Cognition 1 Flashcards
Describe the Cornea
Curved transparent part of the eye that counts as ¾ of the ‘lens’ for the eye and lets light through.
Describe the Lens
This part focuses the light entering the eye onto the retina at the back of the eye.
Describe the Iris
The coloured part, provide adjustable aperture for the pupil.
Describe the Pupil
Hole in the centre of the iris which can contract and dilate depending on the amount of light entering the eye.
Describe the Retina
Made up of photoreceptors at the back of the eye, where the actual visual processing really begins
Name the two types of Photo receptor
Rods and cones
Describe the function of Rod cells
All rods are basically the same and they all contain the same photo pigment. Rods react well to dim light, making them almost completely useless in well-lit conditions
Describe the function of Cone cells
Cones come in three main types, long, middle and short wave cones. They work in well-lit conditions and are heavily centred in the fovea (centre).
Describe the path an image takes to get from the eye to the Primary Visual Cortex
Retina - Optic nerve - paths cross at Optic Chasm (50% split) - Optic Tract - LGN - Primary Visual Cortex (V1)
What does light do when it hits the ON region?
Increases the clicking rate
What does light do when it hits the OFF region?
Decreases the clicking rate
What is Luminance?
The amount of light energy something reflects - a physical property
What is Lightness?
How bright something looks - a perceptual property
Where is the primary visual cortex located?
The Occipital lobe at the back of the brain.
What did Hubel and Wiesel discover about the cells in V1?
That cells close to each other in VI have receptive fields close to each other on the retina.
What are the four types of cues?
Motion, Phsyical, Stereo, Pictoral
What does Euclid’s principle say?
Retinal image size halves as the distance to the object doubles.
Describe Stereo Cues
Binocular Disparity - the slight difference between the image on the right and left retinas
Describe Monocular Cues
Motion Parallax - when a person moves the images of the objects around them move across the retina, the closer an item is the faster it moves.
Physical Cues
Accommodation - this is how the eye focuses light to stop it being blurry, muscles moving in the eye signal distance.
Vergence - – Convergence of the eyes (cross eyed) is needed to fixate the image of a nearby object on both foveas. The angle of convergence gives the distance of the object. Is not very useful at telling us information about distance when objects are far away.
Pictorial cues
Occlusion – covering the image of a further object by the image of a nearer one.
Image size – A nearer object produces a larger image than a farther object of the same size.
Texture – a gradient of texture element size and shape provides a cue for distance over a surface.Shading – Gives clues as to the angle of an object
Where does object recognition happen?
In the lateral occipital complex
What happens if the Lateral Occipital cortex is damaged
Visual Form Agnosia
What are the two types of Visual Form Agnosia?
Associative and Apperceptive
What is Associative Visual Form Agnosia?
when a person cannot describe the content of visual input, people ca draw the item and categorize
What is Apperceptive Visual Form Agnosia?
Cannot process visual input, e.g. cant name and object in front of them.
Why can we recognise faces in every day objects?
Faces are a special sort of stimulus of which we have a cognitive bias towards
Fantz 1961
found that babies as young as young as 2 months old have a cognitive bias towards correctly configured faces
What is Prospagnosia?
Deficit in facial recognition where you cannot recognise any faces, even your own, sufferers describe the emotional feeling of recognition but cant, you can have it from birth (congenital) or acquire is gradually (developmental)
Capgras Syndrome
Patients believes familiar faces have been replaced by imposters, however they show normal autonomic nervous responses.
Yin (1969)
Showed that facial recognition is slower and less accurate in faces are inverted.
Bruce and Young (1986)
Proposed Holisitc Form Theory from a wealth of evidence suggesting faces are processed holistically, with emotional and semantic involved.
What makes a face attractive?
Averageness, Symmetry
What does Jeanneord (1997) propose?
That there are two separate components to graspig something, Reach trajectory and Grip aperture.
At what point does peak grip aperture occur?
70% through the reach
What is Cortical Blindness?
the total or partial loss of vision in a normal functional eye due to brain damage in the occipital cortex, can be aquired, congenital or even temporary
What is a Hemianopia?
Patient is unable to see it the contralateral visual field
What is a Quadrantanopia
patient is unable to see in the upper or lower contralateral quadrant.
What is a scotoma?
any visual defect (can be smaller than a hemi or Quadrantanopia)
What is Blindsight?
Residual sensorimotor control following cortical blindness. Blindsight is the extraordinary phenomenon where people who have damage to parts of V1 and are blind to some parts of the world can actually describe objects placed in their blind field.
What is one explanation of Blindsight?
There is a secondary pathway that connects the retina to the parietal cortex via the superior colliculus meaning it bypasses V1 and is the likely pathway for Blindsight.
Evidence for Blindsight
Patient DB - - Left Hemianopia following surgical resection of the right occipital lobe however he could look towards and point at visual targets he could not consciously see
Milner and Goodale (1992)
concluded from research done on patient DF that there are separate brain systems for using information for perception and for physically controlling your actions (think about the posting task)
What is Optic Ataxia?
Caused by damage to left Parietal lobe which affects visually guided movement.
What is the Ventral Stream?
The ‘What’ stream, used for object processing, colour texture, size. Damage to this area causes perception problems such as visual form agnosia
What is the Dorsal Stream?
The ‘Where’ stream, used for spatial processing, location, movement. Damage to this area causes action problems such as Optic Ataxia.
What is Proprioception?
The bodies ability to sense where our body is in space without having to look.
What is Deafferentation?
Total loss of Proprioception
Describe Phantom Limb Pain
The sensation amputees often feel of unpleasent pains at the sight of their amputation. Treatment includes heat application, relaxation techniques, massage, nerve blockers, mirror box illusion