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PS4529/30 Applications of Cognitive Neuroscience

PS4529/30 Applications of Cognitive Neuroscience. Lectures 7/8 – where is my mind? Lectures 9/10 – what is episodic Memory? Lecture 11/12 – Cognitive neuroscience in the courtroom: the special case of episodic memory. Key concepts that underpin Cognitive Neuroscience. Electrophysiological.

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PS4529/30 Applications of Cognitive Neuroscience

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  1. PS4529/30Applicationsof CognitiveNeuroscience

  2. Lectures 7/8 – where is my mind? Lectures 9/10 – what is episodic Memory?Lecture 11/12 – Cognitive neuroscience in the courtroom: the special case of episodic memory.

  3. Key concepts that underpin Cognitive Neuroscience

  4. Electrophysiological Haemodynamic

  5. Psychophysiology • Aim is to develop mind reading technologies • We are most interested in the PPY of Perception and Cognition. In other words, Cognitive Neuroscience • Can we tell what a person is thinking or experiencing just by looking at their brain activity?

  6. Phrenology Was Odd… • There is no known mechanism that would sculpt the contours of the skull according to underlying brain shape • i.e. there is no correlation between contours of the skull and the underlying size or shape of the brain • Their psychological ‘model’ was based on common sense constructs of personality • I.e. Looking in the wrong place for the wrong thing!

  7. But not entirely wrong… • The idea of functional localisation has survived, but in a different form • Localisation does not respect character traits, like honesty, peevishness • Localisation may respect, for example, sensory modality, ‘cognitive systems’ (e.g. LTM), along with other psychological mechanisms yet to be elucidated

  8. Acceptable ‘modern’ principles of functional neuroanatomy • Functional Segregation • Discrete cognitive functions are localised to specific parts/circuits of the brain (complex tasks are ‘divided and conquered’) • Functional Integration • Coordinated interactions between functionally specialised areas (e.g. during retrieval from episodic memory, reading, perceptual binding etc)

  9. Summary so far • We want to read a person’s mind from the activity of their brain. E.G. are they lying? • Their mind is composed of lots of interacting cognitive processes • Each distinct process is carried out by networks of brain regions, each region is probably performing specific functions, but they all work together • So we need a device or a technique that can detect changes in brain activity specific to any cognitive process

  10. How to proceed? • In an experiment we engage different functions in different conditions. For every condition we • Detect rapid changes in neuronal activity (requires a temporal resolution of milliseconds, 1/100ths of a second) • Locate activity within brain structures that are engaged (may require an anatomical (spatial) resolution of millimeters or better) • Currently no such technique exists. Instead we rely on converging data from many techniques

  11. Electrophysiological Techniques • EEG • non-invasive recordings from an array of scalp electrodes

  12. EEG Signal Averaging

  13. AIR + 10uV - 0 1 2 TIME (sec) Averaging EEG produces ERPs DOG • Portions of the EEG time-locked to an event are averaged together, extracting the neural signature for the ‘event’. SHOE AVERAGE

  14. CONDITION A CONDITION B What do ERP waveforms tell us? + 5uV - INFORMATION ABOUT THE NEURAL BASIS OF PROCESSING IS PROVIDED BY THE DIFFERENCE IN ACTIVITY ONSET OF EVENT 0 1 2 TIME (seconds)

  15. Functional Inferences Based Upon Electrophysiology Early Topography • Timing • Upper limit on time it takes for neural processing to differ • Time course of a process (onset, duration, offset) • Level at which a process is engaged • Engagement of multiple processes at different times or in different conditions Late Topography

  16. The Brain’s Plumbing

  17. Haemodynamic Techniques • Oxygen and glucose are supplied by the blood as ‘fuel’ (energy) for the brain • The brain does not store fuel, so • Blood supply changes as needs arise • Changes are regionally specific - following the local dynamics of neuronal activity within a region • Haemodynamic techniques localise brain activity by detecting these regional changes in cerebral blood supply

  18. Positron Emission Tomography (PET) • Samples the entire brain volume homogeneously • Has an effective anatomical resolution of about 10mm or so in group studies • An ‘indirect’ measure of neuronal activity • Due to radiation dose, only a limited number of scans can be taken from each subject

  19. Magnetic Resonance Imaging (MRI) • Put head into a strong magnetic field • Water protons align themselves with respect to the field • alignment is then perturbed by radio-frequency pulses • non-invasive and fast (few seconds) • protons ‘relax’ back into alignment, giving off a signal • relaxation signals can reveal • tissue type • physiological state (e.g. blood oxygenation) • 3D position in the magnetic field

  20. Our starting point … • Electrophysiological and Haemodynamic techniques • Have different temporal and spatial resolutions • Measure different physiological signals • Constrain experimental design and functional inferences in different ways • May provide complementary information when functional maps from each technique can be formally co-registered ERP PET

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