The Functional Significance of the Late Negative Parietal-Occipital EM Effect

1. The Functional Significance of the Late Negative Parietal-Occipital EM Effect Yael M. Cycowicz

2. Thanks to Michael Bersick Charles Brown David Friedman Cort Horton Letecia Latif

3. Episodic Memory Episodic memory (EM) effects have been demonstrated in the ERP as a series of amplitude differences between old and new events beginning at about 300 ms and often continuing to the end of the recording epoch.

4. Late Onset EM Effects • Retrieval Success • Post Retrieval processes • Strategic processes • Monitoring • Evaluation • Response related processes • Monitoring and evaluation of modality specific information Right prefrontal Symmetrical Posterior

5. The Symmetrical posterior EM effect Is it possible that the late Negative EM effect reflects post-decision visualization processes? Participants may have tried to reinstate the original learning episode which could have involved creating mental images of the visual stimuli, resulted in activity at scalp regions overlying visual cortical areas.

6. Study 2s Tests Red Green Exclusion Inclusion 2s 2s New Old Other Red

7. Performance

8. Parietal EM Parietal EM Parietal Occipital EM

9. Scalp Topography of EM Effects Parietal EM 415-615 ms Occipital Parietal EM 700-950; 955-1200 ms Inclusion Test Exclusion Test Δ = 0.30 µV

10. Results Summary • RT old < RT new in the Inclusion task • RT old > RT new in the Exclusion task • Parietal EM effect is clear in both Inclusion and Exclusion tasks • Late EM effect only in the Exclusion task • Late EM effect is large and wide spread over the scalp

11. Parietal EM Parietal EM Parietal Occipital EM Parietal Occipital EM

12. POE Parietal EM Parietal EM Parietal Occipital EM

13. Conclusions The negative late EM effect reflects: Reactivation of brain areas supporting recapitulation of previously studied Colored Pictures Retrieval and/or evaluation of perceptual visual information (color) may be modality specific and thus elicited activity in visual cortex.

14. Research Questions Does the nature of the source information (perceptual vs. conceptual) can affect the scalp distribution of the late negative EM effect ? If so, can we better understand the functional significance of the late negative EM effect ?

15. Conceptual Source Atypical Typical

16. Study 2s Tests Exclusion Inclusion 2s 2s New Old Other

17. Performance

18. Parietal EM Parietal EM Parietal Occipital EM

19. Scalp Topography of EM Effects Parietal EM 415-615 ms Occipital Parietal EM 700-950; 955-1200 ms Inclusion Test Exclusion Test Δ = 0.30 µV

20. Results Summary • RT old < RT new in the Inclusion task • RT old > RT new in the Exclusion task • Parietal EM effect is clear in both Inclusion and Exclusion tasks • Late EM effect only in the Exclusion task • Late EM effect is smaller and shorter than previously reported • Late EM effect has a different scalp distribution than those previously reported

21. Scalp Topography of EM Effects Parietal EM 415-615 ms Occipital Parietal EM 700-950; 955-1200 ms Inclusion Test Conceptual Exclusion Test Perceptual Δ = 0.30 µV

22. Summary • Retrieval of Conceptual information elicited a small late occipital negative EM effect • In the preliminary analysis no other late effects can be detected

23. Conclusions The magnitude and distribution of the late occipital negativity is modulated by the type of source attribute Differences in retrieval processes are affected by differences in encoding processes