Week 20 Flashcards
1
Q
Phrenology
A
- correlation of a person’s brain anatomy and skull shape with their behaviour/personality
- dividing the skull into sections of different psychological traits that are said to correlate to the brain + depending on the size of that region that determines how much of that trait you have as an individual
2
Q
Modern methods for investigating the brain
A
- examining the effects of brain damage (brain injury/lesions or simulations in the lab, e.g. stimulating electrodes/TMS)
- physiology (recording electromagnetic activity of single of populations of neurons - EEG and MEG)
- imaging (visualising the structure and/or activity of neurons on the whole brain - neuronal staining techniques, MRI, CT/PET scans)
3
Q
Natural brain injuries and lesions
A
- used to determine the correlation of the loss of a specific cognitive function with the area of brain damage
- e.g. Phineas Gage (frontal lobe damage); corpus callosotomy (split brain patients); Broca’s aphasia (link with Broca’s area to sentence structure processing)
4
Q
Stimulating localised brain activity (invasive)
A
- in lab animals or open-brain surgery
- stimulating electrodes used to pierce the skull to activate certain areas of the brain
5
Q
Stimulating localised brain activity (non-invasive)
A
- in healthy patients
- transcranial magnetic stimulation (TMS) can be used to excite/inhibit neurons by externally applying time-varying electromagnetic fields generated by a coil located above the head
- used to induce a temporary “lesion” to see the outcome in a patient (e.g. see if inhibiting a certain brain region specifically inhibits a certain activity in a patient)
6
Q
Single-cell recordings
A
- single neuron behaviour can be examined through the use of microelectrodes which impale the cells of interest
- a nano lead (a submicron scale electrode) is implanted into an intracellular axon or extracellular axon membrane
- records neural activity of a single neuron but doesn’t stimulate it
- e.g. single-cell recordings in hippocampus to see if cells respond to one single stimulus (such as a specific person)
7
Q
Electroencephalography (EEG)
A
- used to measure electrical brain activity on the scalp (recording the electromagnetic activity of a population of neurons rather than just single ones)
- sensitive to postsynaptic dendritic currents generated by populations of neurons that are active in synchrony
- placement of electrodes on the scalp is frontal (F), central (C), parietal (P), occipital (O) and temporal (T)
- very strong time-based resolution (less than 1 ms) but a rather poor spatial resolution (as it is difficult to tell specifically where the sources of signals are within the brain)
- useful for diagnosing epilepsy (characterised by an abnormal spike and wave discharge)
- can also use EEGs to assess brain waves during a specific repeated cognitive task to assess event-related potentials to assign different cognitive domains to activities
8
Q
EEG Rhythms (delta)
A
- 0.5-4 Hz
- most prominent frontally in adults and posteriorly in babies
- seen normally in babies and in sleeping adults
9
Q
EEG Rhythms (theta)
A
- 4-7 Hz
- seen normally in young children
- in adults, seen in drowsiness or sleep arousal or meditation
- excess theta waves for your age represents abnormal activity (e.g. due to focal subcortical lesions)
10
Q
EEG Rhythms (alpha)
A
- 8-12 Hz
- bilaterally in the posterior regions but higher on the dominant side
- emerges with closing of the eyes and with relaxation
- attenuates with eye opening or mental exertion
- abnormally diffused and not responsive to external stimuli alpha waves in a coma
11
Q
EEG Rhythms (beta)
A
- 12-30 Hz
- most evident frontally
- linked to motor behaviour, attenuated during active movements
- absent or reduced in areas of cortical damage
- dominant rhythm in patients who are alert or anxious or who have their eyes open
12
Q
EEG Rhythms (gamma)
A
- 30-100 Hz
- represent binding of different populations of neurons together into a network for the purpose of carrying out a certain cognitive or motor function
