Biological Bases and Memory Flashcards
Vasodilation
Widening of blood vessels due to the relaxation of the blood vessel’s muscular walls
Episodic memory
Memory for personal experiences
Semantic memory
Recollection of ideas and facts
Autobiographical memory
Memory for one’s personal history
Emotional memory
The interaction between memory and emotion, often important for episodic memory
Encoding
Conversion of information into a form that can be stored in memory
Storage
Creation of a trace of information within the nervous system
Retrieval
Attempt to recover memory trace
Hermann Ebbinghaus
Pioneered study of forgetting; discovered the forgetting curve
Forgetting curve
Ebbinghaus found that most information was lost from memory if there was no attempt to retain it; forgetting occurred rapidly at first and then slowed noticeably thereafter
Levels of explanation
Biological, individual, social, and cultural
Peterson & Peterson 1959
Found that without rehearsal, information in short-term memory has a shelf-life of up to 20 seconds
George Miller 1956
Magic number seven; most people can hold no more than five to nine meaningful items in short-term memory
Issues with unitary model of memory
Generalised short-term and long-term memory into one without accounting for differences; memory as an infallible video-recorder
Sensory memory
Briefly holds incoming sensory information; comprised of different subsystems called sensory registers, which are the initial information processors
Scolver & Milner 1957 (Patient H.M.)
H.M. had a bilateral medial-temporal lobectomy; provided evidence for the existence of separate memory systems (impairment of long-term memory can exist alongside intact short-term memory)
Atkinson & Shiffrin 1968-71 (multi-store memory model)
The multi-store memory model viewed short-term memory as a temporary holding station along the route from sensory to long-term memory (information remaining in short-term memory is eventually transferred into more permanent storage)
Multi-store memory model (different stores)
Sensory memory (300-3,000 milliseconds), short-term memory (20 seconds; temporarily holds a limited amount of information), and long-term memory (storage capacity is unlimited and information can be retained for decades)
Serial position effect (primacy and recency effects)
Ability to recall an item is influenced by the item’s position in a series; primacy effect (superior recall for first items) and recency effect (superior recall for last items)
Bias in encoding: Phonetic (STM)
STM memory relies largely on phonetic encoding (the encoding of information based on sound), meaning that it often fails to differentiate between similar-sounding words
Bias in encoding: Semantic (LTM)
LTM relies more on semantic memory (semantic encoding focuses on the meaning of information), meaning it struggles to differentiate between words with a similar meaning
Baddeley & Hitch 1974 (working memory model)
Labelled STM ‘working memory’ because they believed STM to be active in both encoding and retrieval of information
Four components of working memory
- Central executive: directs overall action
- Visuospatial sketchpad: briefly stores visual and spatial information
- Phonological loop: briefly stores mental representations of sounds (two subsystems exist within the auditory component itself: the phonological store and the articulatory loop)
- Episodic buffer: temporary storage space where information can be integrated, manipulated, and made available for conscious awareness
Chunking
The combining of similar items into a group, making them easier to recall
Warrington & Shallice 1970 (Patient K.F.)
K.F. suffered damage to the left parieto-occipital region of the brain and later had a left-parietal subdural haematoma removed. Retained LTM, but had some issues with STM (particularly verbal information and not really visual) –> supports Working Memory Model
Craik & Watkins 1973 (maintenance rehearsal)
Simple repetition of information that keeps it active in working memory; not an optimal method for the transfer of information into LTM
Bransford & Johnson 1972 (elaborative rehearsal/ encoding)
Focuses on the meaning of information or expanding it in some way; Bransford & Johnson found strong effects of prior context on subsequent recall
Shallow processing
Sensory encoding
Deep processing
Semantic encoding - finds meaning in information and links it to other information in the LTM
Stein & Bransford 1979 (elaborative rehearsal/ encoding)
