Volume 34, Issue 5, Pages 831-840 (May 2002) Driving Plasticity in Human Adult Motor Cortex Is Associated with Improved Motor Function after Brain Injury  Chris Fraser, Maxine Power, Shaheen Hamdy, John Rothwell, David Hobday, Igor Hollander, Pippa Tyrell, Anthony Hobson, Steven Williams, David Thompson  Neuron  Volume 34, Issue 5, Pages 831-840 (May 2002) DOI: 10.1016/S0896-6273(02)00705-5

Figure 1 Stimulus Frequency, Intensity, and Duration Effects on Corticobulbar Excitability (A) Cortically evoked pharyngeal EMG responses in one individual are shown before and after pharyngeal stimulation at 5 Hz and 40 Hz. Ten responses are superimposed for each time interval. (B) Group mean % change in cortically evoked pharyngeal response amplitudes before and after stimulation at 1, 5, 10, 20, and 40 Hz. Note the increase in excitability produced by 5 Hz stimulation compared with the suppression by 20 and 40 Hz stimulation. Pharyngeal latencies remained unaffected. (C) 25% and 50% (maximally tolerated) stimulation intensities induced less excitation post-stimulation than 75%. (D) Stimuli train lengths of 5 min and 20 min induced less excitation compared to 10 min. The greatest increase in mean cortically evoked pharyngeal response amplitudes occurred after stimulation at 5 Hz and 75% maximum tolerated intensity for 10 min. All data are plotted as group mean ± SEM, for immediate (closed diamond), 30 min (closed square), and 60 minute (closed triangle) intervals. (*p < 0.05, **p < 0.01). Neuron 2002 34, 831-840DOI: (10.1016/S0896-6273(02)00705-5)

Figure 2 Duration of Stimulation Effect on Corticobulbar Excitability Length of time of stimulation-induced effect (A) and effect of stimulation on brainstem swallowing reflexes (B) are shown. (A) Maximal increase in corticobulbar excitability for pharynx (closed diamond) occurs at 1 hr and persists for more than 150 min. Thenar excitability (closed triangle) remains unaffected. (b) Brainstem reflexes (closed square) remain unaffected, compared to cortically evoked (closed diamond) pharyngeal responses at 1 hr. Data plotted as group mean ± SEM. (*p < 0.05, **p < 0.01). Neuron 2002 34, 831-840DOI: (10.1016/S0896-6273(02)00705-5)

Figure 3 Effect of Pharyngeal Stimulation on Cortical BOLD (Blood Oxygenation Level Dependent) fMRI Signal in Healthy Subjects during Normal Swallowing Group mean activation data are show as a series of normalized transverse brain slices, with no stimulation paradigm across the top, and the stimulation paradigm across the bottom. Activated pixels in red, and brain slice numbers indicated below. Greater bilateral functional activation occurs within sensorimotor cortex (BA 3,4), most overt in slices 17–19, after pharyngeal stimulation compared to no stimulation. Neuron 2002 34, 831-840DOI: (10.1016/S0896-6273(02)00705-5)

Figure 4 Changes in the Organization of the Cortical Projection to Swallowing Muscles and Swallowing Function after Pharyngeal or No Stimulation in 16 Acutely Dysphagic Stroke Patients A marked increase in pharyngeal corticobulbar excitability and topographic representation occurs in the undamaged hemisphere (closed diamond) compared to the affected hemisphere (closed square) in patients receiving pharyngeal stimulation (A). This is mirrored by the changes to swallowing (with stimulation [black] versus without stimulation [gray] with a functionally beneficial reduction in PTT, SRT, and aspiration [B]). PTT = pharyngeal transit time, SRT = swallowing response time, ASP = aspiration. (*p < 0.05, **p < 0.01). Neuron 2002 34, 831-840DOI: (10.1016/S0896-6273(02)00705-5)

Figure 5 Changes in Total Cortical Excitability and Map Size with Aspiration in Dysphagic Stroke Patients after Pharyngeal Stimulation (A) Correlation between fractional change in total hemispheric excitability (calculated as the sum of the change in mean excitability (response amplitude) of each hemisphere divided by the sum of the post-stimulation maximal response amplitude of each hemisphere) and % improvement in aspiration across individuals showing that an increase in excitability is strongly associated to an improvement in swallowing behavior (r = 0.7, p = 0.01). (B) Correlation between % change in cortical map size and % improvement in aspiration across individuals showing that an increase in map size is also strongly associated with an improvement in swallowing behavior (r = 0.6, p = 0.03). Neuron 2002 34, 831-840DOI: (10.1016/S0896-6273(02)00705-5)