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Biology 202
2000 First Web Report
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Familial Dysautonomia and the Brain Behavior Enigma

Avis Brennan

An understanding of the brain is essential to developing safe and effective treatments for disorders of the nervous system and for advancing our understanding of the human experience. Nervous system disorders cost the US more than $400 billion in medical expenses each year (1). In addition to having great clinical significance, such research offers a valuable perspective into the nature of the brain-behavior relationship. The extent to which the brain is organized in terms of overt behavior remains an open question. Because it is difficult to ethically manipulate the neural composition of humans in the laboratory setting, our understanding of the biological and neurophysiological influences on behavior is limited. In the spirit of this class, I have decided to take an alternate route to untangling the connections between brain and behavior. In this paper, I will discuss Familial Dysautonomia, a neurological disease that encapsulates the relationship between sensation, perception, emotion, physiological response and the nervous system.

Familial Dysautonomia (FD), also called Riley-Day Syndrome, is one of five hereditary sensory and autonomic neuropathies (HSANS) (2). FD is an autosomal recessive disease of the Ashkenazi, or European, Jewish population (3). As the name implies, this neurological disorder is characterized by the incomplete development of the autonomic nervous system. The behavioral phenomena observed in FD sufferers can be used as an instrument to gage the inner activities of the autonomic nervous system (ANS). We already know that the ANS is responsible for life-sustaining regulatory processes. The autonomic nerve fibers form a system that regulates the heart, blood vessels, glands, the digestive system and other visceral organs not subject to willful control. The actions of the parasympathetic and sympathetic divisions of this system work in tandem to regulate important processes such as blood pressure (4). What remains unclear is how conscious processing is entwined with these automatic responses.

One way to go about addressing this question is to investigate the perceptual and overt behavioral consequences of damage to this system. The behaviors and responses associated with FD offer a model for such an investigation. The symptoms and conditions associated with FD reveal how closely this involuntary system is linked to our conscious experience. Early symptoms of FD include feeding difficulties, breath holding, sweating while eating, vomiting, poor muscle tone, and a smooth tongue (2,4). FD is also marked by the absence of the lacriminal gland, which is responsible for the production of tears (5,6) and little-to-no sensitivity or response to painful stimuli. It is reasonable to believe that a lack in pain response is connected to an abnormal catecholamine release (7). Catecholamine is released in stressful or painful situations. In conjunction with the ANS, this chemical assists in stimulating the body's internal response to painful or threatening stimuli (i.e. mobilization of energy for response) (8). One may speculate that the possible lack of catecholamine in FD (5) disrupts the circuitry of the autonomic pain response. Is the lack of catecholamine, a pain response, the adaptive result of a lack of sensitivity to pain afforded by more diffuse neural damage? We know that the plastic and compensatory properties of our nervous system allow for adaptations in response to early morphological damage and changes in neurotransmitter concentration. Is it reasonable to assume that early damage to the sensory system can result in the atrophy of response systems? This possibility brings us back to the postulations of William James on the behavioral determinants of emotion. That is, could this malleability work in reverse? Could the lack of an overflow of emotional tears in the FD sufferer result in a muted emotional experience?

FD is a useful and interesting model because the conditions of the disorder suggest that mental phenomena and behavioral response are related to nervous system activity in some lawful way. Although there are no reports of flattened affect, the FD patient's inability to cry and respond to pain implies that the variety of states of consciousness and emotional arousal are tied to the ANS. That the inputs and outputs of our consciousness may be mediated by the activity of an involuntary system makes the concept of free will problematic. Moreover, the disruptions in perception and expression seen in the FD patient demonstrate that consciousness and behavior are not mystical processes that supersede the systematic processing of the nervous system. The FD patient can be sad, but does not cry, and conversely can be hurt but feels nothing. The possible role of psychosocial factors in the perception and response to the outside world is controlled for by the congenital nature of this condition. In this way, the FD patient makes a case that behavior is indeed determined by inner activities. That is, the human experience and physiological response is arguably more dependent on neurological arrangements than direct contact with the outside world.

The attempt to experimentally determine the correspondence of behavior to divisions of the nervous system has lead to many problems. How many behavioral and mental processes are there? How can they be defined or measured in a laboratory setting? I suggest that congenital disease research is one approach to establishing the organization and significance of brain function as it relates to the human experience. However, what I discovered in my search for the neurological and biological underpinnings of FD is that present-day science is still struggling to describe the neural events responsible for "normal" and anomalous brain function. Fortunately, we live in an age of shared information. Therefore, while researchers attempt to isolate the gene locus (2) for potential testing and treatment programs, neuro-philosophers can ponder the neural correlates of human behavior in order to help resolve the more metaphysical mind-brain enigma.

For a more detailed explanation of the incidence, risk factors, symptoms, signs and treatment options of FD please visit one of the websites listed below.

WWW Sources

1) BrainNet-know NFBR, a synopsis of information on the study of neurological disorders in the US.

2) WebMD Health , a list of the symptoms causes tests and treatment options for FD.

3) The Dysautonomia Foundation, Inc. , a comprehensive database of FD related information, offering links to recent press releases, online information and family support networks.

4) Memorial University of Newfoundland , Autonomic Nervous System I.

5) Autonomic Differential Diagnosis , a breakdown of congenital sensory neuropathologies.

6) Newton's Apple , Tears: Why do we cry?

7) Medical College of Wisconsin , Riley-Day Syndrome, respiratory disease and the possible role of catecholamines.

8) Pain and Sedation on the PICU , an outline of the neurophysiology of pain.

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