Psychology AOS2 (copy)

Meninges

Meninges

Three membrane layers covering the brain to protect it

Cerebrospinal fluid

A watery-like liquid that circulates between the membranes

Blood-brain barrier

A barrier formed between capillaries to limit the entry of potentially harmful substances in blood

Grey matter

Darker areas of the brain → composed of nerve cell bodies and their local connections to each other

White matter

Lighter areas of the brain → composed of nerve fibres that connect distant brain areas to one another

Brain versus Heart Debate

Is our brain or heart the source of our thoughts, feelings, and behaviours?

• Egyptians didn’t think the brain had any role at all

• Debate originated from Greek philosophers Alcmaeon (brain) and Empedocles (heart)

• Brain hypothesis is now universally accepted

Mind-Body Problem

Are the mind and body distinct, separate entities or are they one and the same thing?

• Greek philosophers believed they were separate →mind could control the body but not vice versa

• Descartes proposed dualism theory to argue that they are separate entities but interact with each other

• No universally accepted solution

Phrenology

Study of the relationship between the skull’s surface features and a person’s personality and behavioural characteristics

• Franz Gall & Johann Spurzheim thought certain parts of the brain control different traits → as this part of the brain develops it produces a bump in the skull that can be observed externally

• Evidence was biased, there is no scientific research to support this theory

Brain ablation

Destruction or removal of part of the brain

Brain lesioning

Disruption or damaging the normal structure or function of part of the brain

Electrical stimulation of the brain

Electrical activity in the brain is simulated or detected using an electrode → if electrical stimulation of a specific brain area initiates a response, then that area must control that response

Split brain experiments

The band of nerve tissue connecting the two hemispheres of the brain (corpus callosum) is cut

• Information is not able to cross to other hemisphere → this impacts ability to communicate what has been seen in the left visual field since speech centres are in the left hemisphere

Computerised Tomography (CT)

Structural imaging

• Uses x-ray equipment to scan the brain

• Creates images of horizontal cross sections of the brain

• Used for: identifying brain abnormalities and injuries

Magnetic Resonance imaging (MRI)

Structural imaging

• Uses magnetic field to vibrate atoms in the brains neurons and generate a computer image

• Clearer and more detailed than a CT

• Used for: diagnosing structural abnormalities, can display extremely small changes

Positron Emission Tomography (PET)

Functional imaging

• Produces colour images that show brain structure, activity, and function

• Records level of brain activity while participant is doing a task

• Injects a glucose solution with radioactive tracer into blood stream → increased blood flow = high neuronal activity

Function Magnetic Resonance imaging (fMRI)

Functional imaging

• Detects and records brain activity by measuring oxygen consumption → more oxygenated blood = higher activity

• Produces more detailed and precise images than PET scan

• Preferred for psychological research → can take many images in rapid succession detecting changes as they occur

Structural Neuroimaging

Produce images/scans showing brain structure and anatomy

• CT and MRI

Functional Neuroimaging

Provide information about brain structure & function by showing the brain at work

• PET and fMRI

Hindbrain function & main structures

Control or influence various motor functions and vital bodily functions

• Medulla

• Pons

• Cerebellum

Midbrain function & main structures

Structures involved with movement, processing of sensory information, sleep and arousal

• Substantia nigra

• Reticular formation

Forebrain function & main structures

Regulates complex cognitive processes as well as various aspects of emotion and personality

• Hypothalamus

• Thalamus

• Cerebrum & Cerebral cortex

Medulla

Controls vital bodily functions

Pons

Involved in sleep, dreaming and waking, helps control breathing and coordination

Cerebellum

Coordinates fine muscle movements, regulates posture and balance

Substantia Nigra

Important role in the control of voluntary limb movements

Reticular Formation

Screens incoming information to not overload the brain, helps maintain consciousness and regulates arousal & muscle tone

• Reticular activating system (RAS)

Hypothalamus

Maintaining homeostasis → regulate release of hormones and influence behaviours associated with basic biological needs, involved in emotions such as anger and fear

Thalamus

Filters sensory information and passes it to relevant areas of the brain for further processing - relay station

