Dr. Johnson's research involves recording the electrical activity of the brain, using a technique known as event-related brain potentials (ERP), to study the brain mechanisms underlying a variety of cognitive processes. The ERP consists of a series of electrical potentials, referred to as peaks or components, which are elicited as external and internal events are processed in various brain structures. By virtue of its multi-component nature, and the fact that the latency, amplitude and scalp distribution can be quantified for each component, the ERP represents a type of brain imaging that permits the tracking of information through the nervous system on a millisecond time base. By combining information on an ERP component's latency and amplitude, in relation to experimental manipulations, the temporal and functional aspects of a process can be characterized at a wide range of levels within the central nervous system. With the further addition of scalp distribution data (i.e., the pattern of voltage gradient over the scalp at any point in time), it is possible to identify changes in the activity in the brain networks supporting particular cognitive processes. Moreover, since the ERP technique is entirely non-invasive, the neural basis of information processing activities can be studied in normal humans and patients as often as desired across the entire life span.
Currently, Dr. Johnson's research is concerned with using the properties of the ERP to characterize and quantify the nature of the processes and neural systems underlying the cognitive basis of deception. More recently, results from our deception studies have led us to investigate related questions in the realm of social cognitive neuroscience. In addition, Dr. Johnson has been investigating the cognitive and neural basis underlying different types of long-term memory, the basis of memory changes in aging, and the mechanism of action of sedative drugs on memory.