A recent study published in the Journal of Neuroscience explores how the sense of smell is influenced by cues from other senses, particularly sight and hearing. The research focuses on the theory of predictive coding, which suggests that the brain’s main function is to predict what will happen next based on previous experiences. The study, conducted by researchers at Stockholm University Brain Imaging Centre (SUBIC), used a series of experiments to investigate how different senses, such as smell, respond to unexpected events compared to expected events.
The results of the study show that the sense of smell relies more on predictions than the senses of sight and hearing do. This challenges the traditional view of smell as a primitive and reactive sense, highlighting its proactive and sophisticated nature. When unexpected smells are encountered, the olfactory and visual brains are activated, suggesting a unique way in which the brain processes odors. This phenomenon may be related to the sense of smell warning us of unexpected smells and engaging the visual brain to help identify the source.
Participants in the experiments were presented with spoken word cues, such as “lemon,” followed by pictures or smells that either matched or did not match the cue. The study found that expected stimuli led to quicker decision-making, supporting the predictive coding theory. Differences in response times between expected and unexpected stimuli were used to compare how the senses rely on predictions. The findings suggest that the human sense of smell is proactive and uses a unique brain strategy to process unexpected smells in order to understand their origins.
The study included three experiments, two of which were behavioral studies and one that used fMRI imaging to examine brain activity. A total of 69 participants completed the first behavioral experiment, while 50 participants completed the second experiment. For the fMRI part of the study, data from 15 participants were initially collected and analyzed, with an additional 32 healthy volunteers participating in the fMRI portion. The researchers used a set of familiar stimuli, including lavender, lilac, lemon, and pear, presented as smells, pictures, or spoken words to ensure accuracy and unbiased response-time assessments.
Overall, the study sheds light on the complex interplay between different senses in processing sensory information. The sense of smell appears to be more influenced by predictions than sight and hearing, challenging previous assumptions about the nature of olfaction. The findings indicate that the human sense of smell is proactive and uses a unique brain strategy to process unexpected smells, engaging other brain regions in the process. Further research in this area may help broaden our understanding of how the brain processes sensory information and anticipates future events based on past experiences.
