Lecture 4: The Central nervous system and Biological basis

Question 1

What Biological psychology?

Answer 1

The application of the principles of biology to the study of mental processes and behaviour

• William James (1890) argues that the scientific study of psychology should be grounded in an understanding of biology

Question 2

Research methods used:

Answer 2

• Lesion studies: Aphasia→ the inability to speak fluidly. Broca’s area: frontal temporal
  → differences between damaged areas and healthy area to see correlations
• Animal studies
• Enhancing neural function: inject an electrical current into a circuit of neurons to see what it does, Stimulating areas to see how the patient reacts
  → certain areas of the brain cause certain functions
• Measuring neural activity: MRI, Functional MRI, PET
  → every person has an individual biological makeup, more susceptible to certain illness
• Genetic manipulations

Question 3

The nervous system:

Answer 3

Nervous system and endocrine system allow us to coordinate action between internal and external environment

• explains causation of action
• complex system consisting of billions of neurons

Human nervous system comprises the central and peripheral nervous system
- large concentration of neurones in the brain and the spinal cord (CNS)

• peripheral nervous system includes everything else

Question 4

Descartes’ theory of reflex action (1662)

Answer 4

Hydraulic model of causation and brain function ie. fluid comprises ‘animal spirits’

Fire (A) is the stimulus causing a chain of processes between the foot (B) continuing up the nerve tube to a cavity in the brain (F)

The opening of this cavity allows fluid to enter the nerve tube resulting in the reflex action ie. pulling the foot away

Question 5

Spinal reflex

Answer 5

The stimulus ‘triggers’ electrical activity in neuron

• Multiple parallel pathways acting simultaneously
• sequence of events describes a relay of ‘circuit’
• results in sensation of pain

Think about the difference between Descartes’ model and modern understandings of reflex mechanisms

Cells (neurons) > electro-chemical processes > parallel processing

The grey matter in the spinal cord consists of interneurons and cell bodies (soma)
There are three kinds of neurons: sensory, motor and interneurons

Question 6

Action potentials

Answer 6

What do we mean by ‘triggering activity’ in a neuron?

• Infomation is transmitted along neurons as sharp pulses of electricity
• This ‘triggering’ activity’ or ‘activation’ means producing action potentials
• This requires taking a closer look at the neuron, which is the foundation of a connectionist model of cognitive and biological psychology

Question 7

Structure of a typical Neuron

Answer 7

Input and output: the flow of electrical current

Dendrites: areas that connect to other neurons
Nucleus: heart of the cell, DNA
Soma:

Axon: carries the electrical charge
→ Node of Ranvier
→ Myelin Sheath
→ Schwann Cell

Axon terminal: Connecting to another neuron

Question 8

Sensory neuron function:

Answer 8

Sensory neurons are afferent neurons, meaning they convey information from tissues and organs into the CNS.

Question 9

Motor neuron function:

Answer 9

Motor neurons are efferent neurons and transmit signals from the CNS to the effector cells. Interneurons connect neurons within specific regions of the CNS.

Question 10

Neurons size

Answer 10

A real neuron has dendrites (input) and Axon (output)
On average every neuron forms about 1000 synapses, although some can have as many as 5000 or 6000.

There are approximately 100 billion neurones in the human brain and more than 1000 trillion synaptic connections.

Question 11

Real Pyramidal neurons

Answer 11

Found in the cerebral cortex, the hippocampus and the amygdala, Pyramidal neuronsare the primary excitation units of the mammalian prefrontal cortex and the corticospinal tract.

• multi polar structure
• Increases activity between neurons
• Performs memory and other complicated

Question 12

Excitability of neurons and muscle cells

Answer 12

Excitability of neurons and muscle cells:

The action potential (fluctuation of voltage) in a cell, triggers, similar action potentials in other neurons- in effect moving along the axon

• Action potential is when the cell rapidly increases in voltage from a negative to a positive value and then a rapid return to the original negative value
• Excitability of the neurones and muscle cells depends upon the fact that the membrane is semi-permeable
• Depolarization is the process of moving towards zero and (briefly) a positive polarity – during which positively charged Sodium enters through the membrane wall of the neuron rapidly and releasing Potassium.

