Society & Lifestyle
|Random Thoughts||Share This Page|
Memory, Software, Hardware & Evolution
|by Gaurang Bhatt, MD|
As a neurologist trying to diagnose Alzheimer’s, amongst the shortcuts one uses are tests for short term memory. One gives a patient unrelated few phrases to remember, like three red roses, one white envelope, 1700 Sansom Street. One repeats this once again, asking the patient to repeat and remember it and then distracts the patient with irrelevant small talk for a few minutes. Then the demand is made for the patient to repeat the series in correct order without prompting or hints. Alzheimer’s patients in the early phase fail to repeat correctly. It is not that memory is the sine qua non of Alzheimer’s disease. Wernicke Korsakoff syndrome, a disease of alcohol abuse or another one like iatrogenic bilateral temporal lobectomy (including the medial part and both hippocampi for controlling seizures) causes loss of ability to retain recently acquired memory and leads to every repeated recent event to be a fresh new occurrence. Interestingly, the destruction of the prefrontal cortex leads to a change of character, personality and judgment as the classic case of Phineas Gage proves. Where is God when you need her?
The point of the above expostulation is to emphasize the need and importance of working memory as any computer buff will understand. Most normal persons can remember up to seven digits forwards and five digits backwards, with concentration. If you ask subjects to remember ten digits forwards or seven digits backwards, you will find that a large majority of the general population fails. There are rare exceptions with photographic memories and those who can calculate the Greek Pi to the thousandth digit without pen or paper or compose complicated music or perform it without great training, but many of those fall into a class called idiot savants. That is their enhanced ability in music, calculation or one specific talent is inevitably associated with lack of achievements in other common faculties like logic, analysis, speech or even more important functions for survival in the world. It is reminiscent of the choice of Achilles, who was offered a short heroic life of brilliant achievement or a long mundane one.
Memory and even more working memory is an important limiting factor in computation as is stoichiometry in certain chemical reactions. Evolution is constantly confronted with this kind of tradeoff. In fruit flies, the workhorse of some important evolutionary studies, genetically modifying the fruit flies for better memory can only be done like Achilles by shortening their life span. Thus a non-challenging environment is more conducive to a longer boring life. Huxley, Darwin’s bulldog, was asked in a debate about God’s partiality to his creation. He quipped that god had an inordinate fondness for beetles, as they constitute the largest number of species of all animals, over 400,000. They are the ultimate scavengers and clean up everything from dung to dead carcasses and only fungi compete with them in public garbage disposal, a civic necessity.
As I have always felt, social animals need to remember who did them a favor and who bore them a grudge. This happens in vampire bats who cannot survive long without a blood meal, and thus beg for it from neighbors after a not uncommon unsuccessful expedition. To remember such favors and reciprocate the bat’s need to remember who obliged and who refused,
To come back to my title about computing and evolution, I will give you two interesting facts about the behaviors of a rare solitary (non-hive) bee larva and the behavior of an adult female wasp which will confirm that life is a trade off and evolution is a parsimonious arbitrator in this strange game. The information is mainly from Marlene Zuk’s latest book on insects, “Sex On Six Legs” and Richard Dawkins older one, “River Out Of Eden”. While we are all familiar with honey bees, hives and their social lives, there are other bees which are solitary. These lay their eggs in a solitary receptacle and cover the egg with a membrane, after provisioning the egg cavity cell. The mature larva then cuts through the soft covered cell roof to extricate itself and enter the world. Scientists studying this, who were not perverse sadists, installed and additional artificial membrane over the roof of the egg cell. The mature bee larva with its small brain, limited memory and unattended by caring sisters, cut through the natural barrier but failed to use its previously used and adequate cutting mouth parts to cut through an even more flimsy and fragile second artificially erected second barrier to gain freedom and life, because its instinctual mental program lacked the additional line of code and memory telling it to repeat the program, if faced with an identical obstacle.
Evolution in its parsimonious style to get the biggest bang for a buck and not waste its limited repertoire on a highly unlikely natural event, resulted in the perishing of that larva. This kind of problem recurs frequently in nature. The booby, a bird aptly named, lays its eggs on the ground and draws a circle of secretions around the nest. It is not uncommon for a first hatched egg to push its unhatched sibling out of the circle. Take that you Islamic mode of kingdom heritage or primogeniture of the British Crown, just remedied. The parent birds, like programmed Hindus believing in a Lakshman Rekha, then completely ignore their own egg lying outside, and let the potential offspring perish. Equally amazingly, the cuckoo like many contemporary parents in many countries, wants to waste no time in parenting and lays its egg in the nest of another species. It makes sure its egg is laid in the nest of a species whose eggs look like those of the mother cuckoo. There are many variants of mother cuckoos with different colors and speckling of their eggs and like the Jewish custom, the mother’s clan decides the external appearance of a cuckoo’s eggs. What is worrisome and baffling is that the cuckoo egg hatches first and then throws the rest of the eggs out of the nest to monopolize the attention and feeding proclivities of its foster parents. The little nestling because of its species tendencies, extra growth hormone, or whatever, soon is almost the same size as its foster parents and yet when it begs for food, the foster parents enthusiastically feed the crook, which has murdered their real children, with doting parental love.
The final interesting but tragically funny example is that of what is called sphexish behavior. It is an obsessive compulsive behavior which in human beings falls into Obsessive Compulsive Disorder (OCD treated with medications) and requires a circuit involving a part of the basal ganglia of the brain called the caudate nucleus). Wasps are to me the most important animals. They made Darwin loose faith in a benign God and even destroyed Hindu theodicy. Many of them lay their egg in a caterpillar which they have stung and paralyzed. The larva matures, eating the body of the caterpillar from back to front and after consuming the front end of the caterpillar including its primitive brain, emerges as a mature adult. Where is the just or merciful god that most idiots and fools pray to? But this argument is not about justice, mercy or ethics but the constraints of computation.
The experiments were done by Jean-Henri Fabre and repeated by others and confirmed. The female digger wasps stings her prey, paralyzes it and returns to her previously dug burrow. She leaves the stung and paralyzed prey outside the burrow, while she enters, checks and inspects the burrow. The experimenter then moves the paralyzed prey a few inches away from its location. The female wasp comes out of the burrow, searches and relocates the prey and drags it back to the burrow entrance. Only a few seconds earlier, the female wasp had inspected the burrow. But her instinctual program allows no latitude, because of limited working memory and her constrained software. She mechanically leaves the paralyzed prey outside and once again inspects the burrow, before dragging the prey inside and laying her egg. The scientist repeated this forty times before he or she got tired, but the wasp was programmed by its software to repeat the activity ad infinitum and continued to do so because of its limited memory and software as well as hardware.
The point of this essay like in much of finance and ethics is that there is no free ride or lunch and ultimately we have to pay in some form or fashion for everything in time, as even the quantum fluctuations of vacuum insist. So we can run deficits only so long before others stop lending us money and we can only boss over the world so long as the idiots don’t realize that we are bluffing and bankrupt, and even more importantly there is a limit to the gullibility of foolish Americans, which is less than the snake oil selling Republicans and Democrats hope for. And even more importantly, life is a compromise between ought and is.
|More by : Gaurang Bhatt, MD|
|Views: 1835 Comments: 4|
Comments on this Article
11/03/2011 01:44 AM
11/01/2011 12:44 PM
11/01/2011 05:02 AM
11/01/2011 00:11 AM
|Top | Random Thoughts|