Biological Psychology

• Biological psychology is the study of the relationship between psychological events and processes and physical events in the brain

  • Aims: To understand how the brain creates the mind and to uncover distinct psychological processes through their reflection in distinct brain processes
  • Issues: matching methods to the hypothesis being tested and ethical and practical considerations
• Biological Psychology

  • Can discover how the brain works by either observing and measuring or manipulating
  • Biological and physiological method must be appropriate -> measure or manipulating
  • Matching methods to hypotheses
  • Causal or correlative
  • Species psychologically applicable or invasive
  • Spatio-temporal resolution physically applicable
• Biological Psychology

  • Spatial and Temporal Scales
  • e.g., is the hypothesis about individual neurons or cerebral hemispheres
  • e.g., is the hypothesis about individual action potentials or long lasting changes in synapses
• Biological Psychology - Relevant sizes (spatial)

  • Whole brain - 25 cm
  • Typical Topographic Map - 5 mm
  • Cortical column - 250 μm
  • Cortical layer - 50 μm
  • Neuron (varies) - 10 μm
  • Dendrite - 1 μm
  • Synapse - 100 nm
• Biological Psychology - Relevant Times (Temporal)

  • Biological
  • Neural refractory period - 2ms
  • Signal time from eye to brain - 20-100ms
  • Psychological or behavioural
  • Time to make eye movement - ~100ms
  • Time to orient to spatial attention - ~150ms
  • Simple reaction time - ~250ms
  • Learning - seconds-minutes
  • Induced mood change - minutes
• Lesions

  • Changes in psychological function accompanying brain damage may reveal something about the function of the damaged tissue
  • After accidental injury, damage, and abnormal change in humans, or intentional damage in animals
  • Phineas Gage - left frontal lobe highly damaged, leading to changes in personality to do with lacking inhibition and planning
  • Tan - impaired speech production, left frontal damage to 'Broca's Area' leading to 'Broca's Aphasia': limited speech and loss of grammatical structure. Later identification of Wernicke's Area: language comprehension
• Lesion

  • HM - removal of parts of medial temporal lobes, including hippocampus, severe anterograde memory, inability to store and retrieve new memories, normal implicit learning: improved at tasks without memory of learning
  • Logic of Experimental Lesion Method
  • 'Is brain region X important for task A' -> localisationist perspective
  • Ignoring adaptive and 'parallel' brain processes can lead to false conclusions
  • Lashley -> found learning occurred everywhere in the brain: larger lesion = larger deficit, harder task = more brain required -> 'principle of mass action'
• Lesions - Single vs Double Dissociations

  • Single Dissociation - 1 lesion group, 1 control, 2 tasks
  • Believe lesion group to be impaired in one task but intact for other
  • Must assume both tasks are equally sensitive to group differences
  • Single dissociation may be from general effects of trauma
  • Double Dissociation - 2 lesion groups, 1 control, 2 tasks
  • Dorsal lesions impaired at water maze task (spatial impairment)
  • Ventral lesions impaired at fear task (contextual fear impairment)
  • Involvement of hippocampus in contextual fear condition not a requirement for spatial learning
• Deactivation Methods

  • Lesions destroy tissue permanently -> irreversible and invasive -> can't study humans
  • Reversibility allows animals to act as controls but can raise design issues
  • Deactivation - Chemical Methods
  • Drugs in small quantities to specific brain areas can deactivate specific regions temporarily -> i.e., muscimol for GABA
  • DREADDS - engineered receptors can be activated or deactivated by a certain drug allowing for changes over a sustained and short period of time
• Deactivation Methods - Transcranial Magnetic Stimulation

  • An electrical pulse in a coil is used to induce a sudden change in a magnetic field in the area below it
  • This temporarily interferes with brain activity for a hundredth of a second
  • Good temporal resolution for cortical regions
  • Can have reasonable (<1cm) spatial resolution in conjunction with 3D MRI
  • No known side effects in humans
• Neuroimaging Techniques - MRI

  • Manipulates the behaviour of hydrogen ions to yield radio signal - different types of tissue produce different radio signals
  • Maguire (2000) - posterior hippocampal volume correlated with time spent as a taxi driver -> spatial representation of environment and can expand to accommodate elaboration
  • Functional MRI - detecting blood oxygen level, a change in BOLD signal indicates a metabolically active brain region
  • Spatial resolution - 'voxels' - balance resolution with area covered and acquisition time, resolution can vary ~3mm
  • Temporal resolution poor
• Neuroimaging Techniques - Functional MRI

