(A) Top, mice judged object location with a single whisker. Whisker position (azimuthal angle, θ), whisking phase (ϕ), and whisker curvature (κ) were measured from video recordings. Bottom, recordings were made from excitatory cells in the principal barrel (red). L4 excitatory neurons receive excitatory input from VPM and excite each other within individual barrels. (B) Behavioral and electrophysiological data (single trial). θ, whisker position (green); ϕ, whisking phase (green); Δκ, change in whisker curvature (blue), which is proportional to pressure on mechanoreceptors at the base of the whisker; Vex, extracellular spike waveform (black) recorded in loose-seal mode (blue crosses, touch onsets). The black horizontal bar indicates the time when the object was in reach. (C) Spike raster for one example neuron. Same data as in D–H. Pole in reach for all trials (black bar) with variable exit time (grey bar). (D) Peri-stimulus time histogram aligned to the trial onset (bin size, 50 ms). (E) Spike raster aligned to first touch, and sorted according to last touch in the sample period (late on top). Trials without touch are not shown. (F) Peri-stimulus time histogram aligned to first touch (bin size, 1 ms). The grey line represents the proportion of touches with durations >= than time (max of 1). (G) Spikes aligned by whisking phase in a whisking bout (whisking amplitude >2.5° peak-to-peak). Only exploration periods excluding touch were used. (H) Spike histogram aligned to whisking phase (bin size, 30°) Best-fit spike modulation (grey). Average change in whisker position/bout (green).