Laboratory for Multimodal Human Brain Mapping
The Laboratory for Multimodal Human Brain Mapping, led by neurosurgeon Ashesh Mehta M.D./Ph.D., uses multiple methods for measuring brain structure and function to advance our understanding of human brain function and the treatment of epilepsy. The methods used include magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI), electrocorticography (ECoG), and direct electrical cortical stimulation. The main goals of the lab are:

1) Improving the diagnosis of epilepsy patients.
Successfully treating epilepsy requires understanding what regions of the brain are responsible for seizure activity and what regions are critical to cognitive functions such as language and memory. fMRI is a promising method for doing this since it can non-invasively measure the function of the entire brain with millimeter spatial resolution. The lab is investigating the utility of fMRI for identifying regions involved in language function and for identifying networks of areas responsible for epileptic activity.

2) Improving our understanding of the root causes of epilepsy.
As our understanding of epilepsy has grown, it has become increasingly clear that epilepsy is often caused by abnormal interactions between different parts of the brain. In other words epilepsy is often caused by a pathological network rather than a single epileptogenic area. The lab researches the use of fMRI, DTI, ECoG, and cortical stimulation for identifying these pathological networks and is attempting to uncover how their interactions produce seizures.

3) Furthering our understanding of the physiological basis of these multiple measures of brain structure and function.
Different measures of human brain function have complementary strengths and weaknesses. For example, in contrast to ECoG, fMRI provides much more complete coverage of the entire brain but has much lower temporal resolution. Consequently, understanding the function of the human brain in much detail requires combining the findings from these different measures. However, doing so is complicated by the fact that the relationship between these measures is somewhat ambiguous (e.g., activity measured by ECoG might be invisible to fMRI). By obtaining these multiple measures of brain function in the same individuals, we are able to better understand how these measures relate and what inferences can be made from each measure alone.

4) Understanding the physiological basis of human cognitive and sensorimotor brain function.
The neuronal basis for visual and auditory perception, language, memory, motor function and attention are studied using invasive electrodes in patients undergoing seizure monitoring for epilepsy surgery. Results from fMRI, EEG and cortical stimulation mapping are used to define areas and networks of areas involved in physiological function.

Selected Publications:
Keller CJ, Bickel S, Entz L, Ulbert I, Kelley AM, Milham M and Mehta AD. 2011. Intrinsic Functional Architecture Predicts Electrically Evoked Responses in the Human Brain. Proceedings of the National Academy of Sciences (USA). 25:10308-10313.

Besle J., Schevon CA, Mehta AD, Lakatos P, Goodman RR, McKhann GM, Emerson RG and Schroeder CE. 2011. Tuning of the human neocortex to the temporal dynamics of attended events. J Neuroscience. 31:3176-3185.

Keller CJ, Truccolo W, Gale JT, Eskandar E, Thesen T, Mehta AD, Devinsky O, Kuzniecky R, Doyle WK, Madsen J, Schomer D, Brown EN, Ulbert I, Halgren E, Hochberg L and Cash SS. 2010. Heterogeneous Neuronal Firing Patterns During Interictal Epileptiform Discharges in the Human Cortex. Brain. 133:1668-1681.

Mehta AD and Klein G. 2010. Clinical utility of functional magnetic resonance imaging for brain mapping in epilepsy surgery. Epilepsy Research. 89: 126-132.

Mehta AD, Ettinger AB, Perrine K, Dhawan V, Patil A, Jain SK, Klein G, Schneider SJ, Eidelberg D. 2009. Brain Circuits Underlying Seizure Propagation in a Patient with Musicogenic Epilepsy. Epilepsy and Behavior. 14:421-424.

Lakatos P, Karmos G, Mehta AD, Ulbert I and Schroeder CE. 2008. Entrainment of Neuronal Oscillations as a Mechanism of Attentional Selection. Science. 320:110-113.