Participants had a better rate of recall for sentences that were either elaborated on or that they were asked to elaborate on themselves
Schema
Mental framework that helps to organise and encode details about a particular topic
Semantic networks
Network of associated information; recall of one item of information might lead to associated information also being recalled
Anterograde amnesia
Impaired capacity for new learning
Retrograde amnesia
Loss of information acquired before onset of amnesia
Memory consolidation
Strengthening of stored information/ trace of information over time
Method of loci
Memory aid that associates information with mental images of physical locations; Dresler et al. 2017
Godden & Baddeley 1975 (encoding-retrieval context)
Typically easier to remember something in the same environment in which it was originally encoded; lists learned underwater were recalled better underwater and lists learned on dry land were recalled better on dry land
Butters & Albert 1982 (famous faces test)
If you can’t identify the face, then your amnesia extends back to at least when that person was first in the news
Priming
The activation of one unit of information by another; ‘spreading activation’ of related concepts
Habit
Habit formation is the process by which behavioural control shifts from goal-dependence to context-dependence
Conditioning
Stimulus provokes an encouraged response
Skill learning
H.M. retained procedural memory (mirror-drawing task)
Procedural/ implicit memory
Ability to perform skills and actions
Declarative/ explicit memory
Recall of information; involves factual knowledge
Four sins of memory (forgetting)
- Transience/ memory decay (reduced memory over time)
- Blocking/ retrieval failure (can’t remember necessary information)
- Absentmindedness/ encoding failure (reduced memory due to failure to pay attention)
- Persistence (resurgence of unwanted memories)
Trace decay
Long-term physical memory trace of information in nervous system fades with time
Interference-based forgetting
Other items in the LTM impair ability to retrieve information; gets forgotten
Proactive interference
Material learned in the past interferes with the recall of newer material
Retroactive interference
Newly-acquired information interferes with the ability to recall information learned at an earlier time
Retrieval failure (tip-of-the-tongue state)
Cannot recall something, but feel that we are on the verge of remembering it
PTSD
Occurs after an instance/ instances of trauma; symptoms may include: avoidance, psychophysiological reactivity in response to trauma-related stimuli, and the reliving of the traumatic event
Memory distortion (misattribution)
Assigning a memory to the wrong source; source confusion (can’t identify where information came from) is an example of this
Reconsolidation
Memory is changeable, and repeated accessing of a memory can lead to changes in its biological foundations
Memory distortion (bias)
Influence of current knowledge on memory of past events; Sir Frederick Bartlett 1932 (ghost story)
Memory distortion (suggestibility)
Alteration of a memory due to misleading information (a.k.a the misinformation effect); Wade et al. 2002 (led participants to remember fake events); Loftus & Palmer 1974
Chen & Cowan 2009 (capacity of the phonological loop)
Fewer chunks of information would be remembered if individual chunks were particularly lengthy
Pareidolia
Tendency to perceive a meaningful image in a random visual pattern
Four lobes of the human cerebral cortex and their functions
- Frontal lobe (reasoning, motor skills, and higher-order functioning)
- Temporal lobe (interprets sounds and language)
- Parietal lobe (processes sensory information and orientates the body in the external environment)
- Occipital lobe (interprets visual stimuli)
Neuron definition
Specialised nerve cell responsible for neuronal communication
What is neuronal charge determined by?
Na+ (sodium) and K+ (potassium) ions
What happens when Na+ enters the cell?
The charge increases and depolarises the cell
Process of neuronal activation
- Neuron has an electrical ‘resting potential’ due to the distribution of positively and negatively charged chemical ions inside and outside the neuron
- When stimulated, a flow of ions in and out through the cell membrane reverses the electrical charge of the resting potential, creating an ‘action potential’ or nerve impulse
- The original ionic balance is then restored and the neuron is once again at rest, ready to be stimulated again
How is information transmitted within the cell?
