Biopsychology Flashcards
How does the brain send messages to the body?
- Through the nervous system (rapid/costly, network structure determines what cells receive
- Through vascular system (slow/cheap, membrane receptors determine what cells receive
- Think cost benefit trade off
Describe the history of life
- Prokaryotic cell (bacteria)
- Eukaryotic cell (more specialised cell that has more functions)
- Metazoa (first animals, multi cellular, digestive chamber
- Bilateria (digestive tract with separate front and mouth, muscle present)
- Chordates (tail for movement, beginnings of spinal chord)
- Vertebrates
- Jawed fish
- Mammals
- Primates
- Homo
What are the key points of evolution across species?
- Brain areas have associated function
- Humans and vertebrates share a similar gross structure
- Size of relative brain area indicates functional specialisation
How does an FMRI scanner work?
- When neurons become active, blood flows to the part of the brain to provide oxygen to fuel the cells.
- Hemoglobin (the iron-containing oxygen transporting protein present in blood) differs in how it responds to magnetic fields, depending on whether it has a bound oxygen molecule
- The MRI scanner, which is basically a giant magnet, detects these small changes in the magnetic field.
- not directly measuring brain activation. We are measuring blood flow (more precisely, the magnetic properties of oxygenated vs deoxygenated blood)
What are the problems with a bold signal?
-Arbitrary, slow (4-5 second delay), 16 seconds to return to baseline
What is a block design in relation to FMRI scans?
-long periods of alternating task/baseline performance (task/rest/task/rest ect)
What are the weaknesses of block designs?
- Highly predictable occurrence of stimuli: subjects know what is coming and may alter strategies accordingly (not always a pro)
- Inflexible for more complex tasks
- Ecological validity. Does blocking trials change the psychological process
- Can’t separate trials by performance – e.g. to look at activation associated with correct vs incorrect response
What is an event related design?
-Trials of different conditions are randomly intermixed and occur close together in time
What are the advantages of even-related designs?
- Flexible and can be randomised to eliminate practice effects and predictability
- Post hoc sorting of responses from conditions
- Can look at novelty and priming (rare/unpredictable events)
How is data collected from an FMRI?
- Volume of slices is collected (2-3 secs)
- Brain areas are referenced through universal mapping using voxels (3x3x3 mm cube referenced as a coordinate)
How is data processed from an FMRI scan?
- High pass filter (remove low frequency oscillations such as scanner drift)
- Motion correction
- Slice time correction (time between slices being gathered)
- Coregistration (spatial alignment of several images)
- Normalisation (spatial transformation of brains into a common space, making them comparable to each other. Uses a universally recognised “average brain”
- Spatial smoothing (modelling of neurons that may fire around a neuron that has fired)
How is data from an FMRI scan analysed?
- Bold signal correlated with time course of each condition
- T-Test btween values from each condition (seen as differing colour on scan)
- Adjust P value to account for error (130,000 voxels x 0.05 degree of certainty means false positives will be found)
What are the two types of data analysis used in this research and their strengths and weaknesses?
- Whole brain analysis (+ whole brain used, no hypoth needed/- loose spatial resolution, “laundry list of areas” that meaningless and difficult to interpret)
- Region of interest analysis (+hypoth driven no laundry list, simpler analysis, lends itself to meta analysis/- easy to miss other things going on in the brain, not always easy to define regions)
What are the overall limitations of FMRI?
- Correlative
- Low temporal resolution (accuracy in relation to time)
What is the corpus callosum?
-White matter tracts that connect the two brain hemispheres
What is the cerebal cortex?
-Grey matter on the outer part of the brain (nerve cell neurons, dendrites)
Where is white matter situated?
-Under the grey matter of the brain (long elongated axons)
What is a gyrus and a sulcus?
- Gyrus is the plateau on the cortical surface
- Sulcus is the ditch or fold on cortical surface (major ones can be referred to as fissures)
Describe the four lobes and how they’re separated
- Lobes : frontal, parietal lobe, temporal lobe, occipital lobe
- Central sulcus (vertical split from frontal & parietal lobe)/ Lateral fissure (horizontal split from temporal to frontal and parietal lobes)/ Parieto-occipital sulcus (occipital lobe from temporal & parietal lobes)
- The frontal lobe is important for cognitive functions and control of voluntary movement or activity. The parietal lobe processes information about temperature, taste, touch and movement, while the occipital lobe is primarily responsible for vision. The temporal lobe processes memories, integrating them with sensations of taste, sound, sight and touch.
