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Feature Representations in Perception & Localization of Function

Feature Representations in Perception & Localization of Function. Psychology 355: Cognitive Psychology Instructor : John Miyamoto 4/7 /2014: Lecture 02-1.

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Feature Representations in Perception & Localization of Function

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  1. Feature Representations in Perception& Localization of Function Psychology 355: Cognitive PsychologyInstructor: John Miyamoto4/7/2014: Lecture 02-1 This Powerpoint presentation may contain macros that were used to create the slides. The macros aren’t needed to view the slides. If necessary, you can disable the macros without any change to the presentation.

  2. Outline • Examples of feature representations in perception • Motion aftereffects • Localization of function • Double dissociation • Quiz 1 # Psych 355, Miyamoto, Spr '14

  3. Two Major Issues in Cognitive Psychology – Representation & Process • Representational issues – • How is information coded in the cognitive system? • How are different mental representations manipulated in mental processes? • Process issues – • What is the sequence of mental processes that act upon mental representations? • Which processes occur sequentially and which processes occur in parallel? • Feature representations are well-supported in perception.Feature representations are also proposed for higher cognitive processes, although the evidence is often lesssolid. Visual Feature Detectors Psych 355, Miyamoto, Spr '14

  4. Visual Feature Detectors • Hubel & Wiesel used single-cell recordings to demonstrate the existence of feature detectors in the visual system. • Lots of evidence for feature detectors: • Single-cell recordings • Visual illusions that can be explained by lateral inhibition (inhibition of neighboring neurons) • fMRI evidence (not discussed in this lecture) • Many different types of neural feature detectors have been found: edge and bar detectors, motion detectors, texture detectors, color detectors, etc. • Important Hypothesis: Many perceptual and cognitive processes are based on feature representations. Hermann Grid Psych 355, Miyamoto, Spr '14

  5. Hermann Grid Stare at the grid. What do you see? Apply Idea of Lateral Inhibition to Construction of Edge & Bar Detectors Psych 355, Miyamoto, Spr '14

  6. Two Perceptual Phenomena with the Hermann Grid • Phantom dark spots appear at the intersections of the white lines. • The dark spots disappear when you look directly at them. Why? Use Lateral Inhibition to Explain the Perception of the Hermann Grid Psych 355, Miyamoto, Spr '14

  7. Hermann Grid Illusion is Due to Lateral Inhibition? There is more lateral inhibition at the intersection than in the middle of a white bar. Receptive fields are smaller in the fovea (center of vision) than away from the fovea. We see phantom dark spots at the intersections to the side of the focus of vision because ..... Lateral Inhibition & Edge Detectors Psych 355, Miyamoto, Spr '14

  8. Edge Detectors and Bar Detectors in Visual Cortex • Lateral inhibition helps neurons to work together to create edge and bar detectors. • Lateral inhibition enhances the perception of edges. Anderson, Figure 2.07 Anderson, Figure 2.09 More Evidence for Feature Detectors – Motion Aftereffects Psych 355, Miyamoto, Spr '14

  9. Evidence for Motion Detectors – Motion Aftereffects • Waterfall Illusion (this is one of the original discoveries that lead to the study of motion aftereffects)http://www.lifesci.sussex.ac.uk/home/George_Mather/Motion/MAE.HTML • Expanding Buddha: http://www.michaelbach.de/ot/mot-adapt/index.html • Set the display to "Full Screen". Choose whether you want the Buddha to expand or contract. Then click "start." • Motion aftereffects give evidence for motion detectors in the visual system. • Persistent activation of a motion detector reduces its sensitivity (adaptation). When the motion is stopped, we “see” motion in the opposite direction. • These motion aftereffects support the general claim that there arefeature detectors in the visual system. Summary: Visual Feature Detectors Psych 355, Miyamoto, Spr '14

  10. Summary - Visual Feature Detectors • Hubel & Wiesel used single-cell recordings to demonstrate the existence of feature detectors in the visual system. • Lots of evidence for feature detectors: • Single-cell recordings • Visual illusions that can be explained by lateral inhibition (inhibition of neighboring neurons) • fMRI evidence (not discussed in this lecture) • Many different types of neural feature detectors have been found: edge and bar detectors, motion detectors, texture detectors, color detectors, etc. • Important Hypothesis: Many perceptual and cognitive processes are based on feature representations. Two Major Issues in Cognitive Psych – Representation & Process Psych 355, Miyamoto, Spr '14

  11. Localization of Function • Specific functions are served by specific areas of the brain • Cognitive functioning breaks down in specific ways when areas of the brain are damaged • Brain imaging can identify areas of the brain that serve specific functions. Diagram of Areas of the Brain Psych 355, Miyamoto, Spr '14

  12. Lobes of the Left Hemisphere Head is facing LEFT Lobes of the Cerebral Cortex (continued) Psych 355, Miyamoto, Spr '14

  13. Next: fMRI Evidence for Brain Areas with Specialized Perceptual Functions O'Craven, K., & Kanwisher, N. (2000). Mental imagery of faces and places activates corresponding stimulus-specific brain regions. Journal of Cognitive Neuroscience, 12, 1013-1023. FFA: Fusiform face area. Specialized for faces.(“ventral occipito-temporal cortex”) PPA: Parahippocampal place area. Specialized for representing location info.(“ventromedial cortical region”) Graphic Showing Location of FFA & PPA Psych 355, Miyamoto, Spr '14

  14. Location of the fusiform face area and parahippocampal gyrus Graphic from http://labnic.unige.ch/nic/htms/fmri.html • Graphic from the article: Haynes, J-D., & Rees, G. (2006). Decoding mental states from brain activity in humans. Nature Reviews Neuroscience, 7, 523-534. Parahippocampal place area (PPA) Fusiform face area (FFA) Diagram of BrainHead Facing Left fMRI Results for Face & Place Recognition Psych 355, Miyamoto, Spr '14

  15. O’Craven & Kanwisher – Research Hypotheses • Research Goal: To test the claim that the fusiform face area is specialized for face perception. • Prediction: FFA will be activated by face stimuli but not by location stimuli. PPA will be activated by location stimuli but not by face stimuli. Psych 355, Miyamoto, Spr '14

  16. Monday, April 07, 2014: The Lecture Ended Here • Actually, the lecture ended just before the previous slide but I included the previous slide to state the issue that will be addressed in the next lecture. Psych 355, Miyamoto, Spr '14

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