Question 13

Neuronal activity in the brain

Answer 13

• Neuronal activity in the brain is often described in abstract terms such as ‘information’
• In real (biological) terms it is described as action potentials
• Information is the correlation of socially meaningful content and neuronal signals
• Information can also be a spinal reflex registered in the brain

Question 14

Communication between neurones

Answer 14

Communication between neurons

The region where one neuron communicates with another is known as synapse

Synapse consist of part of the cell and the small gap between

Action potential do not cross generally from one neuron to another, communication between neurons occurs by means of a chemical neurotransmitter

Axon terminates into an axon→ synaptic cleft

It was Charles Sherrington who coined to term synapse (from the greek word meaning ‘to join together’)
– > Synaptic cleft refers to the gap between pre-synaptic and posy synaptic terminals ( where the axon terminals)

Question 15

The neurotransmitter

Answer 15

In response to the arrival of action potentials, the neurotransmitter is released at the terminal of the presynaptic neuron influencing the activity of the postsynaptic neuron

Most termed receptors are influencd by neurotransmitters creating a new action potential

Lock and key= when the receptors receive the neuron it triggers a neighbouring response

The remaining neurotransmitters are reuptake using the transport proteins or destroyed using enzymes
Drugs block the reuptake therefore the neurotransmitters stay in the body for longer

Question 16

Neurotransmitters and behaviour: functions

Answer 16

• Mediate the connection between neurones and control behaviour and mental processes eg. emotional states are influences by the release of neurotransmitters
• Drugs can artifically manipulate the acivity of neurons to target certain synapes eg. psychopharmcology
• Mood altering drugs indicate the interdependence betwen mental states and physical events in the brain eg. anti-depressant

Question 17

How does SSRI’s work eg. Prozac

Answer 17

Neurotransmitters are chemicals released from the axon that swim across the synapse to carry the “message” to the cell on the other side. Receptors are molecules that protrude from the receiving cell. Each receptor has a specific shape, and the neurotransmitter fits to the receptor like a key. Common neurotransmitters include serotonin, dopamine, norepinephrine, epinephrine (adrenaline), and many others.

When serotonin is released from the “sending” nerve cell, the leftover serotonin is normally reabsorbed by an uptake pump. By blocking the uptake pump, Prozac increases the amount of active serotonin that can be delivered to the “receiving” nerve cell. This means that the neurons steep for a longer period of time in the serotonin you already produce. Prozac selectively affects only serotonin which is why Prozac and other similar drugs are called selective serotonin reuptake inhibitors, or SSRIs.

Another way is blocking the sensor of the axon tells the cell when enough serotonin has been produced. This causes the axon to release even more serotonin, finally over a period of 2-3 weeks, the recieving cell becomes more sensitive to serotonin, at this point the ani-depressanr becomes effective

Question 18

The cerebrum

Answer 18

Cerebrum: the largest part of the brain, which contains the cerebral cortex and several sub-cortical structures including the basal ganglia and the limbic system.

The cerebrum consists of two cerebral hemispheres which are connected by the corpus callosum (a bundle of axons passing electrochemical signals between the hemispheres)

Question 19

cerebral cortext

Answer 19

the outer layer of neural tissue that plays a key role in ‘higher cognition’ such as attention, perception, awareness, thought, memory, language and consciousness. It comprises folded material resulting in gyri and sulci, which are characteristic of large mammalian brains.

Question 20

Pons: bridge

Answer 20

The part of the brainstem that relays signals to the cerebellum that deal with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture

Question 21

What are the 4 Cerebral lobes?