What terms describe brain orientations?
- Superior/Dorsal refers to surface of the brain, Inferior/Ventral refers to structures within the brain
- Anterior/Rostral refers to front of the brain (forehead), Posterior/Caudal refers to back of the brain (back of the head)
- Medial refers to structures in the middle of the brain (between hemispheres), Lateral refers to structure in left or right hemisphere
What are the different images of slicing referred to as?
- Axial slice (horizontal slices from top to bottom)
- Coronal slice (vertical slice from front to back)
- Sagittal slice (vertical from left to right)
Name three spefic groups of neurons and their functions
- The reticular formation, a complex network of cells in the core of the brainstem involved in the control of arousal and sleep.
- The suprachiasmatic nucleus (Hypothalamus) controls the circadian (24 hr) biological rhythms
- The ventromedial nucleus (Hypothalamus) controls the conversion of blood glucose into body fat
Describe the process of perception
- The cortical areas where the sensory information arrives (via relay nuclei in the brainstem, particularly via the Thalamus) are referred to as primary visual/auditory/sensory-motor areas
- This perceptual information then gets passed to the secondary sensory areas, where more sophisticated processing takes place
- From the secondary sensory areas, the processing moves to the association areas, where information from different modalities and of different types is integrated
Describe the process of motor control
- The primary motor cortex exerts direct control over movement
- However, other areas (premotor and supplementary motor) are involved in the planning of movement and integration of motor behaviour with other behaviour
- In addition, some sub-cortical structures (Basal Ganglia) and brainstem structures and groups of cells (Cerebellum; Substantia Nigra) are also involved in the fine-grained co-ordination and timing of movements
Describe a non-essential activation
- Some process A essential for the task may often co-occur with another process B that is not essential for the task
- For instance, reading on a computer/laptop often goes hand in hand with typing on it, so a task of reading on a computer screen may elicit activations related to typing but typing is unlikely to be causally related to reading performance
What is neuropsychology?
-Neuropsychology is the area of psychology that examines the effects of brain damage on abilities and behaviour.
What are the key approaches to neuropsychology?
- Classical neuropsychology (primarily focuses on localisation)
- Cognitive neuropsychology (focused on cognitive architecture/equipotentialilaty/dissociation’s)
What is a single dissociation and its weakness?
- Analysing psyhcological processes without knowing the exact location of the damage
- However, at close scrutiny this single dissociation is not sufficient for drawing a conclusion
- For instance, it is possible that the same mental computations are used for both, but suppose that consonant letters are easier to differentiate visually from each other than vowel letters
- This could make consonants more resilient to the effects of brain damage, but would not necessarily demonstrate a qualitative difference in the way they are processed (read and written)
- But - if consonants are generally more resilient to the effects of brain damage, one should not find any patients with impaired processing of consonants and relatively spared processing of vowels
What is a double dissociation?
-The existence of such opposite patterns is referred to as double dissociation
What are the strengths and weaknesses of neuropsychology?
- advantage of neuropsychology over electrophysiology and neuroimaging is that it enables causal inference
- The main drawback is that lesions resulting from trauma or neurological degeneration are rarely anatomically selective- they tend to affect multiple brain regions/structures
- Also, brain damage is always associated with general cognitive, emotional and personality changes whose effect on cognitive performance is very considerable and difficult to separate from the effects of damage to a specific region/structure
- Ethically can’t recreate damage
What is TMS?
-Transcranial magnetic stimulation
A large current is briefly discharged into a coil of wire held on the subject’s head.
- The current generates a rapidly changing (increasing) magnetic field around the coil of wire and this field passes into the brain.
- In the cortex, the magnetic field generates electric (ionic) current through neurons’ membranes
- Can stimulate motor cortex (muscle contractions occur) & visual cortices (flashing patterns known as phosphenes)
- Referred to as a virtual lesion as the activation often causes disorganisation of neural activity causing an effect similar to that of a lesion
What are the advantages/disadvantages of TMS?
