Podcast with Ranulfo Romo on decision-making and somatosensory cortex

How does the brain transform a fleeting touch on the fingertip into a deliberate decision seconds later? Neurophysiologist Ranulfo Romo explains how sensory representations are maintained, transformed, and compared across cortical areas , revealing the slow, parametric neural code that bridges perception and decision-making. Subscribe for more from the Convergent Science Network podcast series. Ranulfo Romo joins Paul Verschure and Tony Prescott at the BCBT summer school to discuss decades of work tracing how somatosensory signals travel from primary cortex to frontal decision-making areas in the primate brain. Using a vibrotactile discrimination task in which monkeys compare two temporally separated stimuli, Romo has mapped the transformation of sensory information at each stage , from faithful isometric representations in S1 arriving within 25 milliseconds, to slowly ramping parametric codes in prefrontal and premotor areas emerging around 180 milliseconds. The discussion addresses why Romo insists on unimodal processing in primary sensory cortex, a position he has tested for over a decade against the competing multimodal hypothesis. He argues that the neural doctrine , the idea that cortical territories are defined by their thalamic inputs , still holds, and that the key scientific question is how a sensory representation is progressively transformed as it passes through successive cortical areas, each treating the signal differently before passing it on. During the delay period between stimuli, frontal neurons maintain a ramping activity that preserves the stimulus parameter while discarding irrelevant features , a process Romo links to the ancient philosophical tradition from Democritus and Epicurus about how the brain generates internal representations of the external world. Key topics include the distinction between fast sensory and slow cognitive processing systems, the role of neuromodulators in bridging these timescales, why decision-making is context-dependent and sometimes unconscious, the relationship between Libet's conscious awareness timing and primate neurophysiology, and the challenge of procrastination as a decision-making phenomenon. Part of the Convergent Science Network podcast series from the BCBT Summer School.