New Insights into the Brain’s Visual Imagination
Often referred to as the mind’s eye, visual imagination is a fascinating topic. “I can look at something around me, yet I can close my eyes and picture it,” explains Varun Wadia, a brain scientist at Cedars-Sinai Medical Center and Caltech. This is the same mental capacity that allows us to remember a loved one’s face or navigate our way to work using a mental map.
Interestingly, the neural mechanisms behind this ability have remained elusive until now. Wadia and his team published their findings in the journal Science, revealing that the same neurons light up when we imagine objects as when we perceive them. “This hasn’t been shown at the neural level before,” says Kalanit Grill-Spector, a psychology professor at Stanford, who wasn’t part of the study.
These insights bring researchers one step closer to building computer models that can simulate not only normal vision but also vision disorders like macular degeneration, potentially leading to the development of prosthetic devices for restoring sight. Thomas Naselaris, a neuroscientist at the University of Minnesota, emphasizes how this study helps to explain how our imagination can supplement visual data.
“Objects are three-dimensional and reveal themselves from various angles, yet our brains intuitively create a model of what we can’t see,” Naselaris notes, giving an example of picturing a bumper at the back of a car, even when it’s out of sight. This capability also allows us to mentally assemble familiar items into new, imaginative arrangements—like imagining a unicorn.
Delving into Neural Activity
The breakthrough findings came from a study involving 16 epilepsy patients, who were already equipped with electrodes in their brains to locate the source of their seizures. This setup enabled Wadia’s team to closely monitor over 700 individual neurons as participants viewed various images, including faces, animals, and small objects.
After observing the responses of neurons in the ventral temporal cortex, which is key for object recognition, the study focused on how frequently and which neurons fired for each image. This meticulous recording helped the team decode the way these neurons communicate about visual stimuli.
In the following segment of the experiment, participants were asked to close their eyes and imagine one of the objects they had just seen. Remarkably, around 40% of the neurons that had once fired in response to seeing an object reactivated when it was merely imagined, and to a similar intensity.
The researchers found such strong overlap in neuron activation that they could even determine details about the imagined objects, from their size to their orientation. This not only corroborates previous research using brain imaging but also underscores the uniqueness of this study, which reveals neuron-level interactions that functional MRI technology cannot capture.
On a final note, the research sheds light on a rare condition known as aphantasia, affecting those who can’t voluntarily create mental images. It’s a subject Rutishauser encountered while discussing his research on imagination at a conference, where he learned that some individuals, despite being accomplished scientists, don’t see any images when they close their eyes. While it’s believed they might rely on words or concepts to recall experiences, understanding this phenomenon fully will require more detailed studies on their neural activity.
