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Chapter 4. The Biology of Behaviour. Chapter 4 - The Biology of Behaviour. Sections. The Brain and its Components Studying the Brain Control of Behaviour Control of Internal Functions and automatic behaviour Drugs and behaviour. Chapter 4 - The Biology of Behaviour.

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chapter 4

Chapter 4

The Biology of Behaviour

Chapter 4 - The Biology of Behaviour

sections
Sections
  • The Brain and its Components
  • Studying the Brain
  • Control of Behaviour
  • Control of Internal Functions and automatic behaviour
  • Drugs and behaviour

Chapter 4 - The Biology of Behaviour

the brain and its components
The Brain and its Components
  • The Structure of the Nervous System
  • Cells of the Nervous System
  • The Action Potential
  • Synapses
  • A Simple Neural Circuit
  • Neuromodulators

Chapter 4 - The Biology of Behaviour

structure of the nervous system
Structure of the Nervous System

Steve, show BIO15 overhead here depicted the brain with the

above structures indicated

Chapter 4 - The Biology of Behaviour

protecting the cns
Protectingthe CNS

For protection purpose, both the brain and the spinal cord

are incased in bone (the skull and spine respectively)

In addition, both the brain and spinal cord are separated from

their bony armor by a 3-layered set of membranes called

the meninges.

Between the two layers of meninges is a clear liquid called

the cerebral spinal fluid. This fluid in combination with the

meninges provides a “waterbed” of sorts that protects the

sensitive CNS from becoming damaged by the bone that

surrounds them

Chapter 4 - The Biology of Behaviour

the cerebral cortex
The Cerebral Cortex

Our most complex psychological processes occur within

the thin layer of grey matter on the outside of our brain called

the cerebral cortex

The cortex is connected to the other parts of the brain through

a set of nerve fibers called white matter (see figure 4.3 in the

book for a look at this distinction)

In order to maximize the size of the cortex, the human brain

has become wrinkled, containing fissures and gyri

Chapter 4 - The Biology of Behaviour

structure of the nervous system7
Structure of the Nervous System

Steve, show BIO2 overhead here depicted the brain with the

above structures indicated

Chapter 4 - The Biology of Behaviour

cells of the nervous system
Cells of the Nervous System

The basic unit of the human nervous system is the cell.

The nerve cell is made up of four parts, (1) the dendrites,

(2) the soma, (3) the axon, and (4) the axon terminals.

> BIO7 overhead … note myelin

Neurons transmit information through electrical currents

termed action potentials that flow from the soma, through

the axon, to the axon terminals … where it is then passed

to the dendrites of other neurons

> wave demo & overhead BIO8

Chapter 4 - The Biology of Behaviour

transmission of information between cells
Transmission of Information Between Cells

Information is passed from one cell to another via a process

termed synaptic transmission

This process involves the release of neurotransmitter molecules

from one neuron which then “fit into” receptor sites on the

dendrites on other neurons - BIO9 overhead.

Some neurotransmitters send excitatory signals, some inhibitory.

These signals are summed by the soma of the receiving neuron

which “decides” whether to send an action potential - BIO10

After the signal is sent, the neurotransmitters return to the sending

neuron in a process termed re-uptake.

Chapter 4 - The Biology of Behaviour

a simple neural circuit
A Simple Neural Circuit

To illustrate this system in action, consider the following

two situations:

1. Touching a hot iron … sensory neurons detect the heat and

send an excitatory message to inter-neurons in the spinal cord

or brain. These inter-neurons then send excitatory signals to

the motor neurons to retract the hand immediately

2. Carrying a hot casserole dish … again, the heat may make

you want to drop the dish via the same process described above,

BUT this message is temporarily countered by the brain by

it sending inhibitory signals either to the inter-neurons or to the

motor neurons

Chapter 4 - The Biology of Behaviour

neuromodulators
Neuromodulators

As described, neurons send messages to other neurons via

chemicals calledneurotransmittersorneuromodulators.

These chemicals can effect many sites in the brain simultaneously leading to many different behavioural effects

Humans have also used synthetic versions of these chemicals

sometimes for recreational (or abusive) purposes and sometimes for therapeutic purposes.

> e.g., Marijuana question

Chapter 4 - The Biology of Behaviour

study of the brain
Study of the Brain

Much of our understanding of nerve cells has come from studies conducted on animals

Animal research has also lead to the discovery of a number of

drugs that have helped patients suffering from such diseases as

Parkinson’s syndrome, schizophrenia, depression and others

The use of animals is considered justified in two ways:

1) in some cases in leads to obviously beneficial results

for humans as in the case of drug studies

2) in other cases, it advances our knowledge of the human system which is considered worthwhile in and of itself

Chapter 4 - The Biology of Behaviour

rm lesion studies
RM - Lesion Studies

One of the oldest research methods used by physiological

psychologists involves examining the behavioural effects of

damage to certain parts of the brain.

