Olfactory relies more on predictive coding than vision

summary: Our sense of smell works more based on predictive coding than vision, challenging previous notions of smell as a primitive sense. Through a series of experiments, including behavioral studies and fMRI brain imaging, this study highlights the sophistication of the sense of smell in responding to unexpected stimuli by engaging not only olfactory but also visual brain regions.

This unique sensory processing emphasizes the active nature of odors when navigating the environment, relying heavily on predictions and cues from other senses to accurately identify odors.

Important facts:

1. Olfaction relies more on predictions to process sensory information than vision, demonstrating its complex and active nature.
2. Unexpected odors activate both olfactory and visual brain regions, suggesting unique multisensory processing strategies.
3. In this study, we used behavioral experiments and fMRI to demonstrate how predictive coding theory applies to the sense of smell, revealing the sophisticated capabilities of the human sense of smell.

sauce: stockholm university

A common theory of the brain is that its main function is to predict what will happen next, and that it primarily reacts to unexpected events. Most research on this subject, called predictive coding, focuses solely on what we see, but no one knows whether different senses, such as smell, work in the same way.

To further understand how smell relates to how we process different sensory impressions, researchers conducted three experiments, 2 at the Stockholm University Brain Imaging Center (SUBIC). conducted a study with two behavioral experiments and one experiment using brain imaging fMRI.

“The main finding was that the sense of smell was far more predictive than vision. Many people think that smell is primitive and reactive, when in fact it is highly sophisticated. “This is interesting because our study shows that it is positive,” said Stephen Pearcejillo, a doctoral student in the Department of Psychology and lead author of the study. states.

This study shows how important it is for our different senses to be able to use the correct cues when classifying different sensory impressions.

“We all have the experience of reacting when an unexpected odor appears, for example when we walk into someone's apartment and encounter a new odor. Our research shows that the sense of smell “We found that the effects of visual and auditory sensations are much smaller,'' says Jonas Olofsson, professor in the Department of Psychology and co-author of the book. the study.

The researchers also showed that both the olfactory and visual brains are activated when the brain attempts to identify an unexpected odor, even though the task lacks visual cues.

“Thus, the olfactory brain has a completely unique way of processing odors, which depends on whether the smell is as expected. The sense of smell alerts us to unexpected odors, and the visual brain “This is a smart feature because we humans are very bad at recognizing smells without cues,” says Jonas Olofsson. Masu.

In experiments, participants hear an audio cue, such as “lemon,” and then receive a picture or odor, and the participants immediately decide whether the cue matches or does not match, for example, the picture or smell of a lemon. I have decided. For example, a photo or scent of a rose.

“Overall, we found that expected images and odors led to faster decision-making, which is in good agreement with predictive coding theory. “A larger delay to an unexpected stimulus means the sensation is more dependent on anticipation,” says Stephen Pierzchajlo.

This research is the first completed part of his doctoral research.

“The human sense of smell is a proactive rather than a reactive sense. We use unique brain strategies to process unexpected odors and understand what they are.” Stephen Pearce Chajiro says.

Facts about research

• In this study, three experiments were conducted at Stockholm University Brain Imaging Center (SUBIC): two behavioral experiments and one fMRI experiment using brain imaging fMRI.
• Sixty-nine participants completed the first behavioral experiment. Fifty participants completed his second behavioral survey.
• In the fMRI experiment, data from 15 participants were first collected and analyzed. Next, 32 healthy volunteers participated in his fMRI portion of the study.
• In all three experiments, the researchers used four familiar stimuli (lavender, lilac, , lemon, pear). evaluation.

About this olfactory research news

author: Gunilla Nordin
sauce: stockholm university
contact: Gunilla Nordin – Stockholm University
image: Image credited to Neuroscience News

Original research: Open access.
“Olfactory classification is formed by a transmodal cortical network for evaluating perceptual predictions” by Stephen Pierzchajlo et al. neuroscience journal

abstract

Olfactory classification is formed by a transmodal cortical network for evaluating perceptual predictions

The creation and evaluation of predictions is considered an important function in sensory perception. Little is known about processing differences between sensation and its cortical substrates.

Here we tested the hypothesis that olfaction, or the sense of smell, is highly dependent on (non-olfactory) object-predictive cues and involves different cortical processing functions. We developed a new paradigm to compare prediction error processing across different senses.

Participants listened to a spoken verbal cue (e.g., “lilac”) and judged whether a target stimulus (odor or picture) matched the verbal cue. Two behavioral experiments (total n = 113, 72 women) showed that the difference between congruent and incongruent reaction times was exaggerated for olfactory compared to visual objects, suggesting that predictive language for processing olfactory objects It shows that there is a high dependence on physical cues.

A pre-registered fMRI study (n = 30, 19 women) revealed that the anterior cingulate cortex (a region central to error detection) was more activated by incongruent olfactory targets, suggesting that olfactory prediction It was shown that there is a role in error handling.

Furthermore, both primary olfactory and visual cortices were significantly activated for incongruent olfactory targets, indicating that olfactory prediction errors depend on cross-sensory processing resources, whereas visual prediction errors do not. It was suggested.

We propose that olfaction is characterized by a strong dependence on predictive (nonolfactory) cues, and that odors are evaluated in the light of such predictions by designated transmodal cortical networks.

Our results show that different senses differ in how predictive cues are used in rapid decision making.