Unraveling the Conscious Brain

The lecturer elaborates that the brain actively constructs sensory experiences, such as color, rather than passively receiving them as external facts, reinforcing the idea that perceptions are internal interpretations of an external world.

Cognitive neuroscience is focused on identifying the specific neural correlates that distinguish conscious from unconscious states.

The central challenge lies in mapping the brain processes responsible for this distinction.

The function of consciousness is hypothesized to be the broadcasting of information across the brain, enabling flexible and adaptive actions.

Individuals in this state may show physical movements, such as looking around or moving limbs, without any apparent conscious perception of their surroundings.

This condition presents a significant and complex puzzle for researchers in cognitive neuroscience, challenging definitions of consciousness.

"if you see somebody in a vegetative state, they look around, they move their arms, but they don't seem to be aware of their surroundings."

Lecturer

During REM sleep, individuals typically report vivid visual dreams, often describing themselves as being in a specific location or engaged in activities.

In contrast, NREM sleep reports generally lack the qualitative experience of being in a defined location, with experiences often described as fragmented or abstract.

The question of whether NREM sleep truly represents an unconscious state remains a subject of ongoing debate within the scientific community.

"And when you're when you're in REM sleep, people report experiencing Yeah, a dream. So, they're they are visual. They might be walking them."

Lecturer

Transcranial Magnetic Stimulation (TMS) pulses combined with EEG recordings map how electrical signals propagate through the brain's cortex.

Rich information exchange characterizes the complex and long-lasting signal propagation that follows stimulation during conscious states.

Reduced network interaction during deep sleep and anesthesia causes only localized, simple signal decay.

The Perturbation Complexity Index (PCI) quantifies this complexity, highlighting that consciousness requires efficient and unpredictable information transfer between different brain regions.

"If you're awake, it ricochets and it carries on in this kind of complex way. And that's effectively what this measure is. It's called the perturbation complexity index."

Lecturer

EEG signals during psychedelic states exhibit higher mathematical complexity compared to those observed during normal wakefulness.

Psychedelics potentially represent a mathematically 'higher' state of complexity, supporting the view that consciousness operates on a continuum.

However, increased complexity does not automatically equate to 'better' brain performance or a more optimal state of consciousness.

"And essentially what you find is that it's more complex than being in a wakeful state."

Lecturer

By having patients imagine playing tennis or navigating their homes, Dr. Adrian Owen demonstrated that 20% of non-responsive patients could provide 'yes' or 'no' answers via fMRI patterns.

Imagining playing tennis activates the premotor cortex, while navigating one's home engages the parahippocampal gyrus.

These distinct brain activity patterns allow researchers to pose 'yes' or 'no' questions to seemingly unresponsive patients.

Approximately 20% of patients diagnosed as vegetative have shown the ability to perform these mental tasks, providing a new avenue for assessing awareness.

"One of the key insights was the realization that we could simply get somebody to lie in the scanner and imagine something, and based on the pattern of brain activity, we will be able to work out what it is they were thinking. ... So, we realized that we could use this as a a simple mechanism for asking yes and no questions."

Adrian Owen

The resulting mathematical output provides an estimate of the level of consciousness, aiding in the diagnosis of minimal conscious states versus vegetative states, independently of command following.

"You put an EEG cap on them and you're applying a TMS pulse. So, you're stimulating their brain and you're watching the electrical current kind of ping around and you then get out this mathematical number and you see is this more likely being likely to be conscious or unconscious."

Lecturer

Proponents of IIT argue that if other complex interacting systems, beyond the human brain, display these mathematical principles, they too could be considered conscious.

This perspective aligns with panpsychism, the idea that consciousness is a fundamental and ubiquitous property throughout the universe, present in all matter and energy.

"If you can find this mass measure in other interacting systems, then you can claim that they're conscious. That would be called panpsychism."

Lecturer

"In order to be conscious of something like color, you need a higher order thought about color within your frontal lobe. It's almost as if you need a copy of this. It's like a duplication of information."

Lecturer

Stimuli that fail to ignite this widespread network remain unconscious, explaining phenomena where sensory information is processed but not consciously perceived, as demonstrated in experiments like the 'gorilla experiment'.

"If you've got activity saying your visual cortex and it gets strong enough, it will then ignite this frontoparietal system. It's again to do with attention, action, and selecting information for further processing."

Lecturer

Applying Transcranial Magnetic Stimulation (TMS) to the parietal lobes can alter the rate at which an observer perceives ambiguous visual stimuli, such as the face-vase illusion, switching between interpretations.

This distinction highlights a potential confound where the motor act of reporting might be mistakenly equated with the conscious experience.

Studies employing 'no-report' paradigms, where AI decodes brain states without requiring a behavioral response, show reduced frontal-parietal activity.

The frontoparietal network's role may be specifically tied to the processes involved in task reporting, rather than the raw conscious experience.

"The claim here is that it's more to do with the reporting aspect of consciousness than it is to do with the the experience of the world."

Lecturer

Predictive processing theories propose that conscious experience is exclusively a top-down process, driven by the brain's internal models and expectations, rather than a blend of bottom-up sensory input and top-down interpretation.

Under this view, the brain never directly perceives external reality; instead, it only experiences its own continuously generated 'best guesses' or predictions about what that reality might be.

"So, these theories effectively claim that what we experience is our best guess of external reality."

Lecturer

When subjects are pre-informed about what they are likely to see, the visual stimuli become consciously perceptible much faster.

This priming effect, where expectations facilitate conscious perception, is more readily explained by predictive models of consciousness than by the Global Workspace Theory.

"If you are given some expectations about what it is you're going to see, you can actually experience this breaking through sooner. ... your expectations can really help you see things that are otherwise kind of unconscious and can break through."

Lecturer

Experience sampling studies have confirmed that neural patterns associated with conscious states are present during these internally focused periods.

Consciousness is not solely dependent on visual or external sensory content but is broadly applicable to any form of mental content, whether it originates from external perception or internal processes like memory and imagination.

"That would be one claim is that this is still applicable here, but it's just not your visual cortex. It would be things to do with memory and imagination that are the contents of consciousness in that case."

Lecturer