If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:4:24

Video transcript

what is consciousness well that's not something we can easily answer in one video but in general consciousness is usually defined as awareness of ourselves and our environment we can have different states of consciousness meaning different levels of awareness and they can occur naturally or be induced by external factors such as drugs or internal factors such as our own mental efforts these states range from alertness to sleep and everything in between alertness is what most people think of when they think about being conscious when you're alert you're awake aware of who you are where you are and what's going on in your environment you can focus your attention encode information and memory engage in conversation all the stuff you normally do when you're awake and aware of the world so that's alertness we've all had the experience of daydreaming or being awake but not really aware of the world around you maybe you've had that experience in class or during this video you may feel more relaxed but you're not as focused as you are during normal alertness daydreaming occurs naturally sometimes you'll find yourself daydreaming when you didn't mean to but some people can induce a similar state through light meditation and moving into the less conscious states of consciousness we have drowsiness that state when you're almost asleep but still semi aware of the world you might feel this way just before falling asleep or maybe just as you're waking up and all those drowsiness also comes naturally just like daydreaming some people can induce this state of consciousness through deep meditation and finally we have sleep it's a little strange to call this a state of consciousness because it's really more of a state of unconsciousness you're not aware of yourself or the world around you when you're asleep even though you might be aware of a dream world one thing that's pretty cool is that even though you might not be aware of when you shift from one state of consciousness to an there your brain knows you have sets of neurons that fire rhythmically in your central nervous system leading to neural oscillations or just those rhythmic patterns of firing that we can measure and there is a machine called an electroencephalogram EEG which measures those neural oscillations more commonly called brain waves there are four main types of brain waves that we associate with different states of consciousness Alpha Beta Delta and theta each of these types of brain waves oscillates at a different frequency and is associated with a particular state of consciousness for example beta waves which oscillate at about 12 to 30 Hertz which is pretty fast it means that it's going at about 12 to 30 cycles per second those are associated with normal waking consciousness and concentration so if you maintain this heightened alertness for too long though your beta levels get really high and you might experience increased stress anxiety and restless restlessness just sort of this constant awake and alertness alpha waves though are common during relaxed awake states such as daydreaming or light meditation and as you might expect then alpha waves have a lower frequency than beta waves alpha waves are about 8 to 13 Hertz and although alpha waves disappear as you become drowsy they can reappear later when you're in deep sleep when you do get drowsy or you're in deep meditation and EEG would show theta waves which are even slower than alpha waves they're like four to seven Hertz you also see this pattern right after you first fall asleep when you're sleeping very lately sleep as a state of consciousness is surprisingly complex and involves multiple phases of its own and different cycles of brainwaves and including the Delta waves which we haven't talked about yet so the next video is going to focus on the stages of sleep and what your brain does during those stages