Steven A. Hillyard, PhD
Dr. Hillyard is widely recognized for his investigations in the area of human cognitive processes and is a leading figure in the electrophysiological study of human attention using the event-related potential (ERP) technique.
The Hillyard laboratory is at the forefront of work on the nature of attention and its neuronal substrates. The traditional experimental approach used by the lab entails recording of the electrical and magnetic activity of the brain during task performance. However, over the past several years, new neuroimaging methods have been incorporated into the research program. These include positron emission tomography and functional magnetic resonance imaging (fMRI). Using these complementary neuroimaging methods, Dr. Hillyard has made advances in specifying the cortical areas in which attention facilitates sensory processing and in measuring the timing of these operations.
In a study that combined ERPs, fMRI, and retinotopic mapping, the Hillyard group showed that visual inputs are first enhanced by attention in extrastriate areas V3 and V4 at 80msec-100msec after stimulus delivery. Neural activity in the primary visual cortex (V1) is also enhanced by attention, but only after a further delay, which the researchers attribute to feedback from higher cortical areas. In an ongoing line of investigation, the Hillyard lab has demonstrated that the steady-state visual evoked potential (SSVEP) to a high-frequency flickering light is strongly modulated by selective attention to the stimulus location. Since the SSVEP is enhanced as soon as the "spotlight" of attention is directed toward the location of the flickering light, the time course of its amplitude changes can be used to measure the speed of attentional shifts from one stimulus to another. Based on this work, the group showed in a related study that attentional switching is not completed until 400msec-600msec after a symbolic attention-directing cue.
The laboratory is also widely recognized for studies on auditory selective attention. The group has successfully measured the "gradient" of attention across an array of 7 or 8 speakers that are continually emitting sounds in free-field when subjects are attending to only one speaker at a time. ERP recordings showed that the spatial focusing of attention takes place in two distinct stages, an early broadly tuned filtering of inputs over the first 80msec-180msec, followed by a more narrowly focused selection of target stimuli beginning at 250msec. The ERP data demonstrate that auditory spatial attention is deployed as a finely tuned gradient around an attended sound source in a free-field array of competing sound sources simulating a cocktail party.
In another study, the group found that congenitally blind persons, compared to sighted subjects, had more sharply tuned attentional systems for localizing sounds in their auditory surroundings.
Dr. Hillyard is a sought-after consultant to both federal agencies and private corporations. These include the National Institute of Mental Health, the Office of Naval Research, and the Veterans Administration. He serves on the Advisory Boards of the Kavli Institute for Mind and Brain, the NASA Ames Project, and the Organization for Human Brain Mapping. Dr. Hillyard has been an ad hoc grant reviewer for a variety of governmental agencies and private corporations.
He serves on the editorial boards of seven well-respected journals and referees articles for more than thirty different journals, including Neuron, Nature, and Science. Dr. Hillyard's preeminence in the field was recognized in 1999 by the 1,000-member Society for Psychophysiological Research at its annual meeting in Granada, Spain. The Distinguished Contribution Award has been conferred on only 19 senior investigators in the Society's 40-year history. He is also a recipient of the coveted MERIT Award from NIMH, for the 10-year period 1990-2000.
In 2013 he was elected to the American Academy of Arts and Sciences, one of our nation's most prestigious honor societies.