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Eye Position Signals Modulate Early Dorsal and Ventral Visual Areas

Eye Position Signals Modulate Early Dorsal and Ventral Visual Areas. Paper written by: Joseph F.X. DeSouza , Sean P. Dukelow and Tutis Vilis. Presenter: Nachum Abraham Psychology 3890: Indep . Study. Objectives:.

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Eye Position Signals Modulate Early Dorsal and Ventral Visual Areas

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  1. Eye Position Signals Modulate Early Dorsal and Ventral Visual Areas Paper written by: Joseph F.X. DeSouza, Sean P. Dukelow and TutisVilis Presenter: Nachum Abraham Psychology 3890: Indep. Study

  2. Objectives: • To describe how MT/MST and V4 areas act as visual motion processing sections of the human brain • Provide evidence to support that transformations of Retinotopic to egocentric coordinate frames are necessary for guiding action and recognition in humans • Depict how transformations are modulated by eye positions for humans (the difference in preferred direction of eye position signal reflects differences in transformation)

  3. Background: • Anatomy : • Visual System • V4/V8 • MT • MST

  4. Figures 2A, 2B, and eye http://www.livescience.com/health/051128_eye_works.html

  5. How does our world stay stable? • Helmholtz • corollary discharge for eye position used to achieve consistency • Shifting Locus • Transforming reference frame http://www.physics.gla.ac.uk/Physics3/Kelvin_online/Helmholtz.gif

  6. How does our world stay stable? • Motion • Transformations • Activation of Ventral collateral sulcus: V4v

  7. Hypothesis • Similar modulation by eye position is present in the human equivalent model of the monkey MT/MST and V4 areas = http://williamcalvin.com/portraits/Chimp/Arnhem%20283sml.jpg http://www.oldunterrified.org/sitebuildercontent/sitebuilderpictures/screaming.jpg

  8. Methods: Subject and training • 5 paid male and 2 female paid subjects • 3 training sessions • 1 day prior to experiment • Directly before experiment • During experiment

  9. Methods: Optic Flow Stimulus • Fixation • Optic Flow Stimulus • Alteration: FR, FLof, FL, FRof, FR, FLof, FL, FRof, FR • Length: 16 seconds per epoch, 4-6 reps

  10. Methods: Data Acquisition & Image analysis • 4.0 T Varian UNITY INOVA (whole body imaging) • BOLD imaging technique • Brain Voyager 4.3

  11. Results: Mapping Optic Flow • Stationary fixation stimulus as control • Optic flow produces activation in MT and V4v/V8 • Collateral sulcus activation had retinotopic representation

  12. Results: Signals During Visual Fixation • Comparing left and right fixations • MT after 9 seconds (avg) • V4v/V8 after 7 seconds

  13. Key figures: 4B, 4D, 5A, 5B

  14. Results: Signals During Optic Flow • Comparing left and right flow stimuli • No significant eye position signal difference • Outliers • Variances http://images.inmagine.com/168nwm/photoalto/paa073/paa073000001.jpg http://thailandy.files.wordpress.com/2006/11/eyes-3.jpg

  15. Results: Figure 7 • Visual fixation • Optic flow

  16. Discussion • Absence of moving stimulus and MT • Eye position signal may be to transform coding retinal slip velocity into velocity regarding the head • Disappearing fixation modulation • Apposing V4v/V8 and MT data and coordinate transformations • Ventral and Dorsal streams http://www.biomedcentral.com/graphics/journal/imageofthemonth/1005/200711large.jpg

  17. Questions? • And Thank You Joe!

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