- Strengths: Can determine causation
- Good spatial resolution and excellent temporal resolution
- Is reversible allows for within group analysis and is ethical
- Weaknesses: Can’t be used as a control due to noise and sensation it elicits
- Can’t reach deeper brain regions
- More subtle than actual brain damage
- Can elicit seizures especially in those with epilepsy (is considered safe)
Describe what a micro-electrode recording is
- Electrical activity can be measured from brain tissue using very thin electrodes (micro-electrodes) inserted into the tissue
- The technique is also referred to as single-cell recordings, because typically the data are acquired from single brain cells (neurons)
- Because these recordings are invasive (one needs to perform surgery to do them), they are performed in humans only when they undergo brain surgery
- What is typically measured is the firing rate (or spike rate)- the frequency of action potentials a cell generates
What is a strength and weakness of micro-electrode recordings?
- Strength: most precise and direct measure of brain activity
- Weakness: Highly invasive (restricted in both subjects and brain areas)
What does EEG stand for?
-Electroencephalography
What is field potential?
- A temporary deficit of positive charge develops in the area of extracellular space where sodium enters the neuron
- A temporary surplus of positive charge develops in the area near the soma, where potassium exits the cell
- This creates field potential outside of the neuron
How is an EEG different from micro-electrode recordings?
- EEG can’t detect spiking behaviour (action potential) as they can’t reflect the electrical fields elicited and action potentials are to small/short
- Also are less sensitive to brain structures located deeper within the brain
Give strengths and weaknesses of EEG’s/ERP’s
- Strength: Cheaper and more portable than other methods (fMRI)/ high temporal resolution
- Weakness: Can lack precision as multiple frequencies can be in-bedded in a recording as EEG measures a more general area than single-electrode recordings/ limited spatial resolution
What is an ERP?
- Methodological analysis of EEG, by extracting time-locked specific events from raw EEG data
- Background activity is removed stimulus is shown multiple times to create an average signal
What are the CNS and PNS? and their overall purpose?
- CNS= central nervous system (brain and spinal chord)
- PNS= peripheral nervous system (everywhere else in the body)
- Monitor and regulate inner organs , release chemicals, change internal states (sleep,hunger,emotions)/ Analyse info from the body and environment/ generate responses & motor control
What are the neuron zones?
- Input zone (soma, dendrites) neurons collect and integrate information
- Integration zone (between soma & axon) decision to produce signal is made
- Conduction zone (axon) where information can be transmitted over distances
- Output zone (axon terminals) where neuron transfers information to other cells
How does a neuronal membrane allow transmission from inside and outside of cell
-Selectively permeable membrane allows transmission via channels (have to be specific size & charge)
How do ions move across cell membranes?
- Diffusion (high to low gradient) occurs when ion channel is open
- Electrostatic forces (opposites attract, like charges repel)
Describe the accumulation of ions at a cell membrane?
- Ion distribution differs inside and outside of cell which forms an electrochemical gradient (due to electrostatic forces)
- Neural cell membrane accumulates charges on both sides acting as capacitor (similar to a battery)
Describe what happens when neuronal membrane is in a semipermeable state?
-Ions start to move being pushed or pulled back depending how the electrochemical gradient changes as ions cross the membrane.
For example:
Diffusion through leak channel allows K+ out of the cell, but then there is slightly more positive charge outside, and slightly more negative charge inside. So electrostatic forces rapidly start to pull K+ back in …
Diffusion through voltage-gated Na+channels of Na+ into the cell along the concentration gradient, but the more enters the more positive becomes the intracellular cytoplasm. So electrostatic forces start pushing Na+ back out if the channels do not close or unless equal amounts of K+ flow out at the same time (for example through leak and open voltage-gated K+ channels)
Identify and explain what the three classes of ion channels are?
- Gated ion channels remain closed until activation for a very brief period of time, either by electrical signals (voltage-gated) or by drugs or messenger molecules (ligand-gated).
- Ion pumps actively transport ions in and out of the neuron
- Leak channels allow a specific ion type to freely diffuse (e.g. they are always open and let K+ through but not Na+)
How do ion pumps work? What are the most important?
- Capture small molecules (e.g. Na+, K+ or Ca2+) from one side of the membrane and carry them across to the other side against concentration gradient.
- Powered through temporary phosphorylation of pump’s catalytic subunit which breaks off one phosphate group of ATP, synthesised by mitochondria, which becomes ADP After some time. The phosphate group is uncoupled to free up the binding site for the next transport action.
