The excerpt does not tell us what the authors mean by disruptive white matter. Perhaps they left it vague on purpose. And they use the term integrity, an even more ambiguous word, to explain disruption, and in a circular fashion explain disruption as decrease of integrity of the white matter, within and between cortices.
Why is the communication between these brain areas not up to par in anxious?
If we get out of the mindset that anxiety is our enemy, and a precursor of Depression and Schizophrenia, which many claim it is - actually anxiety is precursor of all mental problems - and must be immediately quashed with drugs, we may be able to better understand the factors that generate anxiety and its adaptive functions.
Amygdala of course, one may smartmouth.
But instead of digressing in to polemics let us examine what we know about anxiety at the clinical level.
The first thing we notice is that anxiety appears to be more prevalent in those whose nervous system appears to be genetically superior not impaired. Maybe we should start appreciating presence of anxiety more as an indicator of superior genetic inheritance and less as a harbinger of more serious mental illnesses.
And this may sound counter intuitive but longevity itself appears to be positively associated with anxiety. Most people I see in their Eighties and Nineties, I find they were worry warts all their lives. As if worrying about something happening to them through illness (hypochondriasis/obsessive somatic anxiety) made them take good care of their health to the very last days of their life. Granted many of them did not show overt anxiety - hiding it through binding it with obsessive behaviors and rituals - but there is little doubt that constant anxiety about something harmful happening to them had made them live extra carefully, enabling them to keep their illnesses at bay longer than non-worriers.
Perhaps we can reject the crude assumption that anxious disposition is due to some inherited abnormality in the development of axonal connections arising out of bad genes. In fact it may be quite the reverse: there may be superior genes lying behind sparse connections.
Anxious people are all the time preparing themselves either to run away or fight with some anticipated danger. But what surprises us is the pathological intensity of the fear and about things that are most unlikely to happen. Depending upon what these dangers symbolize to the worrier in his unconscious, they may worry about such remote things as tornadoes, getting cancer, the family dying with carbon monoxide or food poisoning, financial disaster, taking a business trip to California because of running in to earthquake, skin blemishes that nobody would notice, to name a few. And so the average psychiatrist rightly assumes that such worry warts are out of their mind and deserve to be soaked with drugs and brainwashing - though they euphemistically give the latter the respectable acronym CBT [Cognitive Behavioral Therapy].
Here we make a gratifying discovery.
Higher the intelligence greater is the perspicacity in seeing the dangerous aspect of things. And one who sees more danger than friendliness in one's universe is compelled to practice greater vigilance and preparedness to bolt from and/or attack the source of danger. And why would it be not so. A rock has no intelligence and hence no readiness to react if someone comes to blow it up with dynamite. The tree has no such preparedness either, despite being living and thus having choices, when they come to cut it down. A multipede on the other hand runs when you try to stomp it, while a lion is likely to attack you back instead of taking off. A monkey may pretend to run from a tiger, go up the tree, and then from behind pull the tiger's tail as I recently saw in a hilarious U-tube posting.
So higher the organism in the evolutionary scale, greater is the preparation to deal with the danger through running away or fighting back with it, even making a game of it.
Since neuronal networks often work by strengthening each other if they can make a common cause, and inhibiting each other if they are on cross purposes, the person with a high neuronal load has greater necessity to develop proper networkings - sympathetic harmony - to find sufficient outlets for his drives/needs.
And here the factor of environment comes in to play.
So in genetically predisposed individuals lack of enough or too punitive or too much stimulation during childhood leads to the development of a nervous system where its different parts are in cross purposes; acting independently of each other rather than in sympathetic harmony. And it is this lack of proper connections between different nuclei of the brain, each of them acting more independently than they would have if they had received ideal upbringing, that causes anxiety. For anxiety appears to be a subjective realization that one's nervous system is too revved up. If more neuronal circuits are active and functioning without proper coordination, more will be the subjective sense of anxiety. For anxiety is best conceptualized as highly activated brain nuclei, all ready to go, but with insufficient networking between them to allow a properly coordinated discharge.
Let us see this obtuse theoretical discussion in clinical light.
Now the ideal situation would be for all three neuronal masses to develop rich connections back and forth between them in a manner that will allow maximal expression for each. But such optimal expression - sympathetic harmony between the three subsystems - will occur through mutual compromises (proper inhibitory activities between them), since the three trends are basically opposed to each other.
Now if the environment where the child is being raised is not quite proper, there will be abnormal connections between these three trends; more inhibitions than necessary in some circuitry, while excessive strengthening of others. For example if the parents are emotionally or physically unavailable to the child, or they are in frequent fights with each other, or are excessively punitive or threatening to the child, there will be weak libidinal expression towards both of them, and consequently towards all external objects and auroerotic narcissistic masturbatory activities will become the preferred mode of expression of the libido. The networks connecting the ego (the organized part of the self) with the neuronal substrates (imagos) of parents will become weak (inhibited), while there will be greater activation of the neuronal substrates of one's own ego (narcissism) whenever there is libidinal arousal.
In short growing up involves different brain nuclei coming into their prime at different phases of development, and the absolute quantity of their expression depends upon the facilitatory and inhibitory connections that they make with other nuclei. These connections while mostly phylogenetically determined, also depend upon what kind of environment one is growing up in. If the environment is too punitive or too permissive or simply emotionally unavailable then all kinds of abnormalities develop in their interconnections, leaving these nuclei to function more independently instead of in harmony. This results in their inability to find discharge, which causes the person to be in a state of more or less continous alert, which is perceived by consciousness as anxiety.
Perhaps the above discussion is still too theoretical and incomprehensible, so let us examine case history of an actual child.
A four year old child who was happily adjusted to life - though even from an age as early as 11 months he showed a phobia of elevators and closed places and had shown great difficulty in separating from his parents (neophobia)- suddenly developed fears of all kinds, especially of animals.
But the boy's fever pitch hostility could not go on indefinitely. The hatred was generating images in his consciousness that were showing his father getting eaten up by a leopard or meeting some other equally violent fate. Just before the outbreak of his neurosis he had seen a Disney animated Tarzan movie, which showed in graphic details Tarzan locked in mortal combat with a leopard. The scenes were extraordinarily frightening and unpredictable had highly stimulated and scared the child. Few weeks later he had come down with the fear of animals.
A whole range of Tourettian impulses arose in him as well, which were displacement of motor images to attack his father with knives and other objects. These were derived from his suspicion that his father did similar sadistic things to his mother - a reverberation of infantile sexual theories that children make up at that age to solve the riddle of sexuality and childirth.
How all this is connected with inadequate and disrupted white matter connections between amygdala and other nuclei?
In this boy who had a volcanic eruption of the Oedipal phase of sexuality, within a family structure where there was inadequate love between the parents, and where there was too much closeness between him and his mother, the neuronal networks that were forged by Oedipal conflicts were done in less than ideal manner. His hostility towards his father emerged way too strong, and which could be contained only by turning it against his own ego that left whole range of excessive inhibitions in reading and other cognitive tasks and caused mild Tourette's and moderate obsessions.