Rapid Adaptation of Reward Brain Maps in Response to New Encounters

Title: The Brain's GPS Maps: How Quick Adaptation to Rewarding Experiences Shapes Our Behavior

You take a new route to your favorite coffee shop, and lo and behold, you stumble upon a hidden gem. That change of scenery probably did more than just change up your morning routine. Each time you visit this new locale, time and time again, your brain gradually forms a neural map marking the location of rewarding experiences - a map that guides you back to it, even miles away.

While the idea of a reward map isn't novel, neuroscientists at the Wu Tsai Neuro initiative discovered something fascinating: these maps aren't just static memorizations but rather flexible systems that adapt in real-time when the location of a reward changes.

“No matter where we moved the reward, the reward map adapted almost immediately,” said Lisa Giocomo, a professor of neurobiology at Stanford Medicine. “I wasn't expecting the change to be so quick.”

Here's a peek into how that happens:

To explore the neuroscience behind this spatial-reward mapping, the researchers first replaced a bit of a mouse's skull with a transparent window, making it possible to observe neural activity in real-time in the hippocampus using two-photon microscopy.

Next, the mice navigated virtual environments cunningly designed to simulate the conditions of the real world. As they ran on wheels surrounded by large monitors that played a video of a hallway, the researchers could manipulate the mice's virtual surroundings and program the apparatus to dispense a reward, like a drop of sugar water, when they approached a specific location.

As they expected, one population of neurons in the hippocampus maintained a stable map of the environment, while a separate but fluid population turned on and off as the reward's location changed. This layer of adaptability allowed the mouse to easily adjust when the location of the food changed.

What's more intriguing? The neurons that make up the spatial map and the reward map aren't entirely distinct; instead, they connect and interact, highlighting the overlap between spatial and reward memories.

These findings could shed light on human conditions, such as dementia and addiction, in addition to providing insights into the biology of how animals navigate in the wild.

For instance, patients with dementia may develop spatial disorientation and memory loss due, at least partly, to a loss of the ability to visualize where they were when a task was completed. On the other hand, memories of rewarding experiences are often tied to spatial locations in the brains of addiction sufferers.

"Someone who first uses drugs at a concert might always be triggered to seek out drugs when they're at a concert, for instance," Giocomo added. "And that can be a big problem because it causes people in recovery to relapse when they encounter those triggering environments."

Ultimately, a better understanding of the neural links between spatial information and rewards could lead to therapies that weaken these links, helping people overcome cravings brought on by specific locations, and conversely, therapies that strengthen these links to assist people living with dementia.

As for the researchers, they continue to question the mysteries of the brain. For example, do enjoyable experiences besides food also follow this type of neural structure? How do reward maps guide animals in their natural environments?

The once-shrouded secrets held within the walls of the hippocampus are slowly being brought to light. And who knows, maybe one day, we could retrain our brains to willingly swap out our favorite coffee shop for one that serves a better brew – without the guilty aftertaste of addiction.

Funding Sources: The National Institutes of Health (NIH grants 1R01MH126904-01A1, R01MH130452, BRAIN Initiative U19NS118284, P50 DA042012); The Vallee Foundation; The James S. McDonnell Foundation; The Simons Foundation (grant 542987SPI), the Champalimaud Vision Award, and the Howard Hughes Medical Institute.

Sources:

Lisa Giocomo et al. (2021). A flexible hippocampal population code for experience relative to reward, Nature Neuroscience
Nicholas Weiler, Stanford, "Brain's GPS Maps Adapt to Locations of Rewarding Experiences," Stanford News, November 1st, 2021.
The discovery of flexible reward maps in the brain, revealed by neuroscientists at the Wu Tsai Neuro initiative, suggests that these maps can adapt quickly when the location of a reward changes, a finding that challenges previous beliefs.
Lisa Giocomo, a professor of neurobiology at Stanford Medicine, led a study using mice and two-photon microscopy to observe neural activity in the hippocampus as they navigated virtual environments.
In the study, one population of neurons in the hippocampus maintained a stable map of the environment, while a separate but fluid population turned on and off as the reward's location changed, providing adaptability for the mouse to adjust when the location of the food changed.
These findings could have implications for human conditions such as dementia and addiction, since patients with dementia may struggle with spatial disorientation and memory loss, while memories of rewarding experiences are often tied to spatial locations in the brains of addiction sufferers.
In addition to their impact on health and wellness, these findings could also offer insights into the neurobiology of space and astronomy, as animals navigate through their natural environments to find resources such as food.
Funding for the research came from several sources, including the National Institutes of Health, the Vallee Foundation, the James S. McDonnell Foundation, the Simons Foundation, the Champalimaud Vision Award, and the Howard Hughes Medical Institute.