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Neurological Basis of Behavior (PSY - 610)

Lesson 08

GENES AND EXPERIENCE

Objective:

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

The Nature or nurture debate keeps coming up in research and discussions among scientists working in

behavioural neurosciences. In order to answer this we must remember that

a) Behavior occurs in relation to some event i.e. it has to have an interaction with the environment,

affect it and be affected by it.

b) Organism comes already equipped to face the world in a particular manner, i.e. is programmed

"genetically determined animal possessing biological structures and capabilities and limits".

Thus, behavior is genetically determined as well as exploited when an appropriate environment is

provided. Some behaviors are completely determined while others are somewhat determined whereas

there are some which are not at all controlled by genes. The range of behaviours extends from

completely innate to completely learn. In the lower animals such as fruitflies the behavior is carried out

as per genetic programming in response to the environmental cues. On the other hand in humans

language apparatus is biologically developed, but languages are learnt (language which is taught to the

growing child depends on the environment he is raised in). Similarly culture and traditions are not

biologically determined.

The continuum below shows that in lower animals and simpler organisms behavior is innately

determined, whereas in humans there are some completely learnt

Innate (completely determined)------------------------------------Only learned

Fruitflies-------------------------------------------------------------------------------human languages

The question is do genes produce innate behavior? The answer is No; they only provide templates for

synthesis of appropriate proteins, protein chains and timing of release. There is programming of genetic

proteins and chains which determine the brain program and developments which can flourish in a

certain environment. The triggering cues for genetically programmed behaviors come from the

environment. These can be cues from the external environment e.g. External cue could be lion hunting

for food; deer sees the lion it runs to save itself. The internal cues come from within the organism's

systems the hormones, the needs and the signals form these lead the organism to action. For example,

internal cues may be signals for food/nutrition; the animals feel hungry and seek food. If there is rise in

the prostaglandins levels birds start nest building. There can also be a combination of both the external

and internal cues, that you see food or smell food and immediately feel like eating.

Can experience affect innate behavior? Yes in some cases it can mothering behavior is due to hormonal

changes after birth. However, we cannot induce mothering with drugs only, unless this has been

previously experienced naturally. This experiment was carried out with ring doves.

Nature-Nurture: Interaction

The interaction of nature-nurture has limits. Rats can only learn food related tasks (press lever for food)

as this is the kind of behavior which exists and occurs in their natural survival repertoire, but they would

not groom face for food as this is not part of their innate feeding program.

The fact is that there is greater influence of environment with higher order animals or animals with

larger brains size. Thus, this means there is greater adaptability in animals on the higher evolutionary

scale. These have very few typical behavior patterns. Thus, we can safely state, the higher the animal on

evolutionary scale greater, the greater the encephalization, (larger cerebral cortices and control). And

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Neurological Basis of Behavior (PSY - 610)

the greater the encepahlization (animals with larger cerebral cortices) the more they are affected by

environment.

Ethology: A branch of life sciences which studies behavior in its natural environment. The

underpinning theoretical view is Darwinian evolution. The view is that behavior is predetermined and

preprogrammed, is set in motion by a cue and is carried through in a fixed action pattern. These

processes of behaviours are determined through natural selection (only adaptive are behaviours

maintained).

Fixed Pattern: once a behavior is initiated it will go through the whole innate process to completion.

This behaviour has the following characteristics. It is a)stereotypic: the same behaviour pattern is

repeated again and again : the dance of the peacock, b) innate: the behaviours of the mother toward

young and infant towards mother would be different, so each species and within that young or old, male

or female would have their innate behaviours c) repetitive: same form repeated every time stimuli

presented ( peacocks dance) d) completed once initiated: even if we try we cannot stop it, the animals

would stop when the behavior ends e) cannot be modified through learning.

Ethologists have studied why behaviour occurs in such a manner. They have found that Signs (stimuli)

which act as releasers are important. They have the following characteristics:

A specific sign stimulus will affect one species only. It can affect only males/females or both in

different ways- a sign stimuli can be the sight of another (visual: male sees female) or hear the sound of

a call (acoustic: Males battle call out to another male) smell odor of the other (Olfactory/chemical) and

also behaviour (the male wolf snarls to display his canines to the other males).