Cerebrum/Cerebral Cortex

Primarily responsible for almost everything we consciously think, feeling, and do

• Divided into 2 hemispheres, each hemisphere divided into 4 lobes

Roles of the cerebral cortex

Complex mental abilities → learning, memory, language, problem solving etc

Processing sensory information (sensory areas)

Planning and controlling voluntary movement (motor areas)

More complex functions controlled by areas surrounding sensory & motor areas (association areas)

Contralateral function

Left hemisphere controls and receives sensory information from the right side of the body

Right hemisphere controls and receives sensory information from the left side of the body

Left hemisphere specialisations

Verbal and analytical functions

• verbal tasks → speech production & comprehension, reading, writing

• analytical tasks → maths, sequential tasks, evaluation

• logical reasoning

Right hemisphere specialisations

Non-verbal functions

• spatial & visual thinking → puzzles, map reading, visualisation of a place

• creativity & fantasy

• recognising emotions

• appreciation of art & music

Frontal lobe

Prefrontal cortex: occupies most of the frontal lobe, involved with sophisticated mental abilities (reasoning, planning, problem solving), personality and regulation and expression of emotion

Primary motor cortex: initiates and controls voluntary movements

Broca’s area: speech production

Parietal lobe

Primary somatosensory cortex: receives and processes sensory information from the skin and body parts

Occipital lobe

Primary visual cortex: processes visual sensory information

Temporal lobe

Primary auditory cortex: receives and processes sound → different areas are specialised to identify different sounds

Wernicke’s area: speech comprehension

Neuroplasticity

The ability of the brain and other parts of the nervous system to change in response to experience

Synapse

The site where adjacent neurons communicate by transmitting neural signals to one another

Experience-expectant plasticity

Brain change in response to environmental experience that is ordinarily expected → if experience does not occur when expected the brain may not develop as it should

Experience-dependent plasticty

Involves brain change that modifies some part of its neuronal structure that is already present → depends on exposure to unique environmental experiences and may occur at any stage during the lifespan

Neuroplasticity in response to brain injury

Depends on cause, location, degree and extent of damage, age at which injury occurs

→ neurodegenerative disorders are not preventable

→ injuries to hind brain structures/brain stem are not recoverable

→ neuroplasticity works better when younger

Generation of new networks

Neuronal connections and networks that have been disrupted by injury may change by forming new connections

Brain function lost through injury is rerouted via new connections → for these connections to form they need to be stimulated through repeated activity

Reassignment of function

Functions that were performed by certain areas of the brain can be reassigned to other undamaged areas of the brain

Neurogenesis

The production of new neurons

Brain injury

Any type of brain damage or disorder that impairs or interferes with the normal functioning of the brain, either temporarily or permanently e.g. neurodegenerative disorders, traumatic brain injuries, etc

Acquired brain injury

A brain injury acquired after birth → used to differentiate between brain injury from neurodevelopment disorders that people are born with

• Can have sudden or insidious onset

Traumatic brain injury

A type of acquired brain injury that occurs when an external force causes damage to the brain

• Damage can be caused by a single event of repeated events

• Phineas Gage → metal rod went through his cheek into his frontal lobes

Biological changes from ABI

• movement disorders

• dizziness and balance problems

• eyesight, hearing problems

• impaired speech, reading, writing,

• fatigue and sleep problems

• hormonal imbalances

Psychological changes from ABI

• memory problems

• difficulty problem-solving

• poor concentration and attention

• reduced ability to organise and plan

• lack of insight and awareness, and poor judgment

• personality changes

• mood disturbance, e.g. irritability, anger

Social changes from ABI

• social isolation, e.g. difficulties in making and keeping friends

• disrupted family relationships

• different educational opportunities

• financial hardship

• legal restrictions

• social stigma

Aphasia

A language disorder that results from an ABI to an area responsible for language production or processing

Usually caused by stroke or neurodegenerative disorders

Fluent Aphasia

Damage to Wernicke’s area

• Difficulty understanding spoken and/or written language

• Can produce fluent but incoherent speech

• Little to no consciousness of their condition

Non-fluent aphasia

Damage to Broca’s area

• Considerable difficulty producing speech → speech is laboured and hesitant and usually consists of just the main words in the sentence