13
Q
Magnetoencephalography (MEG)
A
- recording of the magnetic fields produced by electrical currents in the brain using arrays of SQUIDs (superconducting quantum interference devices)
- it is much more expensive but can be more reliably localised to sources within the brain (due to signal being unaffected by the skull, meninges etc. like EEGs are)
- also more sensitive to activity at sulci, whereas EEGs are sensitive to both sulci and gyri activity alike
14
Q
Neuronal staining techniques
A
- in order to stain a slice, the brain cannot be alive (not useful for dynamic imaging)
- e.g. Golgi stain method: randomly stains 5% of neurons, making them visible against the background of neural “chaos”
- e.g. Myelin stains: taken up by fatty myelin that wraps around neurons and thus identifies neural pathways (by visualising white matter)
- e.g. Nissl stains: identify cell bodies of neurons (visualising gray matter)
15
Q
Structural imaging
A
- uses the fact that different types of tissue (e.g. skull, gray matter etc.) have different physical properties in order to construct detailed static maps of the brain
- used to scan alive human brains to view dynamic images
- used to see what is going on in the brain but not too much is revealed about the specific function of different regions
16
Q
CT (computerized tomography) scans
A
- contrast dye is injected into the blood with a series of X-rays sent out from different angles
- the X-rays are combined into a series of horizontal sections of the brain
- X-ray absorption varies with tissue density (bone absorbs most = white; CSF absorbs least = black; gray/white matter = grey)
17
Q
MRI (magnetic resonance imaging) scans
A
- a strong magnetic impulse is applied, with energy released by molecules in the tissue released as a result of the pulse being measured
- differently charged molecules respond differently to the pulses, hence the energy signals reveal brain structures with different molecular compositions (e.g. showing haemorrhage or tumour)
- brain images plotted with such measurements so more precise and detailed than CT scans
18
Q
Functional imaging
A
measures neuronal activity (e.g. brain activity associated with cognitive processing)
19
Q
fMRI (functional magnetic resonance imaging) scans
A
- measures activation by detecting the increase in oxygen levels (active neurons consume more oxygen)
- also measures the ratio of deoxyhaemoglobin and oxyhaemoglobin in the blood in different areas (BOLD/blood oxygen level dependent contrast response)
- change in BOLD response over time is known as the haemodynamic response function so you can localise active points (high spatial resolution)
- peaks 6-8 seconds after the stimulus event and is extended over time (limits the temporal resolution of fMRI for pinpointing the exact time of the activity)
- useful for cognitive research to pinpoint exact locations for brain activity (indicating active regions in a specific activitiy)
20
Q
PET (positron emission tomography) scans
A
- measures local bloodflow into a brain region, measuring levels of glucose/fuel to the brain
- radioactive tracer injected into bloodstream
- slow technique with very imprecise temporal resolution (tracer takes up to 30 seconds to peak) but has good spatial resolution
- fMRI is better as it does not require radioactive tracer and PET scans have worse temporal and spatial resolution
- but PET is faster and sensitive to the whole brain (whereas fMRI such as near sinuses are harder to image)
21
Q
Internal rhythms
A
- circannual (yearly) and circadian (daily) rhythms are endogenously generated, although can be modulated by external cues/zeitgebers like sunlight and temperature but also keep existing without these
- e.g. Mimosa plants still open and close their leaves in the same cycle as it does in darkness as it does in sunlight - suggesting rhythms are generated internally
- human body generates its own circadian cycles of activity and inactivity (including clear patterns of brain wave activity, hormone production, cell regeneration etc.)
