Podcast with Matthew Diamond on whisker system and decision-making

Can a rat perform the same perceptual decision-making tasks that were once thought to require a primate brain? Neuroscientist Matthew Diamond explains how rats trained on complex vibrotactile comparisons reveal fundamental principles of evidence accumulation, working memory, and sensory coding , and why individual differences between rats rival those between humans. Subscribe for more from the Convergent Science Network podcast series. Matthew Diamond joins Paul Verschure and Tony Prescott at the BCBT summer school to present his laboratory's work on whisker-mediated decision-making in rats. Using a paradigm in which rats compare two vibrotactile stimuli separated by a delay, Diamond's team has shown that rats can perform parametric comparisons of stimulus intensity and duration , tasks previously considered beyond rodent capability. The results demonstrate that rats accumulate evidence over time from stochastic stimuli, improving performance with longer stimulus durations, consistent with optimal evidence integration. The discussion distinguishes between two modes of whisker sensing: receptive sensing, where the animal holds its whiskers still to collect an externally delivered vibration, and generative sensing, where the animal actively creates stimulation through its own whisking movements. Diamond argues both are forms of active sensing, since even in the receptive case the animal actively controls whisker state to optimize signal collection. The conversation explores how rats and humans compare on psychometric performance , on average humans outperform rats, but the distributions overlap substantially, with the best rats exceeding the worst human subjects. A key finding is that stimulus intensity and duration combine through summation rather than multiplication, suggesting the brain adds rather than multiplies evidence from these two dimensions. The discussion also addresses why rats show higher lapse rates than humans , possibly reflecting an evolved strategy of continuously exploring whether task contingencies have changed, rather than exploiting a known rule. Diamond explains how these rodent studies complement primate research by revealing how a simpler brain with fewer cortical modules can accomplish similar computations through different circuit architectures. Key topics include parametric versus categorical decision-making, evidence accumulation in stochastic environments, cross-modal comparison between auditory and tactile stimuli, individual variability in rat cognition, and what working memory in rats reveals about prefrontal cortex homology. Part of the Convergent Science Network podcast series from the BCBT Summer School.