1. Brain Areas and Topography http://www.fmri4newbies.com/ Last Update: January 2011 Last Course: Psychology 9224, W2011, University of Western Ontario Jody Culham Brain and Mind Institute Department of Psychology University of Western Ontario

2. 2 What Defines an Area?

3. Definition of an “Area” Neuroimager’s definition of an area: Some blob vaguely in the vicinity (+/- ~3 cm) of where I think it ought to be that lights up for something I think it ought to light up for Neuroanatomist’s definition of an area: A circumscribed region of the cerebral cortex in which neurons together serve a specific function, receive connections from the same regions, have a common structural arrangement, and in some cases show a topographic arrangement may also be called a cortical field 3

4. 4 Cortical Fields: Anatomical Criteria 1.Function –an area has a unique pattern of responses to different stimuli 2.Architecture –different brain areas show differences between cortical properties (e.g., thickness of different layers, sensitivity to various dyes) 3.Connectivity –Different areas have different patterns of connections with other areas 4.Topography –many sensory areas show topography (retinotopy, somatotopy, tonotopy) –boundaries between topographic maps can indicate boundaries between areas (e.g., separate maps of visual space in visual areas V1 and V2)

5. Macaque Visual Maps Over 30 visual areas Visual areas make up ~40% of monkey brain Van Essen et al., 2001

6. Brodmann’s Areas

7. Brodmann Area 17 7

8. Brodmann Area 17 Meets 21 st Century 8 Logothetis fMRI data: image from http://www.bruker-biospin.com/imaging_neuroanatomy.htmlhttp://www.bruker-biospin.com/imaging_neuroanatomy.html Anatomical MRIFunctional MRI Goense, Zappe & Logothetis, 2007, MRI Layer 4 fMRI activation (0.3 x 0.3 x 2 mm spin echo) Layer 4

9. 9 MT: A Case Study Middle temporal area of the macaque monkey Sometimes also called V5 (5 th visual area) Meets all criteria for an area Has an apparent human equivalent

10. 10 MT: Function Single unit recording –Single neurons in MT are tuned to the direction of motion –Neurons are arranged in “direction hypercolumns” within MT cortex

11. 11 MT: Function Lesions –lesions to MT lead to deficits in perceiving motion Microstimulation –stimulation of a neuron affects the perception of motion –e.g., if you find a neuron with a preference for upward motion, and then use the electrode to stimulate it, the monkey becomes more likely to report “upward” motion

12. 12 MT Architecture MT is stained with cytochrome oxidase (which indicates high metabolic activity)

13. 13 MT Connectivity MT receives direct input from V1 –largely from the “fast” magno pathway cells MT projects to specific higher-level areas MT is an intermediate level visual area

14. 14 MT Topography MT has a topographic representation of visual space + -

15. 15 How can we determine areas in the human?

16. 16 Tools for mapping human areas: function and topography Neuropsychological Lesions Temporary Disruption transcranial magnetic stimulation (TMS) Electrical and magnetic signals electroencephalography (EEG) magnetoencephalography (MEG) Brain Imaging positron emission tomography (PET) functional magnetic resonance imaging (fMRI)

17. 17 Tools for mapping human areas: architectonics and connectivity Human architectonics –post-mortem analyses –high-resolution anatomical MRI Human connectivity –diffusion tensor imaging (DTI) –resting state connectivity –TMS-induced network changes

18. 18 How can we map human (visual) areas? 1.Look for homologues (or analogues) of known primate areas Example: Human MT 2.Look for areas that may participate in highly enhanced human abilities Example: Language, calculation, social interaction, tool use

19. 19 Back to our case study: MT A patient with bilateral lesions to MT can no longer perceive motion (Zihl et al., 1983) MT V1 intermediate A temporary disruption to human MT interferes with motion perception (Beckers & Zeki, 1995)

20. 20 fMRI of Human MT+ (V5+) Moving vs. stationary dots activates V1 and MT Flickering vs. stationary checkerboards activates V1 Video: V1MTmovie.mpg

21. Topography of Human MT+ 21 Huk, Dougherty & Heeger, 1002, J Neurosci

22. Why put the plus in MT+? 22 MT MST Dukelow et al., 2001, J Neurophysiolnot shown: divisions of MST, FST If you can’t distinguish the subdivisions, call it MT+

23. Cytoarchitectonics of MT+ 23 Malicovik et al., 2007, Cereb Cortex

24. Probabilistic Cytoarchitectonics 24 Malicovik et al., 2007, Cereb Cortex

25. DTI of MT+ 25 Lanyon et al., 2009, J Neuro-Ophthalmol

26. Functional Connectivity of MT+ 26 Sani et al., 2011, Frontiers in Systems Neuroscience

27. 27 Evolutionary Relationships expected location actual location Macaque: superior temporal sulcus Human: inferior temporal sulcus

