Perception of Electrical Stimuli in Individuals With Stroke

Northwestern University, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)

To successfully manipulate objects in one's surroundings, such as when lifting a cup, one must accurately perceive their physical interactions. This includes accurately interpreting the tactile cues arising at one's fingertips when touching an object. Currently, tactile perception is assessed in individuals with stroke using passive protocols. Research has yet to explore whether activating one's muscles impacts the tactile perceptual process in individuals with stroke despite previous research demonstrating the effect of muscle activation on tactile perception in individuals who are neurologically intact. The proposed research will be the first to address the impact of muscle activation, in addition to stroke, on tactile perception. As such, the proposed research is significant for advancing our understanding of the extent to which tactile deficits occur in individuals with stroke, particularly during volitional movement.

Participants will detect an externally-applied electrical stimulus at their fingertip with the elbow: 1) relaxed and flexed to 2) 25% and 3) 50% of their maximum voluntary torque (MVT). We will compare the detection threshold for these three conditions between each arm of participants with stroke and similarly-aged controls. Based on pilot data, we hypothesize that the detection threshold will be largest at the paretic arm when flexing to 50% MVT due to the greatest inhibition of sensory signals. Findings will indicate whether stroke negatively impacts an individual's ability to detect tactile stimuli during volitional sensorimotor tasks.

We will compare outcome measures across three experimental conditions and each upper extremity in participants with stroke and similarly-aged controls.

Inclusion Criteria: For the participants with stroke, i) a single unilateral cortical lesion that took place at least one year prior and ii) an absence of comorbid neurological impairments Ability to understand and complete the experimental tasks Capacity to provide informed consent At least 18 years of age Exclusion Criteria: Major injury to either arm Sensory neuropathy

Post LJ, Zompa IC, Chapman CE. Perception of vibrotactile stimuli during motor activity in human subjects. Exp Brain Res. 1994;100(1):107-20. doi: 10.1007/BF00227283.

Chapman, C. E., Zompa, I. C., Williams, S. R., Shenasa, J. & Jiang, W. Factors influencing the perception of tactile stimuli during movement. in Somesthesis and the Neurobiology of the Somatosensory Cortex (eds. Franzén, O., Johansson, R. & Terenius, L.) 307-320 (Birkhäuser Basel, 1996).

Seki K, Perlmutter SI, Fetz EE. Sensory input to primate spinal cord is presynaptically inhibited during voluntary movement. Nat Neurosci. 2003 Dec;6(12):1309-16. doi: 10.1038/nn1154. Epub 2003 Nov 16.

Pavlenko, V. B. Self-initiated motor behavioral act-related neuronal activity in the cat Locus Coeruleus. Neurophysiology 35, 29-37 (2003).

Wei K, Glaser JI, Deng L, Thompson CK, Stevenson IH, Wang Q, Hornby TG, Heckman CJ, Kording KP. Serotonin affects movement gain control in the spinal cord. J Neurosci. 2014 Sep 17;34(38):12690-700. doi: 10.1523/JNEUROSCI.1855-14.2014.

Jacobs BL, Martin-Cora FJ, Fornal CA. Activity of medullary serotonergic neurons in freely moving animals. Brain Res Brain Res Rev. 2002 Oct;40(1-3):45-52. doi: 10.1016/s0165-0173(02)00187-x.

Seki K, Fetz EE. Gating of sensory input at spinal and cortical levels during preparation and execution of voluntary movement. J Neurosci. 2012 Jan 18;32(3):890-902. doi: 10.1523/JNEUROSCI.4958-11.2012.