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Unformatted text preview: EXAM #3 KEY WORDS • Motion aftereffect o Seeing motion where there is no change in the position of an object o Due to stimulation by previous image of either inward/outward motion • Kinematogram o Perceived shape is defined by motion o Motion cannot depend only on first seeing a shape & then tracking the shape to infer the motion o Dots shift from one frame to the next Otherwise, the dots are just featureless random b&w pixels that are essentially the same texture in each frame o Shows motion where there is no noticeable object • fMRI o functional magnetic resonance imaging o indicates brain activity in awake behaving humans in response to perceptual stimuli o shows which areas are activated during specific tasks • MT o Medialtemporal area o Nucleus that contains a large number of directionally selective neurons o Almost all neurons are directionally selective (higher proportion than V1) o AKA: V5 o Prefer the motion of patterns o Neurons here have large RFs (much larger than those in V1) Integrate motion signals from V1 neurons Able to detect pattern motion o Damage here causes motion blindness • MST o Medial superior temporal area o Known to be important for movement perception o Properties of MST neurons: Very large RFs (much larger than in MT) Selective to optic flow patterns (expansion, contraction, rotation, shearing) • Motion adaptation o o o • Reichardt detector o Directionally selective unit o Can operate in the retina & visual cortex o Operates when a moving object is presented to two adjacent RFs sequentially Two stationary flashes of light should work just as well o RF 1 sends impulse to neuron 1 which is delayed o RF 2 sends impulse to neuron 2 that adds something to neuron 1, causing brain to register motion o If brain were composed of Reichardt detectors only, we’d only perceive motion (nothing else) • Direction selective neuron o When moving “dot” stimuli coherence increased, the MT neuron fired more rapidly & monkey was able to judge the direction of movement more accurately • Apparent motion o Examples: Lights @ entrance of theaters Vegas Airport runway lights • Motion blindness o Inability to perceive continuous motion o Caused by bilateral damage to the MT or MST o Similar to a strobe light at 8Hz The world is visible only 8x/sec It disrupts the perception of most velocities • Color o Importance: Find food for survival – able to distinguish food from other things Finding mates for reproduction – tell male from female o Cortical color blindness o Damage to V8 o Lose subjective experience of color – the world is like a b&w movie o Can still name objects and tell what color they are o...
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This note was uploaded on 04/14/2008 for the course PSC 131 taught by Professor D.whitney during the Winter '07 term at UC Davis.
- Winter '07