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PSYC3039 Introduction to Cognitive Neuroscience

PSYC3039 Introduction to Cognitive Neuroscience. Weeks 4 and 5: Introduction to Cognitive Electrophysiology.

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PSYC3039 Introduction to Cognitive Neuroscience

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  1. PSYC3039 Introduction to Cognitive Neuroscience Weeks 4 and 5: Introduction to Cognitive Electrophysiology

  2. Case study: Selective attentionAlternative reading to Naatanen, 1992:Naatanen, R (1990) the role of auditory information processing as revealed by event-related potentials and other measures of cognitive function, Brain and Behavioural sciences 13: 201-232 (peer commentary 232-288)

  3. Selective attention on the basis of physical features

  4. Spatial selective attention

  5. The P1-N1-P2 complex and spatial selective attention

  6. Visual P1 and degree of attention

  7. Scalp topography of the P1 attention effect

  8. Sources of the P1 and N2 • PET source of the P1 and N2 in ventromedial posterior fusiform gyrus (FG) and middle occipital gyrus (MOG), respectively • ERPs show activation on scalp over these regions • Dipole modelling with simulated sources in the FG and MOG produce simulated scalp activations that match the empirical data very well

  9. Auditory selective attention

  10. The N1 and Nd components of the auditory ERP • N1 and selective attention • The negative difference wave (Nd) • onset 60-80ms • endures 300-400ms

  11. Difference waves 50 100 400 Increasing amplitude Earlier onset Longer duration Decreasing discrimination difficulty The effects of discriminative difficulty on the auditory Nd TASK INSTRUCTION Attend Low/High Ignore High/Low tones

  12. Multiple sources of the Nd • ISI manipulation of N1 selective attention paradigm exposes multiple sources of Nd • Frontal and central sources

  13. Naatanen’s attentional trace hypothesis Covert orientation

  14. Naatanen’s Processing Negativity theory GOOD MATCH PROCESSING NEGATIVITY FURTHER PROCESSING

  15. Naatanen’s Processing Negativity theory BAD MATCH PROCESSING NEGATIVITY FURTHER PROCESSING

  16. Naatanen’s Processing Negativity Theory • Processing Negativity: PN • Model incorporates exogenous N1/P2 effects • PN concurrent with N1/P2 and reflects stimulus:model comparison process • Negative Difference Wave: Nd • Reflects the difference over trials between PN to relevant and irrelevant stimuli • The smaller the difference, the smaller and later the Nd • N1 • Amplitude attenuates with stimulus repetition – hence smaller overall when difference between relevant and irrelevant stimulus small Relative difference between stimulus and trace

  17. Summary: N1 and attention • Exogenous N1 reflects pre-conscious, stimulus detection; source in modality specific cortex • Attention imposes a slow wave - the Nd, with frontal and central sources • Nd occurs early (~70ms) and reflects top down, cognitive control of physical selection • Nd sensitive to difficulty of discrimination • Processing Negativity theory accounts for phenomena

  18. Some other ERP components associated with simple stimulus processing

  19. Automatic detection of stimulus and of stimulus change

  20. Regular (standard) stimulus New (deviant) stimulus “MMN” Detection of significant events in environment When the brain detects some change in the environment (marked by MMN), the brain must work out if the new event needs attention – is it a threat; is some action required? If so, further (attentional) processing is marked by the N2 and P3a and P3b ERP components

  21. Regular (standard) stimulus New (deviant) stimulus “MMN” The P3 component and attentional processing of significant events • Details • Latency: 300-500ms post-stimulus • Requires conscious attention • Frontal P3 • detection and entry of novel stimuli into consciousness • Parietal P3 • evaluation of significance • context assimilation • correlates with response time • Late slow waves • context & related working memory updating/maintenance

  22. P3 abnormalities ubiquitous in psychopathology • Post-traumatic stress disorder • Parietal P3 reduced • Abnormal LSW • Panic Disorder • Frontal P3 enhanced Fz Cz Pz eog

  23. Preparatory processing • Contingent negative variation (CNV): 500-1000ms pre-stimulus: expectancy and preparation for event • Motor potential and Bereitschaftspotential: 1-2 secs preceding response Bereitschaftspotential

  24. ERPs and stages of processing • N400 • about 400ms post-stimulus • Semantic incongruity • Size affected by degree to which meaning of sentence is derived over sequence of words in sentence Bereitschaftspotential

  25. Summary of components discussed • Automatic processes (obligatory cortical mechanisms) • P50: automatic feature analysis • N1: automatic detection of stimulus • MMN: automatic detection of stimulus change • Controlled processes (working memory) • Nd: controlled selective attention to stimulus • N2b (frontal): stimulus categorisation • P3a (frontal): conscious awareness of novelty • P3b (parietal): evaluation of stimulus significance • N4: contextual processing of language • Late slow waves: updating of working memory content • CNV and Motor potential : preparatory processing for future events

  26. General summary • Stages of processing • Visualisation of non-behavioural processes • Multiple components • Endogenous vs exogenous components • Modality specific vs non specific components • Specific topographies • Parallel distributed processing • Uses in psychopathology • Source localisation issues

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