  • Image Analysis: comparing signal strengths in different behavioural conditions, whole brain analysis involves tests on every voxel -> difficult due to many ways to correct for each test. Region of interest studies only test a few voxels per brain region - care needed picking the region
  • Criticisms
  • New phrenology - careful behavioural designs and statistical analysis
  • Over-emphasis of localisation of function
  • Correlation not causation
  • Early studies apply uncorrected statistical tests to neuroimaging data
• Neuroimaging Techniques - Functional MRI - what it can tell a psychologist (Henson, 2005)

  • Function to structure inference - if different activity is detected under different task conditions, then the tasks are functionally dissociable
  • Structure to function inference - if the same pattern of activity is detected under two task conditions, then the tasks require a common function
  • Inferences rely on the assumption that there is localisation of function within the brain
• Neuroimaging Techniques - EEG

  • Electrodes on the surface of the scalp record electroencephalograms
  • EEG activity is the results of electric fields generated by summing IPSPs or EPSPs in thousands or millions of cells
  • Spatial localisation possible with multiple electrodes
  • Multi-electrode EEG -> temporal resolution good, signals weak so need to be averaged over many trials, spatial resolution poor, poor for deep activity
• Neural Recording - Electrophysiology: Single Cell Recording

  • Implanting a small electrode to pick up extracellular activity
  • Only picks up cells that are near and active at that time
  • O'Keefe (1975) - place cells that fire in the hippocampus in particular contexts/locations
  • High spatial and temporal resolution but small number of cells
  • High channel electrophysiology - thin probe rather than a bundle of electrodes -> hundreds of recording channels that can record thousands of cells in real-time
• Neural Basis of Learning

  • Learning - change in behaviour resulting from experience
  • Looking for a physical change in the brain that corresponds with this learning
  • i.e., Pavlovian conditioning -> 2 stimuli become linked, generating a new behavioural response to a previously neutral stimulus
  • Learning is a psychological process of pairing events together - looking for a neural mechanism that would allow for associations to be formed
• Neural Basis of Learning - Hippocampus

  • Important for learning and memory - cellular basis of learning and memory, processes multimodal sensory and spatial information
  • Kindling - idea that prior stimulation of neurons increases the likelihood of neurons firing
  • Pre-synaptic and post-synaptic populations must be segregated and easily identifiable - Bliss and Lorno (1973) - hippocampus
  • Stimulate the Perforant path, record post-synaptic activity in dentate gyrus
  • Some EPSP prior -> repeated stimulation -> Increased EPSP (long-term) -> weak stimulation now leads to strong response
• Neural Basis of Learning - Long Term Potentiation

  • Key Properties: effects are long-term, and only occurs when firing of pre-synaptic neuron is followed by firing of post-synaptic neuron (co-occurrence)
  • Hebbian Basis of Memory - neurons that fire together, wire together
  • i.e., conditioning rabbit eye blinking -> strong sensory neuron and weak auditory neuron fires onto motor neuron -> repeated pairing leads to strengthened response where tone alone is sufficient to generate a post-synaptic response -> motor neuron more receptive to weak auditory synapse
• Neural Basis of Learning - Properties and Processes of Hippocampal LTP

  • NMDA receptor - 'fussy' - only opens in the presence of the neurotransmitter (glutamate) and when the post-synaptic membrane is depolarised -> pre- and post-synaptic activity coincidence detector
  • Ion-channel associated with the NMDA receptor is normally blocked by a positively charged magnesium ion -> depolarisation means the ion is no longer attracted
  • If pre-synaptic neuron continues to fire, glutamate continues to be released
  • Glutamate binds -> allows calcium to enter the cell
• Neural Basis of Learning - Hippocampal LTP: Post-Synaptic Changes 1: AMPA receptor

  • Muller (1988) - AMPA receptor antagonist prevents LTP expression
  • Tocco (1992) - LTP changes number of AMPA receptor numbers
  • AMPA is not 'fussy' -> only needs glutamate to bind to it
  • LTP requires AMPA receptors
• Neural Basis of Learning - Hippocampal LTP: Post-Synaptic Changes 2: Protein Synthesis