- Na/K pump (three Na out and 2 K in)
- Ca pump (takes Ca out of cytoplasm)
What is a leak channel and how does it work?
-Potassium channels in the cell membrane that are always open and allow only potassium to pass through
What are microelectrode recordings?
-Neuronal signals are measured as difference in potentials on each side of the membrane (units – Volt) by creating an electrical circuit that connects wired electrodes with the fluids of the neural tissue
What is resting potential in a neuron?
-membrane potential of a nerve cell at rest, e.g. neuronal membrane is polarised (typically -70 mV, inside of axon is negatively charged)
What is a neural signal
-change of resting potential to more negative or positive potential when ions move across the membrane
Describe what a graded potential/action potential is and what is meant by hyperpolarisation/depolarisation
- Hyper= more negative than resting potential
- Depolar= more positive than resting potential
- Graded= a potential that can either be hypo or depol
- Action= Always depol that creates a response greater than the neuron specific threshold, greater excitation over the threshold creates greater frequency of actio potentials (size of action potential always stays the same)
Describe an action potential
- Resting potential – voltage-gated channels are closed
- Rising phase – shooting up in the depolarisation caused by the opening of voltage-gated Na+ ion channels
- Overshoot – the membrane potential becomes positive as more and more Na+ flow into the cell (positive feedback loop)
- Falling phase – Na+ ion channels become inactivated and close, while K+ channels open leading to a reduction of positive charge inside of the cell
- Undershoot – K+ ion flow out of the cell through the open K+ channels
- Recovery - refractory period during which all channels are closed and membrane potential returns to resting value
Name three types of synapses
-Axo dendritic, axo somatic and axo axonic
Describe ionotropic receptors interaction in post synaptic transmission
- Action potential opens Ca channels, Ca triggers vesicle fusion and neurotransmitter release, neurotransmitter binds with ionotropic receptors opening ion channels
- This is a fast signal transmission
What are ligandgated ion channels and autoreceptors?
- Channels that opened when bound with neurotransmitters
- Communicate to presynaptic cells the net concentration of neurotransmitter in the cleft
Describe how a metabotropic receptor works
- Neurotransmitter binds to G protein coupled receptor
- G protein is activated
- G protein travels to adjacent ion channel (brief delay)
- Opens ion channel
- This is a slow, long lasting varied process
What is a non-spiking neuron?
A neuron that doesn’t generate action potentials, have no on/off switch and are more sensitive to signal noise
What helps to compensate for signal loss in neuron transmission?
- Thciker axons better insulate signal
- Nodes of ravier work as myelin insulation offers considerable resistance to the flow of ionic currents across the membrane, the action potential jumps from node to node. This process is called saltatory conduction
Describe excitatory synapses and inhibitory synapses
- Action potential in excitatory synapse causes depolarisation in postsynaptic neuron (causes it to fire)
- Action potential in inhibitory synapse causes hyperpolarisation in postsynaptic neuron (doesn’t fire)
- The sum of these signals at a neuron determines the outcome (e.g. if two excitory responses and one inhibitory response are received by a neuron the sum of the three together determine the response)
How is information coded in neural networks?
- In feedforward circuits the signal is distributed to many neurons through divergence of their connections, or is determined by collecting signals from from many neurons through convergence.
- ) Spatial and temporal summation at the synapses determine the strength of the signal when it is passed on from one neuron to the next
How do feedback loops work?
- Feedback loops (positive, negative) provide direct or indirect input influencing signals and thus information
How does training increases synpase efficiency?
- Increased release of neurotransmitter
- Increased membrane size or sensitivity
- Pre and post synaptic size
Describe two forms of synaptic plasticity
- Preysnaptic depression where continued exposure to a stimulus causes habituation and a weaker response. This is because less neurotransmitter is released over time and eventually retraction of some synaptic terminals (sea hare)
- Sensitisation where inter-neuron modulation (neuron gives more neurotransmitter to another neuron) increases strength of response. As seen sea hare which was shocked before given stimulus increasing strength of response. Is an example of non-associative learning
How has the hippocampus been shown to be involved in memory?
- Maquire found taxi drivers have larger hippocampi for spatial learning and route memory
- Morris found that rats with lesions over their hippocampi had their memory impaired
What does LTP stand for?
-First discovered by Terje Lømo in 1966, long-term potentiation (LTP) is a long-lasting strengthening of synapses between nerve cells due to continued strong firing. Psychologists use LTP to explain long-term memories.
