perception week 4

4.1 (mon)

  • dorsal - towards the top of the brain towards parietal lobe (WHERE)

  • ventral - towards the bottom of the brain towards temporal lobe (WHAT)

  • LGN recognizes small dots, V1 orients the object, LOC grasps basic shape of object, VTC recognizes complexities of the object

  • V1 responds to any sort of visual information

  • LOC responds, specifically, to non-scrambled/mostly intact

    • prefers coherent structure

    • recognizes shapes

  • when LOC is damaged → visual agnosia

    • visual agnosia - condition in which a person can see but cannot visually recognize objects

    • patient with visual agnosia CANNOT VISUALLY recognize an object, but they recognize it if they bypass their damaged LOC, and pick the object of (interacting w the object)

    • simply put - they cannot interpret shape perceptually

  • TMS - trans cranial magnetic stimulation

    • giant magnet that disrupts neuronal processing

    • allows researchers to locate function

    • differs from fMRI and EEG as it directly stimulates brain function, then we observe brain function (causal)

    • TMS on LOC impairs ability to name objects but not ability to recognize faces

  • location processing in DORSAL (using lesions in monkeys)

    • object discrimination - find food under particular object (impaired by temporal lobe)

    • landmark discrimination - find food near landmark (impaired by parietal lobe lesions

  • location processing (PET - positron emission topography in humans)

    • dot location task - most activity in dorsal pathway

    • face matching task - most activity in temporal pathway

  • ventral (what), dorsal (where) has competing theory - Perception vs Action

    • dorsal - control of action (HOW one interacts with object)

    • ventral - conscious perception and object recognition (WHAT is the object)

  • woman could not match object to task perceptually but when asked to do the tasl (insert card in card slot), she could match objects

    • perceptual matching vs. active matching

    • this study suggests the dorsal stream, may have its own shape anlysis, meant to accurately guide attention and actions

  • pareidolia - seeing meaning that isn’t intended

    • ex) seeing faces in cars or outlets

    • occurs rapidly and effortlessly

    • humans love to detect faces quickly

    • false alarm better than missed social/threat cues

    • ex) mooney faces

  • faces present various info

    • ethnicity, age, gender, health, emotion

  • ventral stream has selectivity

    • fusiform face area (FFA)

      • selectively responds to faces

      • located in fusiform gyra

    • body area

    • parahippocampal place area (PPA)

    • LOC: things

4.2 (wed)

  • what happens w damage to fac eregions?

    • prosopagnosia - inability to recognize faces of those familiar

  • propagnosia

    • some acquire later in life due to damage, some people born with it (developmental prosopagnosia)

    • difficulty recognizing familiar faces, rely on other cues like voice or hairstyle

  • super recognizers

    • exceptionally strong ability to recognize faces

    • can identify people seen briefly or long ago

  • regions involved in face processing (face processing network)

    • fusiform face area

    • occipital face area

    • superior temporal sulcus

    • amygdala

  • occipital face area

    • in occipital lobe, recognizes parts of face ate early stages of face recognition

  • fusiform face area

    • in fusiform gyrus, responsible for holistic (configural) information, putting together all of processed pieces of the face

    • processes and judges spacing and configuration of of parts of face to determine identity

  • holistic face processing

    • once detected, faces processed as whole

    • face inversion effect - face recognition drops dramatically when faces are inverted

    • efficient perception - holistic face processing happens quickly without intention

  • margaret thatcher illusion - upside down pic w/ right side up eyes/lips

    • shows how FFA processes face identity holistically, with integrated parts

  • inverted faces stop holistic processes

  • composite face effect - recognizing halves of a mismatched face better when the halves aren’t aligned

  • superior temporal sulcus (STS)

    • involved with gaze, intention, dynamic faces, and biological motion

    • people with autism may look at mouth movement more than eyes/hair when watching a movie

  • amygdala - processes one’s own emotions and perceive emotions of others

  • nature v. nurture in facial recognition

    • nature (innate)

      • newborns prefer face like patterns over scrambled stimuli

      • face sensitivity appears early in life

    • nurture (learned)

      • face recognition strengthens in teen years

      • perceptual narrowing - infants become tuned to familiar faces

  • fovea - clear

  • focus of gaze determines which category-selective area will be formed

    • control group - monkeys looked at face

    • face-deprived - monkeys looked at hands

  • nature v nurture are BOTH required for facial processing

    • there is innate…

      • bias to pay attention to faces in infancy

      • specific parts of visual cortex specialized to represent objects in center of vision

    • there is experience in…

      • gaining lots of experience seeing faces in center of vision

      • specific part of visual cortex for selectivity of faces

      • further improvement both in behavior and in brain