(A) Schematic of the experiment. Responses during whisking in air were
recorded across progressive cuts to shorten the relevant whisker and decrease its moment
of inertia, I (resistance to change in angular motion). Bending moment at
the base of the whisker (M⇀), proportional to I
and angular acceleration (α⇀), was thus progressively
reduced. As a control, prior to cutting the whisker was it was handled in a sham
manipulation. (B) Tuning curves for phase (left) and acceleration (right;
± SEM) are shown for an example SA afferent across cutting conditions (colors, as
in A). Afferent showed gradual reduction of spike rates down to zero as the
whisker was progressively cut to its base (i.e. when I ~ 0). Note that
preferred phase remained constant as overall spike rate decreased. (C)
Example SA afferent with little change in responses after progressive cutting even in the
“fully cut” condition. Conventions as in (B).
(D) Example SA afferent with response that were reduced but not eliminated by
cutting. Conventions as in (B). (E) Summary showing spike rate
at the preferred phase for each afferent (n = 13 SA), as a function of the
remaining whisker moment of inertia (normalized to intact condition). Examples from
(B–D) are plotted with thick lines and indicated at
right by corresponding lower case letters (b,c,d).
A log scale for the spike rate axis accommodates the wide range across afferents.
(F) Overlay of normalized phase tuning curves (top) and histogram of
preferred phases (bottom) for each afferent (n = 13 SA) from the intact whisker
condition. Conventions as in Figure 5D–E.
(G) As in (F) but for fully cut whisker conditions (n
= 7; only neurons with ≥ 3 Hz peak response). See also Video S2.