68 • CHAPTER 3 Perception
EXPERIENCE-DEPENDENT PLASTICITY
The brain is changed, or “shaped,” by its exposure to the environment so it can perceive
the environment more effi ciently. The mechanism through which the structure of the brain
is changed by experience, called experience-dependent plasticity, has been demonstrated
in many experiments on animals. These experiments have shown that if an animal is
reared in a particular environment, neurons in the animal’s brain change so they become
tuned to respond more strongly to specifi c aspects of that environment. For example,
when a kitten is born, its visual cortex contains orientation-selective neurons that fi re to
oriented bars like the ones in Figure 3.2b. Normally the kitten’s brain contains neurons
that respond to all orientations, ranging from horizontal to slanted to vertical, but Colin
Blakemore and Graham Cooper (1970) found that rearing a kitten in an environment
consisting only of verticals (● Figure 3.29a) reshaped the kitten’s visual cortex so it even-
tually contained neurons that responded mainly to verticals (Figure 3.29b). Similarly, kit-
tens reared in an environment consisting only of horizontals ended up with a visual cortex
that contained neurons that responded mainly to horizontals. Thus, the kitten’s brain had
been shaped to respond best to the environment to which the kitten had been exposed.
Experience-dependent plasticity has also been demonstrated in humans, using the
brain imaging technique of fMRI (see Method: Brain Imaging, page 30). The starting
point for this research is the fi nding that there is an area in the temporal lobe called
the fusiform face area (FFA) that contains many neurons that respond best to faces
(see Chapter 2, page 32). Isabel Gauthier and coworkers (1999) determined whether
this response to faces might be due to experience-dependent plasticity by measuring
the level of activity in the FFA in response to faces and to objects called Greebles
(● Figure 3.30). Greebles are families of computer-generated “beings” that all have the
same basic confi guration but differ in the shapes of their parts (just like faces). The bars
and the brain scans in ● Figure 3.31a show that for “Greeble novices” (people who
have had little experience in perceiving Greebles), the faces cause more activity than the
Greebles in the FFA. This is also evident in the brain cross section, in which the white
areas indicate higher activity.● FIGURE 3.29 (a) Striped tube used in Blakemore and Cooper’s (1970) selective
rearing experiments. (b) Distribution of optimal orientations for 72 cells from a cat
reared in an environment of vertical stripes. (Source: From C. Blakemore & G. F. Cooper,
“Development of the Brain Depends on the Visual Environment,” Nature, London, 228, 477–478.
Copyright © 1970. Used with permission of Nature Publishing Group.)(a)(b)VerticalHorizontalVertical
● FIGURE 3.30 Greeble stimuli
used by Gauthier. Participants
were trained to name each
diff erent Greeble. (Source:
Reprinted with permissions from
I. Gauthier, M. J. Tarr, A. W. Anderson,
P. Skudlarski, & J. C. Gore,
“Activation of the Middle Fusiform
‘Face Area’ Increases With Experience in
Recognizing Novel Objects,”
Nature Neuroscience, 2, 568–573, 1999.)Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.