by cloudier

What is consciousness?

“Consciousness” refers to several related phenomena, which is why people have such a difficult time agreeing about what it is.

Here are some specific phenomena that fall under the larger umbrella of consciousness and also “the mind”:

awake state — What is different about someone who is awake vs. someone who is in dreamless sleep? In both cases, the brain is highly active and functioning, but in only one case is the individual able to interact with the world and report experiences. Dreams and other altered states of consciousness may lie somewhere between these two extremes. Other variants of non-awakeness include general anesthesia and “persistent vegetative state” (related to coma).

perceptual awareness — What is going on when you are aware of something vs. when you aren’t? In binocular rivalry, two conflicting images are shown to each eye. The information about both images enters the brain, but only one image is seen at a time. Which image is seen changes periodically and spontaneously. There are other examples of information being processed “subliminally” without being perceived “consciously”. In stage magic, what is perceived is different from what is actually happening. What is the difference between sensory signals entering the brain, and something being perceived “consciously”?

subjective (first-person) point of view — Consciousness is private, subjective and experienced from a particular point of view: yours. What accounts for this point of view, for the unique “interiority” that gives the feeling that you exist inside your head somewhere? Is your version of the color red unique to you or the same for everyone? If a machine was conscious, would it have a first-person “experience”? As philosophers would say, is there something that it’s like to be a computer?

unity of experience — Consciousness feels “whole”, indivisible, and irreducible. There is the sense that the world is experienced instantaneously in complete, integrated, and meaningful detail. Hundreds of scientific experiments show that this unity is an illusion (change blindness, attentional filtering, attentional blink, visual illusions, timing errors, split brain patients, mental disorders, various neurological syndromes,  …). But the illusion is so powerful it takes a real force of will to be skeptical of it. When consciousness becomes fragmented, as with dissociative drugs, brain damage, split-brain surgery, or divided attention, has consciousness been degraded?

personal identity (existence, self, ego) — One unique aspect of the human experience is the sense that we exist — that there is an “I” in there somewhere, looking out onto the world. Why do all our experiences come from our body and not someone else’s? Does our uniqueness as an individual come from a “soul” that is somehow attached to the brain, or is it a construct generated by the brain? If someone wakes up with amnesia, or has dementia or dissociative disorder (formerly multiple personality disorder), has their conscious self ceased to exist, even though they seem conscious?

self-awareness — Also uniquely human is our ability to “introspect” onto what is going on in our own mind. Descartes famously said “I think therefore I am.” One complaint about the idea of consciousness in a computer is that a computer seems incapable of answering the question “what is it like to be you?”. If you can’t reflect on your own inner life, are you still conscious?

personal agency — In modern society, an important distinction is made between voluntary action (doing something”intentionally”) and involuntary action (accidental behavior). To do something “consciously” is to do it with forethought and purpose. In Tourette’s Syndrome, people make intentional-seeming actions involuntarily. This ties into the tricky question of “free will” as well as the legal concept of mental competency and the insanity defense. “He was not in conscious control of his actions” the defense might say.

Is the human brain analog or digital?

The brain is neither analog nor digital, but works using a signal processing paradigm that has some properties in common with both.

Unlike a digital computer, the brain does not use binary logic or binary addressable memory, and it does not perform binary arithmetic. Information in the brain is represented in terms of statistical approximations and estimations rather than exact values. The brain is also non-deterministic and cannot replay instruction sequences with error-free precision. So in all these ways, the brain is definitely not “digital”.

At the same time, all of the signals sent around the brain are “either-or” states that are similar to binary. A neuron fires or it does not. These all-or-nothing pulses are the basic language of the brain. So in this sense, the brain is computing using something like binary signals. Instead of 1s and 0s, or “on” and “off”, the brain uses “spike” or “no spike” (referring to the firing of a neuron).