  • Blocking protein synthesis prevents LTP (Nguyen, 1994)
  • The structure of the cell may change due to calcium entering the cell
  • Post-synaptic structural changes: long-term increase in AMPAR's, growth of new synapses, enlargement of synapses, splitting of synapses, enlarged post-synaptic area that glutamate can bind to
• Neural Basis of Learning - Hippocampal LTP: Pre-synaptic effect

  • More radio-activity in synapse after LTP
  • Enhanced glutamate release in pre-synaptic cell -> interacts with increased area and receptivity -> easier to trigger
  • Retrograde transmitters from post-synaptic cell -> release of nitrous oxide that induces changes in the pre-synaptic cell -> production of glutamate is increased
• Neural Basis of Learning - Long Term Potentiation Summary

  • LTP strengthens synaptic connections between neurons
  • Glutamate release activates AMPA receptors, frequent action potentials cause post-synaptic neuron to be depolarised
  • Magnesium ions no longer attracted to NMDA receptor -> calcium ions can flow in
  • Post-synaptic changes -> increases in AMPA receptors -> more receptive to glutamate
  • Post-synaptic cell releases NO (retrograde transmitters) to cause the pre-synaptic neuron to release more glutamate
• Neural Basis of Learning - LTP and learning and memory

  • Associative learning requires the formation of links between different stimuli, LTP is a mechanism for the formation of links between neurons
  • NMDA receptor (coincidence detector) -> LTP only occurs if cell is depolarised and glutamate binds to the receptor
  • Coincidence detection is important in associative learning -> i.e., neurons involved in 'food' are depolarised, and will only form synaptic connections with 'bell' neurons that are concurrently firing and releasing glutamate -> associations only formed with concurrent activity
• Neural Basis of Learning - Is Hippocampal LTP required for Spatial Learning?

  • LTP observed in hippocampus and hippocampus involved in learning and memory, especially spatial learning
  • Morris water maze -> hippocampus-dependent
  • AP5 (NMDA receptor antagonist) failed to improve at task -> impaired spatial learning, but also showed sensorimotor impairment
  • Bannerman (1995) -> water mazes on separate floors
  • AP5 impaired performance when there was no pre-training
  • AP5 did not impair performance when rats had pre-training
  • LTP in hippocampus may not be necessary for spatial learning
• Motivation - Basic Drives: Homeostasis

  • The body strives to maintain a consistent environment -> biological needs impact behaviour, which is impacted by learning
  • When the body is challenged by an unavoidable loss of a regulated variable, there is an effect on motivation that leads to a change in behaviour
  • i.e., losing weight -> body has desire to maintain a certain weight -> restriction of food leads to a reduction in metabolic rate -> limiting extent of weight loss
• Motivation - Basic Drives: Homeostasis - Brain systems for controlling hunger

  • Different regions of the hypothalamus have different roles in feeding behaviour
  • Lesions to the ventromedial hypothalamus result in overeating (hyperphagia) -> involved in satiety
  • Lesions to the lateral hypothalamus results in lack of hunger and weight loss (aphagia) - necessary for hunger
• Motivation - Behaviour motivated by learning, not just immediate needs

  • Schepers and Bouton (2017) - rats trained to press a lever when either hungry or not
  • If behaviour is driven solely by needs, the hungry rat will press the lever more
  • Rats press the lever more in the sated condition -> context-dependent learning: learnt that when they are sated, food will appear -> not just current motivational state
• Motivation - how motivational states affect behaviour

  • Hull's Drive Reduction Theory: drive - motivational state activated by a biological need; reinforcers satisfy needs and reduce drive; habit is what has been learnt about a reinforcer satisfying a need
  • Behavioural strength = Drive x Habit
  • If Drive or Habit = 0, there will be no behaviour
  • Bolles (1975) -> the more motivated (drive) a rat is (23h food deprivation), the more times they will press the lever; the more learning they have (reinforcement), the more times they will press the lever before extinction
• Motivation - is Drive and Habit sufficient enough to describe adaptive behaviour?

