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Janko D, Thoenes K, Park D, Willoughby WR, Horton M, Bolding M. Somatotopic Mapping of the Fingers in the Somatosensory Cortex Using Functional Magnetic Resonance Imaging: A Review of Literature. Front Neuroanat 2022; 16:866848. [PMID: 35847829 PMCID: PMC9277538 DOI: 10.3389/fnana.2022.866848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 05/16/2022] [Indexed: 11/29/2022] Open
Abstract
Multiple studies have demonstrated finger somatotopy in humans and other primates using a variety of brain mapping techniques including functional magnetic resonance imaging (fMRI). Here, we review the literature to better understand the reliability of fMRI for mapping the somatosensory cortex. We have chosen to focus on the hand and fingers as these areas have the largest representation and have been the subject of the largest number of somatotopic mapping experiments. Regardless of the methods used, individual finger somatosensory maps were found to be organized across Brodmann areas (BAs) 3b, 1, and 2 in lateral-to-medial and inferior-to-superior fashion moving from the thumb to the pinky. However, some consistent discrepancies are found that depend principally on the method used to stimulate the hand and fingers. Therefore, we suggest that a comparative analysis of different types of stimulation be performed to address the differences described in this review.
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Affiliation(s)
- Daniel Janko
- Department of Psychology, University of Alabama at Birmingham, Birmingham, AL, United States.,Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Kristina Thoenes
- Edward Via College of Osteopathic Medicine Auburn, Auburn, AL, United States
| | - Dahye Park
- School of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - W R Willoughby
- Department of Radiology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Meredith Horton
- Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Mark Bolding
- Department of Radiology, University of Alabama at Birmingham, Birmingham, AL, United States
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Kaiju T, Doi K, Yokota M, Watanabe K, Inoue M, Ando H, Takahashi K, Yoshida F, Hirata M, Suzuki T. High Spatiotemporal Resolution ECoG Recording of Somatosensory Evoked Potentials with Flexible Micro-Electrode Arrays. Front Neural Circuits 2017; 11:20. [PMID: 28442997 PMCID: PMC5386975 DOI: 10.3389/fncir.2017.00020] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Accepted: 03/10/2017] [Indexed: 11/13/2022] Open
Abstract
Electrocorticogram (ECoG) has great potential as a source signal, especially for clinical BMI. Until recently, ECoG electrodes were commonly used for identifying epileptogenic foci in clinical situations, and such electrodes were low-density and large. Increasing the number and density of recording channels could enable the collection of richer motor/sensory information, and may enhance the precision of decoding and increase opportunities for controlling external devices. Several reports have aimed to increase the number and density of channels. However, few studies have discussed the actual validity of high-density ECoG arrays. In this study, we developed novel high-density flexible ECoG arrays and conducted decoding analyses with monkey somatosensory evoked potentials (SEPs). Using MEMS technology, we made 96-channel Parylene electrode arrays with an inter-electrode distance of 700 μm and recording site area of 350 μm2. The arrays were mainly placed onto the finger representation area in the somatosensory cortex of the macaque, and partially inserted into the central sulcus. With electrical finger stimulation, we successfully recorded and visualized finger SEPs with a high spatiotemporal resolution. We conducted offline analyses in which the stimulated fingers and intensity were predicted from recorded SEPs using a support vector machine. We obtained the following results: (1) Very high accuracy (~98%) was achieved with just a short segment of data (~15 ms from stimulus onset). (2) High accuracy (~96%) was achieved even when only a single channel was used. This result indicated placement optimality for decoding. (3) Higher channel counts generally improved prediction accuracy, but the efficacy was small for predictions with feature vectors that included time-series information. These results suggest that ECoG signals with high spatiotemporal resolution could enable greater decoding precision or external device control.
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Affiliation(s)
- Taro Kaiju
- Graduate School of Frontier Biosciences, Osaka UniversityOsaka, Japan.,Center for Information and Neural Networks, National Institute of Information and Communications Technology and Osaka UniversityOsaka, Japan
| | - Keiichi Doi
- Graduate School of Frontier Biosciences, Osaka UniversityOsaka, Japan.,Center for Information and Neural Networks, National Institute of Information and Communications Technology and Osaka UniversityOsaka, Japan
| | - Masashi Yokota
- Graduate School of Frontier Biosciences, Osaka UniversityOsaka, Japan.,Center for Information and Neural Networks, National Institute of Information and Communications Technology and Osaka UniversityOsaka, Japan
| | - Kei Watanabe
- Center for Information and Neural Networks, National Institute of Information and Communications Technology and Osaka UniversityOsaka, Japan
| | - Masato Inoue
- Center for Information and Neural Networks, National Institute of Information and Communications Technology and Osaka UniversityOsaka, Japan
| | - Hiroshi Ando
- Center for Information and Neural Networks, National Institute of Information and Communications Technology and Osaka UniversityOsaka, Japan
| | - Kazutaka Takahashi
- Department of Organismal Biology and Anatomy, University of ChicagoChicago, IL, USA
| | - Fumiaki Yoshida
- Center for Information and Neural Networks, National Institute of Information and Communications Technology and Osaka UniversityOsaka, Japan.,Endowed Research Department of Clinical Neuroengineering, Global Center for Medical Engineering and Informatics, Osaka UniversityOsaka, Japan
| | - Masayuki Hirata
- Center for Information and Neural Networks, National Institute of Information and Communications Technology and Osaka UniversityOsaka, Japan.,Endowed Research Department of Clinical Neuroengineering, Global Center for Medical Engineering and Informatics, Osaka UniversityOsaka, Japan
| | - Takafumi Suzuki
- Center for Information and Neural Networks, National Institute of Information and Communications Technology and Osaka UniversityOsaka, Japan
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Abstract
To assess the degree of fine-scale somatotopy within the hand area of the human primary motor cortex (M1), functional mapping of individual movements of all fingers was performed in healthy young subjects (n = 7) using MRI at 0.8 x 0.8 mm2 resolution and 4 mm section thickness. The experimental design comprised both a direct paradigm contrasting single digit movements vs. motor rest and multiple differential paradigms contrasting single digit movements vs. the movement of another digit. Direct mapping resulted in largely overlapping activations. A somatotopic arrangement was only recognizable when considering the mean center-of-mass coordinates of individual digit representations averaged across subjects. In contrast, differential paradigms revealed more segregated and somatotopically ordered activations in single subjects. The use of center-of-mass coordinates yielded inter-digit distances ranging from 2.0 to 16.8 mm, which reached statistical significance for pairs of more distant digits. For the middle fingers, the functional somatotopy obtained by differential mapping was dependent on the choice of the digit used for control. These results confirm previous concepts that finger somatotopy in the human M1 hand area emerges as a functional predominance of individual digit representations sharing common areas in a distributed though ordered network.
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Affiliation(s)
- Peter Dechent
- Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany.
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