Ch.4 pt. 1&2

• Feature detectors play a crucial role in perception by establishing a link between stimulus and physiology
• Selective adaptation occurs when neurons tuned to a specific property of a stimulus fire, eventually leading to fatigue or adaptation
• Two physiological effects of selective adaptation are a decrease in the neuron's firing rate and firing less when the same stimulus is presented again
• Selective Adaptation: sensory systems become less sensitive to constant or unchanging stimuli over time

  • neurons firing rate decreases & the neuron fires less
  • can affect orientation perception through the contrast threshold, which is the minimum intensity difference between two adjacent bars that can be detected
• Selective rearing experiments show that neurons responding to specific stimuli become more prevalent when an animal is raised in an environment with those stimuli
• Neural plasticity, or experience-dependent plasticity, suggests that perceptual experience can shape the response properties of neurons
• In the visual cortex, the neural map in the striate cortex (V1) is determined by stimulating various places on the retina and noting where neurons fire in the cortex
• • Retinotopic Map:represents the retina on the cortex
  • Cortical Magnification: refers to allocating a large area on the cortex to the small fovea
• Hubel and Wiesel's experiments in 1965 revealed that neurons in the visual cortex are organized in columns, including location and orientation columns
• Orientation columns and hypercolumns in V1 neurons and columns underlie the perception of a scene by containing information that represents the stimulus, not necessarily resembling it
• The extrastriate cortex and streams provide information about "what" and "where" in visual processing
• Patient D.F. experienced damage to her ventral pathway from carbon monoxide poisoning, affecting her ventral stream and causing difficulties in orienting objects but performing well when action was involved
• Higher-level neurons in the inferotemporal (IT) cortex have larger receptive fields, with receptive field size increasing through the "what" stream to encompass whole objects in the visual field
• Selective Rearing Colin & Grahame: after placing cats in veritcal environment, they develop vertically selective neurons after being in vertical environment only

  • adapts after a long time
• Retinotopic Map: map of retina on the cortex
• Cortical Magnification: how the fovea is represented within the visual cortex

  • large part of visual cortex is dedicated to processing visual information from retina
• Orientation Columns: all neurons lined up in column respond to same orientation
• Hypercolumns: a column composed of each individual column that respond to different orientations

  • location column