Research Projects in the Smith Laboratory
Our research employs neurophysiological and computational approaches to study the primate visual system. Specifically, we are interested in the dynamics of visual processing at the level of individual neurons and populations. We study how the temporal structure of neuronal responses can teach us about cortical circuits, how form processing is accomplished by a distributed network of neurons, and how populations of neurons integrate information provided by inputs within and between cortical regions. The following is a list of projects in which potential laboratory members may be interested:
(1) In regions of the cortex, the interactions between neurons have a particular spatial and temporal structure. This structure is dependent on the distance between neurons, the response properties of the neurons, the cortical layer in which they reside, and the behavioral state of the animal. We seek to characterize the functional connectivity among neurons and understand how changes in that pattern are related to visual perception and cognition. We have primarily focused this work on primary visual cortex (V1) and visual area V4, using implanted 100-electrode "Utah" arrays to record neural activity.
(2) Most studies of cortical function have employed recordings from single microelectrodes in a single cortical region. An understanding of cortical processing requires knowledge of how large populations of neurons interact in response to inputs from other cortical regions. We are interested in exploring how large populations of neurons in cortical areas communicate. Currently we've been aiming our study on a particular pair of areas, V4 and FEF. This project involves simultaneous recording from groups of neurons in both areas, microstimulation, and computational analysis to determine the interactions between neurons. While this project is aimed at a particular pair of regions, the findings will be broadly applicable to studies of connected areas of cortex and understanding the functioning of the cortical hierarchy.
(3) The frontal eye field (FEF), a region of prefrontal cortex that plays an important role in generating eye movements, sits at the junction between sensory perception and motor control. However, the cortical circuits through which neurons in the frontal eye field communicate, and indeed even some of their basic visual properties, are not well understood. We have sought to understand how the functional connections between neurons in the FEF as well as the receptive fields of individual neurons are modulated by the behavioral task. We are utilizing multi-contact electrodes to record from 16 or more sites within FEF simultaneously, with the hope that our findings will lead to a greater understanding of how visual and motor signals interact in the control of eye movements and the role of eye movement signals in visual attention.
(4) Electroencephalography (EEG) is the pre-eminent method for studying the electrophysiology of human brains. However, because in all but exceptional circumstances we are unable to record directly from human neurons, much remains unknown about the relationship between EEG signals measured at the scalp and the underlying neuronal events that give rise to them. By using our neural population recording techniques concurrently with scalp-recorded EEG, our laboratory is engaged in pioneering work to characterize the link between neuronal spiking events and EEG signals. This research is critical to understanding the neural basis of EEG, which is universally fundamental to studies of neurophysiology in both humans and animals. It will also provide insight into how local populations of neurons interact with global fluctuations in brain activity.