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From Dogs to Fruit Flies: How to Measure the Different Levels of Consciousness

Consciousness is a mysterious and complex thing. It’s like a puzzle that scientists are trying to piece together, but unlike a puzzle, there are many different ways to look at it. In this blog post, we’ll explore the different levels of consciousness and how scientists are measuring them more accurately.

Different Levels of Consciousness

First, let’s take a look at the different levels of consciousness. Most of us would agree that there are different degrees of consciousness. For example, a dog is probably more conscious than a fruit fly, and certain drugs can produce higher levels of consciousness. Our brain also functions differently when we’re awake, asleep, or in a coma.

Measuring Consciousness

But can consciousness really be measured by degrees? Many scientists believe it can, and they’re already doing it. The most common measure for consciousness is the “bispectral index” monitor. This is used by doctors during surgery and combines several brain-scan measures into a single number that helps guide the anesthetist. However, in practice, the bispectral index number is sometimes inconsistent with obvious signs of consciousness.

New Methods of Measuring Consciousness

But there are promising new ways to measure consciousness, such as the “perturbational complexity index” (PCI) developed by Italian neuroscientist Marcello Massimini. PCI uses magnetic stimulation to monitor the signal as it spreads across the brain to other regions. Then, an algorithm is used to compress the complexity of the signal pattern throughout the brain. In unconscious states, like when a person is under anesthesia, the signal dies quickly, and the PCI is low. But in more conscious states, it echoes longer and more widely across the brain, and the PCI is high. The PCI value has turned out to be much more accurate than the bispectral index number.


These new types of consciousness meters promise to help doctors give more reliable diagnoses. They could help identify people with “locked-in” syndrome, for example, who can’t move their bodies anymore but are still completely conscious.

Think about consciousness like a symphony, where different parts of the brain are playing their unique roles, and the PCI is like a conductor that helps to measure how well the symphony is playing.

In conclusion, consciousness is a complex and multi-layered thing, and scientists are getting closer to understanding it. With new ways to measure consciousness, such as the PCI, we can better understand the different levels of consciousness, and help those who are suffering from consciousness-related disorders.

The Controlled Hallucinations of Consciousness

Scientists have been exploring the concept that the contents of our consciousness are simply controlled hallucinations for over a century. Our senses are not like windows that allow our brain an unfiltered view of the world, but rather our brain is blind, deaf, and unfeeling, making sense of nerve signals from our sensory organs. The nineteenth century German scientist Hermann von Helmholtz suggested that any perception is a process of unconscious inference, with our brain making predictions and using sensory signals to correct them. This makes the contents of our consciousness like hallucinations, and understanding this can give us a new perspective on the nature of reality and our own minds.

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