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- Brasselet, R, et al.
(författare)
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Fast encoding/decoding of haptic microneurography data based on first spike latencies
- 2009
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Ingår i: BMC Neuroscience. - 1471-2202. ; 10:1, s. 349-350
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- During haptic exploration tasks, forces are applied to the fingertips, which constitute the most sensitive parts of the hand and are prominently involved in object manipulation/ recognition tasks. The epidermis is innervated with thousands of sensory cells, called mechanoreceptors, that encode the mechanical indentations and deformations of the skin. These cells project directly to a dorsal column nucleus called the cuneate nucleus (CN) that constitutes the first synaptic relay to the central nervous system. Recent microneurography studies in humans [1] suggest that the relative timing of impulses from ensembles of mechanoreceptor afferents can convey information about important contact parameters faster than the fastest possible rate code and are fast enough to account for the use of tactile signals in natural manipulation. Here, we study a biologically plausible encoding/decoding process accounting for the relative spike timing of the signals propagating from peripheral nerve fibres onto second- order CN neurons. The CN is modelled as a population of 450 spiking neurons receiving as inputs the spatiotemporal responses of real mechanoreceptors obtained via microneurography recordings in humans. An information-theoretic approach is used to quantify the efficiency of the haptic discrimination process. To this extent, a novel entropy definition has been derived analytically. This measure proved to be a promising decoding scheme to generalize the classical Shannon's entropy for spiking neural codes, and it allowed us to compute mutual information (MI) in the presence of a large output space (i.e., 450 CN spike train responses) with a 1 ms temporal precision. Using a plasticity rule designed to maximise information transfer explicitly [2], a complete discrimination of 81 distinct stimuli occurred already within 40 ms after the first afferent spike, whereas a partial discrimination (80% of the maximum MI) was possible as rapidly as 20 ms. The rationale behind this study was to corroborate our working hypothesis that the CN does not constitute a mere synaptic relay, but it rather conveys an optimal contextual account (in terms of both fast and reliable information transfer) of peripheral tactile inputs to downstream structures (in particular to the thalamus and the cerebellum). Therefore, the CN may play a relevant role in the early processing of haptic information and it would constitute an important component of the haptic classification process (e.g., by facilitating fast discrimination of haptic contexts, minimising destructive interference over lifelong learning, and maximising memorycapacity).
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| 2. |
- Xin, D. L., et al.
(författare)
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Effectiveness of conservative interventions for sickness and pain behaviors induced by a high repetition high force upper extremity task
- 2017
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Ingår i: BMC Neuroscience. - : BioMed Central. - 1471-2202. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Background: Systemic inflammation is known to induce sickness behaviors, including decreased social interaction and pain. We have reported increased serum inflammatory cytokines in a rat model of repetitive strain injury (rats perform an upper extremity reaching task for prolonged periods). Here, we sought to determine if sickness behaviors are induced in this model and the effectiveness of conservative treatments.Methods: Experimental rats underwent initial training to learn a high force reaching task (10 min/day, 5 days/week for 6 weeks), with or without ibuprofen treatment (TRHF vs. TRHF + IBU rats). Subsets of trained animals went on to perform a high repetition high force (HRHF) task for 6 or 12 weeks (2 h/day, 3 days/week) without treatment, or received two secondary interventions: ibuprofen (HRHF + IBU) or a move to a lower demand low repetition low force task (HRHF-to-LRLF), beginning in task week 5. Mixed-effects models with repeated measures assays were used to assay duration of social interaction, aggression, forepaw withdrawal thresholds and reach performance abilities. One-way and two-way ANOVAs were used to assay tissue responses. Corrections for multiple comparisons were made.Results: TRHF + IBU rats did not develop behavioral declines or systemic increases in IL-1beta and IL-6, observed in untreated TRHF rats. Untreated HRHF rats showed social interaction declines, difficulties performing the operant task and forepaw mechanical allodynia. Untreated HRHF rats also had increased serum levels of several inflammatory cytokines and chemokines, neuroinflammatory responses (e.g., increased TNFalpha) in the brain, median nerve and spinal cord, and Substance P and neurokinin 1 immunoexpression in the spinal cord. HRHF + IBU and HRHF-to-LRLF rats showed improved social interaction and reduced inflammatory serum, nerve and brain changes. However, neither secondary treatment rescued HRHF-task induced forepaw allodynia, or completely attenuated task performance declines or spinal cord responses.Conclusions: These results suggest that inflammatory mechanisms induced by prolonged performance of high physical demand tasks mediate the development of social interaction declines and aggression. However, persistent spinal cord sensitization was associated with persistent behavioral indices of discomfort, despite use of conservative secondary interventions indicating the need for prevention or more effective interventions.
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