biopsychology

nervous system is based on ___ +___ signals

electrical

chemical

functions of the nervous system

• collect, process and respond to information from the environment

• co-ordinate working of organs and cells in the body

subsystems of the nervous system

central nervous system

peripheral nervous system

central nervous system function

origin of all complex commands and decisions

central nervous system components

brain

spinal chord

CNS - brain

• centre of conscious awareness

• outer layer = cerebral cortex only found in mammals

• highly developed in humans + distinguishes our higher mental functions form other animals

• divided into 2 hemispheres

• only a few living creatures have no brain eg. jellyfish

cerebral cortex is ___mm thick

3

cerebral cortex function

• most sophisticated part of our brain

• carries out essential functions

• eg. memory, thinking, learning, problem-solving, consciousness, sensory functions

CNS - spinal chord

• extension of the brain

• passes messages to and form the brain

• connects nerve to the PNS

• responsible for reflex actions eg. pulling hand away from something hot

peripheral nervous system function

sends information (via millions of neurons) to the CNS from outside

transmits messages from the CNS to muscles + glands in the body

peripheral nervous system components

autonomic nervous system

somatic nervous system

PNS - autonomic nervous system

involuntary

governs vital functions in the body

transmits information to and from internal body organs

eg. breathing, HR, digestion, sexual arousal and stress responses

PNS - somatic nervous system

voluntary

governs muscle movement

transmits information from receptors cells in sense organs to the CNS

receives information from the CNS that directs muscles to act

transmits + receives information from all sense apart from sight

reflex arc

an automatic and rapid response to a stimulus, which minimises any damage to the body from potentially harmful conditions eg. touching something hot

autonomic nervous system subdivisions

sympathetic nervous system

parasympathetic nervous system

sympathetic nervous system function

associated with the fight or flight’ response with the endocrine system

• SPNS prepares body for physical activity when the hypothalamus detects a stimulus which requires attention/action (eg. running away from or fighting the threat)

• SPNS triggered when the body is in an ‘alert’ state (eg. crossing the road)

• adrenaline realised from adrenal glands to fuel physical activity required along with physiological changes (eg. increased HR, wider bronchial passages, decreased large intestine activity, pupil dilation, sweating)

• SPNS enables fast automatic response to possible threat or dangerous situation

• can also occur when someone is highly elated or excited

fight or flight response limitation - beta bias

• biological research generally favours male animals because female behaviour is affected by regular hormonal changes due to ovulation - therefore ignores any possible differences

• early research into fight or slight response - assumed that both males and female would respond to threatening situations with fight or flight

• more recent research - found that any approach is the tend and befriend

• oxytocin is more plentiful in women, as a stress response women have increased oxytocin production

• this reduces the fight or flight response + enhances the tend and befriend

• therefore the original research minimised gender differences which resulted in a misrepresentation of women’s behaviour

parasympathetic nervous system function

‘rest and digest’ system

• the body at rest to preserve energy

• helps conserve activity levels by decreasing activity which may be needed later

• regulates bodily functions eg. digestion and urination

• slows HR and breathing + lowers blood pressure

• body enters state of relaxation, enables it to go into recovery mode

endocrine system is based on secreting ___ into the ____

hormones

bloodstream

hormone definition

biochemical substance that circulates in the blood but only affects target organs

produced in large quantities but disappear quickly

very powerful effects

endocrine system hormone action

most hormones affect cells in 1+ body organs → leads to many diverse and powerful responses

act slowly but has widespread + powerful effects

eg. puberty = slow release of testosterone/oestrogen

major gland of the endocrine system

pituitary gland - located in the hypothalamus

controls the release of hormone from all other endocrine glands in the body

‘master gland’

endocrine system - thyroid gland

produces thyroxine - affects cells in the heart (increases heart rate) and cells throughout the body (increases metabolic rates)

affects growth rates

endocrine system - pancreas

produces insulin

produces hormones to regulate blood glucose levels + digestive enzymes such as pancreatic amylase + lipase

endocrine system - adrenal glands

produces adrenaline

endocrine system - testes

male sex hormone

produces testosterone

endocrine system - ovaries

female sex hormone

produces oestrogen

structure of a neuron (nucleus, dendrites, axon, myelin sheath, nodes of ranvier, axon terminal)

