within reach. This chapter reviews some of this information, with an emphasis on the neocortex.