Biopsychology

Nervous System

Consists of the central nervous system and peripheral nervous system

Central Nervous System (CNS)

Consists of the brain and the spinal cord and is the origin of all complex commands and decisions

Peripheral Nervous System (PNS)

Sends information to the central nervous system (CNS) from the outside world, and transmits messages from the CNS to muscles and glands in the body

Somatic Nervous System

Transmits information from receptor cells in the sense organs to the CNS. It also receives information from the CNS that directs muscles to act

Autonomic Nervous System

Transmits information to and from internal bodily organs. It’s autonomic as the system operates involuntarily. It has 2 main divisions: the sympathetic and parasympathetic nervous systems

The functions of the nervous system

The nervous system is a specialised network of cells in the human body and is our primary internal communication system. It has 2 main functions:

• To collect, process and respond to information in the environment

• To coordinate the working of different organs and cells in the body

What is the nervous system divided into?

• Central Nervous System

  • Brain

  • Spinal Cord

• Peripheral Nervous System

  • Somatic Nervous System

  • Autonomic Nervous System

    • Sympathetic Nervous System

    • Parasympathetic Nervous System

The Brain

The centre of all conscious awareness. The brain’s outer later, the cerebral cortex, is highly developed in humans and is what distinguishes our higher mental functions from those of animals. The brain is divided into 2 hemispheres

The Spinal Cord

An extension of the brain and is responsible for reflex actions such as pulling your hand away from a hot plate

The function of the peripheral nervous system

It transmits messages, via millions of neurons (nerve cells), to and from the CNS. The PNS is divided further into:

• Autonomic Nervous System (ANS)

• Somatic Nervous System (SNS)

The function of the autonomic nervous system

Governs the vital functions in the body such as breathing, heat rate and digestion

The function of the somatic nervous system

controls muscle movement and receives information from sensory receptors

3 layers of the brain

Central Core- regulates involuntary actions

Cerebrum- regulates our higher intellectual processes

Limbic System- regulates our emotions

4 lobes of the brain

Frontal lobe- planning, decision-making and problem solving

Temporal lobe- processing auditory information

Occipital lobe- visual processing area

Parietal lobe- sensory perception and integration, including the management of the senses

The Endocrine System

Instructs glands to release hormones directly into the bloodstream. The endocrine system acts more slowly but has very widespread and powerful effects

Thyroid Gland

Produces thyroxine which affects the heart rate by increasing it. This increases the metabolic rates and in turn affects growth rates

Pituitary Gland

The master gland because it controls the release of hormones from all the other endocrine gland. It’s located in the brain

Adrenal Gland

Produces adrenaline responsible for the fight-or-flight response

Ovaries

Produces oestrogen and progesterone

Testes

Produces testosterone

Process of fight-or-flight

1. The hypothalamus triggers activity in the sympathetic branch of the autonomic system

2. The ANS changes from its resting state (parasympathetic state) to the physiologically aroused state (sympathetic state)

3. Adrenaline is released from the adrenal medulla into the bloodstream

4. Once the threat has passed, the parasympathetic nervous system returns the body to its resting state

5. The parasympathetic nervous system acts as a ‘brake’ and reduces the activities of the body that were increased by the actions of the sympathetic branch. This is referred to as the rest and digest response

Psychological effects of adrenaline

Increased anxiety, attention and alertness

Physical effects of adrenaline

Increases heart rate and breathing rate, pupils dilating. Digestion and immune system slow down and decreased blood flow to the skin

Neuron

The basic building blocks of the nervous system, neurons are nerve cells that process and transmit messages through electrical and chemical signals. They are specialise to carry neural information. 80% of neurons are located in the brain

3 types of neurons:

• Sensory neuron

• Relay neuron

• Motor neuron

Sensory neuron

Carries messages from the PNS (sensory receptors) to the CNS

Long dendrites and short axons

Relay Neuron

They connect the sensory neuron to the motor neurons or other relay neurons.

