(A) Schematic of wS2 recording with S2L4 stimulation. Silicon probes
recorded single units across layers in wS2. Responses were recorded to
sinusoidal deflections of a single whisker along either horizontal or vertical
orientations, and to optogenetic excitation (via ChR2) of S2L4
neurons that began prior to and spanned the duration of the whisker
stimulus.
(B) Top: schematic of the whisker stimulus and 470 nm illumination (dark cyan).
Middle: spike rasters for an S2L4 unit with (green) and without
(black) optogenetic stimulation of S2L4 (first 100 trials for each).
Bottom: PSTHs (95% CI) for the example unit with (green) and without
(black) optogenetic stimulation.
(C) Population average PSTHs from S2L4 units with (green) and without
(black) optogenetic stimulation (±95% CI; n = 51 units
from 6 mice).
(D) Example units with significantly higher (unit 1, at top) or lower (unit 2, at
bottom) spike rates during a “transient” phase of the
optogenetic stimulus (indicated by purple horizontal bar at top; first 100 ms of
LED illumination, from −200 ms to −100 ms relative to whisker
stimulus onset). Conventions as in (B).
(E) Example units with significantly higher (unit 3, at top) or lower (unit 4, at
bottom) spike rates during a “sustained” phase of the
optogenetic stimulus (indicated by brown horizontal bar at top; 500 ms covering
identical period as the whisker stimulus). Conventions as in (B).
(F) Optogenetic modulation index for the transient phase of the optogenetic
stimulus, plotted for each unit as a function of normalized depth within cortex.
Estimated boundaries of cortical layer 4 are indicated with horizontal dashed
lines. Filled circles indicate significantly excited (red) or inhibited (blue)
units. Example units from (D) are indicated (dark red and dark blue filled
circles). Pie charts show percentages of units with significant optogenetic
modulation for L4 and layers above (“superficial”) and below
(“deep”) L4 (n = 393 units from 6 mice).
(G) Same as (F) but for the sustained phase of optogenetic stimulation.
(H) Schematic of wS1 recording with S2L4 stimulation. Experiments were
identical to those of (A)–(G) except recordings were made in wS1.
(I) Coronal section showing DiI-marked silicon probe recording tracts (magenta)
in wS2 (left tract) and wS1 (right tract), and ChR2-EYFP fluorescence in
S2L4.
(J) Zoom of (I) showing wS2 tract and estimated pia, L4, and white matter
boundaries (white horizontal lines).
(K–N) Same as (D)–(G) but for wS1 instead of wS2 recordings (n
= 347 units from 6 mice).
See also Figure S6.