Perceptual decision making, internal state, and neuromodulation in V1

Abstract

Perceptual decision making is the process to translate sensory signals into meaningful behaviors yet also affected by internally-generated signals called internal states such as decision confidence, arousal, or mood. The present study aims to get insight into the role of some aspects of internal states during perceptual decision making. To this end we needed trained animals to perform a perceptual decision making task. We refined a traditional monkey-training procedure to facilitate this line of research with precise measurements of eye position. The eye data are important because they contain rich information about animals’ internal states. We demonstrated that some aspects of these internal states including their decision confidence during a perceptual decision making task can be inferred from their pupil size. We then used the pupil-inferred confidence to dissect model predictions about how sensory information is used to guide a choice. Finally, we systematically investigated the modulatory role of 5HT, which is linked to decision making and some internal states including mood, in visual processes in the primary visual cortex (V1) of awake macaques by performing extracellular recording with iontophoretic applications of serotonin and pH-matched NaCl. We found that serotonin decreased the gain of visual responses and the functional connectivity in awake macaque V1, suggesting the involvement of serotonin in state-dependent visual processes. Together, these results highlight the importance of studying internal states of trained macaques on a perceptual decision making task and the role of neuromodulators as the substrates of state-dependent visual processes during perceptual decision making.