1. Topographic Maps

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

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

4. EXPECTED RESPONSE PROFILE OF AREA RESPONDING TO STIMULUS
To analyze retinotopic data:
Analyze the data with a set of functions with the same profile but different phase offsets.
For any voxels that show a significant response to any of the functions, color code the activation by the phase offset that yielded maximum activation (e.g., maximum response to foveal stimulus = red, maximum response to peripheral stimulus = green)
time = 0
time = 20 sec
time = 40 sec 20 40 60
time = 60 sec
TIME 
Source: Jody Culham

5. Retintopy: Eccentricity
calcarine
sulcus
left occipital
lobe
right occipital
lobe
foveal area represented at occipital pole
peripheral regions represented more anteriorly
Source: Jody Culham

6. Retintopy on Flattened Occipital Lobe
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)
occipital
pole
2) cut along calcarine
sulcus
upper calcarine sulcus
3) unfold and flatten the cortical surface
lateral surface
(note: retinotopic areas do extend onto the lateral surface but are not shown here in this schematic)
left occipital
lobe
occipital
pole
lower calcarine sulcus
Source: Jody Culham

7. Retintopy: Eccentricity Movie
calcarine sulcus
occipital pole
Movie: eccentricity.mpeg
Source: Marty Sereno’s web page

8. Retintopy in V1: Polar Angle
calcarine
sulcus
horizontal meridian (HM) VM VM HM HM VM VM
left occipital
lobe
right occipital
lobe
vertical meridian (VM)
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)
Source: Jody Culham

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

10. Polar Angle in V1, V2 and beyondVM
} V3 HM
} V2 upper
calcarine
sulcus
} V1 upper
horizontal meridian (HM)
} V1 lower VM HM
} V2 lower HM VM
} VP VM
left occipital
lobe
vertical meridian (VM)
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
Source: Jody Culham

11. Retinotopy
Source: Sereno et al., 1995

12. Retinotopy: Polar Angle Movie
calcarine sulcus
occipital pole
Movie: phase.mpeg
Source: Marty Sereno’s web page

13. Getting Better Retinotopy
use stimuli appropriate to the area (e.g., motion in MT, color in V4v)
use stimuli that are attentionally engaging
Marty Sereno: Buffy-o-topy
UWO: chicken-o-topy

14. Other Sensory “-topies”
Touch:
Somatotopy
Servos et al., 1998
red = wrist; orange = shoulder
Audition:
Tonotopy
cochlea
Sylvian fissure
temporal lobe
Movie: tonotopy.mpeg
Source: Marty Sereno’s web page

15. Face/Place-o-topy
faces activate foveal area (more for foveal than peripheral faces)
places activate peripheral area (more for peripheral than foveal places)
Source: Levy et al., 2001

16. Marty Sereno’s web page
Saccadotopy
delayed saccades
move saccadic target systematically around the clock
Source: Sereno et al., 2001
Marty Sereno’s web page

17. Sulcal Formation
Although sulci vary considerably from person to person (even in identical twins), there is considerable regularity in where the folds occur… Why?
Source: Van Essen, 1997
David Van Essen proposes that as the brain develops, areas that are richly interconnected will be pulled together to form a gyrus (and those that are weakly interconnected form sulci).

18. Development of Sulci
Sulci appear at predictable points in fetal development with the most prominent sulci (e.g., Sylvian fissure) appearing first.
Source: Ono, 1990

19. Sulcal Formation: V1-V2
The V1/V2 border provides one example of two richly interconnected areas that form a gyrus.
This arrangement also explains why maps in V1 and V2 are mirror images of each other!
calcarine
sulcus
Source: Van Essen, 1997

20. Comparative Neuroanatomy
The complexity of sulci increased throughout evolution
Source: Comparative Mammalian Brain Collection

21. Interspecies Comparisons
Figure H shows the macaque monkey visual areas morphed onto human cortex based on the placement of sulcal landmarks (Van Essen et al., 2001)
Can we assume humans are just morphed monkeys?
In some areas the human cortical surface area is slightly larger than in the macaque (e.g., visual cortex: 2X); in others it is considerably larger (e.g., parietal cortex: 20X)
Are individual areas larger?
Are there more areas?