Currently, my eyes are on my laptop’s screen, my fingers are typing on the keyboard, and I continuously observe the outcomes of my actions and keep following the same process. There is another book on my table (The Neuroscience of Language by Jonathan Peelle), 30-40 flipped A4 pages that have notes written with a blue pen with very ugly handwriting, and a lamp. There is also a very big map of the world on the wall. As long as my mind is driven to write these words with a bigger goal of better understanding when the posterior parietal cortex is activated, I become conscious of only the information/events/objects that are related to this specific goal, which are basically my laptop, its screen, my activity of typing these writings, etc., and all the other details in the environment such as the other book, lamp, map on the wall, etc. cannot survive my unconscious process. This is basically what is called attention. (Everyone keeps mentioning that attention is the process of focusing on the details that are relevant to the current moment/goal. Or another definition I keep seeing is about registering only the relevant information. But if my understanding is correct, lots of information is actually registered in our brain every moment, and only some of the relevant ones are activated in specific patterns that result in a feeling of “being conscious of them”. The more I think about this, the more I feel like maybe the key mechanism behind our consciousness and attention is basically the same, and the more I become curious about why exactly these two are defined like they are separate mechanisms. But I guess this topic requires another deep dive later)

And the posterior parietal cortex is a brain region that is typically activated when we orient and shift our attention voluntarily rather than in a reflex. Say we are in a restaurant and sitting at a very small table with our friends, and we see the waitress coming with the food. After seeing this and realizing that there is not much space on the table because of our items/phones, we stop talking and remove all the items from the table to leave a space for the food. This process, which involves gradually shifting our attention from listening to others at the table, keeping whatever they say in our working memory, etc., to taking specific actions to move the items from the table, basically activates the posterior parietal cortex.

When our attention shifts gradually and voluntarily and the main force behind this shift is our goals/expectations, like in the example above, this is also called top-down processing. Here, the “top” represents our intentions/expectations, and the posterior parietal cortex is activated during these moments.

However, sometimes we might change our attention involuntarily and suddenly because of a brand new sensory input that comes from our eyes, ears, skin, etc., and doesn’t fit with the state of the brain at that moment. For instance, we might be studying integrals and trying to solve 200 questions about this topic in a day to get a high score on a high school exam, and hearing a sudden explosion sound, which is quite irrelevant to our state of the brain at that moment, is sufficient for us to change our attention toward that sudden stimulus. The stronger and the more sudden these stimuli are, usually means the stronger activation in the brain regions that were not activate with the brain regions while the person was studying at all.

This is typically called bottom-up processing, which is different from top-down processing. The bottom basically means the activations in some brain regions that happen as a result of an activity entered through our eyes, ears, skin, etc., and these activations progress and activate other brain regions that impact our decision-making process/actions/goals as a result. And this kind of involuntary attention activates the right temporoparietal junction (rTPJ) rather than the posterior parietal cortex.