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Fig. 6. Bode plots for frequency responses to hydrodynamic and tactile stimuli for
primary afferent neurons that innervate lateral line canal neuromasts in the
dorsal pored (Dp), ventral pored (Vp) and ventral non-pored (Vnp)
hyomandibular canals of the Atlantic stingray, Dasyatis sabina.
Hydrodynamic stimuli: Dp primary afferents show peak frequency sensitivity at
20–90 Hz re: velocity (Ai) and a flat, relatively untuned response up to
about 40 Hz when expressed in terms of acceleration (Aii). Vp primary
afferents show flat to low-pass characteristics when expressed in terms of
both velocity (Bi; <70 Hz) and acceleration (Bii; <30 Hz). Variation
among units is likely due to low sample size for this group (N=9).
Tactile stimuli: Vnp primary afferents stimulated by tactile depression of the
skin show a relatively flat response up to 30 Hz re: velocity (Ci) and a
low-pass response re: acceleration (Cii) with a 6 dB drop in neural response
achieved by 5 Hz. Thus, primary afferents from pored canals respond to
hydrodynamic acceleration and units from ventral non-pored canals respond to
the velocity of canal fluid induced by skin depression. Data were normalized
to a relative value of 0 dB assigned to the best frequency for each neuron and
expressed as relative neural gain (dB). All data are plotted as mean ±
S.E.M. for each stimulus frequency relative
to velocity (Ai–Ci) and acceleration (Aii–Cii). Sample sizes
(N) represent the number of animals, number of primary afferents
sampled. Note that some error bars are obscured by symbols.
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