Higher cortical circuits for visual attention

1. Jamie Mazer Neurobiology of Cortical Systems Lecture 8 March 19, 2012 Higher cortical circuits for visual attention

2. Cortical visual system

3. beyond striate cortex: where and what streams Ungerleider & Mishkin 1982

4. Attention What is attention? Every one knows what attention is. It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration, of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others, and is a condition which has a real opposite in the confused, dazed, scatterbrained state which in French is called distraction, andZerstreutheitin German. - William James, The Principles of Psychology (Chap. 11), 1980

5. + + + + + Attention target present/absent? valid X X T T T T T T X X X X T T cue invalid Posner, 1980 Treisman & Gelade, 1980

6. Attention • Attention is “something” that facilitates behavior. • Behavioral facilitation can be quantified using psychophysical metrics like reaction time and accuracy • Attention has a conscious or voluntary component • Attention also has an unconscious or involuntary component • The voluntary component takes measurable time to deploy or move

7. Attentional taxonomy… source class spatial feature-based exogenous top-down conscious automatic reflexive pre-attentive endogenous bottom-up unconscious voluntary attentive dimension value Ulrich Neisser “Dual-mechanism hypothesis”

8. Spatial attention in visual cortex attended > ignored V4 x2 V4 x1 Match-to-sample match/sample location varied in blocks TE V1 REignored REattended Moran & Desimone, 1985 [Haeny, Maunsell & Schiller, 1985]

9. Feedforward and feedback connections of V4 Ungerleider et al, 2008

10. Effects of spatial attention on orientation tuning class spatial feature-based match to sample color trials and orientation trials dimension value n=197 McAdams & Maunsell, 1990

11. Feature attention in V4 Motter, 1994

12. Popout (and memory) in V4 n=30 Motter, 1994

13. Popout (and memory) in V4 Motter, 1994

14. Attention in V1? Roelfsema & Lamme, 1998 human mri (but remember that moran& desimone reported nothing) roeflsema & lamme motter, 199 Motter, 1993

15. Attention in V1? single subject Brefczynski & DeYoe, 1999 [Somers et al, 1999]

16. Attention in V1?? • humans vs monkeys? • spikes vs BOLD? • low SNR? • attentional effects are generally small relative to visual responses… • task differences?

17. Human and monkey V4 appear functionally homologous vs vs vs vs vs

18. Models: Biased Competition Reynolds, Chelazzi & Desimone, 1999

19. Models: Contrast gain vs response gain “contrast gain” contrast “response gain”

20. Models: Contrast gain vs response gain “contrast gain” response contrast contrast “response gain”

21. Models: Contrast gain vs response gain “contrast gain” response contrast contrast “response gain” from Williford & Maunsell, 2006

22. Feature-based attention: MT detect speed/dir change at attended location Treue & Martinez-Jullio, 1999

23. Feature-based attention: V4 – beyond gain changes Mazer & Gallant, 2003

24. Feature-based attention: V4 – beyond gain changes David et al, 2008

25. Feature-based attention: V4 – beyond gain changes David et al, 2008

26. Premotor theory of attention Rizzolatti et al, 1987

27. Premotor theory of attention Rizzolatti et al, 1987

28. Feedback/control-signal sources? source exogenous top-down conscious automatic reflexive pre-attentive endogenous bottom-up unconscious voluntary attentive Buschman & Miller, 2007

29. Feedback/control-signal sources? Buschman & Miller, 2007

30. Feedback/control-signal sources? Armstrong et al, 2006

31. Feedback/control-signal sources?

32. Summary and Caveats • Attentional modulation seems to be ubiquitous in sensory “cortex” • similar results in other modalities and other species (including non-mammalian species) • most similar are results in A1/PFC (Fritz, David & Shamma etc) • Seems like there are two basic effects • gain (either response or contrast) changes and shifts • gain changes seem reasonably easy to model; shifts not so much… • it is possible that feature-based and spatial attention use similar biophysical implementations, but to date, only superficial phenomenological similarities have been described • Source of modulation is generally thought to be frontal • anatomical route is not at all understood • We need to be careful about studying second order effects in a system before understanding the first order mechanisms!

33. Step 1: Understand the representation? Desimone & Schein, 1987 Gallant et al, 1993 Pasupathy & Connor, 1999

34. Step 1: Understand the representation? Desimone & Schein, 1987 Gallant et al, 1993 Pasupathy & Connor, 1999

35. Summary and Caveats • Attentional modulation seems to be ubiquitous in sensory “cortex” • similar results in other modalities and other species (including non-mammalian species) • most similar are results in A1/PFC (Fritz, David & Shamma etc) • Seems like there are two basic effects • gain (either response or contrast) changes and shifts • gain changes seem reasonably easy to model; shifts not so much… • it is possible that feature-based and spatial attention use similar biophysical implementations, but to date, only superficial phenomenological similarities have been described • Source of modulation is generally thought to be frontal • anatomical route is not at all understood • We need to be careful about studying second order effects in a system before understanding the first order mechanisms!

36. Readings