Our bodies are equipped with a multitude of sensors allowing us to discern different temperatures, feel pain, hear sounds, and distinguish subtle shades of blue, etc. We are constantly bombarded with sensory information but we only pay attention to a small fragment of the total information.
Some philosophers, psychologists, and others studying the mind-body problem argue the role of the mind is to sort through the millions of bits of information we generate with our senses every second and figure out which are important.
In this interpretation, the mind is a sorting mechanism which renders information such as the touch of your pants leg on the back of your calf as unimportant whereas the shooting pain in your abdomen means there is something wrong that needs addressing.
Perhaps more to the point, the only thing we would notice is the shooting pain as our mind races through possible alternatives and explanations for its source. Appendicitis? Cramps? Bowel disease? The hot, spicy sausage you had for lunch? While the pain is dominating our sensory input it will also be dominating our thoughts.
Is this a good view of the mind? Perhaps. But it does point out the connection we have between our body and our mind. Our sense of ourselves comes from our interaction with all of the various nerves feeding information into our brain.
Various scientists have experimented with isolating a brain from its body.
Indeed, disembodied brains have been featured in science fiction movies since the early 1960s. Unfortunately, brains without bodies do not survive. Without somatic input, the brain shuts down and withers away.
We are in constant need of input through our sensory network. But what happens if this sensory information gets distorted or deleted?
Many drugs - legal and illegal, natural and synthetic - alter the biochemistry in our brains. For example, selective serotonin re-uptake inhibitors (SSRI) do exactly what their name implies - they selectively prevent the sending neuron from reabsorbing the serotonin releases into the synaptic cleft.
That is, a signal travels down the axon to the sending end of neuron. Within the cell, small packages of the neurotransmitter serotonin are bundled into vesicles. When the signal arrives, these sacks combine with the cell membrane and release their content into the synaptic cleft. The molecules diffuse across the synapse and trigger a response in the receiving neuron - much like inserting a key into a lock.
The serotonin is then reabsorbed by the sending neuron to be recycled in a new vesicle to await the next signal coming down the neuron. What SSRI drugs do is to slow or prevent the re-uptake of the serotonin thereby maintaining artificially high levels in the space between the neurons which then keep activating the receiving neuron causing it to send signals.
This is one of several pathways by which drugs can modify the processing of signals in our brains. How, when, and where these sorts of interactions happen can have profound effects on our minds.
SSRIs treat depression as do mono-amine oxidase inhibitors. The opioids modify the sensation of pain. Amphetamines fiddle with our ability to pay attention.
Some drugs, such as LSD and peyote, have profound effects on many areas of our brain resulting in hallucinations.
The ability to see things which are not actually there is a testament to just how much our minds depend on the chemical clues provided by our senses.
Hallucinations result from the hijacking of neural pathways.
While some of the information on the interaction of drugs with the human brain has been obtained through intentional and unintentional experiments with humans, neuro-scientists also use animal models to examine the interactions. However as animals lack the capacity to articulate the effects of the drug, the scientists observe other physiological responses such as brain wave patterns and respiratory rates.
Animals can also be observed solving amazing complex problems. Their ability to engage in problem solving behaviour while under the influence of a particular drug can be monitored and reveal something about the compound's effects.
For example, scientists at John Hopkins have been studying the effect of MDMA, known as ecstasy, on octopuses. Octopuses have a complex nervous system and are able to use tools or navigate mazes while solving intricate problems. But they are not very cuddly animals inclined to close physical contact.
However, knowing we share similar biochemical hardware, the scientists were interested in seeing the effects of the drug on these solitary animals. The drugged octopuses were much more inclined to spend time with other octopuses instead of solving problems, reaching out multiple arms to engage in physical contact. Non-drugged octopuses avoid contact and typically only use one arm to make contact when necessary.
The mind's perception of the world is formulated by the information provided by the brain through its sensory network. Drugs can have a profound effect on this information.