Chapter 6 - Perception
Perception ±A rapid, automatic, unconscious process by which we recognize what is represented
by the information provided by our sense organs.
Brain Mechanisms of Visual Perception:
-2 successive levels of visual association cortex
-1st level surrounds the primary visual cortex
-2nd level in middle of parietal lobe and lower part of temporal lobe.
The Primary Visual Cortex:
Hubel & Wiesel Æ Mapped visual cortex
-Placed microelectrodes on animal brains and presented them visual stimuli
-Microelectrodes are small wires with points that detect neuron activity
-Modules = 0.5mm*0.7mm, 150 000 neurons each
-2500 modules in the human brain.
-Neurons detected different things (i.e. Some detect horizontal lines, vertical lines, color, etc)
Receptive Field ±The portion of the visual field in which the presentation of visual stimuli will
produce an alteration in the firing rate of a particular neuron.
The Visual Association Cortex:
-Different areas of the visual association cortex deal with different levels of vision.
-From the neurons that detect different things -> send info to particular areas of the visual
association cortex to be analyzed.
Effects of Brain Damage On Visual Perception
-If the primary visual cortex is damaged, the person is blind in that area (remember how what we
see is mapped on the brain)
-No difficulty in perceiving
-Damage to visual association cortex damages perceptive ability.
Achromatopsia ±The inability to discriminate among different hues; caused by damage to the
visual association cortex.
-The brain is contralateral damage to one side affects the other side of body
Î Damage to the achromatopsia causes the person to see no color what so ever.
%DOLQW¶V6\QGURPH±A syndrome caused by bilateral damage to the parieto-occipital region of
the brain; includes difficulty in perceiving the location of objects and reaching for them under
-They can tell that an object has changed positions, but cannot detect movement.