Temporal Integration of Olfactory Perceptual Evidence in Human Orbitofrontal Cortex

Given a noisy sensory world, the nervous system integrates perceptual evidence over time to optimize decision-making. Neurophysiological accumulation of sensory information is well-documented in the animal visual system, but how such mechanisms are instantiated in the human brain remains poorly understood. Here we combined psychophysical techniques, drift-diffusion modeling, and functional magnetic resonance imaging (fMRI) to establish that odor evidence integration in the human olfactory system enhances discrimination on a two-alternative forced-choice task. Model-based measures of fMRI brain activity highlighted a ramp-like increase in orbitofrontal cortex (OFC) that peaked at the time of decision, conforming to predictions derived from an integrator model. Combined behavioral and fMRI data further suggest that decision bounds are not fixed but collapse over time, facilitating choice behavior in the presence of low-quality evidence. These data highlight a key role for the orbitofrontal cortex in resolving sensory uncertainty and provide substantiation for accumulator models of human perceptual decision-making. ► Model-based fMRI revealed cortical integration of an olfactory perceptual decision ► Olfactory evidence is encoded in piriform cortex; this evidence is integrated in OFC ► Olfactory evidence accumulates more gradually in OFC for more difficult odor mixtures ► OFC profiles suggest that decision-bound criteria are lowered for noisy inputs Bowman et al. show that humans accumulate perceptual information over time to more accurately identify complex odor mixtures. Activity in orbitofrontal cortex uniquely conforms to this behavior and reflects activity predicted by decision-making models of temporal integration.