A Sensory Experience Without The Triggering Stimulus Present
I smell toast. Can you smell toast if there isn’t any toast around? Can you feel changes in temperature gradients like feeling icy or cool even though there isn’t anything icy or cool to create the feeling? The answer to these questions is yes and the reason why is pretty extraordinary. But does what this say about our sensory experiences and how we experience the world?
What I am about to write will trigger many of you who read this and not in the best way. Everything about your experience in your existence is something you have created. The majority of the time your adaptive subconscious takes responsibility for this, so you more or less perpetuate it but you always have the capacity to manage this. In the 1930’s neuroscientist Wilder Penfield was in search of a cure for epilepsy and what he ended up doing instead was mapping the sensory and motor functions in the human brain with his famous Penfield diagram. Because the brain itself has no pain sensors he was able to use local anesthesia to remove a piece of the skull to probe the brain with an electrode while the patients were awake to record their responses when the electrode would stimulate different parts of the brain. Depending on where stimulation would occur, the responses varied wildly. From this he was able to construct a working diagram of how much of, and what parts of our brain is used for sensory and motor functions.
One of the responses he received was, “I smell toast.” We are still not clear exactly how memory works in the brain but we do know a few things about memory and learning. (which is a component of memory) Sensory information travels through the hippocampus where our working memory is held. This is where we have immediate recall of something, but it is limited and immediately discarded when it is no longer useful. The default capacity is about seven to nine items. (This is why the telephone numbers are seven digits.) This is greatly expandable by using a technique called chunking but for most of us that don’t work on expanding our working memory, it is limited to seven items. Repeated exposure to an item in our working memory eventually moves it to our reference or long term memory where it can be recalled whenever the corresponding stimulus is present or whenever we “look” for it. When something is deposited into our reference memory, it is now learned. Repetition is not the only way to get something stored into our reference memory. Events attached to significant emotional stimulus automatically makes that item/event immediately stored into reference memory. These are called somatic markers. It is why you can remember every little detail about your experience on September 11, 2001 but can’t recall what you had for dinner on September 10, 2001.
Getting back to the I smell toast comment. How can someone smell toast when there isn’t any toast present? Reference memory is not localized in the brain. There isn’t any one place where reference material is stored. Reference material is stored in the parallel processes of our synapses, neurons, axons, and dendritic branches which when calculated for the number of parallel connections that are possible are exponentially infinite. At some point however this person had a novel experience which involved smelling toast and it was stored in their synapses in their reference memory and is triggered every time the chemical stimulus of toast is present (or if their brain is prodded with an electrode), but the ‘smell’ is always present and the Penfield experiment triggered it with the electrode.
Why is this important to understand? It illustrates just how much of our experiences in life and how we construct reality is subjective. There isn’t really anything ‘out there’ if you look hard at it. The trace of every experience we have lingers in the hardware of our synapses but how we think and the mindset we employ determines it organization, the context. It is believed that there is no limit to what can be stored in our reference memory. The rule of synaptic activity is that the more synapses that are fired the more they recruit more synapses to fire and the more sensitive they are to the triggering stimulus. This applies to every experience we have. Every time we have a thought, create an emotional response, a feeling, develop a motor skill, everything.
Synapses are the spaces between neurons where neurotransmitters create excitatory or inhibitory action for the axons of the neurons. The default state of the brain is calm, peace, and inhibitory action demonstrated by the abundance of gamma aminobutyric acid (GABA). In order for a synapse to fire, GABA must be overwhelmed by the excitatory neurotransmitter glutamate. This can only happen when a sustained excitatory state is present i.e. fear, anger anxiety.
The state or mood you are in colors your sensory experience and this is determined by your mindset. This is true for all of us. The brain has a default setting of survival mode. For many of us our problem is not surviving but knowing when to transition into thrive mode. These are two different states of being and these modes are not interchangeable.
Your thoughts and mindsets have physiological consequences. How you think can trigger neurotransmitters and hormonal releases creating biological changes in your brain and body. Your sensory experiences are preserved in your synapses waiting to be triggered by external stimulus, but you can also create your experience with the proper mindset. It is difficult to grasp a causing the effect mantra when you have been living a cause and effect existence because what we do believe creates expectation and that determines our subjective realities, but the former is the only space in which you can truly be master and commander of your reality and cause your effect.