Sign stimuli would then lead to fixed action patterns in one animal. This then leads to a response of

further sign stimuli. This exchange of signals can lead to full range of behaviors. For example a distress

signal of mother hen for chicks when she sees an eagle, and they respond with distress calls and run to

hide under her feathers. Lehrman developed the goose-hawk model; the same wood board cut looks like

a goose from one end and a hawk from another. Goslings (baby geese) freeze with fear if the model

flown in one direction (hawk) not the other. There have been experiments in which it was shown that

Herring Gull leaves its egg to sit on larger one!

Is there a fixed action pattern in humans? Yes, infant turns away from noxious, smiles at pleasant look

or a smile. When an unpleasant face is made indicating threat, the baby cries. Who teaches the infant?

Further, there are innate fixed emotional expressions. Studies were carried out photographing faces with

expressions across primitive and advanced world). These were rated by judges: anger, surprise, sadness,

and happiness came across the same whether it is from the primitive Island of New Guinea or the US.

Why does the baby stops crying when the mother holds him/her close, the baby s responding to

mother's smells/odor which are signals from pheromones which communicate her presence and

closeness.

However, not everything ethologists say exactly is as they say. Man learns from experience to suppress

anger to smile when angry. Man is a generalized animal whereas other animals are specialized (cheetah

runs faster than man, snake better smeller, but man can change his environment to suit needs)

Genetic basis of behaviour; if we look at the following chromosomal composition it would appear the

genetic makeup does influence behavioural characteristics:

With one X and one Y chromosome we have normal males (XY), however with increase in one

additional Y chromosome (XYY) evidence of aggressiveness in males has been shown in studies of

inmates and it was found that a lagrge percentage of inmates who had committed physically aggressive

and brutal criems in Scottish jails studies).

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Neurological Basis of Behavior (PSY - 610)

With two XX chromosomes we have normal females; with a Y chromosome attached to these we have a

female with male characteristics. The trisomy (three chromosomes) XXO, XYO lead to the Downs

syndrome (abnormalities).

Thus genes determine the female/male but also the expression of characteristics of being a male/female.

Keeping the above in view we do know that genes have an important role in the development of

physical and other characteristic

Genetic basis: fundamental concepts

The basic structures of gene transmission i.e. chromosomes, genes, proteins, genotypes, phenotype,

mutation, DNA, RNA would be discussed in detail.

Chromosomes are strands of chemical proteins found in the nucleus of all cells of the organism. These

are composed of a large # of genes (the basic unit of heredity) located throughout on the threads of

chromosomes. Chromosomes occur in matched pairs one of a pair received from the mother and the

other from father at fertilization. Chromosomes are specific for each species: humans have 23

chromosomes (one pair for sex 22 for other traits) and drosophilia (fruitfly) has 8. Chromosomes are

composed of double strands of DNA molecules (knit like a rope, details in the following lesson).

Genes are located on the chromosomes and these determine the combinations of chains of proteins

involved in growth and development, and maintenance of organism's systems.

Proteins: there are two kinds of proteins a) structural proteins those which determine structure of the

organism i.e. bones teeth, hair, organs b) enzymes; these modulate the metabolism of the organism (and

other physico-chemical events).

Genes express themselves in two ways:

· Genotype: set of genes which form the underlying genetic makeup of the individual e.g. hair

genes could be for straight or curly, brown or black hair.

· Phenotypic: These are observable or measurable traits which form the outward expression of

genetic basis after interaction with the environment. Behaviour in all higher animals is more

phenotypical as compared to lower animals.

As an example we can say that the Drosophilia would develop wings at a particular temperature and

flowers would bloom with the right weather conditions. Children who have undergone severe starvation

during early childhood--(such as children is Ethiopia or Somalia) would not be able to regenerate brain

or other growth cycles

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

Note: References #2, 3, and 4 are followed most closely, as they have been used in teaching as well;

further individual references/pages are also given on the power points of each lesson