"It is a gross mischaracterization to say that we simply open our eyes
and take it all in; what we are in contact with is a constructed product
of many different brain processes."
Kolak, Daniel;
Hirstein, William;
Mandik, Peter;
&
Waskan, Jonathan
(2006),
Cognitive Science: An Introduction to Mind and Brain
(New York: Routledge): 81.
Figure 06-03. The eye. (a) Illustration showing how objects in the
environment are physically projected to the back of the eye&151;the retina. (b) The eye and a cross-section of the retina. The
cross-section of the eye shows where the photoreceptors are located in
the retina. Both the rods and cones are shown. They respond to different
types of light. The neural signal then travels via bipolar cells and
then to the ganglion cells. The axons of the ganglion cells take the
neural information out of the eye and backward toward the cortex.
Source: Squire et al., 2003.
Figure 06-07. The visual pathways from retina to cortex. (a) Example
of a brain slice from a functional magnetic resonance imaging (fMRI)
scan, showing the lateral geniculate nucleus (LGN) and primary visual
areas at the back of the brain (the occipital cortex). The two different
colors denote the two hemispheres of the brain. (b) Schematic
illustration showing the visual pathways from the retina in the eyes to
the primary visual cortex at the back of the brain. You can see here
that the neural information from the nasal or inner sides of the eyes
crosses over at the optic chiasm, to be processed in the contralateral
side of the brain. The left visual field, in blue, is processed by the
right visual cortex (also blue). The LGN, displayed in green, relays the
visual information to the primary visual areas of the cortex. Source:
Squire et al., 2003.
Figure 06-10. The hierarchy of visual processing. A demonstration of
the hierarchical response properties of the visual system to simple and
complex stimuli. The leftmost column shows our house stimulus and what
receptive fields of each visual area we would see in the balloons. Not
only do the receptive field sizes increase in each visual area, but also
the complexity of the shapes they respond to. The rightmost column shows
an estimate of where each area is in the brain. You can see that early
visual areas respond to simple features and, as we move along the
processing stream, areas respond to more complex shapes and objects.
This is a well-established theme of the visual system.