Eyes Offer a Window Into the Mystery of Human Consciousness

Summary: Tracking eye movements as a person views an image of a face in different lights provides vital clues about visual perception and consciousness overall.

Source: Yale

Since he was a kid Hal Blumenfeld has wondered about the nature of human consciousness.

“It’s what makes us human and makes life worthwhile,” said Blumenfeld, now the Mark Loughridge and Michele Williams Professor of Neurology at Yale. “And it’s still a mystery of modern science.”

In a recent study, Blumenfeld and a team of Yale colleagues identified some of the overlapping neural mechanisms that help to illuminate that mystery.

Writing in the journal Nature Communications, they describe how the human brain is capable of sorting through an avalanche of external stimuli—most of which never reach the human consciousness—to create a sense of awareness of the individual’s surroundings.

“Turns out there is a set of very beautiful and rich activities involved in the neural mechanism of conscious thought,” said Blumenfeld, who is also professor of neuroscience and of neurosurgery and director of the Yale Clinical Neuroscience Imaging Center.

One of the challenges facing scientists who study consciousness is the inherent uncertainty that comes with measuring what people are actually aware of.

Oftentimes, these researchers will perform brain imaging on people as they are presented with images of objects or events and are then asked questions, like, “Are you aware of a face?” or “Are you aware of an event?” A key unanswered question, however, is what exactly is being measured? Is it the brain’s actual perception of an object or event or simply the response to the question?

To answer this, Blumenfeld—working with Sharif Kronemer, a former Ph.D. student at Yale who is now a postdoctoral fellow at the National Institutes of Health, and a large group of expert collaborators—used a combination of artificial intelligence, mathematics, and a close examination of the eye movements of individuals as they were shown images of people’s faces.

As it turns out, they found that important clues are revealed in the eyes. When people were shown clear images, their eye movements showed a distinct pattern that indicates they were aware of their surroundings.

However, as the subjects were presented with progressively dimmer images of faces, the pattern of eye movement changed. Tracking these changes, Blumenfeld said, allowed researchers to discern whether the subjects actually perceived the face or not without asking them.

“The eyes are truly the window to our souls,” he said. “We can tell if people are aware of something by simply looking at their eyes.”

The eye-tracking tool allowed researchers to explore the amorphous dividing line between consciousness and unconsciousness, a state most obvious as we awake from sleep. People become progressively more aware of their surroundings as slumber recedes, a process that is controlled in a region of the brain known as the thalamus.

This shows an eye
One of the challenges facing scientists who study consciousness is the inherent uncertainty that comes with measuring what people are actually aware of. Image is in the public domain

The Yale researchers found that when people awake the thalamus discharges a brief pulse which jumpstarts the transition to consciousness. However, this activity is only a first step in a series of actions throughout the brain that leads to full awareness, they found.

For instance, that initial pulse from the thalamus may fail to activate other neural networks, keeping the individual unconscious of most surrounding stimuli. However, the pulse can also activate neurons involved in processing visual cues in the frontal cortex, which in turn amplifies circuits involved in arousal and attention. At the same time, signals irrelevant to the event are turned off.

Ultimately, the pertinent signals are processed to form a conscious experience that can be stored in our memory, Blumenfeld said.

Understanding these processes, he said, may help provide new insights into the treatment of some mental health disorders that are marked by a lack of awareness of surroundings—including Alzheimer’s disease, schizophrenia, and traumatic brain injury.

In addition, it may help doctors better assess consciousness in patients who are unable to talk or in a coma.

Blumenfeld hopes these discoveries will also bring humankind closer to understanding ancient philosophical questions about the nature of human consciousness, and the mysteries he’s always wondered about.

“Investigating the elegant overlapping signals from deep in the brain to the surface may finally provide a satisfactory explanation for consciousness,” he said.

About this consciousness and visual neuroscience research news

Author: Bill Hathaway
Source: Yale
Contact: Bill Hathaway – Yale
Image: The image is in the public domain

Original Research: Open access.
Human visual consciousness involves large scale cortical and subcortical networks independent of task report and eye movement activity” by Sharif I. Kronemer et al. Nature Communications


Human visual consciousness involves large scale cortical and subcortical networks independent of task report and eye movement activity

The full neural circuits of conscious perception remain unknown. Using a visual perception task, we directly recorded a subcortical thalamic awareness potential (TAP). We also developed a unique paradigm to classify perceived versus not perceived stimuli using eye measurements to remove confounding signals related to reporting on conscious experiences.