They have short axons and short dendrites

Motor Neurons

Connects the CNS to effectors such as muscles and glands

Short dendrites and long axons

Cell body

Includes a nucleus and contains genetic material of the cell. D

Dendrites

They carry nerve impulses from neighbouring neurons towards the cell body

Axon

Carries the impulses away from the cell body down the length of the neuron. It’s covered by a fatty layer of myelin sheath

Myelin Sheath

Covers the axon to protect it and speeds electrical transmission of the impulse. It’s segmented by gaps called the nodes of ranvier

The Nodes of Ranvier

Speeds up transmission of the impulse by forcing it to ‘jump’ across the gaps along the axon

Terminal Buttons

Communicate with the next neuron in the chain across a gap known as synapses

Electric Transmission- the firing of a neuron

When a neuron is in their resting state, the inside of the cell is negatively charged compared to the outside. When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a second causing an action potential to occur

Synaptic Transmission

Synaptic transmission is how neurons communicate with each other. Information is passed down the axon of the presynaptic neuron as an electrical impulse known as an action potential. Once the action potential reaches the end of the axon, where the synaptic vesicles, it releases chemical messengers known as neurotransmitters. The neurotransmitters carry the signal across the synaptic gap and binds to the receptor sites on the post-synaptic neuron. Once the receptors have been activated, summation happens to determine whether the post-synaptic neuron produces an inhibitory or excitatory effect making them more or less likely to fire.

Excitation

A neurotransmitter, like adrenaline, increases the positive charge of the post-synaptic neuron. This increases the likelihood that the neuron will fire and pass on the electrical impulse

Inhibitor

A neurotransmitter, like serotonin, makes the charge on the post-synaptic neuron more negative. This decreases the likelihood that the neuron will fire and pass the electrical impulse

Evaluation of the fight-or-flight response

• The ‘tend and befriend’ response

• Negative consequences

• ‘Fight or flight’ doesn’t tell the whole story

• Positive rather than ‘fight or flight’ behaviours

• A genetic basis to sex differences in the fight-or-flight response

The ‘tend and befriend’ response

Taylor et al (2000) suggests that female have a different reposes than ‘fight or flight’ called ‘tend and befriend’. This involves protecting themselves and their young through nurturing behaviours and forming protective alliances with other women. Fleeing at any sign of danger would put the female’s offspring at risk

Negative consequences of fight or flight response

It’s maladaptive in modern world situations. Frequently triggered by stimuli that you can’t run away from or fight like exams. Causing acute stress in the short term and chronic stress in the long term

Fight or flight doesn’t tell the whole story

Gray (1988) argues that the first phase of reaction to a threat is not fight or flee but to avoid confrontation. He suggests prior to attacking or running away, we display the ‘freeze response’ which focuses attention and makes them look for new information in order to make the best response for that particular threat

Positive rather than fight or flight behaviours

Von Dawans et al (2012) challenged the view that under stress, men respond only with ‘fight or flight’ while women are prone to ‘tend and befriend’. Von Dawans et al found that acute stress can lead to greater cooperative and friendly behaviour in both men and women.

A genetic basis to sex differences in the fight or flight response

Lee and Harley (2012) found the SRY gene, found exclusively on the male Y chromosome directs male development promoting aggression and resulting in the fight or flight response to stress. The SRY gene may prime males to respond to stress in this way but the absence of the SRY gene in females prevents this response to stress leading to the ‘tend and befriend’ behaviour

Localisation of Function

Specific areas of the brain are associated with particular physical and psychological function

Contralateral

Each hemisphere of the brain control the opposite side of the body

Motor Cortex

Voluntary muscle motor movements across the body. Its contralateral. It’s in the frontal lobe

Damage: loss of muscle function or if severe then paralysis

Somatosensory Cortex

An area of the parietal lobe that receives sense impressions from around the body. Its contralateral

Damage: loss of sensation in opposite side to damage

Broca’s Area

An area of the frontal lobe in the left hemisphere that is responsible for speech production.

Damage: expressive aphasia/ difficulty producing fluent speech

Wernicke’s Area

An area of the temporal lobe in the left hemisphere that is responsible for speech comprehension

Damage: receptive aphasia/ difficulty understanding speech

Auditory Cortex

Located in the temporal lobe and receives and processes sound information from ears

Visual Cortex

Visual processing each hemisphere receives information from opposite visual field. Located in the occipital lobe

Label areas of the brain

A- Motor Cortex

B- Somatosensory Cortex

C- Broca’a Area

D- Wernicke’s Area

E- Auditory Cortex

F- Visual Cortex

Holistic Theory

Before the discoveries made by Broca and Wernicke, scientists believed that all parts of the brain were involved in the processing of thoughts and actions

The Cerebral Cortex

This separates us from animals as human cortex is much more developed. The cortex appears grey due to the location of the cell bodies, hence the name grey matter

Evaluation of Localisation

• Brain scans evidence

• Neurosurgical evidence

• Case Study: Phineas Gage

• Equipotentiality Theory

• Aphasia studies

• Individual Differences

• Language production may not be confined to Broca’s area

Brain scans evidence

Peterson et al (1988) used brain scans to show how Wernicke’s area was active during a listening task and how Broca’s area was active during a reading task. Tulving et al (1994) revealed semantic and episodic memories reside in different parts of the prefrontal cortex

Neurosurgical evidence

Post-mortem confirm the function of Broca’s area. Walter Freeman tried severing connections in the frontal lobe in an attempt to control aggression. Dougherty et al (2002) reported 44 people with OCD had lesioned their cingulate gyrus. After 32 weeks, a third had a successful response and 14 had a partial successful response

Case Study evidence

Clinical case study research demonstrate the loss of a function if damage is caused to particular areas e.g Clive Wearing and Expressive and Receptive Aphasia Studies

Phineas Gage turned from a calm, reserved person to a quick-tempered and rude person after most of his frontal lobe was removed by the iron pole through his brain

Equipotentiality Theory

Lashley suggested that basic motor and sensory functions are localised but higher mental functions aren’t. He claimed that intact areas of the cortex could take over responsibility for specific cognitive functions following injury to the are normally responsible for that function

Aphasia Studies

• Expressive Aphasia is an impaired ability to produce language. This is caused by damage to Broca’s area

• Receptive Aphasia is an impaired ability to understand language; an inability to extract meaning from spoken or written words. This is caused by damage to Wernicke’s area

Individual Differences in Broca and Wernicke’s area

Bavelier et al (1997) found considerable variability of activation across different individuals when reading. They observed activity in the right temporal, left frontal, temporal and occipital lobes.

Harasty et al (1997) found that women have larger Broca and Wernicke’s areas

Language production may not be confined to Broca’s area alone

Dronkers et al (2007) re-examined the preserved brain of 2 of Broca’s patients including Tan. They used modern high-resolution brain MRI imaging. The MRIs found that other areas besides Broca’s area could have contributed to the reduced speech abilities. Damage to Broca’s area causes temporary speech disruption not severe disruption of spoken language

Hemispheric Lateralisation

Each hemisphere of the brain is specialised to perform different functions

Split-brain research

Research that studies individuals who have been subjected to the surgical separation of the 2 hemispheres of the brain as a result of severing the corpus callosum

Split-brain study

Sperry (1968) studied a unique group of individuals, all of whom have had their corpus callosums severed to separate the 2 hemispheres and control frequent and severe epileptic seizures.

Procedure of Sperry (1968)

An image or word will be projected to an individual’s right visual field and the same or different image could be projected to the individual’s left visual field. In the normal brain, the information would be conveyed to the other hemisphere through the corpus callosum, but for split brain patients the information can’t be transferred between the 2 hemispheres

Findings of Sperry (1968)

When a picture of an object was shown to the right visual field, they could easily describe what they saw. If it was shown to the left visual field, they couldn’t describe it but could draw it and recognise it.

Evaluation of lateralisation

• Related to neural capacity

• Lateralisation and immune system functioning

• Lateralisation changes with age

Related to increased neural capacity

By using only 1 hemisphere to engage in a particular task, this would leave the other hemisphere free to engage in another function. Rogers et al (2004) found that in chickens brain lateralisation has an enhanced ability to perform 2 tasks simultaneously

Lateralisation and immune system functioning

Architects and the mathematically gifted tend to have superior right-hemispheric skills but are also much more likely to be left-handed and to suffer higher rates of allergies and immune system problems.

Tonnessen et al (1993) found a small but significant relationship between handedness and immune system disorder

Lateralisation changes with age

Lateralised patterns found in younger individuals tend to switch to bilateral patterns in healthy older adults. Szaflarski et al (2006) found that language became more lateralised to the left hemisphere with increasing age but after the age of 25, lateralisation decreases with each decade

Evaluation of split-brain research

• Demonstrated lateralised brain functions

• Strengths of the methodology

• Issues with generalisability

• Language may not be restricted to the left hemisphere

Demonstrated lateralised brain functions

Sperry and Gazzaniga’s work produced a lot of evidence that the left hemisphere is geared towards analytic and verbal tasks while the right hemisphere performs spatial and music tasks. The right hemisphere can only produce rudimentary words and phrases but contributes emotional and holistic content to language

The left hemisphere is the analyser and the right hemisphere is the synthesiser

Strengths of the methodology

They used high specialised and standardised procedures. This increased the replicability of the study. Sperry varied aspects of the basic procedure and ensured only hemisphere was receiving the information. Thus he developed a very useful and well-controlled procedure

Issues with generalisability

Split-brain research is rarely carried out nowadays. Andrewes (2001) pointed out that many studies are presented with as few as 3 participants or even just 1 participant. Some conclusions have been drawn from individuals who either have a confounding physical disorder that made split-brain procedure necessary. Only 11 took part in all the variations of the studies

Language may not be restricted to the left hemisphere

Turk et al (2002) found that a patient J.W. developed the capacity to speak out of the right hemisphere with the result that he can now speak about information presented to the left or right brain

Plasticity

The brain adapts its function and structure as a result of a change in the environment

4 reasons for plasticity

• Learning new skills

• A result of developmental changes

• Response to direct trauma to the area of the brain

• Response to indirect effects of damage like brain swelling

Synaptic Pruning

Synapses that are used frequently become stronger over time and unused synaptic connections are lost

Functional Recovery

The functions that were performed by areas of the brain that are lost or damaged are performed by undamaged areas of the brain

Axonal sprouting

Existing neurons grow new axons to connect to other neurons

Research into plasticity

Maguire et al (2000) studied the brains of London taxi drivers and found significantly more grey matter in the posterior hippocampus. This part of the brain is associated with the development of spatial and navigational skills in humans and animals.

Draganski et al (2006) imaged the brains of medical students 3 months before and after exams. Learning-induced changes were seen to have occurred in the posterior hippocampus and the parietal cortex

Factors affecting functional recovery

• Age- children are more likely to recover

• Gender- women are more likely to recover

• Access to rehabilitative therapy

What happens in the brain during recovery?

The brain is able to rewire and reorganise itself by forming new synaptic connections close to the area of damage. Secondary neural pathways that wouldn’t typically be used to carry out certain functions are activated or ‘unmasked’ to enable functioning to continue often in the same way as before. There are a number of structural changes in the brain:

• Axonal Sprouting: the growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways

• Reformation of blood vessels

• Recruitment of homologous (similar) areas on the opposite side of the brain to perform specific tasks. E.g. if Broca’s area was damaged, a right-side equivalent will carry out its functions and then after a while functionality might shift back to the left

Evaluation of Plasticity

• Practical Application

• Support from animal studies

• Negative plasticity

• Age and plasticity

Practical Application

Following illness or injury to the brain, spontaneous recovery tends to slow down after a number of weeks so forms of physical therapy may be required. Techniques may include movement therapy and electrical stimulation of the brain. This shows that although the brain has the capacity to fix itself to a point, the process requires further intervention to be completely successful

Negative Plasticity

The brain’s ability to rewire itself may be maladaptive. Prolonged drug use has been shown to result in poorer cognitive functioning as well as an increased risk of dementia later in life.

