So if we conclude that a distinct VIGILANCE system exists, it certainly involves several neurotransmitters that working together, somehow producing conscious awareness and as necessary, vigilance.
But where is VIGILANCE circuitry located? Certainly, the norepinephrine pathways from the loci coerulei to all parts of the brain are part of the VIGILANCE system (see Norepinephrine action, synthesis, and pathways). But other structures and circuits are certainly involved, such as the suprachiasmatic nuclei, which control the sleep-wake cycle. These nuclei are grouped in pairs and are situated within the hypothalamus. The image to the right, illustrating how the suprachiasmatic nuclei respond to light, is from an NIH website called "The New Genetics" and links to source.
Panksepp explains that as their name implies, the suprachiasmatic nuclei lie directly behind each eye, "above the optic chiasm." Each nucleus is about the size of a grain of rice. Situated close to the optic nerve, and based on levels of incoming light, the suprachiasmatic nuclei control our circadian rhythm. The term "circadian" is Latin for "approximately a day." Panksepp writes: "Even a brief pulse of bright light given once a day will synchronize rhythms under constant 24-hour lighting conditions." He adds that influences such as caffeine and the production of melatonin can influence the function of these nuclei. Panksepp reports that neurons in the suprachiasmatic nuclei "not only maintain their firing rhythm for approximately 24 hours after being disconnected from all other brain areas but also continue to cycle for some time when removed from the body and kept in tissue culture."
Based on some of Panksepp's observations, the suprachiasmatic nuclei play an important part in the SEEKING-VIGILANCE construct, a sort of operating system for the brain. He writes: "The multiple output pathways from the SCN [suprachiasmatic nuclei] control practically all behavioral rhythms that have been studied, from feeding to sleep." Panksepp explains that when both sets of nuclei are destroyed, "animals scatter their behavior rather haphazardly throughout the day instead of maintaining a cyclic routine of daily activities." The location of the suprachiasmatic nucleus within the hypothalamus is indicated in yellow in the image to the right. This image is from S.S. Nussey and S.A. Whitehead,, Endocrinology obtained from the NCBI bookshelf (links to source).
The suprachiasmatic nuclei are linked to the neurons that produce norepinephrine in the loci coerulei, within the pons portion of the brainstem. In a research summary titled "Locus Coeruleus," Gary Aston-Jones provides additional support for the idea that the loci coerulei are part of what is called a VIGILANCE system. According to Aston-Jones, evidence indicates that the loci coerulei are "part of the arousal effector circuit from the circadian pacemaker in the suprachiasmatic nucleus." Aston-Jones explains that he and collaborators have found that suprachiasmatic nuclei and the loci coerulei are connected in a circuit via the "dorsomedial nucleus of the hypothalamus."
So we know that the suprachiasmatic nuclei are somehow interdigitated with the norepinephrine-producing neurons that innervate the entire brain, producing arousal and attentiveness while allowing for rest on a cyclical basis. Toward this point, Panksepp refers to circuitry "especially in the basal forebrain and anterior hypothalamus, from where cortical slow-wave activity can be promoted." He writes: "Repetitive electrical stimulation of these parts of the brain in awake animals readily induces sleep, and a very specific site in the ventrolateral pre-optic area has recently been identified as a potential SWS [slow-wave-sleep] generator." The pre-optic area of the hypothalamus is labeled in the illustration above.
We can be sure that a VIGILANCE system is quite more elaborate and more difficult to delineate, however, than other circuits to which Panksepp has ascribed specific labels (i.e., SEEKING, RAGE, FEAR, PANIC/LOSS, PLAY, MATING, and CARE — see Emotions are Hard-Wired in the Brain: Introduction to Ancestral Brain Systems).
Consciousness, fugues, and OCD:
particularly interested in VIGILANCE mechanisms because of what are called fugues. Some definitions refer to fugues as wandering states. The New Oxford American Dictionary on my MacBook Pro provides a historical psychiatric view of fugue, stating that is is "a state or period of loss of awareness of one's identity, often coupled with flight from one's usual environment, associated with certain forms of hysteria and epilepsy."
Could it be that some of the more severe symptoms of obsessive-compulsive disorder can occur when one is in a kind of fugue, where input from the frontal cortex is not integrated with subcortical activity that is driving behavior? We will discuss such possibilities in Part 3 of CorticalBrain.com.
Next-> Vigilance, the sleep-wake cycle, PGO spikes, and schizophrenia
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