Using fMRI, we discovered three major brain networks driving conscious visual perception independent of report: first, increases in signal detection regions in visual, fusiform cortex, and frontal eye fields; and in arousal/salience networks involving midbrain, thalamus, nucleus accumbens, anterior cingulate, and anterior insula; second, increases in frontoparietal attention and executive control networks and in the cerebellum; finally, decreases in the default mode network. These results were largely maintained after excluding eye movement-based fMRI changes.

Our findings provide evidence that the neurophysiology of consciousness is complex even without overt report, involving multiple cortical and subcortical networks overlapping in space and time.

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  1. Well, as the picture shown here indicates, you ( the person watching the screen to read this article) only see what is shown, but all white, is consciousness.

  2. I’ve always felt like you can determine the way a person feels about you by looking in their eyes. It may sound lame, but I am extremely curious if my observation has any relevance. I guess in a way, I just want to know if I’m crazy, or if I’m actually on to something. For years I swore I could see the love in my husband’s eyes, likewise before things went completely south, I also swear I saw the lack of love in his eyes. It’s just something in the eyes was off. In another toxic relationship I recall arguing with a boyfriend and him often saying hurtful things, but I noticed something strange, when leaving I just happened to look him in the eyes, and I swore I could tell he didn’t mean a single thing he was saying. Of course that didn’t stop me from leaving. Months later him and I reconciled on a plutonic friendship only basis. We became great friends, and I discovered he had a genuine admiration for me, as well deep remorse for the way he treated me. It caught me a little by surprise, because my ex husband may have expressed regret, I never could see it in his eyes, then again, there was no type of love in his eyes for me at the end either, but the ex boyfriend who became a friend only expressed remorse once, however, the authenticity was always there in his eyes. Maybe I’m crazy, and perhaps this has no relevance in science, but it would be interesting to find out one day if things like this can be determined. Similar to the experiment mentioned in article, could the same experiment be used only instead of tracking eye movements with whether or not an image is clear, tracking them while a subject views pictures of random people vs people they claim to have affection for. If that’s possible, is it also possible to determine whether or not emotionally detached people who pretend to feel emotional attachment are different than other subjects, that those type of people have to difference in eye movement no matter what image they view.

  3. It’s becoming clear that with all the brain and consciousness theories out there, the proof will be in the pudding. By this I mean, can any particular theory be used to create a human adult level conscious machine. My bet is on the late Gerald Edelman’s Extended Theory of Neuronal Group Selection. The lead group in robotics based on this theory is the Neurorobotics Lab at UC at Irvine. Dr. Edelman distinguished between primary consciousness, which came first in evolution, and that humans share with other conscious animals, and higher order consciousness, which came to only humans with the acquisition of language. A machine with primary consciousness will probably have to come first.

    What I find special about the TNGS is the Darwin series of automata created at the Neurosciences Institute by Dr. Edelman and his colleagues in the 1990’s and 2000’s. These machines perform in the real world, not in a restricted simulated world, and display convincing physical behavior indicative of higher psychological functions necessary for consciousness, such as perceptual categorization, memory, and learning. They are based on realistic models of the parts of the biological brain that the theory claims subserve these functions. The extended TNGS allows for the emergence of consciousness based only on further evolutionary development of the brain areas responsible for these functions, in a parsimonious way. No other research I’ve encountered is anywhere near as convincing.

    I post because on almost every video and article about the brain and consciousness that I encounter, the attitude seems to be that we still know next to nothing about how the brain and consciousness work; that there’s lots of data but no unifying theory. I believe the extended TNGS is that theory. My motivation is to keep that theory in front of the public. And obviously, I consider it the route to a truly conscious machine, primary and higher-order.

    My advice to people who want to create a conscious machine is to seriously ground themselves in the extended TNGS and the Darwin automata first, and proceed from there, by applying to Jeff Krichmar’s lab at UC Irvine, possibly. Dr. Edelman’s roadmap to a conscious machine is at https://arxiv.org/abs/2105.10461

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