Internal to the neuron, everything works via biochemical pathways, which are somewhat similar to analog. Neurons also perform internal electrical signal integration in an analog fashion. Analogously, the digital logic gates used by computers are implemented internally using transistors and resistors, which are also analog.

What is an understandable, systematic way to understand neuroscience? A source?

The problem you are most likely running up against is the way you’re approaching thinking about neuroscience and the brain.

In short, there is no systematic way to understand neuroscience because every level at which you want to examine the system is incomplete.

First, a caveat: thinking about certain fields of study as “harder” or “easier” than others will do you a disservice. Using those kinds of terms will immediately put other researchers on the defensive, so I’d recommend against thinking in that way so as to protect yourself from unnecessary emotional conflicts when discussion scientific topics.

Philosophy probably feels “easier” to you because philosophy is–by its very nature–a human endeavor built by humans using logical principles as understood by humans. So while there may be difficult concepts in philosophy, those concepts originate from human minds and thus are understandable by humans.

Neuroscience, in contrast, is the study of a natural, not man-made system that doesn’t have to adhere to any logical principles that we can grasp (i.e., the brain is likely deterministic but also chaotic). The issue is that you want to ascribe an orderly, logical system to a messy biological, organic, system that evolved in strange ways over billions of years.

So far you’ve learned about “parts of the brain” and “neurotransmitters”. By way of a physics analogy, so far you’ve learned classical mechanics.

In reality, there is no such thing as a discrete “part” of a brain and the boundary between what is and what is not a neurotransmitter is fuzzy. For example, dopamine is a macromolecule that crosses a synapse and binds to the post-synaptic neuron to modulate the probability of that neuron firing. In contrast, nitric oxide also plays a role in neurotransmission, but because it is a gas it diffuses long distances, can cross a cell’s membrane without any need to bind to a receptor, and yet plays an important role in long-term potentiation (the putative cellular mechanism for learning and memory). Not your traditional neurotransmitter and very hard to study!

Classical mechanics works wonderfully. To a first approximation. Of course the real world is much more complex, and classical mechanics starts to fail and we have to resort to electromagnetics, quantum mechanics, and so on.

So yes, while in general there are “motor” and “vision” parts of the brain, what’s happening is that we’re using language to define an organic system that doesn’t care about your linguistic boundaries and linguistic inadequacies.

Cerebral achromatopsia

Cerebral achromatopsia is a type of color-blindness caused by damage to the cerebral cortex of the brain, rather than abnormalities in the cells of the eye’s retina.

The case of the colorblind painter

The most famous instance of cerebral achromatopsia is that of “Jonathan I.” immortalized in a case study by Oliver Sacks and Robert Wasserman, and published as The Case of the Colorblind Painter.[7] The essay tracks Johnathan I.’s experience with cerebral achromatopsia from the point where an injury to his occipital lobe leaves him without the ability to perceive color, through his subsequent struggles to adapt to a black, white and gray world, and finally to his acceptance and even gratitude for his condition. Especially pertinent is the analysis of how cerebral achromatopsia affects his practice as a painter and artist. Descriptions of cerebral achromatopsia’s effects on his psychological health and visual perception are especially striking. For instance, in recounting Mr. I.’s descriptions of flesh and foods, the authors write:

Mr. I. could hardly bear the changed appearances of people (“like animated gray statues”) any more than he could bear his own changed appearance in the mirror: he shunned social intercourse and found sexual intercourse impossible. He saw people’s flesh, his wife’s flesh, his own flesh, as an abhorrent gray; “flesh-colored” now appeared “rat-colored” to him. This was so even when he closed his eyes, for his preternaturally vivid (“eidetic”) visual imagery was preserved but now without color, and forced on him images, forced him to “see” but see internally with the wrongness of his achromatopsia. He found foods disgusting in their grayish, dead appearance and had to close his eyes to eat. But this did not help very much, for the mental image of a tomato was as black as its appearance.

How well does music predict your politics?

A few highlights: