Johnson K. O., Hsiao S. S. (1992). Neural mechanisms of tactual form and texture perception. Annu. Rev. Neurosci. 15, 227–250 The researchers then similarly marked two other types of touch nerve cells and found that each hair type has a different and specific set of nerve endings associated with it. "This makes every hair a unique mechanosensory organ," says Ginty. Moreover, with their new marking tools, they found that each hair type is evenly spaced and patterned throughout the skin.

That said, occasionally too much ear hair can crowd and clog the ear canal. It could make you more susceptible to mild conditions like swimmer’s ear by narrowing the ear canal so water gets trapped inside. Wessberg, J. ( 1999) Unmyelinated afferents constitute a second system coding tactile stimuli of the human hairy skin.Velocity ERP effects for Experiment 2 (glabrous skin). A) Frontal velocity effect shown for Fz. B) sN400 velocity effect over the right medial region explored in Experiment 1 (rm; Cz, C2, CP2) and a slightly more lateral region adapted for the cortical representation of the palm (rml; C2, C4, CP4). Gray rectangles highlight windows for statistical analysis ranging from 0.7 to 1s for the Fz effect and from 0.3 to 0.5s for the sN400. The topography of each velocity effect (Fz/rm—3cm/s minus 20cm/s; rml—20cm/s minus 0.5cm/s) is printed on a 3D head. Merkel cells are tactile cells of neuroectodermal origin located in the basal layer of the epidermis. Rolls E.T., O’Doherty J., Kringelbach M.L., Francis S., Bowtell R., McGlone F. (2003). Representations of pleasant and painful touch in the human orbitofrontal and cingulate cortices. Cerebral Cortex (New York, N.Y.: 1991), 13, 308–17. [ PubMed] [ Google Scholar] Vallbo Å.B., Olausson H., Wessberg J. (1999). Unmyelinated afferents constitute a second system coding tactile stimuli of the human hairy skin. Journal of Neurophysiology, 81, 2753–63. [ PubMed] [ Google Scholar]

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Smith, E. ( 1999) The representation of pleasant touch in the brain and its relationship with taste and olfactory areas. Neelin, P. ( 1992) A three-dimensional statistical analysis for CBF activation studies in human brain. Analysis of Fz mean voltages from 700 to 1000ms returned a significant velocity effect (F[2,118]=4.86, P=0.009). The linear term was non-significant ( P>0.25), but the quadratic term pointed to the expected concave relationship (ß=−1.91, SE=0.65, P=0.004). The touch stimulus in this study was low force (∼0.3N) stroking of the left forearm. In Experiment 1, the brush stroked the participant’s dorsal forearm, whereas in Experiment 2, the brush stroked her/his palm. Although most studies in the field have probed linear trajectories, recent evidence suggests oval trajectories are more pleasant ( Shirato etal., 2018) and more representative of actual touch interactions ( Lo etal., 2021). We, therefore, opted for an oval rather than a linear trajectory. The set points for this trajectory were a ∼15cm circumference, a minor radius of ∼1cm and a major radius of ∼3.22cm. Small deviations from these set points were necessary due to variation in skin area curvature across participants. Strokes were delivered at five velocities including 0.5, 1, 3, 10 and 20cm/s for a duration of 2.5s. Because different velocities necessarily covered different distances across the skin, we adopted a number of control measures. Specifically, we adjusted the starting position of strokes such that motion along the oval was balanced across trials for a given velocity within participants. Thus, all velocities completed the full oval at least once across trials (for further details see Supplementary Materials).

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