Diversity in High Frequency Cortical Information

Activations in the gamma frequency band from electroencephalography, magnetoencephalography and electrocorticography have been implicated as a phenomenon that localizes cortical activity in time and on the cortical surface.  The importance of gamma band activations in localizing cortical activity associated with a variety of cognitive activities has been well-published. 

Using several experimental paradigms in human subjects, we have discovered that gamma band activations are diverse in their frequency content and can encode information about both the specific tasks and anatomic locations involved in cognitive processing. We have reported task-specific power changes in multiple frequency bands between 30-550Hz that are specific enough to distinguish the behavior the patient was engaged in, or the portion of the cortex that was active.
Time-frequency analyses of an array of electrocorticographic recordings show evidence of distinct power change patterns between different phases of a language task.

When brief windows synchronized to the patients’ behavior are analyzed in further detail, we have shown that at a single cortical location, there are statistically significant differences between two different bands when the patient listened to words, compared to the period when they repeated those words aloud.


 
This phenomenon was evident across a population of seven patients, as summarized by the bar plots of activity over frequency in three different anatomically relevant locations. To date, we have shown that the frequency content of surface cortical potentials adds another dimension of the cortical signal beyond anatomic location and time to be explored. We continue to study high-frequency phenomena across a variety of language, motor and attention tasks as a means to understand the neural correlates of these activities and as a mechanism to increase the degrees of freedom available in brain computer interfaces.