60-80% of amputees develop phantom limb syndrome

Age and Plasticity

Functional plasticity reduces with age. The brain has a greater propensity for reorganisation in childhood as it’s constantly adapting to new experiences and learning. Ladine Bezzola et al (2012) demonstrated how 40 hours of golf training produced changes in the neural representation of movement in participants aged 40-60. This showed that neural plasticity does continue through the lifespan

Support from animal studies

Kempermann et al (1998) suggested that an enriched environment could alter the number of neurons in the brain. They found evidence of an increased number of new neurons particularly in the hippocampus in rats housed in complex environments compared to rats in laboratory cages

Evaluation of functional recovery

• Support from animal studies

• Age differences in functional recovery

• Educational attainment and functional recovery

Support from animal studies

Tajiri et al (2013) randomly assigned rats with traumatic brain injury to 1 of 2 groups. 1 group received transplanted stem cells and the other received no stem cells. 3 months later, the brains of stem celled rats showed clear development of neurone-like cells in the area of injury

Age differences in function recovery

Functional plasticity reduces with age. According to this view, the only option following an injury beyond childhood is to develop compensatory behavioural strategies to work around the deficit (such as seeking social support). However, studies have suggested that even abilities commonly thought to be fixed in childhood can still be modified in adults with intense retraining

Educational Attainment and Functional Recovery

Schneider et al (2014) found that patients with the equivalent of a college education are 7x more likely than those who didn't finish high school to be disability-free one year after a moderate to severe traumatic brain injury

4 ways of investigating the brain

• fMRIs

• EEGs- Electroencephalogram

• ERPs- Event-related potentials

• Post-mortems

fMRIs

Works by detecting the changes in the blood oxygen levels and flow that occur as a result of neural (brain) activity in specific parts of the brain. When a brain area is more active it consumes more oxygen and to meet this increased demand, blood flow is directed to the active area.

fMRI produces 3-dimensional images (activation maps) showing which parts of the brain are involved in a particular mental processes and this has important implications for our understanding of localisation of functions

Strengths of fMRIs

• It doesn’t use radiation- it’s risk-free, non-invasive and straightforward to use

• Produces images with very high spatial resolution- depicting detail by mm and provides a clear picture of how brain activity is localised

• Offers a more objective and reliable measure of psychological processes than is possible with verbal reports

• Precisely identifies brain regions and patterns of activation over time

Weaknesses of fMRIs

• It’s expensive and can only capture a clear image if the person stays still

• Poor temporal resolution- there’s a 5 second time lag behind the image on screen and the initial firing of neuronal activity

• Only measures blood flow in the brain and doesn’t hone in on the activity of individual neurons, so it’s difficult to tell exactly what kind of brain activity is being represented

EEGs (Electroencephalogram)

Measure electrical activity in the brain via electrodes that are fixed to an individual’s scalp using skull caps. The scan recording represents the brainwave patterns that are generated from the action of millions of neurons, providing an overall account of brain activity. EEG is often used by clinicians as a diagnostic tool as unusual rhythmic patterns of activity may indicate neurological abnormalities like epilepsy, tumours or disorders of sleep

Strengths of EEGs

• Invaluable in the diagnosis of conditions like epilepsy

• It has contributed to our understanding of the stages of sleep

• High temporal resolution

• Can accurately detect brain activity at a resolution of a single millisecond

• Cheaper than fMRI

• Can be used while the participant completes a task

• Provides a recording of the brain’s activity in real time rather than a still image of the passive brain