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Multimodal evidence for direct corticospinal projections from the human supplementary motor area (SMA)
NemoImage 11, Number 5, 2000, Part 2 of 2 Parts I@ E
SENSORIMOTOR
Multimodal
evidence for direct corticospinal projections from the human supplementary motor area (SMA)
Nitin Tandon*,
Peter Fox*, Meenakshi, B. lyer*, Shalini Narayana*, Roger Inghamt, Jack Lancaster*
*Research Imaging Center, UTHSCSA, San Antonio, TX TDepartrnent of Speech and Hearing Sciences, University of California, Santa Barbara Background
Electrical stimulation of the SMA in animals and humans produces complex, synergistic motor movements involving multiple muscle groups. It has been shown in animals (macaque monkeys, rhesus monkeys, raccoons) that the SMA has direct corticospinal output. However, there are no data confirming the presence of direct spinal efferents from the SMA in humans. Methods
A 29 year old right handed male underwent TMS-PET with concurrent EMG. The TMS paddle (B shaped coil) was positioned 1.2 ems anterior and 1 cm, right of the midline relative to the location for primary motor cortex (Ml) for the right hand. This location for right SMA was determined by a metanalysis using the BrainMap@ database. The paddle was held immobile for the duration of the scanning session by a nemosurgical robot (Neuromate’“) to ensure precise targeting and consistency of the site of SMA stimulation. TMS was delivered at 2 Hz, started at 2 minutes prior to injection of H:‘O, and stopped after 40 seconds of PET count aquisition. The subject was scanned at rest and while undergoing TMS to the SMA. EMG recording from the L biceps bra&ii, L wrist extensors, L quadriceps and L biceps femoris during SMA and during primary motor cortex stimulation was carried out. A total of 120 electrophysiological epochs were recorded from each muscle for each site of stimulation. Statistical parametric images of z scores of PET count changes between rest and TMS activation - SPI(z] were made and sites for positive z scores are plotted in Fig 1. The spatial location of the most highly significant scores (p < 0.0001) corresponds with generally accepted locations of SMA and its projections. Additionally, TMS stimulation of the right SMA produced synergistic, complex, rhythmic movements of the contralateral arm and leg. These involuntary movements were greatly exaggerated during vohmtional activity and were phenomenologically different from the focal contractions produced by the stimulation of primary motor cortex. Additionally, the TMS-defined locations for the primary motor cortical representations of the muscle groups stimulated were marked on the subject’s skull cap and noted to be distinctly separate from the site of SMA stimulation. EMG recordings reveal that the onset of contraction latencies of individual muscle groups were identical during both SMA and Ml stimulation (Table 1). Table
1.
AVG Latency to Onset of EMG Response (MSEC)
Site of TMS
Biceps bra&ii
SMA
Primary motor cortex
12.76 12
Wrist extensors
Quadriceps
Biceps femoris
12.92 13.55
20.17 20.3
20.85 20.3
Averaged values for 120 epochs.
To our knowledge, this is the first unequivocal demonstration of the existence of direct corticospinal efferents from the human supplementary motor area. Acknowledgements:
Funding for this research was provided by the Clinical Hypothesis Program of the Charles A. Dana Foundation.
S876
SENSORIMOTOR
Multimodal
evidence for direct corticospinal projections from the human supplementary motor area (SMA)
Nitin Tandon*,
Peter Fox*, Meenakshi, B. lyer*, Shalini Narayana*, Roger Inghamt, Jack Lancaster*
*Research Imaging Center, UTHSCSA, San Antonio, TX TDepartrnent of Speech and Hearing Sciences, University of California, Santa Barbara Background
Electrical stimulation of the SMA in animals and humans produces complex, synergistic motor movements involving multiple muscle groups. It has been shown in animals (macaque monkeys, rhesus monkeys, raccoons) that the SMA has direct corticospinal output. However, there are no data confirming the presence of direct spinal efferents from the SMA in humans. Methods
A 29 year old right handed male underwent TMS-PET with concurrent EMG. The TMS paddle (B shaped coil) was positioned 1.2 ems anterior and 1 cm, right of the midline relative to the location for primary motor cortex (Ml) for the right hand. This location for right SMA was determined by a metanalysis using the BrainMap@ database. The paddle was held immobile for the duration of the scanning session by a nemosurgical robot (Neuromate’“) to ensure precise targeting and consistency of the site of SMA stimulation. TMS was delivered at 2 Hz, started at 2 minutes prior to injection of H:‘O, and stopped after 40 seconds of PET count aquisition. The subject was scanned at rest and while undergoing TMS to the SMA. EMG recording from the L biceps bra&ii, L wrist extensors, L quadriceps and L biceps femoris during SMA and during primary motor cortex stimulation was carried out. A total of 120 electrophysiological epochs were recorded from each muscle for each site of stimulation. Statistical parametric images of z scores of PET count changes between rest and TMS activation - SPI(z] were made and sites for positive z scores are plotted in Fig 1. The spatial location of the most highly significant scores (p < 0.0001) corresponds with generally accepted locations of SMA and its projections. Additionally, TMS stimulation of the right SMA produced synergistic, complex, rhythmic movements of the contralateral arm and leg. These involuntary movements were greatly exaggerated during vohmtional activity and were phenomenologically different from the focal contractions produced by the stimulation of primary motor cortex. Additionally, the TMS-defined locations for the primary motor cortical representations of the muscle groups stimulated were marked on the subject’s skull cap and noted to be distinctly separate from the site of SMA stimulation. EMG recordings reveal that the onset of contraction latencies of individual muscle groups were identical during both SMA and Ml stimulation (Table 1). Table
1.
AVG Latency to Onset of EMG Response (MSEC)
Site of TMS
Biceps bra&ii
SMA
Primary motor cortex
12.76 12
Wrist extensors
Quadriceps
Biceps femoris
12.92 13.55
20.17 20.3
20.85 20.3
Averaged values for 120 epochs.
To our knowledge, this is the first unequivocal demonstration of the existence of direct corticospinal efferents from the human supplementary motor area. Acknowledgements:
Funding for this research was provided by the Clinical Hypothesis Program of the Charles A. Dana Foundation.
S876