28. Topographic Maps

29. Macaque Retinotopy Source: Tootell et al., 1982

30. Distorted maps 30

31. EXPANDING RINGS Retintopy: Flickering Checkerboard 8 Hz flicker (checks reverse contrast 8X/sec) good stimulus for driving visual areas subjects must maintain fixation (on red dot) ROTATING WEDGES

32. time = 0 time = 20 sec time = 60 sec time = 40 sec 0204060 TIME  STIMULUS EXPECTED RESPONSE PROFILE OF AREA RESPONDING TO STIMULUS color code by phase of peak response

33. Retintopy: Eccentricity calcarine sulcus left occipital lobe right occipital lobe foveal area represented at occipital pole peripheral regions represented more anteriorly

34. Retintopy on Flattened Occipital Lobe 2) cut along calcarine sulcus left occipital lobe 3) unfold and flatten the cortical surface upper calcarine sulcus lower calcarine sulcus lateral surface (note: retinotopic areas do extend onto the lateral surface but are not shown here in this schematic) 1) virtually cut off the occipital lobe (remember, it’s a cup shape and the lateral surface is on the side we can’t see from this viewpoint) occip ital pole occipital pole

35. Retintopy: Eccentricity Movie occipital pole calcarine sulcus Movie: eccentricity.mpeg http://cogsci.ucsd.edu/~sereno/phasemovie2.mpg Source: Marty Sereno’s web pageMarty Sereno’s web page

36. Retintopy in V1: Polar Angle calcarine sulcus left occipital lobe right occipital lobe left-right hemifields reverse (left field to right hemisphere) upper-lower hemifields reverse (upper field to below calcarine) horizontal meridian lies ~along calcarine (not always exactly) HM VM vertical meridian (VM) horizontal meridian (HM) HM VM

37. Polar Angle and Eccentricity in V1 calcarine sulcus left occipital lobe right occipital lobe retinotopic areas are like polar coordinates: eccentricity and polar angle

38. Polar Angle in V1, V2 and beyond left occipital lobe V2 is mirror image map of V1 V1-V2 border occurs at vertical meridian V2-V3 border occurs at horizontal meridian situation gets more complex in higher-tier areas (V4v, V3A) that have representations of whole hemifield HM VM vertical meridian (VM) horizontal meridian (HM) } V1 lower HM } V2 lower VM } VP } V1 upper HM } V2 upper VM } V3 calcarine sulcus

39. Retinotopy Source: Sereno et al., 1995

40. Retinotopy: Polar Angle Movie occipital pole calcarine sulcus Movie: phase.mpeg http://zakros.ucsd.edu/~sereno/movies/phasemovie1b.mpg Source: Marty Sereno’s web pageMarty Sereno’s web page

41. Similarities Between Macaque and Human Maps Tootell et al., 1996, Trends Neurosci. MacaqueHuman (fMRI) (single neurons)

42. Getting Better Retinotopy use stimuli appropriate to the area (e.g., motion in MT+, color in V4v) use stimuli that are attentionally engaging

43. Other Sensory “-topies” Touch: Somatotopy Servos et al., 1998 red = wrist; orange = shoulder Audition: Tonotopy cochlea Sylvian fissure temporal lobe Movie: tonotopy.mpeg http://cogsci.ucsd.edu/~sereno/downsweep2.mpg Source: Marty Sereno’s web page

44. Saccadotopy Source: Sereno et al., 2001 delayed saccades move saccadic target systematically around the clock http://kamares.ucsd.edu/~sereno/LIP/both- closeup+stim.mpg Marty Sereno’s web page

45. There’s even maps in the frontal lobe Intraparietal Sulcus (IPS) Lateral Occipital (LO) Ventral Occipital (VO) Hagler & Sereno, 2006, NeuroImage

46. Maps, Maps, Maps 46 Important Points: 1.Maps are everywhere (the better our techniqes, the more maps we find) 2.Some maps represent ¼ of the visual field (e.g., lower left visual field in green-blue, as in V1); some maps represent ½ of the visual field (e.g., left visual field in red-green, e.g., IPS0); some maps represent whole visual field (yellow too) 3.Regardless of ¼ vs. ½-field representation, maps are always mirror images that flip at the horizontal meridian (blue; solid line) or vertical meridian (red-green; dashed line) Wandell et al., 2007, Neuron

47. Foveal Confluences 47 one foveal confluence a separate foveal confluence Wandell et al., 2007, Neuron

48. Clustering of Areas Wandell et al., 2007, Neuron foveal representation