Scientists think a lot about thought, but what they've come up with so far seems to ask more questions than it answers.
Emerging is a body of theory suggesting that the brain has four distinct functions. I'll list them in order of how much we seem to understand about each.
Perception is the flow of information as raw data from our sense organs to the brain. We know that data flows from our organs to the brain through nerves allowing us to "tap into" those transmissions, giving us a pretty clear picture of what's going on. Scientists can even trace data flowing through the optic nerve to re-create the image our eyes send to our brain, (although not very well). Scientists understand enough about this function to create working artificial eyes.
Thought itself seems to be the interaction between different parts of the brain. We may know more about thought than other brain functions because technology allows us to make images of thought as it happens.
While nobody has legitimately been able to use science to "read" thoughts yet, we can see pretty clear patterns of activity within the brain based on what the subject is doing or thinking about. We're also pretty good about tracking the effect of damaging or disabling particular parts of the brain on the activity of thought.
Memory we know a lot less about. Some say memory is entirely electrical, some say it's electro-chemical, almost nobody believes it's entirely chemical anymore. Some believe memory is the interaction between clusters of brain cells, but there is study showing that individual brain cells might be capable of holding memory by themselves.
Invariably, when scientists write about or think about memory in the brain, they tend to relate it to memory as we know it in computers. I often wonder if that paradigm isn't holding us back. It's entirely possible that memory in the brain is nothing at all like memory in computers, which might explain why we've made far fewer advances in artificial intelligence than we thought we would by now.
Consciousness we know the least about. We think that consciousness is the merger of perception, thought and memory, but it might be something completely different. Although you'll never get scientists to admit it, at this point along the way, religion tells us about as much about consciousness as science does.
There's a growing number of scientists who draw a relationship between consciousness and quantum physics. If this is true, then the intelligence in "intelligent design" might be our own. If it's true that consciousness creates reality on some quantum level then that changes everything we ever thought about everything.
Image: Leonardo Da Vinci sketch-study of the brain