Center for Cognitive Brain Imaging

at Carnegie Mellon University


Brain Imaging and TMS Studies of Individual Differences in Cognitive Processing

TMS coilTMS coil inside the fMRI head coil
This project addresses the goal of understanding the brain systems that underlie individual differences in cognitive performance, and uses this understanding to enhance performance of individuals and organizations. The acquisition of fMRI brain images concurrently with repetitive transcranial magnetic stimulation (rTMS) provides new leverage with which to address this issue. Low-frequency (1Hz) repetitive TMS applied over a brain region for several minutes causes a temporary depression of function in that region. The concurrent use of rTMS in the MRI scanner allows us to observe the adaptation of the cortical system as that key cortical center becomes less available.

TMS behavioralApplication of TMS ouside of the scanner
These studies also examine how various psychometric measures of cognitive abilities are related to brain function. In particular, the neural attributes being studied are network adaptability (dynamic changes in the recruitment of cortical networks), network connectivity (inter-center communication), and neural efficiency (amount of brain resources required to perform a given task). Thus, these studies apply rTMS to manipulate the availability of a given task-critical brain center while participants are performing a cognitive task in the MRI scanner, and then uses fMRI to assess how the brain network adapts to the unavailability of the affected center. Comparisons between task performance before and after TMS are made, as well as comparisons to the application of rTMS to non-task-critical regions. For example, it is possible to determine how the usual network of brain areas that activates during reading comprehension adapts itself when a key language center, such as the left posterior temporal area (Wernicke's area), becomes less available. At the same time, the behavioral effects of the TMS (speed and accuracy of comprehension) can also be assessed. These approaches help characterize the cortical dynamics of brain function, as well as the cognitive consequences and the individual differences.