Cognitive Neuroscience Flashcards
What is episodic memory?
Specific episodes in the past
Often autobiographical
What is semantic memory?
Knowledge of facts about the world
Derives from episodic memory
What is procedural memory?
How to do things e.g. drive a car
What is priming?
Exposure to one stimulus influencing response to subsequent stimulus
What is classical conditioning?
Pairing of stimuli
What is non-associative learning?
Habituation, sensitisation
Where is the hippocampus located?
Medial temporal lobe
Where do the main inputs to the hippocampus come from?
Parahippocampal gyrus
Where do the main outputs from the hippocampus go?
Via the fornix to mammillary bodies
What is the cortico-hippocampal information flow?
Primary sensory cortices Association cortices Parahippocampal cortices Entorhinal cortex Hippocampal formation
What is the name of the anatomical connection between the hippocampus and the cortex?
Parahippocampal cortex
What symptoms did patient HM show post surgery? What does this imply about which memory types were effected?
- Memory of past intact - long term memory intact
- Can participate in conversation - short term memory intact
- Can learn new skills normally - procedural memory intact
- Could not form new memories - anterograde amnesia
How can we manipulate the hippocampus in animals to test its role in behaviour?
Lesions
Pharmacological inactivation
What does the Morris Water Maze test?
Spatial memory
What happens when CA1 cells are infused with muscimol?
Blocks spatial memory retrieval
Would blocking NMDA receptors block spatial memory?
Yes
What is a place cell?
Hippocampal pyramidal cell that fires when in a specific location
Creates a cognitive map
What is a grandmother cell?
A theoretical neuron which represents a single complex concept/object
What natural behaviour in rats would you exploit if wanting to test recognition memory?
Novel object preferance
How do we calculate a discrimination ratio?
(Novel - Familiar)/(Novel + Familiar)
Which brain structure is responsible for recognition memory?
Perirhinal cortex
How does reinforcement shape behaviour?
Negative reinforcement rapidly reduces response
Positive reinforcement increases response but needs repeated more frequently and numerously
What is associative learning?
When an association develops between an unconditioned stimulus and an initially neutral stimulus
What is the difference between classical and operant conditioning?
Classical - a stimulus comes to predict an outcome
Operant - sees responses, actions, have a causative role (leads to goal directed behaviour)
What is the outcome devaluation procedure?
- Two responses produce different rewarding food outcomes
- One food devalued - produces nausea
- Rats given the opportunity again to press either lever
- A reduced response for the devalued outcome shows goal direction
- If press levers equally, responses reflect habit
What are the pros and cons of EEG?
Pros: very high temporal resolution, can measure the cortex, non-invasive, painless
Cons: low spatial resolution, correlational not causational, potential for false positives
How does EEG work?
Shows voltage changes between pairs of electrodes
Amplitude depends on how synchronous activity is
How does PET work?
Positrons (+ve charged electrons) introduced into bloodstream
Interact with electrons to produce photons
Detected by powerful detectors
How can PET measure metabolic activity in the brain?
- Active neurons need more glucose/oxygen
- Positron isotope of oxygen attached to 2-deoxyglucose
- Taken up by metabolically active neurons
- Phosphorylated in neuron, radioactive 2DG accumulates, as does positron emissions
- Generates an activity map (not anatomical image)
What are the pros and cons of PET?
Pros: short scan times, high resolution
Cons: radiation exposure (can’t scan same person many times), expensive
How does MRI work?
Quantifies hydrogen in water/fat of the brain
H can be low energy or high energy - many exist in each state
MRI uses electromagnetic waves to change H energy states (resonant frequency)
H fall from high state to low state, emitting radio waves that are detected
What is the physiological basis of fMRI?
As brain activity increases, deoxyhaemoglobin increases
Overcompensation occurs
Oxyhaemoglobin increases more, signal increases and is detected
How are MRI readings analysed?
- Brains morphed to fit standard template
- BOLD compared voxel by voxel - t-test for signal intensity for each (mass univariate approach)
- Ignores patterns across groups of voxels
- Computationally simple but high false positive rate from multiple comparisons (fixed by region of interest analysis)
What are the practical difficulties of MRI?
Signal to noise ratio is poor - can’t do a single scan
Need multiple activation tasks and continuous scanning
Average all results together
What are the pros and cons of MRI?
Pros: non-invasive, reasonable amount of anatomical detail, no exogenous ligand
Cons: poor temporal resolution (up to 6 seconds for BOLD to appear)
What are the two different TMS methods?
Motor evoked potential
Temporary Leisons
What is TMS MEP?
Can directly stimulate pathway
Priming - anticipation of movement increases TMS effect
What are the different temporary lesions TMS can create?
Short term - single pulse, 1-2cm2 region disabled for up to 50ms
Medium term - repetitive stimulation (e.g. 5Hz for 10 seconds), longer lasting and wider ranging effects
Offline TMS - ‘intense stimuli’ can impair function for ~45 minutes
What are the pros and cons of TMS?
Pros: very high temporal resolution, high spatial resolution, causal inferences
Cons: requires detailed hypothesis
