Fig. 4.

Unimodal PLLS neurons show multisensory effects. The subset of unimodal neurons (37/233) that showed a statistically significant response modulation at the single neuron level during the combined visual-auditory condition (i.e., subthreshold multisensory neurons) all demonstrated an increased multisensory response change (a), with an average response change of 42 ± 3% (b). The bar graph (c) summarizes this effect, where the average response for the group of subthreshold multisensory neurons was significantly greater for the combined visual-auditory (VA; 11.4 ± 1.4 spikes/trial) condition than the visual (V) condition (8.7 ± 1.2, P < 0.05, paired ‘t’-test). The vast majority (81%, 159/196) of seemingly ‘unisensory’ neurons in the PLLS, despite failing to achieve the statistical criterion of multisensory processing at the neuronal level, demonstrated modest group response facilitation during the VA condition (hence, plotted above zero on the y-axis in d). For these unimodal neurons, the average response change was 11 ± 1% (e). Consequently, as seen in the bar graph (f), the population average mean spikes/trial for these neurons was significantly greater for the VA condition than the V condition (5.5 ± 0.4 vs. 6.0 ± 0.4, P < 0.05, paired ‘t’-test)