A recent grant from the National Institutes of Health (NIH) will help fund research for the Dragoi Lab to study how unconscious information impacts brain activity and daily behavior. The grant is the result of research published in Nature Communications titled, “Cortical encoding of unconscious visual information and its impact on behavior.”
Though the neural bases of conscious experience are well-studied and understood, the process of how unconscious information affects brain activity and daily function is relatively unknown.
“Our daily behavior is influenced by conscious and unconscious processes,” said Valentin Dragoi, PhD, Rochelle and Max Levit Distinguished Professor in the Neurosciences. “For instance, we can still drive ourselves home despite being fully engaged in a phone conversation and apparently not paying much attention to the traffic.”
By recording populations of neurons in the primary visual cortex (VI), the lab discovered that subliminal stimuli (brief, irrelevant natural images) repeatedly presented in the absence of awareness are encoded by neural populations in a way that facilitates their future perception.
“We believe that this form of unsupervised adaptation may constitute a vestigial pre-attention system using the mere frequency of stimulus occurrence to change stimulus representations even when sensory inputs are perceptually invisible,” Dragoi said.
Using an animal model that entailed sophisticated neurophysiological, behavioral, and computational experiments and analyses, animals were exposed to trials of movie strips composed of random oriented gratings except for two frames (about 32 milliseconds in length), which consisted of a perceptually invisible, natural image such as the face of an animal.
The animals were then required to distinguish between the previously exposed subliminal images and novel images when both classes of stimuli were presented above the detectability threshold, or when they were both fully visible.
“We found that repeated exposure to perceptually invisible stimuli presented below the level of awareness (consisting of weak visual stimuli too faint to be seen) induces an active process of plasticity in visual cortex that subsequently improves sensory processing and perception,” Dragoi said. “These results were surprising, since they provide evidence that subliminal stimuli that do not cross the level of awareness, and were previously believed to have no effect on our conscious behavior, can actually impact our behavior and actions when they are repeatedly presented.”
The results of the research show that the bombardment of irrelevant information and weak stimuli that we receive throughout the day, and actively try to ignore, can unconsciously influence subsequent actions if they are repeatedly presented. One instance in which subliminal stimuli may be beneficial in the future is through education.
“This could be important in the future to facilitate learning by passively exposing humans to behaviorally irrelevant, unconscious information that will subsequently constitute the focus of learning,” Dragoi said. “For instance, our results imply that we can learn a complicated task or motor skill faster if we are passively, and repeatedly, exposed to elements of the task without requiring any conscious effort.”
The grant will help extend that research to further understand the neural bases of conscious and unconscious processes and their impact on perception and cognition.
“We will build on the studies published in Nature Communications to perform a large-scale brain investigation to answer the question of what makes a stimulus imperceptible or unconscious, which is a key issue in neuroscience,” Dragoi said. “We will examine how large-scale brain circuits encode conscious and unconscious processes, what exactly is different in the brain between conscious and unconscious experience, and how we can ‘fool’ the perceptual system and bias behavior by exposing the system to subliminal information.”
Funding for the grant is $1.9 million for five years and began on Sept. 30, 2020.
First author of the manuscript published in Nature Communications is Sorin Pojoga, PhD, postdoctoral fellow in the Dragoi Lab, while Natasha Kharas, MD/PhD candidate and holder of the Ruth L. Kirschstein Predoctoral Individual National Research Service Award, also contributed to the paper and research.