Biopsychology

Localisation of brain function

Localisation of brain function

Different areas of the brain are responsible for different behaviours, cognitive processes or activities

Brain lobes

Frontal lobe, parietal lobe, occipital lobe, temporal lobe

Frontal lobe

Front section of the brain, contains: Broca's area (left hemisphere), motor cortex.

Parietal lobe

Top middle section of the brain, contains: somatosensory cortex. Separated from frontal lobe by central sulcus

Occipital lobe

Back of the brain, contains: visual centres

Temporal lobe

Bottom middle of the brain (by your temples), contains: primary auditory cortex, Wernickes area (left hemisphere)

Somatosensory cortex

Processes input from sensory receptors in the body that are sensitive to touch. Produces sensations of touch, pressure, pain and temp which it localises to specific body regions

Visual centres

Receives and processes visual information, visual cortex contains several different areas, with each processing different types of visual info, e.g. colour, shape, movement

Auditory centres

Analyses speech-based info, i.e. hearing. Damage to auditory cortex may cause hearing loss; more extensive damage = more extensive loss

Motor cortex

Responsible for generation of voluntary motor movement. Different parts of it contain different parts of body, they're arranged logically next to each other.

Broca's area

Responsible for speech production

Broca's aphasia

Speech production is affected, not understanding. Often speak in short, not very fluid, but meaningful sentences which take great effort

Wernicke's area

Responsible for understanding language

Wernicke's aphasia

Speak fluidly but its often nonsense, words that don't make sense

Aphasia

Inability to use or understand language because of brain damage

Strengths of localisation of brain function

Supporting evidence - Phineas Gage (frontal lobe = personality = support); studies of people with Broca's and Wernicke's aphasia, had damage to that area = support as language areas are localised

Weaknesses of localisation of brain function

Undermining evidence - Lashley removed areas of cortex in rats that were learning to complete a maze, no part more important than another - learning is too complex to be localised = processes can be more holistic

Lateralisation of brain function

When some functions are dominated by one hemisphere

Functions of left hemisphere

Control of right side of body, right visual field, speech, understanding written + spoken language, logical thinking, analytical tasks

Functions of right hemisphere

Control of left side of body, left visual field, spatial awareness, creativity, recognising faces, musical ability, emotional content of language, drawing

Cerebral cortex

The outer layer of both hemispheres

Corpus callosum

The thick bundle of nerves that connects the two hemispheres

Sperry and Gazzinga's aim and method

11 individuals who had their corpus callosum severed to treat severe epilepsy. Showed stimuli to one hemisphere using a tachistoscope and compared how they did to a control who didn't have epilepsy.

Sperry and Gazzinga: describing what you see

Pic of object shown to left or right visual field, right = easily named, left = couldn't describe it - often said nothings there

Sperry and Gazzinga: recognition by touch

Object shown to left visual field, asked to choose matching object from a bag using only left hand - could select matching object but not describe it

Sperry and Gazzinga: composite words

2 words simultaneously show, 1 to left and 1 to right visual field, asked to say what it was or draw it if couldn't see it. Could write/draw left 1, say right 1

Sperry and Gazzinga: matching faces

Shown different faces to each visual field, asked to match it to one from a series of others, one shown to right hemisphere selected, one to left ignored. Also shown composite faces (made of 2) - half shown to left hemisphere dominated description, half shown to right selected more

Strength of split-brain research

Highly specialised, standardised procedure - using tachistoscope to flash image for 1/10th sec - ensured only one hemisphere saw the task/object = high internal validity and can be used to establish cause and effect

Weaknesses of split-brain research

Small sample, all of which had epilepsy, could have unique brain changes that effect the results = lacks validity + data = artificially produced = lacks mundane realism; lateralisation isn't fixed - healthy older adults had less lateralisation = older peoples brains recruit both hemispheres to maximise processing power

Plasticity

The brains tendency to change and adapt (functionally and structurally) as a result of experiences, new learning or training. Functional plasticity decreases with age

Functional recovery

The brains ability to redistribute or transfer functions usually performed by damaged areas, to not damaged area(s)

Spontaneous recovery

Functional recovery occurs quickly after trauma, but slows down after several weeks/months

Neural reorganisation

The transfer of functions to undamaged areas

Neural regeneration/axon sprouting

When new neurons may grow and/or new connections may form to compensate for the damaged areas where neurons are lost

Functional recovery plasticity

Allows the brain to cope better with the 'indirect' effects of brain damage, e.g. swelling, haemorrhaging

McGuire et al

Looked at the brains of London cab drivers who had taken 'The knowledge': found significantly more volume of grey matter in posterior hippocampus compared to a control

Draganski et al

Brain scanned students 3 months before and after an exam, found changes in the posterior hippocampus and parietal cortex, presumably because of the exams

Kuhn et al

Compared a control group with a group that trained for 2 months, playing super mario for at least 30mins per day: found they had significant increase in grey matter in the cortex and hippocampus compared to a control

Strengths of plasticity and functional recovery

Supporting evidence: McGuire et al, Kuhn, Draganski = suggest brain changes + adpats functionally = supports theory; real world application, can be used in neurorehabilitation =

Weaknesses of plasticity and functional recovery

Schneider et al found patients with college equivalent education were 7x more likely to be disability free 1 year after a moderate - severe brain injury than those who didn't finish high school = education may influence how the brain functionally adapts = moderating factor.