Through transient alterations in the membrane potential
Dendrites
Specialised receiving units like antennae that collect messages from neighbouring neurons and send them on to the cell body
Cell body (soma)
Central processing unit of the neuron
Axon hillock
Situated between axon and soma, controls propagation of action potential
Axon
Conducts electrical impulses away from the cell body to other neurons; neuronal signal flows down the axon if the signal is strong enough
Myelin sheath
Fatty substance covering the axon, acts to conduct the action potential down the axon
Pre-synaptic terminal
End of axon, specialised for release of NTs
Post-synaptic terminal
End of dendrite, specialised to receive NTs from pre-synaptic cell
Graded potentials
Changes in the negative resting potential that do not reach the -50 mV action potential threshold; graded potentials created by several neurons may add up to trigger an action potential in an adjacent neuron
Synthesis
Creation of the NT in the presynaptic terminals
Storage (NTs)
NTs are stored in the presynaptic vesicles
Release (NTs)
NT released into the synaptic cleft
Binding (NTs)
When the NT released by the presynaptic cell binds to the postsynaptic terminal
Re-uptake
NTs that have been released at a synapse are reabsorbed by the pre-synaptic neuron that released them
Agonists (facilitator influence)
Drug that increases the activity of a NT
Antagonists (suppressive influence)
Drug that inhibits or decreases the action of a NT
Parkinson’s treatment
Deep brain stimulation (DBS)
Parkinson’s vs. schizophrenia
- Low dopamine levels (Parkinson’s) vs. high dopamine levels (schizophrenia)
- Dopamine antagonists can have anti-schizophrenic effects, whereas dopamine agonists can have anti-Parkinsonian effects
Reflex
A simple, automatic neural circuit that causes a response to a stimulus
Monosynaptic stretch reflex
Single neuronal loop connecting sensory neurons to motor neurons to cause a movement
Polysynaptic reflex
Neuronal circuit involving multiple inter-neurons
Vestibulo-ocular reflex (VOR)
Modifiable; causes movements of the eyes that are intended to compensate for movements of the head and body, thus ensuring that vision remains stable
Olds & Milner 1954 (intracranial self-stimulation [ISS])
ISS activates dopaminergic pathways; Olds & Milner found that reward phenomenon was most reliable when the electrodes were placed in the septal region
Ventral-tegmental area (VTA)
Pleasure area of the brain
Robert G. Heath
Found that cerebellar electrode implantation and stimulation appeared to have positive effects on the patient’s mood
Tetrodotoxin (TTX)
Blocks ion flow through channels that generate action potentials
Acetylcholine (ACh)
Excitatory NT involved in muscle activity and memory, underproduction of acetylcholine is an important factor in Alzheimer’s disease
How can neuronal circuits be strengthened?
- Increases in NT release
- Post-synaptic response
- Synaptic connections between neurons
William Greenough (learning and synaptic connectivity): Cognitive reserve hypothesis
Rats and different conditions; stimulation allows for an increase in synaptic connections, and thus decreases the likelihood of neural disease (cognitive reserve hypothesis)
Michel Siffre: Evidence for endogenous clock
Lived in a cave; 25-hour days
Suprachiasmatic nucleus (SCN) of the hypothalamus
Controls the endogenous clock
How long does it take to re-set circadian rhythm?
Typically six days
Phase delay
Wake up later
Phase advance
Wake up earlier
Evolutionary explanation for sleep
Core function of sleep is to adapt animals to their specific environmental niche
Inactivity theory
Sleep forces humans to remain quiet during periods of vulnerability
Energy conservation theory
Sleep forces humans to conserve energy at times when they would be relatively inefficient at searching for food
Sleep repair/ recovery theory
Need sleep to function psychologically and physically; Peter Tripp 1959; Randy Gardener 1964
Touitou et al. 2017
Sleep disruption linked to several health and psychiatric issues
Glymphatic system
Slow waves of neural activity, as occur during sleep, are associated with changes in vasodilation in the brain (thought to pump cerebrospinal fluid [CSF] around the brain) –> the CSF interacts with interstitial (extracellular) fluid and picks up the waste products of metabolism to be transported out of the brain
Beta-amyloid as impacted by sleep
Protein associated with impaired brain function and Alzheimer’s disease; less sleep means more of the protein
Freud and dreaming
Dreams fulfil unconscious wishes
Cognitive-process dream theories
Dreams and waking thoughts are products of the same mental systems
Activation-synthesis theory
Dreaming as the brain’s attempt to fit a story to random neural activity
Electroencephalogram (EEG)
Measures gross brain electrical activity
Electrooculogram (EOG)
Measures eye movements
Electromyogram (EMG)
Measures muscle activity
Sleep stages: Awake
Low-voltage, high-frequency beta waves
Sleep stages: Drowsy
Alpha waves prominent
Stage 1 sleep
Theta waves prominent
Stage 2 sleep
Sleep spindles and mixed EEG activity
Stage 3 and 4 sleep (slow-wave)
Progressively more delta waves
Rapid-eye-movement (REM) sleep
Low-voltage, high-frequency waves (EOG detects rapid eye movements; EMG shows loss of muscle tone)
Plihal & Born 1997 (sleep and memory)
Sleep generally enhanced recall