22
Q
Mechanisms of the biological clock
A
- when the brain is awake: neurons in the upper pons produce acetylcholine –> passed onto the thalamus (relay station) –> signals to cortex to maintain the brain in the conscious/awake state; also neurons in the pons produce noradrenlaine/dopamine etc. –> signals to hypothalamus –> signals distributed across cortical areas
- when the brain is tired: SCN in hypothalamus signals to activate VLPL neurons in thalamus –> GABA released and sent to hypothalamus and pons –> inhibits excitatory signals to the cortex –> cortex shuts down and loses consciousness (i.e. is asleep)
23
Q
Suprachiasmatic nucleus (SCN)
A
- present in the hypothalamus and termed the master clock
- main control centre of the circadian rhythms of sleep and temperature
- generates circadian rhythms even when disconnected from the rest of the brain/body
- modified donor rhythms persevere in the recipient’s brain (SCN by itself is sufficient to perserve its own properties)
- the SCN’s zeitgeber is light (provided by neurons in the retina) so that when a light stimulus is present this resets the body’s biological clock
- also SCN corresponds to pineal gland that secretes melatonin (that is also influenced by light hitting retinal neurons)
24
Q
Polysomnography
A
- used to study the stages of sleep
- EEG (brain wave activity) + eye tracking + breathing rate + amount of oxygen in the blood
25
Q
Awake brain wave activity
A
dominated by beta waves
26
Q
Drowsy/relaxed brain wave activity
A
dominated by alpha waves
27
Q
Stage 1 sleep
A
- light sleep stage with fleeting thoughts
- slow eye movement and minimal muscle activity
- dominated by slower theta waves
28
Q
Stage 2 sleep
A
- light sleep
- contains sleep spindles (0.5+ second long bursts of 10-15 Hz waves) and K-complexes (sharp biphasic waves)
29
Q
Stage 3/4 sleep
A
- slow wave, deep sleep
- heart rate, breathing rate and temperature all go down (as does brain activity and muscle tone)
- hard to awake from this state
- dominated by slow high amplitude delta activity
30
Q
REM sleep
A
- heart rate and blood pressure increase (as does brain activity, dreaming and partial paralysis)
- more brain activity than other sleep stages (activity in the pons, limbic system, parietal/temporal cortex, amygdala - quite involved during threatening/stressful situations; but decrease in PFC - less involvement of planning and executing actions in a sensible way, motor cortex and primary visual cortex)
- REM sleep begins with PGO waves (transmitted from pons to lateral geniculate nucleus in occipital lobe)
- dominated by sawtooth/alpha-like waves
31
Q
Dreams
A
- considered an altered state of consciousness (a form of experience that departs significantly from the normal subjective experience of the world and the mind)
- feeling emotion more intensely, dream thought is illogical, however we experience uncritical acceptance and also have difficulty remembering the dream when it is over
- hypnagogic state = presleep consciousness
- hypnopompic state = postsleep consciousness
32
Q
Activation-synthesis hypothesis (dreams)
A
- believes that dreams are the brain’s attempts to make sense of the information reaching it (mind attempts to make sense of random neural activity during sleep)
- based mostly on the haphazard input originating in the pons
33
Q
Neurocognitive hypothesis (dreams)
A
- believes that dreams originate mostly from the brain’s own motivations, memories and arousal
- the stimulation often produces peculiar results as it does not have to compete with normal visual input and does not get organised by the PFC
34
Q
Brain arousal systems
A
- pontemescenphalon, hypothalamus and basal forebrain (contain neurons that promote wakefulness and others that promote sleep)
- locus coeruleus is active in response to meaningful events (facilitates attention and new learning)
- orexin (maintains wakefulness and is released in the lateral and posterior nuclei of the hyopthalamus)
- during sleep, enhanced GABA release limits neuronal activity and blocks the spread of activation
35
Q
Sleep cycles throughout the night
A
- throughout the night, there are typically five 90 min long sleep cycles of non-REM and REM sleep
- non-REM proportion is higher in the early hours (11pm-3am) and REM sleep increases across the course of the night (3am-7am)
36
Q
Pattern of sleep across different ages
A
- newborns (very little time in awake state, high level of REM sleep may help brain development)
- children (more time in slow-wave sleep than adults, intensity of this electrical activity is linked to how well they learn)
- teenagers (reduced REM sleep, a lack of slow-wave sleep can hamper learning ability)
- adults (awake for longer throughout the day, reduced REM sleep, slow-wave sleep declines as the ageing brain loses gray matter from the medial frontal cortex, making adults less able to lay down new memories)
37
Q
Sleep deprivation
A
- affects thermoregulation (over or underheating of body temperature occurs)
- immune system (initial response to disease and restoration are disrupted)
- metabolism (conversion of stored resources into energy is impaired)
- memory (sleep is critical for integrating memories into an ordered framework and assimilating new memories with older semantic knowledge; shown that place cells show an exact memory replay of an event that occurred during the day being repeated during sleep to consolidate it)
- e.g. total sleep deprivation (TSD) in rats - all TSD rats died within 11-32 days, showed to have a debilitated appearance and lack of immune response, weight loss etc.
