Monday Cognitive Electrophysiology

1. MRes Psychophysiology Monday Cognitive Electrophysiology Wednesday Pupillometry

2. 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?

3. 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)

4. Where We At? • We want to read a person’s mind from the activity of their brain • 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

5. So What Do We Need? • In an experiment we (think 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

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

8. 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

9. 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)

10. 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

11. Electrophysiological Techniques • Principle advantages • non-invasive • high temporal resolution • direct reflection of neuronal activity • easy to produce event-related potentials by selective averaging of EEG epochs. • topographic mapping • Cheap (for EEG but not MEG)

12. 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 PET ERP

13. Stimuli Time 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Familiarity? Implicit Memory? Ecphory? Monitoring?

14. Stimuli Time 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 ‘selective attention’ Retrieval Perception/attention Ecphory/inhibition Monitoring Patterncompletion/ Binding cueonset CMF{retrieval}

18. Can We Deliberately Forget? What functional changes in memory produce deliberate forgetting? Encoding: differential rehearsal / encoding of TBR items (likened to a ‘dop’ manipulation) Retrieval: Selective inhibition of TBF items

19. WILD Encoding R or F Cue Time - 0 2.5s 5.0s The Ullsperger et al DF Experiment

20. WILD Encoding D or S Cue Time - 0 2.5s 5.0s The Ullsperger et alDepth of Processing Experiment

21. Ullsperger’s Conclusion Differential encoding hypothesis does not account for the DF and DOP findings:- The enhanced RF effect does not appear to be a response to the mere difficulty in remembering TBF items. Can ERPs be used to explore mechanisms that overcome retrieval inhibition? With consequences for our understanding of normal memory function, cognitive aging, functional amnesias and affective disorders with strong memory components (e.g. P.T.S.D.)?

23. Time - 0 1 2 3 4 5 6 7 8 9 Face DF Experiment Methods + + Stimuli 120 study items, 60 male / 60 female. 240 test items, 120 male / 120 female. Encoding and Retrieval phase trial structure were identical. EEG was recorded continuously throughout encoding and retrieval.

24. Why We Did It Like We Did • ERPs from the study phase may reveal, directly, neural correlates of differential encoding of TBR and TBF items. • Hence, these may contrasted, directly, with neural correlates of retrieval processing for TBR and TBF items. • Processing of cues belonging to the TBF and TBR classes may differ in a way that is functionally related to forgetting. • What is the fate of genuinely forgotten items? • A change is as good as a rest!

25. 32-ch Montage

26. ERP ‘Associates’ of Differential Encoding S1 I6 M8 S10 S2 M1 I1 6 uV C1 Remember Forget M7 S9 C5 C2 S3 M2 CZ S8 C4 C3 S4 M6 S7 S5 M3 S6 I5 M5 M4 I3 I4

28. ERP Associates of Differential Encoding Have not been reported, yet, in the literature (I think!) Are sustained, onsetting around 400ms, still present at ~2s post-stimulus. Change topographically over time, indicating engagement of multiple regions/functions. Ironically, they differ from ‘associates’ of DOP effects at encoding! Bear a family resemblance to old/new effects… What about the test phase performance and ERP data?

29. Recognition Performance

30. ‘TBRemembered ’ Old/New Effect 6 uV HIT CR S1 I6 M8 S10 S2 M1 I1 C1 M7 S9 C5 C2 S3 M2 CZ S8 C4 C3 S4 M6 S7 S5 M3 I2 S6 I5 M5 M4 I3 I4

32. ‘TBforgotten’ Old/New Effect 6 uV HIT CR S1 I6 M8 S10 S2 M1 I1 C1 M7 S9 C5 C2 S3 M2 CZ S8 C4 C3 S4 M6 S7 S5 M3 I2 S6 I5 M5 M4 I3 I4

34. ‘Strong’ Right Frontal Effectfor Remember-Items

35. Relative-Absence of Right Frontal Effect for Forget-Items

36. Effects of DF on ERPs at Retrieval 1. The functional state of the brain captured by old/new effects is different when remembering TBF and TBR items, though not in a way that reveals the operation of ‘retrieval inhibition’. DF eliminates (effectively) the right frontal component of the old/new effect and the earlier left parietal component too. 2. So contrary to Ullsperger et al, no evidence here for a link between the right frontal effect and the overcoming of ‘retrieval inhibition’. But what is the fate of items that are forgotten – i.e. items that are truly ‘inhibited’?

37. A True Associate of Retrieval Inhibition? 6 uV Forgotten CR S1 I6 M8 S10 S2 M1 I1 C1 M7 S9 C5 C2 S3 M2 CZ S8 C4 C3 S4 M6 S7 S5 M3 S6 I5 M5 M4 I3 I4

39. ERP Associates of Forgetting 1. Resemble the early left parietal component of the old/new effects! Did the subjects disregard ‘weaker’ memory, or have we detected a lie? 2. Resemble an ‘inverted’ right frontal effect! Are items forgotten when the RF generators are particularly inactive (i.e. below the correct rejection ‘baseline’)? Perhaps they are not responding to the weak memory output reflected by the LP effect?)

40. Conclusions from Electrophysiological Findings 1. We may be able to use the ERP encoding effects to explore differential encoding as it relates to subsequent forgetting. 2. Contrary to Ullsperger, ‘Inhibition’ can be overcome without the help of enhanced processing reflected by big RF effects. 3. However, we found that ‘inversion’ of the RF effect accompanies genuine forgetting. Can we both be right?