• cell body containing nucleus - where DNA is stored

• dendrites - receive/transmit signals from other neurons

• axon - carries electrical charge from the cell body down the length of the neuron, covered in protective fatty myelin sheath

• gaps in the myelin sheath = nodes of ranvier (speed up electrical transmissions)

• axon terminal - end of the axon, communicate with the next neuron across the synapse

neuron + function + location

sensory neuron - carry messages from the PNS to the CNS

located in the PNS in clusters = ganglia

sensory neurons have __axons and __dendrites

short

long

neuron + function + location

relay neuron - connect sensory neurons to the motor/other relay neurons

located mostly within the brain and the visual system

___% of all neurons are relay neurons

97

relay neurons have __axons and __dendrites

short

short

neuron + function + location

motor neuron - connect the CNS to effectors eg. muscles + glands

cell bodies located in the CNS but their long axons form part of the PNS

motor neurons have __axons and __dendrites

long

short

neuron action potential

causes when a neuron is activated by a stimulus and the inside of the cell becomes positively charge for a split second

creates an electrical impulse that travels down the axon towards the end of the neuron

signals within neurons are transmitted ___

electrically

signals between neurons are transmitted ___ across the ___

chemically

synapse

process of synaptic transmission

• electrical impulse reaches the presynaptic terminal

• triggers the release of neurotransmitters in synaptic vesicles

• neurotransmitters diffuse across the synapse

• taken up b the postsynaptic receptor site on the dendrites of the next neuron

• chemical message is converted back into an electrical impulse

• process repeats

neurotransmitters

brain chemicals

only travel in one direction (presynaptic → postsynaptic)

each has its own molecular structure that fits perfectly into a postsynaptic receptor site (lock&key)

each have specialist function

have either an excitatory or inhibitory effect on the neighbouring neuron

inhibitory neurotransmitters

• prevents an action potential in the post-synaptic neuron

• increases the neurons -ve charge

• makes it less likely to fire

• eg. serotonin

excitatory neurotransmitters

• stimulate an action potential in the post-synaptic neuron

• increases the neuron’s positive charge

• makes it more likely to fire (send electrical signals down its axon to communicate with other cells)

• eg. adrenaline

summation

• process deciding whether a postsynaptic neuron fires or not

• inhibitory/excitatory are summed

• if final effect on the post-synaptic neuron is inhibitory → less likely to fire (+vice versa)

• action potential is only triggered if the sum of the inhibitory/excitatory signals at any one time reaches the threshold

phineas gage case study

• worked on railroad - preparing to blast a section of rock with explosives to create a new railway line

• explosion hurled a metre-length pole through his left cheek, behind his left eye and exiting his skull form the top of his head

• took a portion of his brain with it - most of his left front lobe

• survived but his personality changed

• went from calm+reserved to quick-tempered + rude

• suggests the frontal lobe may be responsible for regulating mood

localisation theory

Broca + Wernicke

theory that different areas of the brain are responsible for specific behaviours, processes or activities - therefore if a certain area is damaged then the function associated with that area is also affected

previous theories supported the holistic theory - all parts of the brain involved in the processing of thought + action

cerebral cortex function

• outer layer of both hemispheres

• divides into 4 centres = lobes all associated with different function

• frontal, parietal, occipital, temporal

location + function of the motor area

back of the frontal lobe

controls voluntary movement in the opposite side of the body

location + function of the somatosensory area

front of both parietal lobes

processes sensory information eg. touch, heat,pressure

location + function of the visual cortex

in the occipital lobe

receives and process visual information

left visual cortex receive info from the right visual field + vice versa

location + function of the auditory area

temporal lobes

analyses speech-based information - damage may produce partial hearing loss

function of the cerebellum

monitors + regulates motor behaviour

learning centres of the brain

restricted to the left side of the brain (in most people)

Wernicke and Broca

Wernicke’s areas + aphasia

• in the temporal lobe

• responsible for language comprehension

• damage causes:

• Wernicke’s aphasia - produce language fine, but difficulty understanding, words produced were nonsense words

