A new study shows that the sense of odor is more affected by other senses and relies more on predictive coding compared to sight and hearing. The research highlights how the olfactory system is distinctively proactive, utilizing both visual and olfactory brain areas to process unforeseen smells.A brand-new research study published in the Journal of Neuroscience shows that the sense of smell is substantially affected by hints from other senses, whereas the senses of sight and hearing are much less affected.A popular theory of the brain holds that its primary function is to forecast what will happen next, so it responds primarily to unexpected events. The majority of research on this subject, called predictive coding, has only focused on what we see, but nobody understands if the various senses, such as smell, work in the exact same way.To determine more about how smell associates with how we manage various sensory impressions, the scientists performed a study with 3 experiments, 2 behavioral experiments, and one experiment utilizing the brain imaging approach fMRI at Stockholm University Brain Imaging Centre (SUBIC).”The primary finding is that smelling was a lot more based on forecasts than vision was. This is intriguing because numerous individuals believe that smell is primitive and reactive, when our research reveals it remains in reality rather advanced and proactive,” says Stephen Pierzchajlo, PhD Student at the Department of Psychology, and primary author of the study.The study demonstrates how important it is for our different senses to be able to use right cues when we categorize various sensory impressions.Sensory Interactions and Predictions”We have all experienced that we react to when an unexpected smell appears, for example when we go into someones flat and encounter a new odor. Our research shows that the sense of smell is highly influenced by the cues from other senses, while the sense of sight and hearing are impacted to a much lesser degree,” states Jonas Olofsson, teacher at the Department of Psychology, and co-author of the study.The researchers likewise show that when the brain tries to recognize odors that it had not expected, both the visual and olfactory brains are triggered, despite the lack of visual hints in the job.”The olfactory brain thus has an entirely unique way of processing smells and it is about whether the smells are anticipated or not. The sense of odor cautions us of smells that we had actually not anticipated, and engages the visual brain, perhaps to be able to see what it is that smells. Its a clever function since we people are so bad at acknowledging smells if we do not get hints,” says Jonas Olofsson.In the experiments, participants listened to spoken word cues, such as “lemon”, and after that received an image or smell, and individuals rapidly chose whether it matched with the hint, for example with a lemon photo or odor, or did not match, for instance with a rose image or odor.”We saw that total, the anticipated photos and smells resulted in quicker decisions, which fits well with predictive coding theory. We utilized the difference in response speed to compare the senses with each other– a bigger delay for unforeseen stimuli means that the sense relies more on forecasts,” states Stephen Pierzchajlo.The research study is the first concluded part of his PhD research.”The human sense of smell is not a reactive, but a proactive sense. It utilizes a distinct brain technique to process unexpected smells in order to comprehend what the smells are,” says Stephen Pierzchajlo.Reference: “Olfactory categorization is formed by a transmodal cortical network for assessing affective forecasts” by Stephen Pierzchajlo, Teodor Jernsäther, Lara Fontana, Rita Almeida and Jonas K. Olofsson, 31 March 2024, Journal of Neuroscience.DOI: 10.1523/ JNEUROSCI.1232-23.2024 The study was funded by the Knut och Alice Wallenbergs Stiftelse, Swedish Research Council, Stockholm University.