  • Balleine (1992) -> pressing lever leads to food when either sated or hungry; sated or hungry during test
  • Hull assumes that motivational state during learning is not important and that you learn the 'habit' either way
  • Sated group -> increasing drive (hunger) did not increase behaviour -> have to learn that outcomes have a rewarding property
  • Hull: drive is a response to need, state of depletion motivates behaviours; evidence indicates behaviour is motivated by a desire to anticipate or avoid need
• Learning and Motivation - Anticipating Need (Fitzsimons and Le Magnen, 1969)

  • Rats on a high protein diet need to drink a lot; when rats on a low protein diet switch to a high protein diet, they initially drink lots after meals
  • Eventually, rats increase their water intake prior to meals -> learnt association and anticipated future need for thirst
• Learning and Motivation - Optimising Time and Effort (Collier and Johnson, 1997)

  • When it is easy to obtain food, animals will eat small amounts frequently
  • As it gets more costly and effortful to obtain food, meal size increases -> overall intake remains constant -> eating in an optimised way
  • Behaviour is structured in anticipation of needs and reduction of expenditure of effort
• Learning and Motivation - Anticipation (Birch, 1991) - pre-school children

  • Children played in rooms where snacks were either available or not. Prior to test, children ate ice cream until full, then played in same room with snacks fully available
  • Children who played in room associated with snacks showed potentiated eating -> less time elapsed before they ate the snacks even when full; learning can lead to overeating
  • Association between cues and reinforcers can lead to a state of depletion being avoided
• Learning and Motivation - Cue Potentiated Feeding (Johnson, 2013; Corbitt and Belleine, 2011)

  • Cues associated with food can lead to overeating when sated, even when drive is 0
  • Pavlovian to Instrumental Transfer: Stage 1 - Pavlovian, auditory cues; Stage 2 - Instrumental, lever pressing; Stage 3 - PIT, combined levers and audio cues
  • General PIT - behaviour usually increases -> response heightened if another cue shows that food will be available
  • Specific PIT - sound and lever associated with same reward leads to enhanced performance -> behaviours can be enhanced with cues to signal rewards
• Learning and Motivation - Acquired Motivation

  • Rewards can also have an emotional effect that impacts behaviour
  • Contrast Effect: Negative Contrast -> Flaherty (1991) -> rats who went from a 32% to 4% sucrose solution drank less than rats who only ever drank 4%
  • Lick clusters show palatability -> as concentration increases, lick cluster size increases -> Austen and Sanderson (2016) -mice from 32% to 4% drank it like it was less palatable -> like they were disappointed
• Learning and Motivation - Incentive Motivation (Spence)

  • Drive - motivation state driven by need; habit - the extent of learning; K - incentive motivation (motivating effect of reward) driven by prior experience
  • Behavioural Strength = Drive x Habit x K
  • i.e., Birch (1991) -> preschool children, during test drive was low but incentive motivation was high
  • i.e., Flaherty -> rats and sucrose, negative contrast effect reduced incentive motivation, even though drive was high
• Learning and Motivation - Drive and Habit: conclusion

  • The need to maintain homeostasis results in motivational states that affect behaviour
  • Changes in behaviour are not just in response to biological needs, but also in anticipation of need
  • These anticipatory behaviours reflect learning of signals of reward and the incentive value of rewards
• Learning and Motivation - Neural Basis of Reinforcement

  • Olds (1958) - rats with electrode in ventral tegmental area pressed lever to provide stimulation up to 700x per hour -> preferred lever pressing over food -> rewarding behaviour
  • Dopamine: stimulation of VTA leads to dopamine release, nucleus accumbens have dopaminergic neurons; also assesses value of stimuli, motor cortex leads to consequential behaviour
  • Nucleus accumbens - Mobbs (2003) - funny cartoons led to activation of the NAc -> integrating information and rewarding properties
• Learning and Motivation - Dopamine and Reward

  • Wise (1978) - rats given Pimozide (dopamine receptor antagonist) stopped pressing lever to receive food -> like food was no longer rewarding
  • Anhedonia Hypothesis (Wise, 1982) -> good stopped tasting good; general reduced liking of stimuli -> dopamine = 'pleasure' chemical of brain?
• Learning and Motivation - Dopamine and Liking

  • Parkinson's damages dopamine producing neurons, Seinkiewicz (2013) - patients did not differ in pleasantness rating of sweets
  • Non-verbal behaviour -> automatic reactions: hedonic vs aversive: Berridge and Robbinson (1998) - rats given 6-OHDA drug that selectively destroys dopaminergic neurons -> no reduction in hedonic reactions to sucrose -> no evidence that dopamine depletion reduces liking