title: Single tactile afferents outperform human subjects in a vibrotactile intensity discrimination task.
abstract: We simultaneously compared the sensitivity of single primary afferent neurons supplying the glabrous skin of the hand and the psychophysical amplitude discrimination thresholds in human subjects for a set of vibrotactile stimuli delivered to the receptive field. All recorded afferents had a dynamic range narrower than the range of amplitudes across which the subjects could discriminate. However, when the vibration amplitude was chosen to be within the steepest part of the afferent's stimulus-response function the response of single afferents, defined as the spike count over the vibration duration (500 ms), was often more sensitive in discriminating vibration amplitude than the perceptual judgment of the participants. We quantified how the neuronal performance depended on the integration window: for short windows the neuronal performance was inferior to the performance of the subject. The neuronal performance progressively improved with increasing spike count duration and reached a level significantly above that of the subjects when the integration window was 250 ms or longer. The superiority in performance of individual neurons over observers could reflect a nonoptimal integration window or be due to the presence of noise between the sensory periphery and the cortical decision stage. Additionally, it could indicate that the range of perceptual sensitivity comes at the cost of discrimination through pooling across neurons with different response functions.
authors.affiliation: School of Psychology, University of Sydney, Sydney, Australia; Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia; ARC Centre of Excellence for Integrative Brain Function, Australian National University Node, Canberra, Australia; ehsan.arabzadeh@anu.edu.au.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Arabzadeh
authors.affiliation: School of Psychology, University of Sydney, Sydney, Australia; School of Psychology, UNSW Australia, Sydney, Australia;
authors.forename: Colin W G
authors.initials: CW
authors.lastname: Clifford
authors.affiliation: School of Psychology, University of Sydney, Sydney, Australia;
authors.forename: Justin A
authors.initials: JA
authors.lastname: Harris
authors.affiliation: School of Medicine, University of Western Sydney, Sydney, Australia;
authors.forename: David A
authors.initials: DA
authors.lastname: Mahns
authors.affiliation: School of Medicine, University of Western Sydney, Sydney, Australia; Neuroscience Research Australia, Sydney, Australia; and.
authors.forename: Vaughan G
authors.initials: VG
authors.lastname: Macefield
authors.affiliation: Neuroscience Research Australia, Sydney, Australia; and School of Science and Health, University of Western Sydney, Sydney, Australia.
authors.forename: Ingvars
authors.initials: I
authors.lastname: Birznieks
mesh_terms: D000200:Action Potentials; D004192:Discrimination, Psychological / Q000502:physiology*; D005260:Female; D006225:Hand / Q000502:physiology; D006801:Humans; D008297:Male; D009475:Neurons, Afferent / Q000502:physiology*; D010812:Physical Stimulation; D011601:Psychophysics; D055698:Touch Perception / Q000502:physiology*; D014732:Vibration
keywords: microneurography; neural coding; neurometrics; psychometrics