Lab Mission  

The global mission of the NeuroCognition Lab is to provide a better understanding of the neuronal basis of cognition in hearing adults and children as well as adults who are deaf. We are part of a relatively new discipline known as Cognitive Neuroscience. To understand this discipline you have to know something about the two parent fields: Cognitive Psychology and Neuroscience. Traditional cognitive psychologists seek to understand the general principles and properties of cognitive processes such as perception, attention, problem solving and language production (speaking and writing) and comprehension (listening and reading) -- generally without much interest in the brain. Neuroscientists come in a variety of flavors and study the nervous systems of humans and other species, but by-in-large they focus on relatively low level mechanisms within a specific system (e.g., some neurophysiologists seek to understand the workings of the fundamental units or cells of the nervous system known as neurons). Cognitive Neuroscientists are specifically interested in how the brain accomplishes the very complex tasks of perception, memory, attention problem solving and language. They do this by using a combination of theoretical and methodological techniques from both parent disciplines.

    The primary question our lab is interested in is how language and other, possibly related, cognitive systems are organized and function in the human brain. This turns out to be one of the most vexing questions in psychology! This is partly because language use is such a complex skill and partly because unlike many other cognitive systems (e.g., memory, attention, object recognition) there are no suitable animal models. Humans are the only species (on earth) that have evolved a complex, learned communication system with a rich set of structural rules. The lack of animal models has made it almost impossible to perform the kind of invasive controlled manipulation of the brain necessary to better understand how language works. Therefore, we have been forced to rely on less invasive procedures.

    In the last several years a number of new and exciting non-invasive techniques have become available for directly examining brain structure, and more recently brain function. CAT, MRI, PET, fMRI and ERP are some of the new techniques that allow the experimenter to take a snap-shot of the awake and intact human brain. Using a computer the experimenter can then construct a series of pictures of different regions/areas of the brain. While CAT and traditional MRI show what the brain looks like structurally (i.e., they show the anatomy of the brain), PET, fMRI, MEG and ERP show areas of the brain that are active or functioning (i.e., they show the physiology of the brain). It is these latter techniques that have been a boon to Cognitive Neuroscientists, as they allow the investigator to actually see brain areas involved in different cognitive activities.

    PET, fMRI and MEG are very expensive (millions of dollars) as they require a substantial investment in computer and imaging (scanner) hardware. Typically these systems can only be afforded by large medical centers that use them for clinical procedures. Psychologists interested in using this equipment must squeeze in whenever a time slot opens (frequently in the middle of the night). The advantage of these techniques is that they have relatively good spatial resolution. This means that they can tell with some accuracy where in the brain activity is occurring (within a few centimeters or even millimeters in the latest equipment).

    ERPs, which record the electrical activity of the brain, are within the budget of most psychological researchers, but traditionally they have suffered from relatively poor spatial resolution. This means that while they can measure different brain functions (i.e., activity in different cognitive systems) they cannot easily determine where the activity is coming from. However, recently advances in signal analysis and increases in electrode arrays have improved the resolution of ERPs and there is now some hope that this technique, especially when coupled with PET or fMRI, will be better able to determine which brain regions are active in different cognitive tasks.

    One thing that has become very apparent in the study of human cognition is that time is of the essence. Although neurons (the basic processing units of the brain) operate at a relatively slow rate (they can fire at best up to 1000 times per second), most of the higher level processes that neurons are responsible for (and that we are interested in) take place relatively rapidly -- on the order of less than a second. For example, the typical reader can process, on average, about three to four words a second. That means that, on average, a word is perceived, recognized and understood in about 250 to 400 milliseconds! The rate for processing spoken words is more variable, but is on the same basic time scale. Therefore, any technique that aspires to measure word comprehension as it unfolds in the brain will have to have sufficient temporal resolution to differentiate the sub-processes (e.g., perceiving, recognizing, understanding) involved in the task of reading or listening to words. PET and fMRI, because they measure the dynamics of blood flowing in the brain, have resolutions on the order of, at best, a few seconds (i.e., it takes a few seconds after a change in brain state for it to show up in blood flow changes). Clearly, this is too slow to resolve the sub-processes involved in word comprehension (or most other cognitive skills for that matter). However, ERPs, because they directly monitor the electrical activity of the brain, have millisecond level resolution -- that is, they are on-line. ERPs are therefore sensitive to brain activity well within the range of the component processes of most cognitive tasks -- including word comprehension. A substantial body of research now exists suggesting that ERPs are sensitive to a variety of language subprocesses as well as other cognitive processes.

    In the NeuroCognition Lab we use ERPs to study the neuronal basis of reading and listening to language and more recently the production of language as well. Since our arrival at SDSU in 2013 we have also begun an exciting new collaboration with the Laboratory for Language and Cognitive Neuroscience. In this research we are studying reading comprehension, comprehension of ASL signs and production of ASL in individuals who are deaf.

    Some of the questions that we are interested in are reflected in our on-going projects.