Typically, this involves having the researcher creating alesion

through a surgical procedure in order to wipe out the specific part of the brain they are interested in - see BIO1 overhead for

a depiction of thestereotopic apparatusused to do this

The “destruction” of brain tissue is usually done by touching a

small wire to the brain site of interest, then passing an electrical current through the wire in order to heat and destroy the area

A similar procedure is also sometimes used on humans to alleviate symptoms of some diseases

Chapter 4 - The Biology of Behaviour

rm measurement stimulation
RM - Measurement & Stimulation

Electrodes inserted via surgical procedures can also be used

to measure the activity in nerve cells in response tostimulation

The electrode is then connected to a recording device and

measuresof electrical activity can be taken while the animal

performs various tasks

Electrodes can also be used to stimulate brain areas without

destroying them … and effects of stimulation can be studied

> famous rat self-stimulation experiment

Sometimes the stimulation and measurement are combined to

examine things like learning … long-term potentiation example

Chapter 4 - The Biology of Behaviour

enter the reaper
Enter the Reaper

Irrespective of the study, after it is done the researcher has to

verify that the electrode was in the location (s)he thought it

was in. The typical procedure for doing this involves

> sacrificing the animal via drug overdose

> removal of brain

> slicing up of brain

> dying of the brain slices

> examination of the sliced and dyed brain to verify

location

Sometimes, in order to stain the brain appropriately a more

complicated procedure must be used callprofusion… Steve

will explain

I’ll be leaving

now, thanks!

Chapter 4 - The Biology of Behaviour

human subjects
Human Subjects

Clearly, many of the procedures we perform on animals would

not be considered ethical if performed on humans

However, there are now means of doing things that parallel the animal work … thanks largely to brain scanning technology

CT (computerized tomography)scans send a narrow beam of

X-rays through the head and the computer calculates the amount of radiation that passes through, then is able to generate a “slice” of the brain, showing brain density at specific regions - BIO13

MRI (magnetic resonance imaging)do the same thing as CTs, but with more detail (uses magnetic fields and radio waves instead of X)

PET (positron emission tomography)scans measure processing rather than structure by examining blood flow

Chapter 4 - The Biology of Behaviour

methods that parallel animal work
Methods that Parallel Animal Work

Given these scanners, we can now describe at least two methods

that parallel those done with animals

First, due either to natural (e.g. stroke) or unnatural (e.g., accident) situations, human brains become damaged -- or lesioned. Scanners can now be used to localize the damage, and behavioural methods can be used to assess the relation between certain brain areas and certain behaviours

Second, we can also measure processing in the brain (via a PET)

while the subject engages in some activity … much like using

electrodes to measure processing in the rat brain

Chapter 4 - The Biology of Behaviour

so what have we learned about the brain from all this
So, what have we learned about the brain from all this?

The cerebral cortex vs. lower level brain structures

The cerebral cortex is the place where high level perception of

the world occurs, and is also the place where controlled motor

activities originate. In this sense, it is the place where all our

controlled interactions with the external world occur.

This contrasts with a number of more basic brain regions

which are more devoted to monitoring and controlling internal

behaviours and automatic responses to external stimuli.

Each will now be discussed in turn

Chapter 4 - The Biology of Behaviour

the cerebral cortex19
The Cerebral Cortex

Primary Motor and Sensory Cortex:

> There most definitely are certain parts of the brain that

are responsible for very specific tasks, especially when

it comes to sensation and motor responses - BIO18, and

FIG 4.23

> These areas are organized in a contralateral manner,

such that the left side of the brain represents the right

side of the body, and vice-versa

> The amount of brain dedicated to various regions is not

determined by the size of the region but, instead, by the

sensitivity of it - sensory homunculus

Chapter 4 - The Biology of Behaviour

the cerebral cortex20
The Cerebral Cortex

Association Cortex

The remainder of the cerebral cortex is termed “association

cortex” and is thought to be where sensations are drawn

together to support higher level cognitive functions such as

perception, learning, and memory - Penfield’s surgery

Perception, then, is not the same as sensation but, instead,

is the interpretation of that sensation as performed by the

association cortex - CAT IN THE HAT example

The association cortex is often discussed in terms of lobes of

the brain; frontal, occipital, parietal & temporal - FIG 4.24

Distinction between somatosensory vs motor association cortex

Chapter 4 - The Biology of Behaviour

sensation is not perception
Sensation is not Perception

Chapter 4 - The Biology of Behaviour

the cerebral cortex22
The Cerebral Cortex

Lateralization of Function

The two hemispheres of the brain do not perform identical

functions … rather, each hemisphere seems to specialize in

certain things - BIO23

We are not aware that the hemispheres perceive the world

differently because they completely communicate with one

another via a brain structure called the corpus collosum

In certain extreme cases of epilepsy, the corpus collosum of a

patient is severed, in order to prevent the siezures. This leads

to an interesting splitting of experience from awareness -

BIO24 … more to come in Chapter 9

Lateralization is less clean than implied

Chapter 4 - The Biology of Behaviour

the occipital temporal lobes
The Occipital & Temporal Lobes

The occipital (and lower part of the temporal) lobes are devoted

to vision.

