Midterm 1

1. Midterm 1 Oct. 21 in class

2. Read this article by Wednesday next week!

3. Cognitive Psychology • High resolution instrumentation is of no use if you don’t understand the cognitive operations that you are trying to image • Cognitive psychologists have worked to understand mental operations for over a century • The enterprise of Cognitive Neuroscience is predicated on cognitive psychology

4. Temporal and Spatial Resolution are Traded Off

5. fMRI ubiquitous high spatial resolution non-invasive/safe PET quiet labels variety of molecules Comparing Imaging Techniques - Advantages • EEG/ERP • inexpensive • high temporal resolution • non-invasive/safe • MEG • high-temporal resolution • good but limited spatial resolution • non-invasive/safe • Unit Recording • very high spatial resolution • high temporal resolution • Lesions • real-life

6. fMRI loud expensive limited temporal resolution PET very expensive limited safety invasive limited temporal resolution Comparing Imaging Techniques - Disadvantages • EEG/ERP • limited spatial resolution • can be difficult to interpret • MEG • limited spatial resolution • difficult to interpret • Unit Recording • very invasive • can be hard to see “big picture” • Lesions • very invasive

7. There is no “best” level of explanation • There is only a level of explanation that is most appropriate for your goals • E.g. cognitive psychologist exploring behavioural treatments for ADHD vs. Molecular neuroscientist pursuing “rational drug design” for ADHD

8. Cognitive Operations • What does the brain actually do? • Some possible answers: • “The mind” • Information processing… • Transforms of mental representations • Execution of mental representations of actions

9. First Principles • “cognitive operations are processes that generate, elaborate upon, or manipulate representations” • As patterns of activity in one or more neurons • We often lack conscious access to these representations • Neuroscientists still know very little about how information is represented in the brain

10. Mental Representations • Mental representations can start with sensory input and progress to more abstract forms • Local features such as colors, line orientation, brightness, motion are represented at low levels How might a neuron “represent” the presence of this line?

11. Mental Representations • Mental representations can start with sensory input and progress to more abstract forms • Local features such as colors, line orientation, brightness, motion are represented at low levels • A “labeled line” • Activity on this unit “means” that a line is present • Does the line actually have to be present?

12. Mental Representations • Mental representations can start with sensory input and progress to more abstract forms • texture defined boundaries are representations arrived at by synthesizing the local texture features

13. Mental Representations • Mental representations can be “embellished” - Kaniza Triangle is represented in a way that is quite different from the actual stimulus -the representation is embellished and extended

14. Mental Representations • Mental Representations can be transformed • Rubin Vase, Necker Cube are examples of mental representations that are dynamic

15. Mental Representations can be transformed Shepard & Metzlar (1971) mental rotation is an example of transforming a mental representation in a continuous process Mental Representations Mentally rotate the images to determine whether they are identical or mirror-reversed SAME MIRROR-REVERSED

16. Mental Representations can be transformed Shepard & Metzlar (1971) mental rotation is an example of transforming a mental representation in a continuous process Mental Representations

17. Mental Representations can be transformed Shepard & Metzlar (1971) mental rotation is an example of transforming a mental representation in a continuous process Mental Representations

18. Mental Representations can be transformed Shepard & Metzlar (1971) mental rotation is an example of transforming a mental representation in a continuous process Mental Representations

19. Mental Representations can be transformed Shepard & Metzlar (1971) mental rotation is an example of transforming a mental representation in a continuous process The time it takes to respond is linearly determined by the number of degrees one has to rotate Somehow the brain must perform a set of operations on these representations - where? how? Mental Representations

20. Mental Representations • Mental Representations can be transformed into abstract information representations • Posner letter matching task • Are these letters from the same category (vowels or consonants) or are they different?

21. Mental Representations • Mental Representations can be transformed into abstract information representations • Posner letter matching task • Are these letters from the same category (vowels or consonants) or are they different? • Are they physically the same or are they the same in an abstract way - they are in the same category? A A A a SAME A U S C A S DIFFERENT

22. Mental Representations • Mental Representations can be transformed into abstract information representations • Posner letter matching task • Participants are fastest when the response doesn’t require transforming the representation from a direct manifestation of the stimulus into something more abstract

23. Mental Representations • Mental Representations can interfere • Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

24. Mental Representations • Mental Representations can interfere • Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour RED

25. Mental Representations • Mental Representations can interfere • Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour BLUE

26. Mental Representations • Mental Representations can interfere • Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour GREEN

27. Mental Representations • Mental Representations can interfere • Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour RED

28. Mental Representations • Mental Representations can interfere • Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour BLUE

29. Mental Representations • Mental Representations can interfere • Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour GREEN

30. Mental Representations • Mental Representations can interfere • Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour • The mental representation of the colour and the representation of the text are incongruent and interfere • one representation must be selected and the other suppressed • This is one conceptualization of attention

31. Mental Representations • These are some examples of how a cognitive psychologist might investigate mental representations • The cognitive neuroscientists asks: • where are these representations formed? • What is the neural mechanism? What is the code for a representation? • What is the neural process by which representations are transformed?

32. First Principles • What are some ways that information might be represented by neurons?

33. First Principles • What are some ways that information might be represented by neurons? • Magnitude might be represented by firing rate (e.g. brightness) • Presence or absence of a feature or piece of information might be represented by whether certain neurons are active or not – the “labeled line” (e.g. color, orientation, pitch) • Conjunctions of features might be represented by coordinated activity between two such labeled lines • Binding of component features might be represented by synchronization of units in a network