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Attention, Learning, and Memory: The VIGILANCE System

It is surprising that Jaak Panksepp, in Affective Neuroscience: The Foundations of Human and Animal Emotions (1998), did not add VIGILANCE to his list of innate emotional systems in the brain since he does talk about what can be called vigilance functions.

If the SEEKING system engages to solve problems, to drive motivated action to find or create access to food, water, shelter, mate, or resources (see The Brain's SEEKING System), then what is the function of a VIGILANCE system if in fact, it does exist? Perhaps a VIGILANCE system analyzes information from our senses combined with past learning and memory—salience—and thereby 1) determines threat as soon as possible, 2) takes notice of potential sources of food or water for later use, and 3) maintains watch over young offspring. We humans more often call this kind of behavior "attentiveness." We often do not think about how such behavior involves filtering through all the incoming stimuli from the environment while simultaneously choosing to focus on only those stimuli that, for now, best serve our interests. This kind of vigilance often involves switching from one activity to another, as circumstances change. When a person lacks such ability, he/she is often diagnosed with an attention-deficit disorder (ADD or ADHD).

From a broad perspective, whereas it is dopamine that primarily drives the SEEKING system, it is both norepinephrine and dopamine that drive the VIGILANCE system, while serotonin modulate these neurotransmitters (see Brain Neurotransmitters—an Introduction). It is surely not as simple as that, since other neuromodulators are certainly involved, but It framed this way to help conceptualize the process by which we become sentient—aware and engaged with our environment. It is norepinephrine which is most associated with learning and attention problems in our modern-day life. In Brain Neurotransmitters—an Introduction, we discuss how neurons in the loci coerulei, a pair of structures located within the pons, synthesize norepinephrine. The pons, within the anciently evolved brain stem, is pictured below in an image courtesy of John A. Beal of Louisiana State University (image links to source). Given the location of the loci coerulei, the VIGILANCE system has been around a very long time.

Brain Anatomy Coronal

The axons of neurons in the loci coerulei project throughout the entire brain. The release of norepinephrine in the neocortex is of particular concern to those who study ADD and ADHD. Amy F.T. Arnsten, in "Norepinephrine Has a Critical Modulatory Influence on Prefrontal Cortical Function"* (2000), writes: "NE [norepinephrine] cells of the locus ceruleus increase their firing in response to behaviorally relevant stimuli. Selective depletion of NE in the forebrain makes animals more distractible." Arnsten cites dysfunction in the prefrontal cortex as a fundamental component of attention-deficit hyperactivity disorder (ADHD). She points out that the prefrontal cortex "uses working memory to intelligently guide behavior, inhibiting inappropriate impulses or distractions and allowing us to plan and organize effectively." It is the neurotransmitters norepinephrine and dopamine that accomplish this attentiveness in the prefrontal cortex, explains Arnsten.

* Arnsten's article was at one time available in full on the internet. It has since been removed, however, and one is redirected to The Yale Child Study Center.

In Affective Neuroscience, Panksepp points out that many distinct emotions "share generalized components such as acetylcholine, norepinephrine, and serotonin systems for the control of attention and general arousal functions." Regarding serotonin, John Allman, in Evolving Brains (2000), emphasizes that there are at least 14 types of serotonin receptors and that "some of them came into existence long before brains first appeared about 500 million years ago." Allman explains that serotonin receptors in the brain "appear to regulate the responses of neurons to other neurotransmitters." He writes:

The axons of the serotonergic neurons project in rich profusion to every part of the central nervous system (the brain and spinal cord), where they influence the activity of virtually every neuron. This widespread influence implies that the serotonergic neurons play a fundamental role in the integration of behavior. Our sense of well-being and our capacity to organize our lives and to relate to others depend profoundly on the functional integrity of the serotonergic system.

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