The selectively focused, attention aware brain
The brain's ability to hone in on a particular stimulus (or a group of) amid a cacophony of stimuli is endlessly intriguing. For the longest time, neuroscientists thought that the brain's prefrontal cortex (hereafter PFC) shone a spotlight on the stimulus that is deemed essential, selectively ignoring what is considered extraneous. Francis Crick (human DNA) theorized that the thalamus, a more interior (and thus ancient) part of the brain, is involved in receiving information and deciding which sensory inputs to pass along and which to gate.
More recently, researchers found that such ancient regions as the thalamus and basal ganglia are involved, but the essential participants here are the thalamic reticular nucleus (TRN). The TRN wraps around the thalamus and is engaged in suppressing sensory inputs when the person is asleep. Similarly, it allows a person to focus on the task at hand by ignoring the unnecessary sensory streams to the brain. It doesn't just do this by turning sensory streams off as required, but also has the elegance and the fine-tuned control to selectively stream sensory data. It can selectively tune background noise out, allowing you to hone into the voice of the person you are speaking to.
Researchers at MIT verified this on mice by training them on a goal (run on a track) directed by their response to specific audio and light signals. They found that if a task required visual senses, turning those senses fully on, negatively affected their performance. More interestingly, the same act also affected their ability to focus on the auditory senses. This is because the neurons are being selectively silenced, not being excited as conventionally thought.
The TRN wraps the thalamus, which is right next to the basal ganglia, interior parts of the brain, and some of the brain's oldest components. Some of the oldest fish which retain their original brain structure through evolution have basal ganglia that aid in attention. Attention, which can be thought to be the set of activities that need to happen in a certain order and making sure you don't get distracted by things you shouldn't be is then not a byproduct of the PFC, (the shiny new human-specific part of the brain) but an eons-old process that optimized your chances of survival while also preventing an analysis paralysis.
This exciting finding could leak information about consciousness, what it is, and the mechanics of how we have it. Another assumption that has come into question is the brain being a passive sensory input machine, whereas it turns out that the brain takes an active role in choosing which sensory data (information) to process. The flicker of an eye, or the twitch of a finger may play part in the active reconstruction of our surrounding.
It is also important to note that ancient structures like the basal ganglia probably didn't evolve filters to protect against social media and electronic notifications. Humanity has collectively developed ADHD through the dopamine inducing stream of electronic data synthesized in a data-science lab to sneak by your hyper-vigilant TRN and basal ganglia to force attention focus. Aren't these interventions starting to sound uncannily like a virus?
Source: https://www.quantamagazine.org/to-pay-attention-the-brain-uses-filters-not-a-spotlight-20190924