Spatial resolution

The smallest feature (or measurement), greater spatial resolution to allow discrimination between different brain regions with greater accuracy

Temporal resolution

The accuracy of the scanner in relation to time (how quickly it can detect changes in brain activity)

fMRI

Measures the blood flow in the brain when a task is performed - most active neurons requires most energy = more oxygen needed = more blood flow. Creates dynamic 3D map of brain

Strengths of fMRIs

Non-invasive unlike PET scans = more patients able to have one = more data = more understanding of localisation of function; Good spatial resolution (1-2mm) = can determine areas of function with greater accuracy

Weaknesses of fMRIs

Poor temporal resolution (1-4 secs) = unable to predict with high accuracy the onset of brain activity; Don't provide direct measure of neural activity - changes in blood flow indicate activity, but can't associate it with a specific function

EEG

Measures electrical activity on surface of brain - electrodes placed on scalp, detecting small electrical charges from neural activity directly underneath them. Looks at general brain activity

ERP

Uses statistical averaging technique to show only the responses that relate to a specific stimulus presented to the patient. Repeated many times, with responses averaged together to eliminate extraneous activity

Strengths of EEGs

Used in clinical diagnosis, e.g. epilepsy = useful for diagnosing people = real world application; high temporal resolution (detect changes at 1 millisecond) = accurately measure particular task with associated brain activity; cheap = large sample sizes = higher external validity

Weaknesses of EEGs

Only detect superficial brain activity = can't look at deeper parts, e.g. hippocampus = can't ethically implant electrodes in brain to measure with humans, but can with animals; poor spatial resolution - can't pinpoint where electrical signal originated from = unable to distinguish between activities from different but adjacent parts

Strengths of ERPs

Measure processing of stimuli in absence of behavioural response, e.g. reaction to seeing an unfamiliar object = can monitor processing of stimulus without requiring person to respond

Weaknesses of ERPs

Lack validity as can't completely eliminate background noise, materials etc = could be influenced by extraneous variables, so cautious generalising

Post-mortems

Analysing the brains of someone after they've died, most likely if they have a rare disorder/have experienced unusual deficits in mental processes or behaviour. Areas of damage examined to try and correlate to structural abnormalities.

Strengths of post-mortems

More detailed exam of anatomical and neurochemical aspects of brain, e.g. areas like hippocampus and hypothalamus; Contributed massively towards understanding of key processes in the brain, e.g. making link between language and the Brocas and Wernickes areas

Weaknesses of post-mortems

Can't establish cause and effect as: only shows physiology, not actual brain activity; many confounding influences, e.g. disease, time between death and examination, medications, age. Retrospective = can't follow up on interesting findings = difficult to explain all behaviours

Biological rhythms

Cyclic changes in body activity

Circadian rhythms

Type of biological rhythm where a pattern of behaviour occurs, or reoccurs, approx. every 24 hours. Its set and reset by environment (light and temp), e.g. sleep wake cycle

Siffre (1962)

Spent time underground (no natural light, sounds) for 2 and 6 months (he did it twice). Found that his biological rhythm settled to 25 hours, with him falling asleep on a regular basis

Aschoff and Wever (1976)

Group of participants spent 4 weeks in a WWII bunker (no natural light). Most had a 24-25 hour circadian rhythm, but one had a 29 hour one

Strengths of circadian rhythms

Practical application to shift work - many practical + economic implications as can maintain worker productivity + prevent workplace accidents; Practical application to pharmacokinetics - can give drugs at optimal times using circadian rhythms = useful for timing drug dosing; supporting evidence (Siffre) = increased validity

Weaknesses of circadian rhythms

Issues with case studies (Siffre and Aschoff & Wever) = lacks external validity as small sample, doesn't look at gender or age influence; poor control in studies, e.g. only assuming natural not artificial light having an influence = lacks validity

Endogenous pacemakers

Internal body clocks, control the SCN and pineal gland for the circadian sleep-wake cycle

Exogenous zeitgebers

External cues that affect our biological rhythms, e.g. light on sleep-wake cycle

Ep supporting evidence

DeCoursey: destroyed SCN in 30 chipmunks = sleep-wake cycle disappeared; Ralph: bred mutant hampsters with 20 hour sleep wake cycle, transplated SCN tissue to normal ones and their sleep wake cycle became 20 hours

