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Ch. 6 notes

7 Pages
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Department
Psychology
Course Code
PSYA01H3
Professor
Steve Joordens

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Ch. 6 Perception
Perception: the process by which we recognize
what is presented by the information provided by
our senses.
-A rapid, automatic, unconscious process
-We dont feel the process of perception
-We are just presented with the final
product
Problem solving: when we see something we dont
know and we gather evidence to decide what it is
Brain Mechanisms of Visual Perception
Visual perception: hierarchy of information
processing
-Circuits of neurons analyze particular
aspects of visual information
-Results are sent to another circuit
-Further analysis is performed
- More and more complex features are
analyzed
-Higher process interact with memory
Primary Visual Cortex
Knowledge in earliest stages of visual analysis
has come from:
-Investigations of the activity of individual
neurons in the thalamus and the primary
visual cortex
-Inserting small electrodes into various
regions of visual systems of cats and
monkeys
-^ Action potentials created by individual
neurons were studied
Process:
-Animal anaesthetized with eye open
-Electrode inserted close to a neuron
-Animal placed in front of a screen
-Stimulus presented on screen
-Position of stimulus moved around to
detect the location that created the largest
effect on the electrical activity of the
neuron
-Stimuli of various shapes was presented
to detect which one created the greatest
neuron response
Conclusion:
-Geography of the visual field is retained
in: primary visual cortex
-Surface of retina: mapped on surface of
primary visual cortex
- Map is like tiles containing pieces of the
entire picture
Module(tile): blocks of tissue with approx. 150
000 neurons
-Each module receives info from a small
region retina
-Neural circuits in each module analyze
dif. characteristics of their own particular
part of the visual field
Receptive field: part of the visual field where
the firing rate will be altered by the presentation
of a stimuli
Ex.
-One module sees a line
-Some circuits in module detect the present
of lines
-Other circuits orientation of these lines
(angle)
-Other circuits detect width
-Other circuits detect colour
Therefore, orientation of lines passing through
the receptive field is signalled by an increased
rate of firing of particular neurons in the cluster
The Visual Association Cortex
Two streams of visual analysis:
1. (recognition of objects and colour, WHAT)
a. Ventral stream: Perception of Form
- recognition of visual patterns + identification of
particular objects takes place in the inferior
temporal cortex
- Inferior temporal cortex: located at the end of
ventral stream
www.notesolution.com
Visual Agnosia: inability to perceive or identify
a stimulus that exists within a specific sensory
modality
- ppl can still see the object
- they cant identify common objects by
sight
- they have to literally figure out what it is
- touching seeing the object in action helps
- Prosopagnosis: inability to recognize
faces
- feel familiarity but cant recognize...
Fuciform face area (FFA) region of ventral
stream located at base of brain where face
recognizing circuits are found
-Face recognizing circuits: put features of
faces together to recognize the person
-These circuits develop as a result of
experience in seeing peoples faces
Extrastriate body area (EBA) region next to
the primary visual cortex, activated by
photographs or drawings of tools...
-When EBA was inactive, people lost
ability recognize photographs of body
parts but not parts of faces motorcycles
Parahippocampal place area (PPA) activated
by visual scenes and backgrounds...
-ppl with damage cant recognize specific
object in these scenes
b. Ventral stream: Perception of Colour
-Individual neurons in this stream respond to
particular colours
- This region involves in the combination of
information from red/green and yellow/blue
signals that originate in ganglion cells
Cerebral achromatopsia: different hues cant
be distinguished (damage: visual association
cortex)
-Damage of one side of brain: loose colour
vision on half of the visual field
-Bilateral damage: lose all colour vision,
cannot even imagine colours or remember
the colour of objects
2. (Space and Movement, HOW to perform
action)
a. Dorsal Stream: Perception of Spatial
Location
Parietal lobe: receives: visual, auditory,
somatosensory, vestibular information + is
involved in spatial and somatosensory perception
Damage to ^ P Lobe:
- cant perceive or remember the location
of objects
- cant control movement of eyes and limbs
End of dorsal stream: located in the posterior of
Parietal cortex
Dorsal stream:
-Tells us how to perform actions
Ppl with damage^
-Cant pick up objects
-Can tell the difference in size
-Cant show the size with their hands
Women with surgery in bilateral lesions:
Intact ventral stream:
-Could recognize line drawings
-Could tell the size of objects with hands
Damage to ventral stream:
-Cannot distinguish between objects of
different sizes
Damaged Dorsal stream:
-Cannot tell us the size of object by hand
-Can tell us which object is smaller
b. Dorsal Stream: Perception of Movement
- knowing an object is not enough
- we need to have the ability to perceive its
velocity
- certain neurons in the extrastriate cortex
respond differently to movement
- ppl with damage^ can see an object but cant
tell if its moving
Akinetopsia: inability to see motion
Form From Motion:
- ^ our ability: tell an 3-D object by its movement
www.notesolution.com

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Description
- Stimuli of various shapes was presented Ch. 6 Perception Perception: the process by which we recognize to detect which one created the greatest neuron response what is presented by the information provided by our senses. Conclusion: - Geography of the visual field is retained - A rapid, automatic, unconscious process - We dont feel the process of perception in: primary visual cortex - Surface of retina: mapped on surface of - We are just presented with the final primary visual cortex product - Map is like tiles containing pieces of the Problem solving: when we see something we dont entire picture know and we gather evidence to decide what it is Module(tile): blocks of tissue with approx. 150 000 neurons Brain Mechanisms of Visual Perception - Each module receives info from a small Visual perception: hierarchy of information region retina processing - Neural circuits in each module analyze - Circuits of neurons analyze particular dif. characteristics of their own particular aspects of visual information part of the visual field - Results are sent to another circuit Receptive field: part of the visual field where - Further analysis is performed the firing rate will be altered by the presentation - More and more complex features are of a stimuli analyzed Ex. - Higher process interact with memory - One module sees a line Primary Visual Cortex - Some circuits in module detect the present Knowledge in earliest stages of visual analysis of lines has come from: - Other circuits orientation of these lines - Investigations of the activity of individual (angle) neurons in the thalamus and the primary - Other circuits detect width visual cortex - Other circuits detect colour - Inserting small electrodes into various Therefore, orientation of lines passing through regions of visual systems of cats and the receptive field is signalled by an increased monkeys rate of firing of particular neurons in the cluster - ^ Action potentials created by individual neurons were studied The Visual Association Cortex Two streams of visual analysis: Process: 1. (recognition of objects and colour, WHAT) - Animal anaesthetized with eye open a. Ventral stream: Perception of Form - Electrode inserted close to a neuron - recognition of visual patterns + identification of - Animal placed in front of a screen - Stimulus presented on screen particular objects takes place in the inferior temporal cortex - Position of stimulus moved around to detect the location that created the largest - Inferior temporal cortex: located at the end of ventral stream effect on the electrical activity of the neuron www.notesolution.com
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