Rasch et al. 2007
‘Cueing’ memories during SLOW-WAVE SLEEP enhances subsequent performance
Declarative memory and sleep
Declarative memory is enhanced by early or slow-wave sleep
Procedural memory and sleep
Procedural memory is enhanced by late or REM sleep
Wagner et al. 2004 (sleep and insight)
String of digits; insight gained greater for participants who had slept prior to the task and had training
Lacaux et al. 2021: Hypnagogia (transition between wakefulness and sleep)
Woke participants in the middle of sleep stage 1 (performed better on insight task)
Mechanism for memory consolidation: Sharp-wave ripple (SWR) events
Hippocampal cells encode experience –> during SWS, the hippocampus replays events as sequences of cell-firing during SWR events –> may underlie episodic memory consolidation
Saletin & Walker 2012 (sleep spindles and memory)
Neocortical sleep spindles co-occur with SWRs; sleep spindle density predicts memory
Central nervous system
Made up of the brain and spinal cord
Peripheral nervous system
Made up of nerves that branch off from the spinal cord and extend to all parts of the body
Axon terminal
Branched out end of an axon
Resting potential to action potential
- Resting potential of -70 mV
- Depolarisation: If neuron is sufficiently stimulated, sodium channels open and sodium ions flood into axon, reversing electrical potential from -70 mV to +40 mV; potassium channels still closed
- Repolarisation: Sodium channels close and potassium channels open to allow potassium ions to exit, thereby restoring the interior negative potential; adjacent sodium channels are opened and the above processes are repeated, while action potential moves down length of neuron
Absolute refractory period
Following the production of one action potential, there is a brief period of time in which the neuron cannot be stimulated
Action potential: All or nothing
Action potentials occur at a uniform and maximum intensity or they do not occur at all
Action potential threshold
Negative potential inside of axon has to be changed from -70 mV to approx. -50 mV by influx of sodium ions into axon before action potential can be triggered
Temporal summation
Pulses from the same neuron at different times (can add up to generate an action potential)
Spatial summation
Pulses from multiple neurons at the same time (can add up to generate an action potential)
Node/s of Ranvier
Interrupt the myelin sheath at regular intervals (exist where myelin is extremely thin/ absent), act to continue the propulsion of action potential
Synapse process
- Action potential travels to axon terminals and stimulates release of transmitter molecules from synaptic vesicles
- Transmitter molecules travel across the synapse and bind to specially keyed receptor sites on cell body or dendrite of the post-synaptic neuron
- Lock and key nature of neurotransmitters and receptor sites: only transmitters that fit receptor will influence membrane potentials
- De-activation of the NTs by the presynaptic terminals
Sequence of neurotransmitter activity
- Synthesis of neurotransmitter
- Storage in synaptic vesicles
- Release into synaptic space
- Binding to receptor sites
- Deactivation through re-uptake or breakdown
Neurotransmitters
Chemical substances that carry messages across the synaptic space to other neurons, muscles, and glands
Synaptic vesicles
Chambers within the axon terminals
Receptor sites
Large protein molecules embedded in the receiving neuron’s cell membrane
Synaptic cleft
Space between the axon terminal and the next neuron, across which a nerve impulse is transmitted by a NT
Dopamine neurotransmitter
Excitatory NT; involved in voluntary movement, emotional arousal, learning, memory, and the experience of pleasure and pain; associated with Parkison’s disease (under-supply) and schizophrenia (over-activity)
Excitatory NT
Excitatory NT binds to receptor –> chemical reaction causing the post-synaptic neuron’s sodium channels to open, allowing sodium ions to flow into cell and depolarise it –> creates either a graded or action potential
Inhibitory NT
Inhibitory NT binds to receptor –> chemical reaction causing positive potassium ions to flow out of neuron or negative chloride ions from outside to flow into it through the chloride channels in the membrane, thereby increasing neuron’s negative potential –> makes it harder to elicit an action potential
What activates the human reward system (VTA and nucleus accumbens)?
Activated by a wide range of enforcers, including food and sex
Wake maintenance zone (WMZ)
Period of wakefulness lasting for two to three hours before nocturnal bedtime
Melatonin
Hormone produced by the pineal gland, signals a ‘biological night’ to the brain
Zeitgeber
External/ environmental cue that can be used to activate or time a biological rhythm (example: sleep-wake cycle)
Role of melanopsin receptors in sleep:
- Melanopsin receptors in the eye respond to light by transmitting signals to the suprachiasmatic nucleus (SCN)
- Light-induced activation of the SCN prevents pineal gland from producing melatonin
- Light-dark entrainment of the SCN synchronises ‘peripheral oscillators’ throughout the body, although these can be shifted by other factors (examples: exercise or eating)
Did studies find that experienced dream-time was the same as time spent in REM sleep in real-life?
Time experienced during dream time matched time measured in REM in real-life