Broca’s areas + aphasia

• in the frontal lobe

• responsible for speech production

• damage causes:

• Broca’s aphasia - slow + laborious speech that lacks fluency, often struggle with prepositions and conjunctions, can understand language

localisation of brain function strength - evidence from neurosurgery

• neurosurgery sometime last resort method for treating some mental disorders by targeting specific areas of the brain which are involved

• eg. cingulate gyrus implicated in OCD

• 44 people with OCD underwent the surgery

• after 32 weeks - 30% met criteria for successful response to the surgery, 14% for partial response

• success of the procedures suggests that behaviours associated with some mental disorders may be localised - supports the theory

localisation of brain function strength - supporting evidence

• Phineas Gage case study - supports localisation

• Petersen - brain scans demonstrated how Wernicke’s area was active during a listening task + Broca’s area was active during a reading task

• review of LTM studies - semantic/episodic memories reside in different parts of the PFC

• confirm localised areas for everyday behaviours

• therefore objective methods for measuring brain activity have provided scientific evidence that many brain functions are localised

localisation of brain function limitation - challenging evidence

• Lashley - removed 10-50% of rat’s cortex

• rats were learning the route through a maze

• no area found more important than others in terms of their ability to learn the route

• process of learning seemed to require every part of the cortex rather than one particular area

• suggests that higher cognitive process (eg. learning) may not be localised but instead distributed holistically in the brain

hemispheric lateralisation

theory that the 2 halves of the brain function entirely separate

some localised areas appear in both hemispheres (eg. vision, motor, somatosensory)

left hemisphere function

language centres (analyser)
Broca and Wernicke’s areas

right hemisphere function

emotion linked to language (synthesiser)

only produce basic words + phrases

lateralisation - motor function

• contralateral wiring

• right hemisphere controls movement on the left side of the body

• left hemisphere controls movement on the right side of the body

lateralisation - vision function

• contralateral and ipsilateral wiring

• each eye receives light from the left and right visual fields

• left visual field of birth eyes is connected to the right hemisphere

• right visual field of birth eyes is connected to the left hemisphere

• enables the visual areas to compare slightly different perspectives + aids depth perception

contralateral meaning

cross wiring of brain functions

ipsilateral meaning

same sided wiring of brain functions

hemispheric lateralisation strength - research support

• PET scans used to identify which brain areas were active during a visual processing task

• participants asked to look at the global elements of an image - regions of the RH were more active

• asked to focus on the finer detail - specific areas of the LH were more active

• suggests that in terms of visual processing, hemispheric lateralisation is a feature of the connected brain as well as the split-brain

hemispheric lateralisation limitation - LH and RH roles may be wrong

• general idea that LH is the analyser and RH is the synthesiser

• research suggests that people don’t have a dominant side of their brain that creates a different personality

• analysis of brain scans from 1000+ people aged 7-29 - found that people used certain hemispheres for certain tasks (supports lateralisation)

• but there was no evidence of a dominant side of the brain

• therefore suggests that the notion of right/left brained people in incorrect

reason for split-brain procedure

• corpus callosum connects the right and left hemisphere

• epileptic seizure - brain experiences excessive electrical activity that travels between the hemispheres

• when the corpus callosum is cut it prevents these connections and splits the brain in 2 halves that can’t communicate with each other

Sperry’s split-brain research procedure

• 11 people who had already had a split brain operation

• set up - image could be projected to a participants RVF and the same/different image could be projected to the LVF

• normal brain - corpus callosum would share information between hemispheres + give a complete picture of the visual world

• split brain - information can’t be conveyed between hemispheres

Sperry’s split-brain research findings

• object shown to RVF, processed by LH, could describe what was seen

• object shown to LVF, processed by RH, said nothing was there

• messages from the RH weren't relayed to the language centres in the LH, preventing them from being spoken aloud

• asked to select the matching object without seeing their hands - could do this correctly using their left hand, connected to the RH

• image shown to LVF, could correctly pick up the matching object using their left hand

• funny picture shown to LVF, emotional response happened eg. giggle, but responded saying they saw nothing

• show how certain functions are lateralised in the brain + supports the view that LH is verbal and the RH is silent, but emotional

split-brain research strength - support from recent research

• recent findings show that split-brain participants performed better than control group with connected brains on certain tasks