How do AMPA/NMDA receptors work?
- AMPA receptors are ionotropic receptors that open when glutamate binds to them allowing Na to pass through them into postsynaptic neuron causes a excitatory response
- NMDA are both ligand and voltage gated, they are blocked by a Mg plug. Open if glutamate binds to them and membrane depolarises (Because of AMPA receptors) to expel Mg plug. This leads to an influx in Ca and creates EPSP and LTP (EPSP stands for excitatory response)
How do AMPA and NMDA receptors help LTM?
-AMPA activating NMDA allows for Ca to activate CREB that then targets genes responsible for growing new dendritic spines and synapses
What evidence is there that shows NMDA receptors are important in spatial learning?
Morris gave rats AP5 treatment which inhibited NMDA receptors (blocks them). The rats could not learn spatial learning task
Describe synaptic transmission of Ca
- When the action potential reaches the axon terminal, it opens Ca2+ voltage-gated channels
- Ca2+ has higher concentration outside, hence the concentration gradient pushes it into the cell
- Ca2+ ions have a specific property: they interact with neurotrasmitter vesicles (storage), pushing them towards the membrane
Describe synaptic transmission
- Once the vesicles containing the neurotransmitter reach the membrane, they open up and the neurotransmitter is released into the “synaptic cleft”
- The neurotransmitter then binds to its receptors in the postsynaptic neuron. If these receptors are themselves ion-channels, they open when the neurotransmitter interacts with them
- If the receptors are not ion channels, they interact with specific ion channels and eventually open them
- As a consequence, ions enter the postsynaptic neuron, resulting in a Post-Synaptic Potential
What is inactivation and recycling of neurotransmitter?
- Inactivation= Diffusion: the transmitter is “lost” in the inter-cellular space & Enzymatic degradation: enzymes break down the transmitter
- Recycling = re-uptake where the transmitter is recycled either in the pre-synaptic or the post-synaptic neuron. This is the most economical way to inactivate the transmitter
Name four ways drugs can influence the synaptic sequence with an example
- propagation of the action potential e.g. TTX is toxin, found in some fish, that block ion channels in nodes of ravier in the respiratory system leading to death (paralyses muscles)
- the release of the transmitter e.g. tetanospasmin toxin interferes with GABA vesicles and binds to cell membrane, instead of vesicle, reducing amount of GABA released. Leads to muscle contractions as GABA inhibits this/ aphetamines in contrast effect dopaminergic pathways (increases dopamine) such as VTA linked to reward
- modulate how the transmitter interacts with the post-synaptic channels (receptors) e.g. curare acts as a ANTAGONIST (blocks but does not activate a channel) in acetylcholines receptors in excitatory synapses causing paralysis/ Heroin is an AGONIST (imitates behaviour of a neurotransmitter increasing its effect) of endorphines which bind to opiate receptors reducing muscle pain and inducing relaxation
- modulating its inactivation and recycling e.g. cocaine blocks the transporter of dopamine and nor-adrenaline preventing re-uptake and boosting their effect.
What is a monoamine?
-Neurotransmitter with a single amino group such as dopamine, adrenaline, serotonin and melatonin
Describe how two psychoactive substances work
- Caffeine= Many of the neurons that release substances like dopamine and adrenaline (catecholamines) also release a self-inhibiting transmitter- adenosine. Adenosine binds to its receptors in the pre-synaptic neuron and inhibits the release of catecholamines. Caffeine competes with adenosine for its receptors (it is an antagonist), blocking adenosine and thus reducing its inhibitory effect. It also inhibits cAMP which regulates energy levels in cells thus increasing glucose metabolism in them
- Alcohol= agonist of GABA so induces relaxation and in higher doses binds to GABA channels leading to sedation. Indirectly stimulates dopamine releases leading to small euphoria.
Describe psychoactive substances are used to treat psychiatric conditions
-Benzodiazepines (valium) are used to treat anxiety disorders. Anxiety disorders are characterised by deficits in GABA, valium act as agonists of GABA. They are non-competitive and bind to other sites than what GABA binds to
-MAO inhibitors prevent MAO enzyme from breaking down serotonin, dopamine and noradrenaline, used to treat depression
/ SSRIs inhibits transporter and re uptake of serotonin
