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- Open Access
Sensory limits in the rodent whisker system predict an internal forward model for sensorimotor estimation of object touch
© Gyring and Aldo Faisal; licensee BioMed Central Ltd. 2011
- Published: 18 July 2011
- Trigeminal Ganglion
- External Object
- Neuron Command
- Sensorimotor Integration
- Object Contact
However, the above biomechanical reasoning for object detection ignores any noise limits to the detectability of beam deformations. To estimate the size of bending that would have to be determined by such mechanoreceptors we analyzed whisker bending using the Euler-Bernoulli beam equation, with relevant parameters taken from the anatomical literature, in order to test this assumption. For a whisker deflection of ~2°, which is factor two above the animal's discrimination threshold, we find a maximum deflection within the follicle on the order of ~1μm. This is likely an overestimate of the true deflection, as we assume a rigid geometry of the follicle and the hinge points. Given the small value of this deflection, and also considering common levels of noise in neurons and detection thresholds in the most sensitive known mechanoreceptors, inner hair cells , it is unlikely that object contact is directly detected.
We propose that object contact may be reliably inferred using recursive state estimation of whisker position, akin to findings in human sensorimotor integration , by combining sensory information with motor neuron commands moving the follicles. However, during object contact, the force from the object on the whisker would render the internal, forward model biased. The recursive position estimate would thus deviate systematically from a direct position estimate of the whisker orientation from the whisking cells, indicating object contact. The use of recursive state estimation by touch cells would also have additional advantages, such as improving the system performance in the face of noisy sensors and muscle contractions, as well as sensory delays. We predict that receptors driving touch and whisking cells, the putative computations may be carried out monosynaptically using pre-synaptic inhibition and dendritic computation.
- Szwed M, Bagdasarian K, Ahissar E: Encoding of Vibrissal Active Touch. Neuron. 2003, 40 (3): 621-630. 10.1016/S0896-6273(03)00671-8.View ArticlePubMedGoogle Scholar
- Ahissar E, Knutsen PM: Object localization with whiskers. Biol Cybern. 2008, 98: 449-458. 10.1007/s00422-008-0214-4.View ArticlePubMedGoogle Scholar
- Diamond ME, Heimendahl MV, Knutsen PM, Kleinfeld D, Ahissar E: ´Where' and ´what' in the whisker sensorimotor system. Nature Reviews Neuroscience. 2008, 9: 601-612. 10.1038/nrn2411.View ArticlePubMedGoogle Scholar
- Faisal AA, Selen LPJ, Wolpert DM: Noise in the nervous system. Nature Rev Neurosci. 2008, 9: 292-303. 10.1038/nrn2258.View ArticleGoogle Scholar
- Wolpert DM, Ghahramani Z, Jordan MI: An internal model for sensorimotor integration. Science. 269: 1880-1882. 10.1126/science.7569931.Google Scholar
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