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Neurological Basis of Behavior (PSY - 610)

LESSON 10

GENES AND EXPERIENCE

Objective:

· To understand the Brain behaviour relationships from the perspectives of biological systems.

In this section of the module the students would go through and understand Biological systems- their

genetic basis and similarities with other animals. Mendelian Genetics. Where is the genetic

programming of behaviour ( if any) Watson Crick Model. What are the similarities and differences

between species, progenies of higher order animals, including homosapien? How much do genes

contribute to behavior: The discipline of Behavior genetics?

Genetic Basis of behavior

Genes not act directly on behaviour, but on the proteins/aminoacids which are responsible for

the structure and metabolism of the organism.

Behavior geneticist and studies in this area agree that a) environment and experience are

important as they interact with genetic material. The researcher try to pinpoint how much of

each contribute to behavior. b) a single gene at a single location cannot lead to one behaviour.

Behavior is the sum total of different genes at different loci. It is not an all or none

characteristics. It is always a combination of different genes, polygenic systems.

Experimental Studies: Genetic Manipulation

There have been experimental studies which manipulate genes using artificial selection and other

conditions in animals reared in labs. This is done because the environmental conditions in the laboratory

are held constant (temperature, day/night cycle , food and the social environment),selection of specific

traits of interest which can be followed up, and animals with those characteristics mated and progenies (

offspring ) followed up and tested for behavioral as well as other characteristics.

How do the behavioural geneticists measure and test behaviour of interest in the laboratory animals. The

characteristics of interest are taken and animals tested and their scores/ performance looked at carefully.

Then animals scoring on both extremes separated form the group that is the High and Low scorers taken

and separated. Then low scorer females and low scorer males mated. The same procedure was carried

out for the high scorers. The progenies were then developed into two separate populations by repeated

selective testing and mating. This has been done as early as in the 1930's.

Tryon ( 1934) carried out an experiment at the University of Berkley where he bred maze bright ( who

did extremely well on maze tests) and maze dull( those who made a lot of errors in maze) rats for 21

generations. By the 8th generation no overlap in two he found that there was no overlap in the two

populations. The question that it could be possibly due to rearing as bright mothers were rearing bright

offspring. This was ruled out as he designed an experimental cross fostering design in which the maze

bright offspring were reared by maze dull parents; they still made significantly less errors. Similarly,

using the same cross fostering procedure he had dull rats reared by bright rats. Since then many

behaviors such as open field activity, alcohol and morphine preference has been identified using such

designs. However we must remember that behaviour is complex, and has multiple variables. There is

not just one single gene for maze running, (there are a lot of cues involved). Further, Searle (1949)

reported that in comparing two groups, he conducted 30 different tests on the maze bright and maze

dull. He reports that maze bright rats were superior in performance and less emotional, therefore the

better learner may learn because there is more emotional stability not because they are more intelligent!

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Neurological Basis of Behavior (PSY - 610)

Are there any Environment effects? Cooper and Zubeck ( 1958) raised the maze bright/dull rats in three

different environments a) impoverished( cage made from wire netting with groups living), b)

stimulating and enriched housing with wire netting, group housing but it had toys, ramps for animals to

play with. His findings showed that the maze dull rats perform similar to the maze bright if reared in

stimulating environment. Bennett, Diamond, Krech and Rozenweig (1964) found that rats in richer

environment have thicker cortices! This means that their brain development is affected by early

stimulation (more on this later in the chapter on brain development)

The foremost names in the field of genetics and behaviour are Theodosius Dobzhansky and Seymour

Benzer. Their work on Drosophilia (fruitfly) is pioneering work. They took a genetically heterogenous

population and through selective breeding created new breeds to show that behaviour genetically linked.

A lot of work was needed to identify which behaviours were linked to which genes and were located on

which chromosome! Further, constant selection was to be maintained or genetic pool could be broken

into, genes may get re-assorted and effort gone waste (and behaviour under observation may get lost). It

could be a simple careless mistake of a stray fly getting into the experimental breeding cage.

In Dobzhansky and Benzer's experiments, the gene material was also changed through radiation and bio

engineering manipulations. They developed mutants who were sluggish (slow movers) hyperkinetic

(very fast movers, who died soon as they consumed more oxygen and body metabolism faster) non

climbers (those who could not climb against gravity), easily shocked (goes into seizure) negatively

phototactic (those who move away from light source- normal flies move towards light).

Similarly dogs were identified for characteristics by John Paul scott in his laboratory in bar harbor

Maine. The breed beagle (snoopy dog of the cartoons) became the model for hyperactivity.

Mouse strains were identified and bred for different characteristics; aggressive behaviors, alcoholics vs.

nonalcoholic, hoarders vs. non-hoarders, emotionality (defecate in a novel situation), waltzing mice

(inner ear defect). All of this is a consequence of in breeding

In breeding

Simply defined this is repeatedly using the same gene pool which leads to expression of recessive genes

which may carry both behavioural and physical defects.

In a study Theisen (1972) reports that the death rate in children below 10 years of age is 24 per 1000 in

normal population. In interrelated marriages it rises to 81 per 1000. In closer marriages the rate rises

even more. There are other more serious effects such as physically less capable, weaker and age when

they walked and talked was much later than normals. This showed developmental lags. Other deficits

that Theisen (1972) reports are lower Intelligence scores, with lower verbal scores, and language scores

were even lower than normals.

In summary, it is well documented that if the gene pool is reduced more recessive disorders show up.

Larger gene pools lead to a healthier and longer surviving offspring which can compete in a wide range

of environments.

References:

1. Kalat J.W (1998) Biological Psychology Brooks/ Cole Publishing

2. Carlson N.R. (2005) Foundations of Physiological Psychology Allyn and Bacon, Boston

3. Pinel, John P.J. (2003) Biopsychology (5th edition) Allyn and Bacon Singapore

4 Bloom F, Nelson and Lazerson (2001), Behavioral Neuroscience: Brain, Mind and Behaviors (3rd

edition) Worth Publishers New York

5. Bridgeman,B (1988)The Biology of Behaviour and Mind. John Wiley and Sons New York