FACULTY and AFFLIATED SCIENTISTS
John Foxe
Nathan S. Kline Institute for Psychiatric Research
140 Old Orangeburg Road
Orangeburg, New York 10962
Vox: (845) 398-6547
Fax: (845) 398-6545
e-mail: foxe@nki.rfmh.org
Web Site: http://cogneuro-nki.rfmh.org/
Publications
The goal of my research:
Is to investigate and characterize the neural mechanisms of cognitive operations that lead to human perception and action. To achieve a full understanding of such cognitive operations, our investigations must encompass knowledge from the macroscopic brain structural level to the microscopic level of single neurons and receptor channels. We must also embrace issues of brain connectivity, functional specificity within brain modules and the spatiotemporal dynamics of activations across the brain network. Thus, our approach is to 1) identify underlying brain regions, neuron populations and connections (i.e., the "active circuits"), 2) to identify physiological and, if possible, pharmacological processes within active circuits and 3) to define temporal activity patterns within each active brain module and across the modules comprising a given active circuit.
The Specific Questions:
My research has focused on two main questions within human perception and cognition.
Deploying Attention: The first main goal of my research program focuses on investigating the neural mechanisms of deploying and switching attention between different attention-demanding tasks. These tasks can be within different stimulus feature channels (e.g. colour versus texture), different sensory modalities (e.g. vision versus audition) or different spatial locations. While the vast majority of attention research has focused on the stimulus processing effects that result from preceding attentional switches, my work has been focused on the switches themselves. That is, I am primarily interested in establishing the mechanisms by which the brain establishes a 'bias' or 'anticipatory set' for a given task. It is these 'sets' that then give rise to the subsequent stimulus processing effects that are seen, and it is these 'sets' that are most allied to the perceptual phenomenon of voluntary attention. It is essential that we fully understand how the brain makes these switches and establishes these biased brain states if we are to gain a real understanding of the nature of attentional processing in the brain. Impairment in the ability to effectively deploy attention is a core deficit in a number of psychiatric disorders including schizophrenia, autism and attention deficit disorder.
Multisensory Integration: The second main goal of my research program focuses on investigating the neural mechanisms of integrating information from multiple sensory systems. Most studies of perception have examined the various sensory systems in isolation, and these endeavors have been remarkably fruitful. However, our experience and subsequent memory of events is multisensory. Clearly, the information provided by the various senses is combined to form a single integrated experience of the world. Consequently, a complete understanding of perception must include the processes that produce multisensory integration. While a tremendous amount of work has been conducted in animals, particularly in subcortical structures, this facet of perception has been largely unexplored in humans at the cortical level. Only a small number of cross-sensory studies have been conducted using functional imaging (fMRI and PET). In particular, high-density event-related potentials (ERPs) have only been used to measure the spatio-temporal dynamics of cortical interactions in the past 2 years. My laboratory has been conducting multisensory integration experiments in an attempt to detail a basic taxonomy of integration effects. A long-term goal is to define the network of cortical brain areas responsible for integrating inputs from the various combinations of sensory inputs. Recent data from my laboratory have challenged a generally held notion that multisensory cortical integration is a higher-level process that occurs after extensive processing of input to the constituent unisensory systems. We have uncovered evidence in both human and monkeys that initial cortical multisensory integrations may occur in an early feedforward manner.
The Experimental Techniques:
My means of investigating these questions incorporates 3 complementary components: 1) high-density event-related potential (ERP) recordings (128-channels), 2) functional Magnetic Resonance Imaging (fMRI) and 3) parallel intracranial investigations in non-human primates. I am firmly convinced that by fully optimizing the spatial resolution of the ERP through current density analysis and inverse source localization, we can then fully exploit this techniques exceptional temporal resolution. One of the best ways to optimize the spatial resolution of high-density ERPs is to combine/constrain the source solution with data from event-related functional hemodynamic imaging studies (fMRI) that use identical paradigms in the same subjects. In this manner, we can define the spatio-temporal interaction dynamics as a given network of cortical areas, an active circuit, interacts to achieve a given sensory or cognitive function. Finally, in collaboration with Drs. Charlie Schroeder and Dan Javitt, I have been conducting studies in monkeys using identical paradigms to those used in our human subjects, while recording intracranially from multi-contact linear array electrodes. By this approach, we can step from the macroscopic level of inter-areal interactions that we can define non-invasively in humans, down to the neuronal ensemble level in monkeys, where we can differentiate feedforward from feedback processes, inhibitory from excitatory potentials and relate the post-synaptic potentials to concurrent multi-unit activity. This three-pronged approach is allowing for unprecedented insights into the neural bases of sensory processing and cognitive function.