Psych - The Brain

Brain ablation

Involves disabling, destroying or removing selected brain tissue followed by an assessment of subsequent changes in behaviour

Benefits: provides evidence that different parts of the brain were responsible for different functions

Limitation: Extremely unethical

Brain lesioning

Involves disrupting or damaging part of the brain. This may be a small area of brain tissue or a specific structure.

Benefits: may be an effective treatment for brain-related disorders that are not responsive to other treatments

Limitation: the surrounding areas may be damaged too

Electrical stimulation of the brain (ESB)

Is the stimulation or detection of electrical activity in the brain using electrons

Split-brain experiments

involve cutting the band of tissue that connects the left and right hemispheres. This tissue is called the corpus callosum.

Benefit: Minimal impact on everyday mental abilities.

Limitation: Invasive and irreversible

Neuroimaging techniques

are non-invasive techniques for capturing images or scans of the brain.

CT (Computerised Tomography) Scan

A neuroimaging technique that uses x-ray equipment to scan the brain at different angles and build up a picture of the brain.

Advantages:

• non-invasive

• radiation dose is considered harmless

• useful for identifying precise location and extent for damage or abnormalities

Disadvantages:

• patient must lie still

• created 2D images

MRI (Magnetic resonance imaging)

A neuroimaging technique that uses harmless magnetic fields to vibrate atoms in the brain’s neurons and generate a computer image of the brain.

Advantages:

• more sensitive, detailed and clear than a CT

• doesn’t use x-rays or radiation

• non-invasive and harmless

Disadvantages:

• can’t be used by people who have internal metallic devices

• only shows brain structure not function

• costly

Position Emissions Tomography (PET)

A neuroimaging technique that produces 2D and 3D colour images showing brain structure, activity and function

Advantages:

• shows brain function

• can compare ‘normal’ and mentally ill brains

• shows detailed images as it works

Disadvantages:

• required injection of radiation (harmless)

• need 40 second breaks inbetween and takes 30 seconds to complete a scan, therefore, may not pick up rapid changes

Functional magnetic resonance imaging (fMRI)

A neuroimaging technique that detects and produces images of brain activity by measuring oxygen consumption across the brain

Advantages:

• does not require exposure to radiation

• easy to interpret with the use of colour coding

Disadvantage:

• costly

• There is no scope for cause-and-effect relationship between active and inactive areas and mental processes and behaviours under investigation

The hindbrain

Main job: controls survival functions and coordination

Pons: are involved in sleeping, dreaming and waking, as well as helping to control breathing and coordination of some muscle movements

Medulla: controls vitals, heart rate, blood pressure, vomiting, saliva, and body functions such as breathing, swallowing, coughing and sneezing

Cerebellum: coordinates fine muscle movements and regulates posture and balance. Damage to the cerebellum makes it difficult to move limbs smoothly, speak without slurring and maintain balance.

The midbrain

Main job: relay station and information processing

The reticular formation helps screen incoming information so the brain isn’t overloaded. It alerts the brain to important sensory information and helps maintain consciousness. Also controls sleep and arousal. Severe damage can include a coma.

The forebrain

Main job: thinking, emotions, memory and control of the body

Hypothalamus: It has a vital role in maintaining the body’s internal environment. This includes regulation of body temperature, hunger and hormones. Damage could result in an inability to regulate internal body functions, problems with the normal sleep and waking cycle, an overwhelming urge to eat, or the degeneration of sex organs and a significant reduction in sex drive.

Thalamus: relay station in the brain for incoming sensory information (except smell) and for information from the cerebral cortex to lower brain structures. Damage may result in coma, visual or hearing impairment, or an inability to feel sensation when touched

Cerebrum: consists of an outer surface called the cerebral cortex and masses of neural tissue where neurons form connections with each other and receive and process incoming and ongoing information. Primarily responsible for almost everything we consciously think, feel, and do. Divided into two cerebral hemispheres, connected by the corpus callosum which enables information exchange.

Cerebral hemispheres

The left hemisphere receives sensory information from the right side of the body and controls movements on the right.

The right hemisphere receives sensory information from the left side of the body and controls movements on the left.

Left hemisphere: Language, logical, math, facts

Right hemisphere: spatial awareness, art, emotion, context

Hemispheric specialisation

is the idea that one hemisphere has specialised functions or has greater control over a particular function.

Cerebral cortex

It is involved with complex mental abilities such as perception, learning, memory, language, thinking and planning.

The frontal lobe

It is the largest of the four lobes and is located in the upper half of each hemisphere. Where all higher thinking/cognitive abilities happen

Prefrontal cortex: higher mental functioning such as thinking, organising, planning, abstract thinking, judging and deciding. Associated with emotional behaviour and certain personality characteristics.

Primary motor cortex: directs and controls movements of the skeletal muscles. The amount of motor cortex devoted to a body part is related to the precision of movement, not the size of the body part

Broca’s area: located in the left frontal lobe. Crucial role in the production of clear and fluent speech. Damage to Broca’s area causes Broca’s Aphasia, an inability to produce fluent speech but without disruption to comprehension of spoken or written words.

The parietal lobe

Receives and processes information from bodily sensory receptors.