- non-REM sleep deprivation leads to impairment of declarative memory; whereas REM sleep deprivation leads to impaired consolidation of learned motor skills
38
Q
Irregular sleep
A
- too short + long sleep and sleep issues are associated with poorer cognitive function
- sleep deprivation decreases attention and working memory, especially vigilance but also auditory and visuospatial attention and reaction time tasks
39
Q
Insomnia
A
- inadequate sleep may be due to shifts in circadian rhythm (e.g. trying to sleep whilst body temp rises)
- estimated prevalence in 10-35% of the population in Western Europe
- may also be due to noise, stress, pain, diet, medication etc.
40
Q
Sleep apnea
A
- inability to breathe during sleep
- leads to sleepiness during the day, impaired attention, depression and sometimes heart issues
41
Q
Narcolepsy
A
- frequent unexpected periods of sleepiness during the day (REM sleep intruding into wakefulness)
- caused by lack of hypothalamic cells that produce and release orexin
- treated with stimulant drugs (e.g. Ritalin)
42
Q
Periodic limb movement disorder
A
- repeated involuntary limb movements that can cause insomnia and mostly occur during non-REM sleep
43
Q
REM behaviour disorder
A
- vigorous movement during REM periods leading to acting out during dreams
- inability to paralyse limbs that normally happens during REM sleep
44
Q
Night terrors
A
abrupt, anxious awakening from non-REM sleep
45
Q
Sleepwalking
A
- normally occurs in deep sleep stages 3/4 early in the night
- more common in children but can occur in adults suffering from sleep deprivation or stress
46
Q
Differences in sleep across species
A
- all mammals and birds need sleep
- some utilise unihemispheric slow-wave sleep (e.g. dolphins so they can still resurface regularly to breathe) but it is mainly bihemispheric
- fish, reptiles and amphibians have periods of inactivity
- for most animals, sleep conserves energy during times when the animal is in an inactive period
- animals increase sleep during food shortages (hibernation)
47
Q
Auditory system
A
- primary domain for two sensory experiences most uniquely human (speech/language and music)
- how the brain translates sensory information into a perceptual representation of our environment
48
Q
Sound
A
- the periodic compressions of air, water or another medium
- in some spaces, air is rarefied and in other it is compressed
- bouncing back of sound waves is called echo
- hearing is the detection of sounds and constructing a model of the world based on this
- especially in a noisy environment, many sounds overlap at one time so the brain needs to use incoming sensory input and prior knowledge about sounds to separate them into different streams
49
Q
Auditory cortex
A
- located in the temporal lobe in Heschl’s gyrus (Brodmann’s areas 41 & 42)
- right hemisphere specialises in rhythmic sound and music; left hemisphere specialises in language
50
Q
Perception of sound
A
- outer ear (pinna) first captures the sound and amplifies it by funneling it into the smaller auditory canal
- middle ear contains the eardrum which collects the tiny vibrations
- eardrum transmits the vibrations to the ossicles (hammer, anvil and stirrup)
- their lever action transfers the vibration to the cochlea, via the oval window
- vibrations bend the hair cells on the Organ of Corti (3 rows of OHCs and 1 row of IHCs)
- this opens potassium and calcium channels to depolarise cells and set off signals in the neurons
- exciting cells of the auditory nerve (part of the 8th cranial nerve)
51
Q
Auditory pathway
A
- signal is first carried from the ear along auditory nerve
- first relay is the ispalateral cochlear nuclei in the brainstem
- here signal is decoded based on duration, intensity and frequency and most of the signal crosses over to the contralateral side of the brain
- second relay in the brainstem is the superior olivary nucleus in the pons
- third relay is in the inferior colliculus of the midbrain
- final relay occurs in the medial geniculate body of the thalamus
- then projects into the auditory cortex
52
Q
Sound intensity
A
- corresponds to how much air fluctuation (compression/rarefraction) a sound creates, i.e. the energy in the sound
- e.g. large vibration of speaker –> creates a lot of energy –> intense (loud) sound
- also correlates to amplitude
- intensity is measured in decibels (logarithmic scale)
- there is a non-linear correspondence between intensity and loudness (so we can determine whether a sound is louder or quieter but not whether it is exactly twice as loud etc.)