• Comprehension is not impaired

• Usually aware of their condition

Stroke

Occurs when blood supply to part of the brain is interrupted which deprives the brain of oxygen

• Ischaemic → when blood supply to the brain is restricted or stopped in one of the blood vessels because it is blocked often by a blood clot

• Haemorrhagic → when a blood vessel supplying the brain becomes weak and bursts, causing bleeding in the brain

Effect of stoke depends on the individual, type of stroke, and location of the blocked or burst artery (hemisphere & lobe/cortex)

• Can lead to permanent brain damage, disability or death

Symptoms of stroke

• numbness or weakness in the face, arm, or leg

• speech disturbance

• trouble walking, dizziness, loss of balance or lack of coordination

• trouble seeing in one or both eyes

• headache, usually severe with no known cause

• difficulty swallowing

• nausea or vomiting

Diagnosis and treatment of stroke

F - facial droop

A - arms above head

S - speech disruptions

T - time to call 000

• No medical way to repair damage but skills can be relearned through rehabilitation

Neurological disorders

Diseases of the nervous system (brain, spinal cord, central/peripheral nervous system)

Epilepsy

A neurological disorder involving recurrent, spontaneous seizures brought on by interference in normal brain activity

• Seizures are triggered by bursts of electrical activity from clusters of neurons that start and spread throughout the brain

• Considered a spectrum disorder because of different causes, different types of seizures, ability to vary in severity and impact people differently

Symptoms of epilepsy

Onset of an aura → an unusual subjective, perceptual, or motor experience

Loss of consciousness → a loss of awareness, brief moment to complete loss

Movement → abnormal movements

Focal seizures

Originate in one brain area in one hemisphere and affect the part of the body controlled by that area

• usually lasts for less than 2 minutes

• can spread to both hemispheres

Generalised seizure

Originates in both hemispheres simultaneously and involves the whole body

• no focal onset

• almost always affect awareness, loss of consciousness is common

Seizures with unknown onset

Neither focal or generalised because onset of seizure is not known

• due to insufficient evidence to diagnose or unusual seizure symptoms

Causes of epilepsy

Anything that disrupts the normal pattern of neuronal activity in the brain can lead to seizures

• traumatic brain injury

• lack of oxygen to the brain for long period

• brain infection

• brain abnormality at birth

• brain tumour

• neurodegenerative diseases

• genetic factors

Epilepsy is idiopathic in at least half of all cases

Diagnosis and treatment of epilepsy

Diagnosis: involves assessment of brain’s electrical activity using an EEG and brain scans such as CT or MRI

Treatment: epilepsy cannot be cured but effect/number of seizures can be reduced with treatments such as anti-epileptic medication and brain stimulation (Vagus Nerve Stimulation, Responsive Neurostimulation, Deep Brain Stimulation)

Concussion

A type of TBI caused by a blow to the head or by a hit to the body that causes the head and brain to move rapidly back and forth

• Not life threatening and usually short lived

Chronic traumatic encephalopathy (CTE)

A progressive brain degeneration and fatal condition thought to be caused by repeated blows to the head/repeated episodes of concussion.

Symptoms of CTE

• loss of memory

• mood/personality changes

• difficulty controlling impulsive or erratic behaviour

• increasing confusion and disorientation

• difficulty thinking - making decisions, impaired judgements

• motor impairments - tremor, slow movement, slurred speech

Diagnosis of CTE

Cannot be diagnosed in a living person, only during an autopsy → diagnosis is based on a history of contact sports, symptoms, repeated concussions

• Autopsy may show atrophy of the brain and/or a build up of tau protein that interferes with the functioning of neurons

CTE research

CTE is not very well understood and it an emerging area of research

• uncertain about the number and types of head injuries that increase the risk of CTE

• not all athletes who experience repeated concussions develop CTE

• CTE has been diagnosed in people without a history of brain injuries

• contribution of confounding variables (e.g. genetic predisposition, alcohol/drug use, co-existing dementia) is not accounted for in research