And even if those little packets of data do make it to the waiting dendrite, the precise information they’re carrying may get distorted. Neurochemicals on the receiving end may change the effect, when they get there. Biochemical variations, based on both biochemistry and past experience, kick off reactions that can be totally different, from person to person, scenario to scenario, interpretation to interpretation. A teenage girl who spent her first twelve years in a war zone may leap out of her chair and dive under her desk at the “thunderclap” sound of a textbook falling flat on a classroom floor. Her entire body may fire off a PTSD panic response, her heart pounding, her mouth dry, and with every nerve feeling like it’s on jagged edge… while her bored classmates who grew up in a sheltered corner of the world may barely notice the “Bang!” as they doodle in the margins of their notebooks and trade notes behind the teacher’s back. The original sensory input was identical, but the end result was very different. The time, space, and processes between the clap of the book and the reaction of listeners created a completely different experience.
Was one experience more valid than the other? Nope. It was all completely logical and reasonable, given the individual circumstances. The autonomic nervous system will do what it will without our say-so. That’s its job. Of course, the classmates rolling their eyes at the terrified girl probably have no idea, because their internal processes are as invisible (and normal) to them, as the war zone survivor’s are to her.
It’s not just external situations that can prime us differently. Our unique individual biochemistry can produce extreme variations, as well. Some individuals are more sensitive to pain, while others are less. Some are fine with extreme cold and heat, while others can’t tolerate any variations. You may have an intensely painful reaction to bumping into a door frame as you carry a box inside your new home, or you may barely notice it and not even realize why you have a bruise the next day. Arguing can be exciting for some people, who relish the feel of adrenaline and love to jump into a fight… while others dread the feel of all that energy and run from even the hint of conflict. An abundance of testosterone can produce certain patterns of behavior, while estrogen, progesterone, and oxytocin can produce very different behaviors – under identical circumstances.
The “payload” of all that sensory information is continuously changed in subtle and obvious ways, as it makes its way along our interconnected neuronal connections. Each jump across a synaptic cleft alters the data ever so slightly… but that happens more times than you and I can count by ourselves. It adds up. Each reception of the data, interpretation of it, and relay to the next step in the perceiving process introduces additional variations on the original theme. The tiny packets of sensory information – which may prompt you to yell “Ow!” and stop to rub your shoulder, or disguise what happened so you can keep going back to the truck for another box – can be slightly different than they were, when they first came across that synaptic cleft.
That whole transmission process, involving thousands, hundreds of thousands, even millions of synaptic connections, happens countless times, each and every moment of our lives. It’s an intricately networked interaction of of neurochemical richness that sustains constant contact between the world outside and all our interconnected pieces inside. And every single connection that happens involves at least some small portion of data loss – neurotransmitter loss – sensory information getting dropped between sensation and perception, not because there’s necessarily anything wrong, but because that’s just how we work.
In some ways, it’s really for the best that data gets lost en route to our brains. We are continuously inundated by sensory inputs, many of which we don’t need to make sense of. To get through life, you really don’t need all the details about how bright the sun is and the variations on its glare when it reflects off the windshields of passing cars… the feel of a breeze stirring the hairs on the back of your neck… the sound of every single cicada buzzing in the trees outside your home at 10:00 p.m. Hypersensitive individuals report how disruptive a steady stream of sensory data can be. It disrupts concentration with an intermittent flurry of unrelated details about what’s going on in the immediate environment and interrupts thought processes to the point of making simple communication next to impossible, thanks to a steady stream of “noise”.
What would happen, if we picked up on every single sensory input that comes our way? Sights, sounds, scents, touches, tastes would crowd out any chance of concentration. And the additional senses mentioned above – where our bodies are in space, whether we’re balanced or not, the levels of gasses in our bloodstream, our body temperature, various pains and discomforts that don’t normally register – would reduce our available processing resources even more. Our very brains seem designed to cull all that input via a process called “synaptic pruning”.
Beginning in the earliest embryonic stage and lasting until approximately 2 years of age, new neurons and synapses are formed at an amazing rate, at times reaching 40,000 new synapses formed per second. By the end of this process individuals are left with far more neurons and synapses than are functionally needed and/or preferred. Synaptic pruning is the process by which these extra synapses are eliminated thereby increasing the efficiency of the neural network. The entire process continues up until approximately 10 years of age by which time nearly 50% of the synapses present at 2 years of age have been eliminated. The pattern and timeline pruning follows varies based on brain region. Again the process is intended to increase the efficiency of the neurological system.
If we didn’t prune all those extra synapses, would we even be able to function over the long term? It seems like an awful lot of data to take in and process.