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Topographic Maps. Macaque Retinotopy Source: Tootell et al., 1982.

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Presentation on theme: "Topographic Maps. Macaque Retinotopy Source: Tootell et al., 1982."— Presentation transcript:

1 Topographic Maps

2 Macaque Retinotopy Source: Tootell et al., 1982

3 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 Source: Jody Culham

4 time = 0 time = 20 sec time = 60 sec time = 40 sec TIME  STIMULUS 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)

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 2) cut along calcarine sulcus left occipital lobe Source: Jody Culham 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) occipital pole occipital pole

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

8 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 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 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 Source: Jody Culham

11 Retinotopy Source: Sereno et al., 1995

12 Retinotopy: Polar Angle Movie occipital pole calcarine sulcus Movie: phase.mpeg Source: Marty Sereno’s web pageMarty 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 Source: Levy et al., 2001 faces activate foveal area (more for foveal than peripheral faces) places activate peripheral area (more for peripheral than foveal places)

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

17 Sulcal Formation Source: Van Essen, 1997 Although sulci vary considerably from person to person (even in identical twins), there is considerable regularity in where the folds occur… Why? 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 Source: Ono, 1990 Sulci appear at predictable points in fetal development with the most prominent sulci (e.g., Sylvian fissure) appearing first.

19 Sulcal Formation: V1-V2 Source: Van Essen, 1997 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

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

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?


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