Answer 21

• Temporal
• Frontal
• Parietal
• Occipital

Question 22

Temporal lobe

Answer 22

Responsible for heairng, language, comprehnsion, memory and learning, possibly smell, perception, detection and identification

Question 23

Frontal lobe

Answer 23

The frontal lobe contains most of the dopamine-sensitive neurons in the cerebral cortext; the dopamine system is associated with reward, attention, long term memory, planning and drive

Question 24

Parietal lobe

Answer 24

Associated with bodily sensation such as touch, perception and touch discrimmination, parietal lobe also contains the motor cortex

Question 25

Occipital lobe

Answer 25

It’s is the visual processing centre of the brain

Question 26

Spinal cord:

Answer 26

Outside made of axons, encased in a column of bone called vertebral column; spina; cord ends in a collection of spinal roots (horse tail)

Question 27

Spinal nerves

Answer 27

31 pairs of spinal nerves on each side of the cord, grey matter extend along the length of the cord containing neurons, which send axons to higher levels of CNS

Question 28

Brain stem

Answer 28

Contribution of the spinal cord, made up of medulla, Pons, the mesencephalon and diencephalon

Question 29

Reticular formation

Answer 29

The core of the brainstem and contains a mass of neurons

Question 30

Brodmann’s areas

Answer 30

Clockwise:

Auditory: 41

Motor speech, grammar phonology: 44

Voluntary motor: 4, 6,6,4

Somatic senory: 3, 1, 2

Angular Gyrus: 39

Visual: 17

Question 31

White and Grey Matter

Answer 31

• White matter is composed of bundles of myelinated axons which connect the various grey matter regions together
• Myelin acts as an insulator and hence nerve signals are transmitted at greater speed through white matter
• Grey mater is composed of the neuronal cell bodies and dendrites, as well as unmyelinated nerve fibres
  –> Grey matter functions as the regions of the brain where infomation is processed

Question 32

Infomation processing

Answer 32

The brain is a super system of systems

• Composed of an elaborate interconnection of small but macrocopic cortial regions and sub cortical neuceli
• these are made up of microscopic local circuits (neurons) which are connected by synapses
• The brain makes decisions based on internal and external events
• Different parts of the brain process different types of infomation

Question 33

Connectionist neural net

Answer 33

• Parallel distributed processing (PDP)
• Has important theoretical and pratical consequences
• Items of infomation are not stored at specific sites; they are distributed throughout the whole net

Question 34

Learning according to Toates (2011)

Answer 34

• Acquisition of knowledge or skill triggered in a particular situation
• A form of behaviour which results in the potential to change behaviour
• Results in physical changes in the brain
• Western, priviledge decarlative knowledge

Question 35

Two types of learning

Answer 35

• Non associative
  –> Habituation
  –> Sensitisation
• Associative
  –> Classical conditioning
  –> Operant conditioning

Question 36

Non- Associative learning: Habituation

Answer 36

Habituation: exposure to a situation which results in a change of behaviour, consequence of change at the neural level; habitation has an adaptive value

Presentation of stimulus (eg. noise, puff of air) initially stimulus might result in a response

• Banner blindness: in a phenomenon in web usability where vistors on a website ignore-banner like infomation (Benway and Lane (1998)
• Most basic form of learning
• Decouping of association
• Progressive decline of response to stimulus
• Facilites attention to new simuli

Question 37

Non-associative learning: sensitisation

Answer 37

Progressive response following repeated exposure to stimulus

• Efficient firing of neuron (LTP)
• both adaptive and maladaptive
• eg. pain response= adaptive
• eg. drug sensitivity= maladaptive

Question 38

Associative learning: Classical conditioning

Answer 38

Pavlovian conditoning

• involves the pairing of two stimuli to result in a change if behaviour

example:
Begins with an unconditioning reflex–> eye blinks when exposed to a puff of air—> Pair the puff of the air with the auditory tone –> Eventually just the tone will result in the eye blink

Before conditioning
Unconditioned stimulus (UCS) = ‘air puff’
Unconditioned response (UCR) = ‘eye blink’

Question 39

Long-Term Potentiation (LTP)

Answer 39

• Bliss and Lomo (1973) discovered a persistent strengthening of synapses in the hippocampus of anesthezed rabbits
• Electrical stimulation in the hippocampus produced an increased response (potentiation) in the connecting synapse- a phenomenon they called long-term potentiation

