Fig. 1: Tone-specific response enhancement at a subset of multimodal neurons after audio-visual pairing.

a–b Expression of GCaMP6f in L2/3 excitatory neurons enabling 2-P imaging in awake or lightly anaesthetised animals in V1. Scale bar: 20 µm. c Raw (grey) and smoothed (red) calcium responses to tone presentation. Scale bars: 50%ΔF₁/F₀ and 4 s. d Average response of multimodal neuron to tones (top) and gratings (bottom). Scale bars: 50%ΔF₁/F₀ and 4 s. e Percentage of non-responsive, visually-responsive, auditory-responsive and multimodal neurons in anaesthetised conditions. f Timeline depicting baseline, audio-visual pairing or repeated unpaired presentation and testing. Icons depict stimuli with resting state activity depicted by the mouse in the dark. g Percentage of neurons showing greater (>20% of baseline) responses to the paired (red) or unpaired (black) tone or grating after audio-visual pairing. h Neurons with an increased response to the paired tone vs. baseline sensory response profiles. Icons depict response to stimuli. i Average calcium activity (ΔF₁/F₀/s) following Log₁₀ transformation for multimodal neurons to the paired (red) or unpaired (black) tone before (open) or after (filled) paired and unpaired trials. Inset: response to paired tone before (grey) and after (red) pairing. Scale bars: 50%ΔF₁/F₀ and 4 s. j Percentage of multimodal neurons showing an enhanced (>20%) tone response to either the paired (red) or unpaired (black) tone. Neurons grouped by baseline sensory response profiles to separate presentation of paired auditory and visual stimuli. Responsive to, (Left) paired visual and auditory stimuli, (Middle) paired visual stimuli only and (Right) paired auditory stimuli only. Icons depict visual/auditory baseline response. k V1 region and responses during baseline (left) and 24-h after pairing (right) in awake animals. Scale bars: 20 µm, 100%ΔF₁/F₀ and 30 s. l Average calcium (ΔF₁/F₀/s) response of multimodal neurons to pairing in awake animals. Open circles are tone presentation in the baseline (BL), re-testing and testing 24-h after pairing. Calcium response to pairing stimuli is shown as filled circles. m Average calcium activity (ΔF₁/F₀/s) for paired tone before (red, open) and after (red, filled) pairing and for unpaired tone (black bars). Figure 1b–j uses 332 neurons from six regions across six animals in light anaesthetic conditions and Fig. 1k–m uses 408 neurons from four regions across four animals in awake conditions. In all panels, *p < 0.05 (see Table 1 and associated Supplementary Table 1). Error bars: mean and ± S.E.M. Source data are provided as a Source Data file.