Inhibition

1. Inhibition Chris Jung Department of Integrative Physiology 09/23/08

2. Outline • Prefrontal Neurons Coding Suppression of Specific Saccades • Hasegawa RP, Peterson BW, and Goldberg ME • The role of inhibitory control in forgetting unwanted memories: A consideration of three methods. • Anderson MC • In Opposition of Inhibition • MacLeod CM, Dodd MD, Sheard ED, Wilson DE, and Bibi U

3. Prefrontal Neurons Coding Suppression of Specific Saccades Hasegawa, R.P., Peterson, B.W., & Goldberg, M.E. (2004). Neuron, 43, 415-425. • Introduction • Methods • Results • Conclusions

4. Introduction • Monkey and humans that do not avoid looking at something can be seen as socially offensive, unacceptable.

5. Introduction • Eye fixation is an active process • Two mechanisms have been proposed: • An inhibition of the saccadic system by the fixation system • When fixation occurs, the threshold for evoking saccades increases by electrical stimulation from the frontal eye field (FEF) and the superior colliculus, which are apart of the fixation system • Some neurons of the FEF are activated if a stimulus is present to cancel the saccade such as in a “go/no go task”

6. Methods • Caudal part of dorsolateral prefrontal cortex • Match/Non Match Task Figure 1

7. Sample Period: 3 Different Responses • Look neurons • Enhanced response if the monkey knew a priori of a saccade target • 10% of samples

8. Sample Period: 3 Different Responses • Don’t look neurons • Enhanced response if the monkey knew a priori of a non-saccade target, or to avoid looking at the original stimulus • 10% of sample

9. Sample Period: 3 Different Responses • Pure visual neurons • No difference between tasks • 80% of sample

10. Delay Period: 3 Different Responses • Look neurons 53% • Greater activity if the stimulus was to saccade to the original sample stimulus • Don’t look neurons 19% • Greater response if the stimulus was to not look where the sample stimulus was • Memory neurons 28% • Responded equally to both stimuli • Believed to be working memory

11. Conclusions • The authors report to have located neurons that help to plan a behavior or suppress it, whether immediately or during the delay. • Temporal progression • Neurons often switched functions during the different phases of the test

12. The role of inhibitory control in forgetting unwanted memories: A consideration of three methods Anderson, M.C. (2005). In C. MacLeod & B. Uttl (Eds.) Dynamic Cognitive Processes (pp. 159-190). Tokyo: Springer-Verlag. • Central claim • Retrieval-induced forgetting • Directed forgetting • Conlusions

13. Central claim: • Humans can control memory by overriding prepotent responses to unwanted memories Figure 1

14. Within-Category Retrieval-Induced Forgetting Study Figure 2

15. Retrieval-Induced Forgetting • Inhibition or response competition theory of interference? • Response competition theory of interference • Target will suffer because increased competition from the alternative response is strengthened • Practiced items become so strongly linked to the practice cue that they block other examples

16. Retrieval-Induced Forgetting • Inhibition or response competition theory of interference? • Inhibition • Recall specific • Retrieval practice impairs the delayed recall of competing items • Cue independence • Retrieval induced forgetting when novel cues are used

17. Directed Forgetting Roach--Ordeal

18. Directed Forgetting • Dorsolateral prefrontal cortex • Lateral premotor cortex

19. Conclusions • Controlled inhibition may be recruited for our goals, regardless if the goals are to forget (Flexible inhibition hypothesis) • Can help to explain the directed forgetting and retrieval induced forgetting

20. In Opposition of Inhibition MacLeod, C. M., Dodd, M. D., Sheard, E. D., Wilson, D. E., & Bibi, U. (2003). In B. H. Ross (Ed.), The Psychology of Learning and Motivation, Vol. 43 (pp. 163-214). San Diego, CA: Academic Press. • Problem • Examples • Proposed Solution

21. The Main Problem: “…the concept of inhibition at the cognitive level cannot derive directly from the concept of inhibition at the neural level.” • The term “inhibition” is too flexible of a term

22. Negative Priming • They report: • No conclusive evidence that inhibition can explain negative priming.

23. RED

24. GREEN

25. Automatic memory retrieval • If there is disagreement between the task at hand and a recent memory, this will take longer because you need to resolve the conflict

26. Inhibition of Return

27. Inhibition of Return

28. Inhibition of Return • Inhibition of Return • Past researchers have concluded that there is an inhibitory mechanism to look towards the area of a stimuli that was already presented • Attentional Momentum Hypothesis • MacLeod et al. believe that attention can be more easily and faster oriented in a direction of a location in which it already has been rather than shifting to another location

29. Inhibition is too broad of a term • The terms “interference”, “selective rehearsal” should be used instead depending on the task • Inhibition has been labeled as below baseline performance. • For a decrement in baseline performance, the term “cost” should be used. • For an increment in baseline performance, the term “benefit” should be used.

30. Two mechanisms that are inhibition free: • Automatic memory retrieval • If there is disagreement between the task at hand and a recent memory • Conflict resolution