Sensations Evoked by Microstimulation of Single Mechanoreceptive Afferents Innervating the Human Face and Mouth

Dept. of Dental Medicine, Karolinska Institutet, Box 4064, S-14104 Huddinge, Sweden.
Journal of Neurophysiology (Impact Factor: 2.89). 04/2010; 103(4):1741-7. DOI: 10.1152/jn.01146.2009
Source: PubMed


Intraneural microneurography and microstimulation were performed on single afferent axons in the inferior alveolar and lingual nerves innervating the face, teeth, labial, or oral mucosa. Using natural mechanical stimuli, 35 single mechanoreceptive afferents were characterized with respect to unit type [fast adapting type I (FA I), FA hair, slowly adapting type I and II (SA I and SA II), periodontal, and deep tongue units] as well as size and shape of the receptive field. All afferents were subsequently microstimulated with pulse trains at 30 Hz lasting 1.0 s. Afferents recordings whose were stable thereafter were also tested with single pulses and pulse trains at 5 and 60 Hz. The results revealed that electrical stimulation of single FA I, FA hair, and SA I afferents from the orofacial region can evoke a percept that is spatially matched to the afferent's receptive field and consistent with the afferent's response properties as observed on natural mechanical stimulation. Stimulation of FA afferents typically evoked sensations that were vibratory in nature; whereas those of SA I afferents were felt as constant pressure. These afferents terminate superficially in the orofacial tissues and seem to have a particularly powerful access to perceptual levels. In contrast, microstimulation of single periodontal, SA II, and deep tongue afferents failed to evoke a sensation that matched the receptive field of the afferent. These afferents terminate more deeply in the tissues, are often active in the absence of external stimulation, and probably access perceptual levels only when multiple afferents are stimulated. It is suggested that the spontaneously active afferents that monitor tension in collagen fibers (SA II and periodontal afferents) may have the role to register the mechanical state of the soft tissues, which has been hypothesized to help maintain the body's representation in the central somatosensory system.

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Available from: Mats Trulsson, Apr 14, 2014
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    • "Instead, it seems more likely that tiny particles could be detected by forces at contact because mechanoreceptors in the periodontal ligament that can detect these have been located (Trulsson & Essick 2010). In fact, periodontal receptors regularly respond, not to the scale of forces of mastication in general (Trulsson 2006), but to the range of sub-Newton forces (Trulsson & Johansson 1994, Trulsson & Essick 2010) that we have shown would be required to detect those particles that could cause wear (Lucas et al. 2013). "

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    • "In contrast, the canines play a guiding role during lateral jaw movement. The inferior alveolar nerves were more sensitive to the central incisor stimulation than the canine (Trulsson and Essick, 2010). Thus, periodontal mechanoreceptors of the central incisors may carry more information than those of the canines, or the canine-driven PMR may be more strongly influenced by other proprioceptive factors from intra-and juxta-oral organs: e.g., the temporomandibular joint, muscle spindles, and tongue (Takada et al., 1996). "
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