• were faster at identifying the odd one out in an array of similar objects

• this is because in the normal brain - the LH’s better cognitive strategies are weakened by the influence of the inferior RH

• therefore supports Sperry’s earlier findings that the left and right brain are distinct

split-brain research limitation - generalisability

• difficult to establish causal relationships from Sperry’s research

• behaviour of the split-brain participants was compared to a neurotypical control group

• however none of the participants in the control group had epilepsy = major confounding variable

• any observed differences between the groups may have been the result of epilepsy rather than the split brain

• therefore some of the unique cognitive abilities of the split-brain participants may have been due to their epilepsy, limited support for the lateralisation theory

split-brain research limitation - ethics

• the split-brain procedures were already performed, not for the research

• procedures were explained to participants + informed consent was obtained

• however, trauma from the operation may have meant they didn’t fully understand the implication of what they’d agreed to

• they were tested repeatedly over a length period which may have been stressful over time

• therefore the ethics behind the research are questioned

brain plasticity

• the brain is able to change throughout life

• during infancy - brain experiences a rapid growth in the number of synaptic connections, peaking at 2-3 years

at 2-3 years the brain has around ____synaptic connections per neuron which is ___than an adult brain

15,000

x2 more

synaptic pruning

• as we age, rarely-used connections are deleted

• frequently used connections are strengthened

• enables lifelong plasticity - new neural connections are formed in response to new demands on the brain

research into plasticity - taxi drivers

Maguire

• studies brains of London taxi drivers

• found more grey matter in the hippocampus than a matched control group

• associated with spatial and navigational skills in humans + animals

• London taxi drivers take a test in their training - assess recall of the city street + possible routes

• finings show that this learning experience alters the structure of the taxi drivers brains

• longer they’d been on the job = more structural difference (+ve correlation)

research into plasticity - medical students

• imaged brains of medical students 3 months before and after their final exams

• learning-induced changes were observed in the hippocampus + parietal cortex

• presumed to be a result of their learning

brain plasticity limitation - -ve consequences

• evidence shows the brains adaptation to prolonged drug use leads to reduced cognitive functioning in later life and increases chance of dementia

• also 60-80% of amputees develop phantom limb syndrome, due to reorganisation in somatosensory cortex after limb loss - unpleasant and painful experience

• therefore the brain’s ability to adapt is not always beneficial

brain plasticity strength - life-long ability

• study - participants aged 40-60

• found that 40 hours of golf training produced changes in the neural representations of movement

• using fMRI - observed increased motor cortex activity in the noise golfers compared to a control group → suggests more efficient neural representations after training

• therefore suggests that neural plasticity can continue throughout the lifespan

brain plasticity limitation - research on seasonal changes

• research suggests that there may be seasonal plasticity in the brain in response to environmental changes

• eg. suprachiasmatic nucleus regulates the sleep/wake cycle - evidence suggests that it shrinks in all animals during spring and expands throughout autumn

• however - most research on seasonal plasticity has been done on animals (mostly songbirds) which has limited application to human behaviour

functional recovery

• occurs in the brain after trauma = neural plasticity

• healthy brain areas may take over functions of damaged areas

• can occur quickly (spontaneous recovery) then slow down after weeks/months

• brain can rewire/reorganise itself by forming new synaptic connections

functional recovery - axonal sprouting

when axons with a similar job become aroused to a higher level to compensate for lost ones

functional recovery - denervation super sensitivity

when a nerve cell axon is damaged, a new one is sprouted

can have the -ve consequence of oversensitivity to messages eg. pain

functional recovery - recruitment of homologous areas

if damage occurs in the LH, RH may pick up the task

eg. damage to Broca’s area → equivalent area in the RH may develop language skills to make up for lost ability

functional recovery strength - real-world application

• understanding the processes of plasticity has contributed to the field of neurorehabilitation

• understanding of axonal growth encourages new therapies to be tried

• eg. constraint-induced movement therapy is used with stroke patients - repeatedly practise using the affected part of their body, while the unaffected arm is restrained

