Minds and Computers : An Introduction to the Philosophy of Artificial Intelligence

temporal lobe
parietal lobe
occipital 
lobe
cerebellum
frontal lobe
Broca’s
area
pr
ima
ry m
ot
or cor
tex
somatosenso
ry stri
p
primar
y auditor
y
corte
x
Wernicke’s
area
Figure 4.3
Intact brain – left view.

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hemispheres. So the left hemisphere processes information from the
right-hand sense organs and controls movement on the right-hand
side of the body. Vision is even more peculiarly cross-lateralised. The
right-hand side of each eye’s visual field is processed in the left-
hemisphere and the left-hand side of each eye’s visual field is
processed in the right hemisphere.
Each cerebral hemisphere divides into four lobes: the frontal lobe,
the parietal lobe, the temporal lobe and the occipital lobe. The func-
tions of the cerebrum are not as well understood as the more evolu-
tionarily antecedent areas of the brain we’ve examined so far;
however, there are certain canonical cognitive functions associated
with each lobe and there are important areas of localised functional
specialisation – notably the primary processing areas for each sensory
modality and the two speech areas.
The frontal lobe is implicated in a whole range of ‘higher’ cognitive
functions. This is sometimes loosely glossed as being responsible for
‘planning and prediction’ or ‘executive control’. The frontal lobe con-
tains the primary motor cortex which, as the name suggests, is impli-
cated in the execution of bodily movement. It also contains one of the
speech areas of the brain – Broca’s area.
Broca’s area, named after Paul Broca, is adjacent to the primary
motor cortex. Damage to this part of the brain gives rise to a distinct-
ive kind of aphasia (language deficit) known as Broca’s aphasia.
Broca’s aphasia is characterised by an inability to produce fluent
grammatical utterances, even though the su
fferer retains linguistic
comprehension and is aware of their deficit. This can be a particularly
pernicious aphasia as su
fferers struggle to make themselves under-
stood but can only produce utterances with few, if any, grammatical