Tactile Pressure Levels are Encoded in the Ipsilateral Primary Somatosensory Cortex
Poster No:
2061
Submission Type:
Abstract Submission
Authors:
Anna Feldbush1, Nahid Kalantaryardebily1, Neha Reddy2, Rebecca Faubion-Trejo3, Jeff Soldate3, Jonathan Lisinski3, Molly Bright2, Netta Gurari1, Stephen LaConte3
Institutions:
1Virginia Tech, Blacksburg, VA, 2Northwestern University, Chicago, IL, 3Virginia Tech, Roanoke, VA
First Author:
Co-Author(s):
Introduction:
Tactile perception is fundamental to how we engage with and interpret our surroundings. While the contralateral primary somatosensory cortex (SI) is primarily responsible for processing tactile information, responses in both the contralateral (cSI) and ipsilateral (iSI) have been observed with unilateral stimuli. Features of iSI activity patterns including sensitivity to changes in stimulus magnitude, response timing, and response directionality, could offer key insight into the signaling pathways and functional significance of bilateral response in the primary somatosensory cortex. This work aims to characterize the prevalence and response patterns of the iSI to unilateral tactile stimuli, providing insights into the neural mechanisms underlying sensory integration.
Methods:
14 healthy right-hand dominant participants between the ages of 18-23 (21±1.8 years) were scanned. Tactile stimuli were applied using a custom pneumatic actuator. This device provides sustained tactile stimuli through the inflation of a small balloon. Stimulus magnitude was manipulated by changing pressure inside the balloon. Three magnitudes were presented, all of which were above the perceptual threshold.
A series of multi-echo EPI scans were collected at 3T (FA=70°, TR=2000 ms, slice thickness=4 mm, FoV=180 mm, multi-band factor=2, TE={13.4,39.5,65.6 ms}). An anatomical MPRAGE scan was also collected (FA=9°, TR=2300 ms, slice thickness=1 mm, FoV=256 mm, multi-band factor=1 s, TE:2.9 ms).
The EPI data were preprocessed via slice time correction, motion correction based upon the first echo time, and brain extraction (modified FSL BET with erosion). TEDANA was used for optimal echo combination and multi-echo independent component analysis (ME-ICA) (DuPre et al., 2021). We applied a Gaussian blur (4 mm) and data were scaled to have a mean of 100. To account for the 3 magnitudes of the tactile stimuli an amplitude-modulated (AM) generalized linear model (GLM) regression was run on each participant's data. The anatomical scan was skull-stripped, and the EPI data underwent alignment to the anatomical scan and were warped to MNI space.
A series of multi-echo EPI scans were collected at 3T (FA=70°, TR=2000 ms, slice thickness=4 mm, FoV=180 mm, multi-band factor=2, TE={13.4,39.5,65.6 ms}). An anatomical MPRAGE scan was also collected (FA=9°, TR=2300 ms, slice thickness=1 mm, FoV=256 mm, multi-band factor=1 s, TE:2.9 ms).
The EPI data were preprocessed via slice time correction, motion correction based upon the first echo time, and brain extraction (modified FSL BET with erosion). TEDANA was used for optimal echo combination and multi-echo independent component analysis (ME-ICA) (DuPre et al., 2021). We applied a Gaussian blur (4 mm) and data were scaled to have a mean of 100. To account for the 3 magnitudes of the tactile stimuli an amplitude-modulated (AM) generalized linear model (GLM) regression was run on each participant's data. The anatomical scan was skull-stripped, and the EPI data underwent alignment to the anatomical scan and were warped to MNI space.
Results:
The number of voxels that responded to tactile stimuli was statistically equivalent in the contralateral and ipsilateral hemispheres and spanned BA1, BA2, and BA3b (fig.1b). However, we found an apparent difference in blood-oxygen-level-dependent (BOLD) responses between the contralateral hemisphere and the ipsilateral BA1 and BA3b (fig.1a,c).
While most regions demonstrated a positive BOLD response, ipsilateral BA1 and BA3b had an initial negative BOLD response, followed by a delayed response that was dependent on tactile stimulus magnitude (fig.2).
While most regions demonstrated a positive BOLD response, ipsilateral BA1 and BA3b had an initial negative BOLD response, followed by a delayed response that was dependent on tactile stimulus magnitude (fig.2).
Conclusions:
This pattern of BOLD responses corroborates previous studies that show region-specific activation within the ipsilateral primary somatosensory cortex (Hlushchuk & Hari, 2006). The delayed, stimuli-specific modulation of the BOLD signal may indicate a subsequent phase of serial processing in the ipsilateral BA1 and BA3b, paralleling findings in the contralateral SI (Klingner et al., 2016). In this stage, iSI could differentiate between stimulus magnitudes, reflecting a more refined analysis of sensory input (Chung et al., 2014). This transition from an early, generalized response to a later, stimuli-specific one may represent a shift from parallel processing, which handles broad aspects of sensory input, to serial processing, which focuses on the detailed properties of the stimuli. Understanding these mechanisms can provide valuable insights into the complex neural processes underlying sensory integration and processing in the brain.
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI)
Other Methods
Novel Imaging Acquisition Methods:
BOLD fMRI 2
Perception, Attention and Motor Behavior:
Perception: Tactile/Somatosensory 1
Keywords:
FUNCTIONAL MRI
Hemispheric Specialization
NORMAL HUMAN
Perception
Somatosensory
Other - Tactile
1|2Indicates the priority used for review
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Provide references using APA citation style.
DuPre, E., Salo, T., Ahmed, Z., Bandettini, P. A., Bottenhorn, K. L., Caballero-Gaudes, C., Dowdle, L. T., Gonzalez-Castillo, J., Heunis, S., Kundu, P., Laird, A. R., Markello, R., Markiewicz, C. J., Moia, S., Staden, I., Teves, J. B., Uruñuela, E., Vaziri-Pashkam, M., Whitaker, K., & Handwerker, D. A. (2021). TE-dependent analysis of multi-echo fMRI with *tedana*. Journal of Open Source Software, 6(66), 3669. https://doi.org/10.21105/joss.03669
Hlushchuk, Y., & Hari, R. (2006). Transient Suppression of Ipsilateral Primary Somatosensory Cortex during Tactile Finger Stimulation. Journal of Neuroscience, 26(21), 5819–5824. https://doi.org/10.1523/JNEUROSCI.5536-05.2006
Klingner, C. M., Brodoehl, S., Huonker, R., & Witte, O. W. (2016). The Processing of Somatosensory Information Shifts from an Early Parallel into a Serial Processing Mode: A Combined fMRI/MEG Study. Frontiers in Systems Neuroscience, 10. https://doi.org/10.3389/fnsys.2016.00103