- intensity is encoded by neuron firing rate within the auditory cortex (neurons fire more frequently as sound intensity grows)
53
Q
Hearing loss above what intensity
A
90 dB
54
Q
Sound frequency
A
- correlates to the number of air compression/rarefraction cycles per second that the object creates
- perceptual correlate is pitch (but again there is not a linear correspondence)
- in reality, most sounds we hear our complex tones (combinations of many frequencies)
55
Q
Encoding frequency
A
- frequency is encoded by the Place code (different locations in the cochlea have different elasticity in the basilar membrane so correspond to different sound frequencies) –> tonotopic organism
- cells close to the apex respond to very low sounds; nearer the base respond to very high sounds
- primary auditory cortex is also tonotopically organised to correspond to the cochlea (more anterior = lower pitch; more posterior = higher pitch)
- for sounds < 200 Hz: lower frequencies are encoded by firing of individual neurons (temporal coding) and intensity is encoded by number of firing neurons (spatial coding)
56
Q
Normal human hearing range
A
20 Hz - 20 kHz
57
Q
Stereophonic hearing
A
- the placement of our ears on opposite sides of our head
- due to timing/intensity difference of sound reaching each ear we can perceive the location of sound
- also integrate this with visual orienting (produce an enhanced percept of a situation)
58
Q
Conductive hearing loss
A
- results from damage to the ear drum or ossicles in the middle ear
- failure to transmit sound waves to the cochlea
- can be corrected by medication (e.g. if due to inflammation of the middle ear), surgery or sound amplication from hearing aids or bone conduction
59
Q
Bone conduction
A
- sound is used to vibrate the mastoid bone
- cochlea receives the vibrations and turns them into electric signals to pass to the auditory cortex as usual
- allows hearing issues in outer or middle ear to be bypassed
60
Q
Sensorineural hearing loss
A
- damage to part of the cochlea/hair cells of the inner ear
- can be conginetal, as a result of disease or by repeated exposure to loud noises
- can be corrected by cochlear implants
61
Q
Cochlear implants
A
- surgically implanted electronic devices which receive sound signals via a microphone and digitally convert them to coded electrical signals
- communication coil used to transmit these signals through the skin to the implant
- electrical pulses transmitted along the electrode array to stimulate specific locations on the cochlea (for frequency perception as normal)
- delivers signals to auditory nerve and interpreted as sound by the auditory cortex
62
Q
Tinnitus
A
- sound perception within the ear in the absence of external input
- can be ringing due to abnormal patterns of activity sent to the brain by a damaged ear (e.g. due to ageing, sound damage) –> cured by surgically severing the auditory nerve that corresponds to the ringing frequencies
- or ringing can be caused by activity in the auditory cortex even in the absence of sound –> not curable surgically, but CBT can be used to help patients ignore the sound
63
Q
Auditory hallucinations
A
- MRI activations during auditory hallucinations in schizophrenia show ventricular enlargement
- also fMRI shows changes in brain activity even in absence of external input within the right inferior colliculus, right superior temporal gyrus (primary auditory cortex) and right thalamus
- can also be caused by brain damage (e.g. Shostakovich had damage to left temporal lobe so heard random sounds which inspired his music)
64
Q
Perfect pitch
A
ability to name and reproduce a musical note without external reference
65
Q
Relative pitch
A
ability to identify intervals between given tones
66
Q
Amusia (tone deafness)
A
- present in birth in 4% of the population or acquired as a result of brain lesions
- receptive: inability to recognise familar melodies, read musical notes and detect out of tune notes
- expressive: lack of ability to sing, write musical notes and play an instrument