Primary visual cortex is directly related to sight, and damage to

it produces a hole in a persons visual field … a scitoma

Association cortex in this area

performs the function of providing

an interface between visual input

and memory … allowing one to

categorize visual images. Damage

can lead to agnosia, the inability to

name common objects

A Pencil?

Chapter 4 - The Biology of Behaviour

the temporal lobe
The Temporal Lobe

Most of the temporal lobe is devoted to audition

Primary auditory cortex is mostly hidden from view, lying on

the inside to the upper temporal lobe. Damage to this leads to

hearing problems

Auditory association cortex is located on the lateral surface

of the upper temporal lobe

> Damage to left leads to severe language deficits … patients

losing the ability to comprehend or produce meaningful speech

> Damage to the right affects the patients ability to properly

perceive non-speech sounds, like the rhythm in music

Chapter 4 - The Biology of Behaviour

the parietal lobe
The Parietal Lobe

Primary sensory function involvesperception of the body

The association cortex here seems to be involved incomplex

spatial functions, that differ across the hemispheres

The left parietal appears to keep track of the spatial location

of our body parts - proprioception

> Damage often associated with poor motor movements

The right parietal appears to keep track of the spatial location

of things in our external world

> Damage can lead to problems of neglect and spatial

integration of parts

Chapter 4 - The Biology of Behaviour

the frontal lobes
The Frontal Lobes

Thought to be responsible for many very high level cognitive

functions such as planning, strategy shifting, self-awareness,

and the initiation of motor activity.

Damage to the motor area of frontal cortex causes paralysis of

the associated motor functions in the opposite side of the body

Damage to the pre-frontal cortex ( e.g. frontal labotomies)

causes very complex and interesting effects including:

1. The slowing of thoughts and loss of spontaneity

2. Perseveration errors - Card sorting example

3. Loss of self-awareness and flat affect, especially empathy

4. Deficiencies in foresight and planning

5. Tendency to confabulate

Chapter 4 - The Biology of Behaviour

wisconsin card sorting task
Wisconsin Card Sorting Task

Sort by number

Sort by shape

Sort by colour

Chapter 4 - The Biology of Behaviour

sub cortical brain regions
Sub-cortical Brain Regions

The brain stem is involved in many of our

most basic behaviours including the control of

heart rate, blood pressure, and respiration (medulla),

sleep (pons), fighting and sexual behaviour (midbrain)

Thecerebellum, in co-ordination with the frontal lobes,

carries out the detailed computations necessary for precise motor

movements … in addition it also controls adjustments for posture,

and corrects for things like head movement when controlling eyes

In addition, there are also a number of regions within the cerebral

hemispheres that also play a role including thethalamus, the

hypothalamus, and thelimbic system

Chapter 4 - The Biology of Behaviour

the thalamus and hypothalamus
The Thalamus and Hypothalamus

The thalamus, located in the very center of the brain, performs

two basic functions; (1) the reception and integration of perceptual

information, and (2) the passing on of this information to the

relevant cortical regions … attention??

The hypothalamus is located below the thalamus and is very small.

It monitors a number of characteristics of the blood that flows thru

the brain (e.g., temperature, composition) and controls the

pituitary gland, an endocrine gland attached to the base of the skull

Endocrine glands release hormones which act like neurotransmitters

except over longer distances … they stimulate receptor sites causing

physiological reactions

The pituitary is the master endocrine, as it can command target

receptors on other endocrine glands

Chapter 4 - The Biology of Behaviour

the limbic system
The Limbic System

Includes two structures, the amygdala, and the hippocampus.

The amygdala appears to control emotional reactions, especially

negative ones. In addition it provides energy for fighting and

fleeing

> damage to the amygdala causes a loss of “stress” and “anger”

reactions … which is actually bad news for survival

The hippocampus plays an important role in memory. It is

especially critical for learning new information … many of those

most striking cases of amnesia are caused by damage to the

hypocampus

Chapter 4 - The Biology of Behaviour

drugs and behaviour
Drugs and Behaviour

This section I leave to you … I will not discuss it beyond

that which we have done already … you are responsible

for it though, so read up!

Chapter 4 - The Biology of Behaviour

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