Abstract Details

Title Neuroimaging Somatosensory Perception and Extinction

Topic Behavioral Neurology

Presentation(s) P01 - (-)

Poster/Presentation
Number 001

Objective

Background Corticothalamic regions have been implicated in the mechanisms of conscious perception and extinction, but the specific areas are uncertain.

Design/Methods Electrical pulse (5ms) trains (10Hz) included targets (7 pulses to the right index finger) and masks (8 pulses to the left index finger bracketing targets). Intensities of masks were held constant, but targets were adjusted trial-to-trial to compensate for threshold drift. The task was to detect target stimuli. Each run consisted of 68 trials with interstimulus intervals (ITIs) varying pseudorandomly from 4.5 to 6s (mean 5.2s). Approximately 10% of trials had sham targets. A red light cued stimulation onset and ended 2s after stimulation to cue response via foot-pedals (right: target detected; left: no target detected). Initial stimulation strengths were determined from training sessions. Mask strength was set at [sim]2.2x detection threshold. Neuroimaging included: T1-weighted MPRAGE images (TR=3200ms, TE=354ms, 256[times]256 matrix, 160 slices, 1[times]1[times]1mm resolution), homogeneity field maps, and standard-resolution functional MRI (iPAT T2* EPI scan, 90-degree flip angle, TE= 35ms, TR=2000ms, 64[times]64 matrix, 192[times]192mm FOV, 36 ascending 3mm thick slices with 20% slice gap (effectively 3[times]3[times]3.6mm between voxel centers) with continuous fMRI acquisition (five [sim]6-minute runs).

Results 15 healthy dextral adult volunteers (mean age 22, range 18-28; 5M/10F) completed the study and performed the task well. Compared to undetected targets, areas activated with target detection included contralateral postcentral gyrus, insula/claustrum, and thalamus (centromedian, dorsolateral, and ventral-posterolateral nuclei). In contrast, areas more active for undetected targets included largely homogolous ipsilateral regions.

Conclusions The findings suggest that perception of lateralized somatosensory stimuli depends on a specific contralateral corticothalamic network (detailed above), and that failure of perception is associated with greater ipsilateral activation in homogolous regions.

Authors/Disclosures
Kimford J. Meador, MD, FAAN (Stanford University School of Medicine) PRESENTER	The institution of Dr. Meador has received research support from NIH. The institution of Dr. Meador has received research support from The Epilepsy Consortium.
	No disclosure on file
Charles M. Epstein, MD	No disclosure on file
Krish Sathian, MD, PhD, FAAN (Penn State Health Milton S. Hershey Medical Center)	Dr. Sathian has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Association for Psychological Science. The institution of Dr. Sathian has received research support from NIH. Dr. Sathian has received research support from University of Pennsylvania. Dr. Sathian has received publishing royalties from a publication relating to health care. Dr. Sathian has received personal compensation in the range of $500-$4,999 for serving as a Study section member with NIH, VA.
David W. Loring, PhD, FAAN	Dr. Loring has received personal compensation in the range of $5,000-$9,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Springer Nature. Dr. Loring has received personal compensation in the range of $5,000-$9,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for ILAE. The institution of Dr. Loring has received research support from NIH. Dr. Loring has received publishing royalties from a publication relating to health care.
Daniel Kaufer, MD, FAAN	No disclosure on file
	No disclosure on file

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