36 • CHAPTER 2 Cognitive Neuroscience
the physiology of language processing is more complex than proposed by Broca and
Wernicke, both because the idea of a strict separation of “production” and “comprehen-
sion” is too simple and because many areas in addition to Broca’s and Wernicke’s areas
are involved in language processing (Binder et al., 1997; Dick et al., 2001; Dronkers
et al., 2004; Friederici, 2002, 2009; Friederici et al., 2006).
The picture that is emerging from all of this research is that (1) specifi c language
functions are localized in specifi c brain areas, so that localization of function is an
important part of language processing; and (2) language processing is distributed over
a large area of the brain. In the next section we will see that this widespread processing
across the brain is an important principle that holds not only for language, but for other
cognitive functions as well.- How did early brain researchers describe the brain in terms of a nerve net?
How does the idea of individual neurons differ from the idea of a nerve net? - Describe the research that led Cajal to propose the neuron doctrine.
- Describe the structure of a neuron. Describe the synapse and neural circuits.
- How are action potentials recorded from a neuron? What do these signals look
like, and what is the relation between action potentials and stimulus intensity? - How has the question of how action potentials indicate different qualities been
answered? - Describe evidence for localization of function for perception, including the pri-
mary receiving areas of the brain and evidence from brain damage and brain
imaging. Be sure you understand the principle behind brain imaging. - How did Broca and Wernicke use the behavior of patients with brain damage
to provide evidence for localization of function? - What behavioral evidence caused a modifi cation of the idea of two areas, one
for language production and one for language understanding? What is the ERP,
and how has it been used to demonstrate different aspects of language func-
tioning? What basic conclusions about localization of function have emerged
from research on the physiology of language?
Distributed Processing in the Brain
The idea of distributed processing is that specifi c functions are processed by many dif-
ferent areas in the brain. Although this might at fi rst seem to contradict the ideas of
localization of function and modules described above, we will see that these two ideas
actually complement each other.
We can describe distributed processing by starting with localization of face perception
in the brain. We saw that brain imaging experiments have identifi ed an area called the FFA
that is strongly activated by faces and responds more weakly to other types of stimuli. But
just because there is an area that is specialized to respond to faces doesn’t mean that faces
activate only that area. Faces strongly activate the FFA, plus other areas as well.
What is particularly signifi cant about faces is that while a number of areas of the
brain participate in perception of a face, other areas also respond to various reactions
to a face. For example, when you see someone walking down the street, looking at the
person’s face activates many neurons in your FFA plus neurons in other areas that are
responding to the face’s form. But your response to that person’s face may go beyond
simply “That’s a person’s face.” You may also be affected by whether the person is looking
at you, how attractive you think the person is, any emotions the face may elicit, and your
reactions to the person’s facial expression. As it turns out, different areas in the brain are
activated by each of these responses to the face (see ● Figure 2.15). Looking at a face thusTEST YOURSELF 2.1
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