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Odors prompt brain cells to make decisions before ‘you’ know what’s happening

In an exciting development, researchers have made a significant discovery that sheds light on the intricate process of decision-making by brain cells triggered by odors.

The study from the University of Colorado Anschutz Medical Campus reveals how specific brain cells, stimulated by odors, may be crucial in the rapid decision-making processes we often take for granted.

Role of the hippocampus in decision-making

The focus of this research is the hippocampus, a vital part of the brain known for its roles in memory and learning.

While it has been established that “time cells” within the hippocampus are key to its functioning, their exact contribution to associative learning was previously unclear.

“These are cells that would remind you to make a decision — do this or do that,” explains Diego Restrepo, PhD, the study’s senior author and a renowned neuroscientist and professor at the University of Colorado School of Medicine.

Understanding associative learning

In their experiments, researchers observed mice faced with a choice: respond to a fruity odor by licking a spout to receive sweet water or do nothing when presented with the scent of mineral oil.

The mice’s brains quickly learned to associate the fruit odor with the reward, demonstrating the fundamental process of decision-making based on sensory cues.

“They have to associate the odor with the outcome of what they are doing so that’s why they learn decision making,” said Ming Ma, PhD, a first author of the study and a senior instructor in cell and developmental biology at the CU School of Medicine. “When it’s a fruit odor, they lick and get a reward. When it’s mineral oil they stop licking.”

The study further revealed that as the mice’s learning progressed, the stimulated brain cells allowed for faster decoding of odors, enabling the mice to proficiently choose the fruity smell.

“The more they learned, the more the cells were stimulated leading to more rapid decoding of the odors and allowing the mice to quickly become proficient at choosing the fruity smell,” said Fabio Simoes de Souza, DSc, another first author of the study and an assistant research professor in cell and developmental biology at the CU School of Medicine.

Neural pathway: From an odor to the brain’s decision

This process begins with the odor traveling through the nose, sending neural signals to the olfactory bulb and then to the hippocampus, highlighting the close connection between these two organs.

The swift processing of this odor information leads to immediate decision-making. This discovery is a leap forward in understanding the hippocampus’s multifaceted role in decision-making, a function previously unrecognized.

Restrepo speculates that these decision-making cells are not always active to prevent sensory overload.

This insight opens new avenues in our comprehension of the brain’s decision-making capabilities, especially in the context of quick, instinctive choices that both mice and humans constantly make.

Restrepo elucidates the significance of this discovery, stating, “The hippocampus turns on decision-predicting time cells which would give you a hint of what to remember.”

This challenges the traditional view of time cells as mere markers of events and time, revealing their critical role in memory encoding and retrieval during decision-making.

In summary, this research expands our understanding of the brain’s decision-making mechanisms and paves the way for future studies that could explore how these processes are altered in neurological conditions, offering hope for new therapeutic strategies.

The University of Colorado’s study is a testament to the ever-evolving nature of neuroscience, promising exciting developments in our understanding of the human brain.

The full study was published in the journal Current Biology.


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