LTP is widely considered one of the major celluar mechanisms that underlies learning and memory

Question 40

Associative LTP

Answer 40

• Activity in presynaotic neurons also influences the ‘sensitivity’ of nearby synapses
• ‘if weak and strong synapse are active simulaneously then the weak synapse will be potentiated’

Diagram
(a) Initially the weak synapse produces only a very small excitatory postsynaptic potential

(b) Associative LTP is induced by simultaneous activation of a strong synapse along with activity in the weak synapse

(c) Later, the much larger excitatory postsynaptic potential indicates that the weak synapse has been potentiated

Researcher’s believe that associative LTP is the basis of classical conditioning – it explains how in Pavlovian conditioning, for example, certain forms of stimuli (bell ringing) can be associated with a response (dog salivating)

Question 41

Operant conditioning

Answer 41

Learning and behaviour can be shaped by external cues and responses

A random response to a particular situation can be shaped as a consequence of :

• Reinforcement is a consequence that causes a behaviour to occur with greater frequency.
• Punishment is a consequence that causes a behaviour to occur with less frequency.
• Extinction is the lack of any consequence following a behaviour . When a behaviour is inconsequential (i.e. producing neither favourable nor unfavourable consequences) it will occur with less frequency.

Question 42

Positive reinforcement

Answer 42

Positive reinforcement (Reinforcement): occurs when a behaviour is followed by a reward, increasing the frequency of that behaviour

Question 43

Negative reinforcment

Answer 43

Negative reinforcement (Escape): occurs when a behaviour is followed by the removal of an aversive stimulus, increasing the frequency of that behaviour

Question 44

Positive punishment

Answer 44

Positive punishment (Punishment): occurs when a behaviour is followed by a stimulus, such as introducing a shock or loud noise, resulting in a decrease in that behaviour

Question 45

Negative punishment

Answer 45

Negative punishment (Penalty): occurs when a behaviour is followed by the removal of a stimulus, such as taking away a child’s toy following an undesired behaviour, resulting in a decrease in that behaviour.

Question 46

The organisation of Behaviour (1949) Donald Hebb

Answer 46

Hebbian learning commonly refers to the adaptation of neurons during the learning process especially synaptic plasticity whereby an increase in synaptic effciency arises from the presynapic cell’s repeated and persistent simulation of the postsynaptic cell

Organisation of behaviour (1949)

• Suggested that learning involved the strengthening of connections between neurons
• Events are represented as activity flow through a neuronal loop
• Repeated activation of two neurons leads to formation and strengthening of a functional link

Question 47

Hebb’s law: ‘Neurons that fire together wire together’

Answer 47

When an axon of cell A is near enough to excite cell B and repeatedly persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency as one of the cells firing B, is inceased

Question 48

Repeated stimulation of synpase results in pre-synaotic and post-synaptic change

Answer 48

Repreated stimulation of synapse results in pre-synpatic and post-synaotic change

• increases the number if receptors
• increases transmitter release
• Increases dendrite density

Question 49

Implications for learning

Answer 49

• Hebbian learning highlights the role of synaptic plasicity in learning as structural changes in neuronal connectivity

The Hebb Synapse:
- Refers to a synapse which has increased in strength due to learning

• Transformation of a neural stimulus to a conditioned stimulus
• Describes a process of long-term changes (LTP)

Question 50

Synaptic pruning - Branching and weeding

Answer 50

Synaptic pruning refers to changes in the neural structure by reducing the overall number of neurons or connections, leaving more efficient synaptic confirgurations

• often used to describe the maturation of behaviour and cognitive intelligence in children in terms of ‘weeding out’ the lesser used synapses

Question 51

Summary

Answer 51

There are different types of learning within biological psychology: associative and non-association learning

• According to Hebb, learning occurs through the forming and strengthening of neural circuits in the brain
• The Hebb synapse highlight the plastcity of learning through building mental associations and making both long-term changes in the brain
• Processes of plasticity are also regulated and shaped by synaptic pruning- a metaphor to describe maturation of behaviour and cognition