Perception of Auditory, Visual, and Audiovisual Motion in Macaque Monkeys

Abstract

The ability to perceive moving objects, which tend to engage multiple sensory systems, is critical for navigating everyday environments. This dissertation examines how motion cues are processed and integrated across auditory and visual modalities in rhesus macaques. In Chapter 1, macaques performed a direction discrimination task using auditory motion stimuli that systematically varied in displacement, duration, and velocity. Behavioral analyses revealed that displacement had the strongest influence on motion direction sensitivity, with duration exerting a moderate effect (particularly at short timescales) and velocity contributing the least. These findings support a “snapshot” model of auditory motion perception, in which motion is inferred from sequential spatial samples, rather than encoded directly through dedicated velocity-tuned mechanisms. Chapter 2 builds on this by presenting experiments utilizing matched auditory, visual, and audiovisual motion stimuli. In most conditions, audiovisual stimulation produced multisensory gain, i.e., enhanced motion sensitivity relative to the unisensory condition eliciting the highest sensitivity. However, these effects were often suboptimal relative to predictions from the Maximum Likelihood Estimation (MLE) model, which assumes cues are integrated based on their relative reliability. These results suggest that crossmodal motion integration in macaques does not consistently follow MLE predictions and may reflect more flexible strategies, such as those described by Bayesian causal inference models. Taken together, this work provides a detailed behavioral account of motion processing and multisensory integration in a nonhuman primate model. The results also lay a foundation for future neurophysiological studies,and highlight the importance of naturalistic sensory stimulation in studies of auditory and visual perception.