Neurodiversity Part 4:
Research on Cortical Arousal

As mentioned in Part 2, human behavior research into introversion and extroversion does not align with the public view of these terms. It isn't culled down to how shy or outgoing a person is. And the research dating back to brain scans in the 1960's and 70's shows similarities to the public definition of neurodiversity (coined in the 1990's by Judy Singer.)

In Part 3, we looked at blood flow in the brain. Now we'll be going over research on cortical arousal. Then we'll look at studies on anticipation and behavioral systems in subsequent parts.

Also, here is a link to the seven executive functions listed in a Psychology Today article for reference.

Cortical Arousal
In 1967, Hans Eysneck published his work on cortical arousal and how it relates to the introversion-extraversion facet of his theories of personality. His findings noted that introverts tend to have higher levels of cortical arousal while extraverts had lower levels. (Source)

There are multiple neurotransmitters that help stimulate the mind. The most well-known in the general public is dopamine, especially in regards to ADHD stimulant medication. But acetylcholine is also important, particularly for arousal and cognitive task performance.

"Teles-Grilo Ruivo et al noted in their study of mice implanted with electrochemical biosensors that tonic release  non-synchronized release from multiple presynaptic boutons over a period of minutes  of acetylcholine was associated with arousal and transition between certain vigilance states. But phasic release  highly synchronized release within a few seconds  occurred during the highest levels of arousal like cognitive tasks. They also noted that the latter occurred preferentially at the reward delivery locations, but that both modes were coordinated between the medial prefrontal cortex and dorsal hippocampus." (Source)

The force of acetylcholine during phasic release appears to be hard to break in absence of serotonergic modulation based on the commentary from Sparks et al:

“What would be the benefit of 5-HT attenuating the cholinergic enhancement of task attention? While our society rewards strong task attention, interference by 5-HT appears consistent with the growing understanding of serotonergic modulation of cognitive and behavioral flexibility (Nonkes et al., 2012; Matias et al., 2017). Clinically, this phenomenon appears relevant to attention abnormalities seen in neurological and psychiatric disorders that are accompanied by serotonergic disruption. For example, some types of focused task attention can be difficult to disrupt in people with autism, a condition associated with low 5-HT levels in the brain (Dougherty et al., 2013; Adamsen et al., 2014; Muller et al., 2016). Conversely, increases in 5-HT may contribute to adverse consequences of selective 5-HT reuptake inhibitors on attention (Ramaekers et al., 1995; Riedel et al., 2005; Graf et al., 2013; Golub et al., 2017).” (Source)

Given these findings, cortical arousal differences may affect the following executive functions: self-awareness, inhibition, motivational regulation, and planning and problem-solving.

This sensitivity to cues and processing information is not necessarily seen as a deficit in biological processes. In the right circumstances, it may even be praised as an ability to be more efficient with time. Flexibility can be key to survival in the most basic of senses. If an organism isn’t agile enough or has the ability to pivot easily, it may not survive against predators. And innovation often uses a similar approach of topic switching to formulate hypotheses or prototypes.

But in environments with excess noise and movement (such as open office floorplans at work), the mechanisms behind acetylcholine and arousal can be hard to control. And in stressful scenarios — for example, trying to adhere to quick-turnaround deadlines that can be common in desk jobs — cortisol (the biomarker for stress) may inhibit serotonin release, making it harder for those sensitive to acetylcholine to modulate between states. Both of these can hinder immediate attention and focus, as well as long-term motivation. (Especially if someone is more sensitive to what Gray called the behavioral inhibition system where aversion motivation can be powerful. But we’ll get to that in another section.)

(An Additional Thought Before We End This Section) 
From a cultural perspective, open office floorplans are becoming increasingly common especially in what communication experts call monochronic cultures. (The term “chronemics” was coined in the 1970’s by TJ Bruneau. ET Hall and J Ivers each discussed how time is tangible and a commodity in cultures like the US after the Industrial Revolution.) 

Monochronic and polychronic orientation haven’t been explicitly tied to the research on extroversion and introversion. However, there are enough similarities between the studies behind these terms that it is relevant to the discussion on executive functioning.

The awareness of time is broken down into two types per the theory of chronemics:

  • Monochronic time is based on the artificial constructs of seconds, minutes, and hours. Time is more strict and considered an indicator of efficiency. Multi-tasking is discouraged, micromanaging is normal, and time commitments are more important than objectives. Days tend to be broken down into 30-minute or one-hour chunks.


  • Polychronic time is based on the changes of the earth, with natural cues like sunrise and sunsets as more tangible constraints. Some cultures even use things like the tides to help track the day. Time is considered more flexible and achieving overall objectives tends to be an indicator of efficiency. Multi-tasking is normal, micromanaging time can halt or hinder progress, the focus is on longer term solutions, and hitting objectives is the ultimate end goal.

In 1991, Kaufman-Scarborough & Lindquist developed a polychronic attitude index.
And in a subsequent article published in 2003, Kaufman-Scarborough provided a contrast table between monochronicity and polychonicity:


  • Do one thing at a time
  • Concentrate on the job
  • Take time commitments (deadlines, schedules) seriously
  • Are low-context and need information
  • Are committed to the job
  • Adhere religiously to plans
  • Are concerned about not disturbing others; follow rules of privacy and consideration
  • Show great respect for private property; seldom borrow or lend
  • Emphasize promptness
  • Are accustomed to short-term relationships


  • Do many things at once
  • Are highly distractable and subject to interruptions
  • Consider an objective to be achieved, if possible
  • Are high-context and already have information
  • Are committed to people and human relationships
  • Change plans often and easily
  • Are more concerned with those who are closely related (family, friends, close business associates) than with privacy
  • Borrow and lend things often and easily
  • Base promptness on the relationship
  • Have strong tendency to build lifetime relationships

The observed behavior in the theory of chronemics shows some consistencies with the research on introversion and extroversion, especially the flexibility mentioned with higher levels of cortical arousal: distractible, change plans often, and focus on completing objectives. A preference for mono or polychronic time — whether biological or psychological — may ultimately affect executive functions such as self-awareness, nonverbal working memory, and planning and problem-solving.

It’s important to note that polychronic techniques aren’t necessarily less productive. In fact (if done correctly), it pushes the individual to be more accountable with their time and proactive in getting things done. It can also reduce procrastination and reactive tendencies.

For example, a polychronic workplace may only schedule meetings for the start of the day. This allows workers to finish their projects at times that work best for them. Team members then have to review projects ahead of time to see if they have questions or need to schedule a meeting. It also requires the people who set up the projects to outline objectives ahead of time, and document any changes needed in order to shift priorities. Especially because constant “fire drills” can easily diminish productivity.

Next we'll discuss anticipatory reactions >

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