• therefore shows that research into functional recovery is useful as it helps medical professionals know when intervention need to be made

functional recovery limitation - cognitive reserve

• level of education may influence recovery rates

• study revealed that the more time people with a brain injury had spent in education (indication of their cognitive reserve), the greater their chances of a disability-free recovery

• 40% of those with a DFR had 16+ years of education compared to 10% for those with less than 12 years of education

• therefore implies that people with brain damage who have sufficient DFR are less likely to achieve a full recovery

functional recovery limitation - small samples

• 1 study treated patients with Total Anterior Circulation Stroke (TACS) with stem cells

• all patients recovered compared to the typical level of 4% recovery - provides strong support for the use of stem cells helping functional recovery

• however this study only had 5 participants and no control group

• therefore the research may lack validity and is difficult to draw conclusions from

ways of studying the brain

fMRI - functional magnetic resonance imaging

EEG - electroencephalogram

ERP - event-related potentials

Post-mortem examinations

fMRI

• detects changes in the blood oxygenation + flow that occur as a result of neuron activity in specific parts of the brain

• more active area consumes more oxygen so more blood is directed there

• produces 3 dimensional images showing which parts of the brain are involved in a particular mental processes

• important implication for our understanding of localisation of function

fMRI +ve

• doesn’t rely on the use of radiation - virtually risk-free + non-invasive + straightforward

• produces images with very high spatial resolution - clear detail by mm, clear picture of how brain activity is localised

fMRI -ve

• expensive compared to other neuroimaging techniques

• poor temporal resolution - 5 second time-lag behind the image on the screen and the initial firing of neuronal activity

• therefore may not truly represent moment-to-moment brain activity

EEG

• measures electrical activity within the brain via electrodes fixed to an individual’s scalp using a skull cap

• scan recording represents the brainwave patterns that are generated from the action of thousands of neurons

• provides an overall account of brain acitivty

• often used as a diagnostic tool - unusual arrhythmic patterns of acidity activity can indicate neurological abnormalities

• eg. epilepsy, tumours, sleep disorders

EEG +ve

• useful in studying the stages of sleep + diagnosis of conditions eg. epilepsy

• extremely high temporal resolution - (today) can accurately detect brain activity at a resolution of 1 millisecond

• real-world usefulness

EEG -ve

• generalised nature of the information received - from thousands of neurons

• not useful for pinpointing the exact source of neural activity

• doesn't allow researchers to distinguish between activities originating in different but adjacent locations

ERPs

• EEG has scientific + clinical applications, but the raw data is an overly general measure of brain activity

• EEG data contains all neural responses associated with sensory/cognitive/motor events that may be of interest

• researchers developed ways of isolating these responses by using a statistical averaging technique

• extraneous brain activity is filtered out, leaving only those responses need for the presentation of a specific stimulus or the performance of a specific task

• ERPs = remaining data - type of brainwave that are triggered by particular events

ERPs +ve

• bring more specificity to the measurement of neural processes that could be achieved from raw EEG data

• excellent temporal resolution

• frequently used to measure cognitive functions + deficits

• eg. allocation of attentional resources + maintenance of working memory

ERPs -ve

• lack of standardisation in ERP methodology between different research studies - difficult to confirm findings

• in order to establish pure data, background noise + extraneous material must be completely eliminated - not always easy to achieve

Post-mortem examination

• technique involving the analysis of a person’s brain following their death

• brains tested are likely to be from those who have a rare disorder + have experience unusual deficits in cognitive processes or behaviour during their lifetime

• damaged areas of the brain are examined after death to establish the likely cause of the affliction that the person experienced

• may also involve comparison to a neurotypical brain to assess the extent of the difference

Post-mortem examination +ve

• vital in providing a foundation for early understanding of key processes in the brain

• Broca + Wernicke relied on them to establish links between language, brain and behaviour - decades before neuroimaging was possible

• used to study HMs brain to identify areas of damage - then associated with his memory deficits

Post-mortem examination -ve

• observed damage to the brain may not be linked to the deficits under review, but instead due to some other unrelated trauma or decay

• ethical issues of consent from the individual before death - some may not be able to provide informed consent

• eg. HM couldn’t provide this consent, but post-mortem research was still conducted on his brain

• challenged usefulness of post-mortem studies in psychological research