title: The neural basis of perceived intensity in natural and artificial touch.
abstract: Electrical stimulation of sensory nerves is a powerful tool for studying neural coding because it can activate neural populations in ways that natural stimulation cannot. Electrical stimulation of the nerve has also been used to restore sensation to patients who have suffered the loss of a limb. We have used long-term implanted electrical interfaces to elucidate the neural basis of perceived intensity in the sense of touch. To this end, we assessed the sensory correlates of neural firing rate and neuronal population recruitment independently by varying two parameters of nerve stimulation: pulse frequency and pulse width. Specifically, two amputees, chronically implanted with peripheral nerve electrodes, performed each of three psychophysical tasks-intensity discrimination, magnitude scaling, and intensity matching-in response to electrical stimulation of their somatosensory nerves. We found that stimulation pulse width and pulse frequency had systematic, cooperative effects on perceived tactile intensity and that the artificial tactile sensations could be reliably matched to skin indentations on the intact limb. We identified a quantity we termed the activation charge rate (ACR), derived from stimulation parameters, that predicted the magnitude of artificial tactile percepts across all testing conditions. On the basis of principles of nerve fiber recruitment, the ACR represents the total population spike count in the activated neural population. Our findings support the hypothesis that population spike count drives the magnitude of tactile percepts and indicate that sensory magnitude can be manipulated systematically by varying a single stimulation quantity.
authors: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
authors: Emily L
authors: EL
authors: Graczyk
authors: Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH 44106, USA.
authors: Matthew A
authors: MA
authors: Schiefer
authors: Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA.
authors: Hannes P
authors: HP
authors: Saal
authors: Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA.
authors: Benoit P
authors: BP
authors: Delhaye
authors: Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA.
authors: Sliman J
authors: SJ
authors: Bensmaia
authors: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA. dustin.tyler@case.edu.|Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH 44106, USA.
authors: Dustin J
authors: DJ
authors: Tyler
mesh_terms: D000671:Amputation, Surgical / Q000534:rehabilitation; D000674:Amputees / Q000534:rehabilitation*; D001186:Artificial Limbs; D003198:Computer Simulation; D004558:Electric Stimulation; D004566:Electrodes; D006801:Humans; D008297:Male; D008328:Man-Machine Systems; D009474:Neurons / Q000502:physiology*; D010525:Peripheral Nerves / Q000473:pathology*; D017933:Peripheral Nervous System / Q000473:pathology*; D011594:Psychometrics; D055698:Touch Perception