• Damage to the right parietal lobe can cause spatial neglect. Spatial neglect is an attentional disorder in which the suffer fails to notice or attend to stimuli on the left side of their body

Primary somatosensory cortex: receives sensory information from receptor cells in the skin and body. The amount of space devoted to each body part corresponds to its sensitivity.

The occipital lobe

Is devoted to processing visual information.

Primary visual cortex: receives information from visual sensory receptors located on the retina at the back of the eye

The temporal lobe

is involved in auditory perception, memory and emotional responses.

Primary auditory cortex: receives and processes sounds from both ears, enabling us to detect and identify different sounds

Wernicke’s Area: Located in the left temporal lobe. Has a crucial role in the comprehension of speech. It is responsible for understanding spoken/written words and putting them into meaningful sentences. Damage to Wernicke’s Area is called Wernicke’s Aphasia, an inability to comprehend the meanings of spoken words or written language. Speech production or fluency of speech is not disrupted, however, the person’s speech is meaningless.

Broca’s vs Wernicke’s Aphasia

Brocas’s Aphasia:

• difficulties with speech production without disruption to comprehension of language

• speech is slow, requires concentration and effort

• very short sentences and mostly nouns and verbs

Wernicke’s Aphasia:

• difficulty with speech comprehension and speaking meaningfully

• production or fluency is not disrupted

• can string long word sequences and phrases but not in an understandable way

Neuroplasticity

Refers to the ability of the brain and other parts of the nervous system to change in response to experience. This includes the brain’s capacity to recover from or compensate for the loss of function through injury.

Neurons can abandon a lost connection to seek a new active neuron (rerouting) and grow additional dendrites to reach new neurons (sprouting).

Developmental plasticity

refers to changes in neural connections that occur as the brain grows and develops. This is why children learn new skills far quicker than adults.

Adaptive plasticity

refers to changes in neural connection due to experience and/or to compensate for damage/injury.

Factors influencing brain plasticity

• Experience-expectant plasticity

involves brain change in response to environmental experience that is expected across lifespan development.

• Experience-dependent plasticity

involves brain change that modifies some part of the neuronal structure that is already present.

Neuroplasticity in response to brain injury

After a brain injury, the following types of changes occur for the brain to recover and reorganise its structure. These changes involve adaptive plasticity.

• Generation of new networks (sprouting and rerouting)

• reassignment of function (use other brain areas)

• neurogenesis

Generation of new networks (sprouting and rerouting)

• Sprouting is the ability of a neuron to develop new branches on the dendrites or axons.

• Rerouting is a neuron’s ability to form a new connection with another undamaged neuron.

Reassignment of function (use other brain areas)

• The brain can sometimes be reassigned to other undamaged areas of the brain to compensate for changing input from the environment

Neurogenesis

• the production of ‘new neurons’ in the brain

• these new neurons migrate to other brain areas where they become part of the circuitry

Case Studies

Jody Miller:

• Jody was a normal little girl until the age of 3 (she lost control of the left side)

• until she started to have seizures (she was diagnosed with rasmussen’s encephalitis)

• ending in her having to get her right hemisphere of the brain removed (a surgery called hemispherectomy)

• after the surgery, Jody’s brain adapted, called adaptive plasticity, and could practically use the left side of her body like normal, with a lot of physical therapy

Cameron Mott:

• Cameron was born as a healthy baby, and until her life changed at the age of 3

• diagnosed with Rasmussen’s syndrome, she would have many seizures a day

• She stopped talking, and her cognitive abilities started to decline

• she had surgery and had her right hemisphere removed

• She woke with the left side of her body paralysed

• With lots of physical therapy, her left brain adapted and compensated for the removal of her right hemisphere, and now she is practically a normal girl

Impact of an acquired brain injury

Brain injury refers to damage that impairs and/or interferes with the normal functioning of our brain

• this impairment can be temporary or permanent and attained in many ways acquired brain injury is a term we use to differentiate between brain injury and neurodevelopmental disorders which are obtained at birth.

• It’s a brain injury sustained after birth

• traumatic brain injury are caused by a blow to the head or by the head being forced to move rapidly forward or backward (usually with some loss of consciousness)

Impact on Biological Functions

Biological functioning can be observed through changes in:

• behaviour including motor activities

• organ function

• cellular and neuronal function

eg:

• seizures

• movement impairment

• smell impairment

Impact on Psychological Functions

Psychological functioning can be observed through changes in:

• cognition

• behaviour

• emotions

eg.

• memory loss

• personality changes

• increased susceptibility to mental health disorders

Impact on Social Functions

Social functioning can be observed through changes in:

• relationships

• interactions with the environment

• interpersonal skills

eg.

• job productivity

• social support

• antisocial behaviour

Phineas Gage case study

Biological: physical trauma to the frontal lobe, initial uncontrolled shaking and seizures, loss of brain tissue, bone and left eyesight

Psychological: extreme personality shift. loss of emotional regulation and executive function moved from being quiet spoken to impatient, aggressive and irresponsible

Social: breakdown of interpersonal skills became ‘hard to get along with’ used crude language, leading friends to claim ‘he was no longer Gage’

Aphasia

Is a language disorder that results from an acquired brain injury to an area responsible for language production.