PSYC 213 Lecture Notes - Lecture 5: Superior Temporal Sulcus, Fusiform Face Area, Visual Cortex
16 May 2018
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Lecture 005 -1/23/2018
Visual perception: context & theories
Last class:
• Sensation:
o Energy from a physical stimulus in the environment that is picked up by
sense organs
• Perception:
o Follows sensation
o When the brain organizes sensed info and translates it into something
meaningful
• McGurk effect and the brain: they compared brain activity for people who
experienced the McGurk effect and people who did not experience this effect
• W/ fMRI, they saw that the left superior temporal sulcus is important for
audiovisual integration during speech perception
o It was more active for people who experienced the McGurk effect
o Shows that individual differences are seen in the brain
• Early visual system
1. Light wave enters the eye and are focused onto the retina, a thin layer of
tissue at the back of the eye
2. PR in the retina convert light to electrical activity
3. Electrical signal is sent to BC and then GC
4. The signal exits through the optic nerve to be sent to the brain
• Functional specialization, retinotopic map in the primary visual cortex
• 2 pathways from the visual cortex:
o What ventral pathway: object recognition
o Where dorsal pathway: spatial location > if damaged, motion perception is
impaired (called akinetopsia: world is like a series if snapshots)
This class:
• Damage to the visual processing area (what pathway) of brain results in selective
problems recognizing objects → visual agnosia
o Basic sensory systems are intact: supports a dissociation between being
able to see visual features and interpreting the visual features
o Specific area of the brain that is damaged determines which types of
feature of objects cannot be recognized: supports higher level functional
specialization
• Prosopagnosia: a form of visual agnosia, an inability to recognize faces while
still being able to recognize other visual objects (selective loss)
o Caused by damage to fusiform face area
• There are different forms of prosopagnosia:
o Problem perceiving faces
▪ Face looks contorted
find more resources at oneclass.com
find more resources at oneclass.com
o Problem attaching meaning to faces
▪ Faces cannot be identified
• Different causes
o Acquired (brain injury)
o Congenital (genetic)
• Apperceptive visual agnosia: a failure to recognize objects because of
problems perceiving the object
o Not a deficit in sensory processing: they can detect visual features
o This is a problem with grouping visual features into meaningful perception
• Evidence: ask them to copy simple line drawings → they will not be able to bring
the diff visual features together
• Associative visual agnosia: an inability to associate visual forms (what you
see) with the intended meaning
o Lost ability to access memories of meaning
• They can’t draw objects from memory, can’t name them, can’t match function to
objects
• Evidence: cannot tell if an impossible animal/ object visually is real or not
• Visual illusions: perception is an active and constructive process
• We use quick and dirty estimate of the world when we perceive: heuristics
• Motion illusions: this is a static image but it looks like its moving
• What we learn from illusions: evidence that top down processing supports vision
• Information is lost as it moves from the eyes to the brain & we bring our
knowledge to help guess what you are seeing
o This suggest we perceive what we know
• Visual cues in our envi for perception: an ecological approach
• Object recognition theories: how we analyze visual input
• Context and expectation on perception: top down processing & Gestalt
• One ecological approach: J.J Gibson: against ‘top-down’ approach to
perception
o There is enough info in our visual envi to perceive aka we don’t have to
transform sensory info to understand it
• A passive bottom-up approach to perception: info from the visual envi guides
perception: what reaches the retina has all the info we need to perceive
• Gibson’s view:
o If info used for perception is in the sensory rich environment, perception
must be studied in the real world
o Perception & action interact: goals/ actions will determine how we
perceive
• Perception in the real visual world:
o Cues in the optic array (visual input) determine what we see
find more resources at oneclass.com
find more resources at oneclass.com
