A new study published in the Journal of Neuroscience indicates that the sense of smell is significantly influenced by cues from other senses, whereas the senses of sight and hearing are much less affected.
A popular theory of the brain holds that its main function is to predict what will happen next, so it reacts mostly to unexpected events. Most research on this topic, called predictive coding, has only focused on what we see, but no one knows if the different senses, such as smell, work in the same way.
To figure out more about how smell relates to how we handle different sensory impressions, the researchers conducted a study with three experiments, two behavioral experiments, and one experiment using the brain imaging method fMRI at Stockholm University Brain Imaging Centre (SUBIC).
“The main finding is that smelling was much more dependent on predictions than vision was. This is interesting because many people think that smell is primitive and reactive, when our research shows it is in fact quite sophisticated and proactive,” says Stephen Pierzchajlo, PhD Student at the Department of Psychology, and main author of the study.
The study shows how important it is for our different senses to be able to use correct cues when we classify different sensory impressions.
Sensory Interactions and Predictions
“We have all experienced that we react to when an unexpected smell appears, for example when we enter someone’s flat and encounter a new smell. 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 affected to a much lesser extent,” says Jonas Olofsson, professor at the Department of Psychology, and co-author of the study.
The researchers also show that when the brain tries to identify odors that it had not expected, both the olfactory and visual brains are activated, despite the absence of visual cues in the task.
“The olfactory brain thus has a completely unique way of processing smells and it is about whether the smells are expected or not. The sense of smell warns us of smells that we had not expected, and engages the visual brain, perhaps to be able to see what it is that smells. It’s a smart function because we humans are so bad at recognizing smells if we don’t get clues,” says Jonas Olofsson.
In the experiments, participants listened to spoken word cues, such as “lemon”, and then received a picture or smell, and participants quickly decided whether it matched with the cue, for example with a lemon picture or smell, or did not match, for example with a rose picture or smell.
“We noticed that overall, the expected pictures and smells led to quicker decisions, which fits well with predictive coding theory. We used the difference in response speed to compare the senses with each other – a bigger delay for unexpected stimuli means that the sense relies more on predictions,” says Stephen Pierzchajlo.
The study is the first concluded part of his PhD research.
“The human sense of smell is not a reactive, but a proactive sense. It uses a unique brain strategy to process unexpected smells in order to understand what the smells are,” says Stephen Pierzchajlo.
Reference: “Olfactory categorization is shaped by a transmodal cortical network for evaluating perceptual predictions” 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.
News
NIH Scientists Discover Gene Responsible for Rare Eye Disease
Findings supported by the NIH pave the way for the development of genetic testing, clinical trials, and therapies. Researchers at the National Institutes of Health (NIH) and their collaborators have discovered a gene linked to certain [...]
Alzheimer’s Breakthrough: Synthetic THC Pill Proves Effective in Clinical Trial
Patients tolerated synthetic THC (dronabinol) well, without the adverse effects commonly associated with existing Alzheimer’s agitation medications. A study conducted by researchers from Johns Hopkins University School of Medicine and Tufts University School of Medicine found that a pill form [...]
The Future of Rare Disease Treatment with Precision Medicine
Understanding rare diseases Rare diseases affect less than 5 people out of 10,000. However, this still amounts to about 7% of the world’s population, with over 10,000 such conditions. Almost all are genetic in [...]
Doctors issue warning for upcoming ‘tripledemic
The term ‘tripledemic’ has hit headlines this week as the NHS begins its Covid and fluvaccine roll-out for vulnerable adults. As the cold weather sets in, many of us have experienced a decline in health, and this may [...]
The FDA approved a gel that can stop bleeding from wounds in seconds
Aug 15 (Reuters) - The U.S. Food and Drug Administration has cleared Cresilon's gel to quickly control bleeding, the privately held company said on Thursday, potentially giving emergency medical technicians and combat medics a [...]
High levels of microplastics found in prostate tumors, possibly linked to take-out food
The presence of microplastics in prostate tumors points to potential health risks, and researchers are calling for urgent studies to explore how take-out food may be driving this exposure. In a recent study published [...]
AI outperforms radiologists in brain tumor diagnosis
As artificial intelligence advances, its uses and capabilities in real-world applications continue to reach new heights that may even surpass human expertise. In the field of radiology, where a correct diagnosis is crucial to ensure [...]
Breakthrough Study Reveals Molecular Clues to Dementia Origins
Work could lead to the discovery of new therapeutic targets. For the first time, researchers have identified “molecular markers” linked to degeneration—detectable changes in cells and their gene-regulating networks—that are common across several types [...]
Better than blood tests? Nanoparticle potential found for assessing kidneys
In a study published July 29 in Advanced Materials, University of Texas at Dallas researchers found that X-rays of the kidneys using gold nanoparticles as a contrast agent might be more accurate in detecting kidney [...]
Greener nanomaterials could transform how our everyday stuff is made
Tiny nanoparticles are at the forefront of materials science—with special properties that make them great at absorbing light in solar panels, cleaning wastewater, and delivering drugs precisely. Some nanoparticles take the form of sheets or fibers. But nanomaterials all [...]
AI could predict breast cancer risk via ‘zombie cells’
Women worldwide could see better treatment with new AI technology, which enables better detection of damaged cells and more precisely predicts the risk of getting breast cancer, shows new research from the [...]
Through the eyes of a cat – biomimicry of feline eyes may revolutionize robotic vision
In a recent study published in the journal Science Advances, researchers leveraged crucial aspects of feline eyes, particularly their tapetum lucidum and vertically elongated pupils (VP), to develop a monocular artificial vision system capable of [...]
New Alzheimer’s Therapy Shows Remarkable Results in Animal Trials
A study from TUM demonstrates a promising therapeutic approach. Researchers at the Technical University of Munich (TUM) have made promising advances in preventing Alzheimer’s by developing a new therapeutic strategy. Their approach focuses on targeting the amyloid beta [...]
Rewriting Cancer’s Blueprint: New Study Challenges Old Theories
A new study argues for a revised clonal evolution model of cancer, incorporating genetic and non-genetic factors to improve understanding and treatment. Like all living organisms, cancer cells are driven by the fundamental need [...]
Microplastics Everywhere: Experts Demand Worldwide Treaty Before It’s Too Late
A new report calls for global action on plastic pollution, urging reductions in plastic production and microplastic emissions. Researchers stress the importance of addressing plastic pollution through both scientific and social science perspectives. A [...]
Blood tests could soon predict your risk of Alzheimer’s
Scientists are closing in on biomarkers that reflect the progression of Alzheimer’s disease and could improve treatments. Like many Alzheimer’s researchers, neurologist Randall Bateman is not prone to effusiveness, having endured disappointments in his [...]