Ez supporting evidence

Campbell and Murphy: 15 participants were woken by light being shone on back of knees = change in sleep-wake cycle without eyes seeing light; Burgess: exposure to bright light before east-west flight reduced period of jet lag

Strengths of Ep and Ez

Supporting evidence; real life applications to reducing jet lag

Weaknesses of Ep and Ez

Issue of generalising animal studies to humans, especially due to ethics; lack of reliability found for Ez results; total isolation of Ep and Ez unlikely = lacks validity

Infradian rhythms

Infrequent - biological rhythm with duration of over 24 hours, e.g. the menstrual cycle

Menstrual cycle

approx. 28 days, ovulation occurs in middle when oestrogen is highest, next progesterone increases to prep for pregnancy, if pregnancy doesn’t occur egg is absorbed and leaves with womb lining

Stern and McClintock

29 women with irregular periods, collected pheromones from 9 from armpit using cotton wool, other 20 had it rubbed on their upper lip; pads were collected on different days of the cycle: 68% experienced changes to their menstrual cycle which bought it closer to their ‘donors’

Ultradian rhytms

Biological rhythm that lasts less than 24 hours, e.g. stages of sleep

Sleep cycle

Has 5 stages it goes through (1-4, REM) that altogether spans 90-120 mins

Stage 1

Light sleep, easily awoken, mucscles less active, eye movement slows, can suddenly twitch; have alpha (restful) and theta (between sleep and wake) brainwaves

Stage 2

Between light and deep sleep, breathing + heartrate slows; slower brainwaves, mainly theta

Stage 3

Deep sleep begins, muscle activity decreases; slow delta waves, but also some fast ones

Stage 4

Deep sleep (very hard to be awoken); almost all delta waves

REM

Dreaming occurs, eyelids can be seen flickering; brainwaves reach similar levels to when awake

Strengths of ultradian/infradian rhythms

Supporting evidence (Derment and Kleitman stages of sleep + Ericsson BRAC + Stern and McClintock); evolutionary value to Stern and McClintock’s findings

Weaknesses of ultradian/infradian rhythms

Differences in sleep is often environmental not biological

Central nervous system

The brain and spinal cord - processes + interprets information and reacts to it

Peripheral nervous system

Transmits info to and from CNS, contains autonomic and somatic nervous system

Autonomic nervous system

Controls involuntary functions, includes: sympathetic and parasympathetic nervous system

Sympathetic nervous system

Mobilises the body for action, energy output and is primarily involved in responses that help us deal with emergencies (flight or fight)

Parasympathetic nervous system

Conserves energy, maintains quiet state - restores normal physiological functioning when danger has passed

Neuron

Cells of the nervous system that process and transmit messages through chemical and electrical messages/signals

Sensory neuron

Carry messages from sensory receptors via the PNS to the CNS

Relay neuron

Connect with other neurons, e.g. allow sensory and motor neurons to communicate with each other. When impulses reach brain, they're translated into sensations so the organism can work out how to respond

Motor neuron

Connect CNS to effectors, e.g. muscles, glands. Located in CNS and their axons spread outside it to directly or indirectly control muscles

Synaptic transmission

Action potential reaches presynaptic terminal, triggers synaptic vesicles, release neurotransmitters into synaptic gap, diffuses across, binds to post-synaptic receptor on post-synaptic dendrite, converts chemical to electrical impulses, repeats. Effects terminated by reuptake (neurotransmitters absorbed by pre-synaptic neuron, stored in vesicles for later use)

Excitatory neurons

Causes excitation of the post-synaptic membrane = more likely to fire an action potential (on switches), e.g. Noradrenaline

Inhibitory neurons

Causes inhibitory post-synaptic potentials (IPSPs) = less likely to fire an action potential (off switches), e.g. Serotonin

Summation

Exhibitory and inhibitory influences are summed together

Endocrine system

A network of glands throughout the body that manufacture and secrete hormones: 'a chemical system of communication'

Glands

A group of cells in an animals body that syntheses substances for release into the bloodstream

Hormones

Chemical messengers that travel throughout the bloodstream to target sites and cells

Key functions of pituitary gland

Produce hormones that control release of hormones from other glands; regulated many bodily functions

Hormones released by pituitary gland

Oxytocin, ACTH, LH + FSH

Effect of oxytocin on behaviour

Stimulates contraction of the womb in childbirth and is important for mother-infant bonding

Effect of ACTH on behaviour

Stimulates adrenal glands to release cortisol in response to stress

Effect of LH and FSH on behaviour

Stimulates the ovaries to produce oestrogen and progesterone. In males, stimulates testes to produces testosterone

Key functions of adrenal glands

Supports bodily functions, e.g. cardiovascular and anti-inflammatory functions; causes physiological changes associated with arousal + prepares body for fight or flight