Continuation of Chapter 3:
Association areas: composed of neurons that help provide sense and meaning to
information registered in the cortex
Cerebral cortex can adapt to changes in sensory input-plasticity.
The brain is plastic: functions that were assigned to certain areas of the brain may be
capable of being reassigned to other areas of the brain to accommodate changing input
from the environment. This suggest that sensory inputs “compete” for representation in
each cortical area
Physical exercise can increase the number of synapses and even promote the
development of new neurons.
Development and Evolution of Nervous System
The nervous system is first major bodily system to take form in an embryo-this begins
during third week of fertilization
Neural tube begins to develop and you being to form cerebral hemispheres. The hindbrain
forms the cerebellum and medulla and the midbrain forms the tectum
Ontogeny of the brain: how it develops within an individual. Within 15 week semester
the basic structures of the brain are in place and rapidly developing
Phylogeny of the brain: how it developed within a particular species-is a much slower
Evolutionary Development of the Central Nervous System:
Even the simplest animals have sensory neurons and motor neurons for responding to the
environment (e.g. protozoa)
The first nervous system worthy appeared in a flatworm (collection of neurons in the
The emergence of the brain are a pair of tracts that form the spinal cord
The tracts are connected by smaller neurons called ganglia-integrate info and coordinate
The organization of nervous system occurred between invertebrate animals and vertebrate
In vertebrate animals the central nervous system is composed of a lower levels of brain
and spinal cord while the higher levels form more complex functions
The midbrain responsible for responding to stimulus in the environment and the forebrain
deals with the more complex task.
The forebrains in mammals have the most highly developed cerebral cortex which
develops multiple areas.
The forebrain allows us to be self-aware, use sophisticated language, social interact,
abstract reasoning, empathy etc.
Primate brains evolved quickly compared to those of other species, but the brain of the
primates who eventually became human evolved even more rapidly.
The genes for human brains took particular advantage of a variety of mutations
Genes may direct the development of a larger brain and even the development of the
Genes and the Environment Nurture vs. nature suggests that either genetics or the environment played a major role in
producing particular behaviours, personality traits and psychological disorder.
It’s the interaction of genes and environmental influences that determines what humans
What are Genes?
A gene us the unit of hereditary transmission. Genes are section of DNA and are
organized into large threads called chromosomes
Chromosomes are strands of DNA wound around each other in a double helix
configuration. There are 23 chromosomal pairs in humans
You inherit one pair from your mother and the other from your mother, the selection of
each pair is random.
The probability of sharing genes is called degree of relatedness.
The most genetically related people are homozygote twins who develop from the splitting
of a single fertilized egg and therefore share 100 percent of their genes
Dizygotic twins develop from two separate fertilized eggs and share 50% of their genes,
the same as any two siblings born separately.
Genetics can contribute to the development, likelihood, or onset of a variety of trait
Role of Environmental Factors
Your environmental experiences have made it unlikely for you to live that way
Behavioural genetics used calculations based on relatedness to compute the heritability of
Heritability is a measure of the variability of behavioural traits among individuals that
can be accounted for by gene factors.
Hereditability ranges from 0 to1(0 means that none of the genes contribute to the
behavioural trait and 1 means that genes are the only reason for the individual
Environmental influences also play a significant role in predicting the basis of
Heritability is an abstract concept: tells us nothing about the specific genes that contribute
to a trait. Heritability is a population concept; tell us nothing about the abilities within an
Heritability dependant on the environment: behaviour occurs within certain contexts as
well as genetic influences
Heritability is not fate: it tells us nothing about the degree to which interventions an
change a behavioural trait.
Learning about Brain Organization
Observing the behavioural problems that result from damage to a certain areas of the
brain enable researches to identify the function of those areas
Neuroscience correlates the loss of specific perpetual, motor, emotional, conjunctive
functions with specific areas of the brain damage.
Emotional Functions of the Frontal