TY - JOUR T1 - Electrocorticographic activity over sensorimotor cortex and motor function in awake behaving rats. JF - J Neurophysiol Y1 - 2015 A1 - Chadwick B. Boulay A1 - Xiang Yang Chen A1 - Jonathan Wolpaw KW - brain-computer interface KW - cortex KW - H-Reflex KW - Motor control KW - Spinal Cord AB -

Sensorimotor cortex exerts both short-term and long-term control over the spinal reflex pathways that serve motor behaviors. Better understanding of this control could offer new possibilities for restoring function after central nervous system trauma or disease. We examined the impact of ongoing sensorimotor cortex (SMC) activity on the largely monosynaptic pathway of the H-reflex, the electrical analog of the spinal stretch reflex. In 41 awake adult rats, we measured soleus electromyographic (EMG) activity, the soleus H-reflex, and electrocorticographic activity over the contralateral SMC while rats were producing steady-state soleus EMG activity. Principal component analysis of electrocorticographic frequency spectra before H-reflex elicitation consistently revealed three frequency bands: μβ (5-30 Hz), low γ (γ1; 40-85 Hz), and high γ (γ2; 100-200 Hz). Ongoing (i.e., background) soleus EMG amplitude correlated negatively with μβ power and positively with γ1 power. In contrast, H-reflex size correlated positively with μβ power and negatively with γ1 power, but only when background soleus EMG amplitude was included in the linear model. These results support the hypothesis that increased SMC activation (indicated by decrease in μβ power and/or increase in γ1 power) simultaneously potentiates the H-reflex by exciting spinal motoneurons and suppresses it by decreasing the efficacy of the afferent input. They may help guide the development of new rehabilitation methods and of brain-computer interfaces that use SMC activity as a substitute for lost or impaired motor outputs.

VL - 113 UR - http://www.ncbi.nlm.nih.gov/pubmed/25632076 IS - 7 ER - TY - JOUR T1 - Temporal evolution of gamma activity in human cortex during an overt and covert word repetition task. JF - Front Hum Neurosci Y1 - 2012 A1 - Leuthardt, E C A1 - Pei, Xiao-Mei A1 - Breshears, Jonathan A1 - Charles M Gaona A1 - Sharma, Mohit A1 - Zachary V. Freudenberg A1 - Barbour, Dennis L A1 - Gerwin Schalk KW - cortex KW - Electrocorticography KW - gamma rhythms KW - human KW - Speech AB -

Several scientists have proposed different models for cortical processing of speech. Classically, the regions participating in language were thought to be modular with a linear sequence of activations. More recently, modern theoretical models have posited a more hierarchical and distributed interaction of anatomic areas for the various stages of speech processing. Traditional imaging techniques can only define the location or time of cortical activation, which impedes the further evaluation and refinement of these models. In this study, we take advantage of recordings from the surface of the brain [electrocorticography (ECoG)], which can accurately detect the location and timing of cortical activations, to study the time course of ECoG high gamma (HG) modulations during an overt and covert word repetition task for different cortical areas. For overt word production, our results show substantial perisylvian cortical activations early in the perceptual phase of the task that were maintained through word articulation. However, this broad activation is attenuated during the expressive phase of covert word repetition. Across the different repetition tasks, the utilization of the different cortical sites within the perisylvian region varied in the degree of activation dependent on which stimulus was provided (auditoryor visual cue) and whether the word was to be spoken or imagined. Taken together, the data support current models of speech that have been previously described with functional imaging. Moreover, this study demonstrates that the broad perisylvian speech network activates early and maintains suprathreshold activation throughout the word repetition task that appears to be modulated by the demands of different conditions.

VL - 6 UR - http://www.ncbi.nlm.nih.gov/pubmed/22563311 ER -