Chapter
Four
Neuroscience
They pressed keys to indicate which they were consciously seeing. These very
different stimuli allowed the experimenters to investigate activity in brain areas
specialised for the analysis of faces, as well as for colour and form. They looked
for areas where activity was significantly higher during periods when the face
was seen than when the grating was seen. They found this bilaterally (on both
sides of the brain) in occipito-temporal areas of the ventral pathway, including
some parts of the fusiform gyrus that are known to be involved in the processing
of faces. In addition, they found many prefrontal areas where activity correlated
with the image seen.
They also investigated the flipping process itself. To do this, they recorded a
participant’s series of key presses and then played back the same sequence of
images to the participant. They could then compare brain activity for exactly
the same sequence of images, but with the important difference that in one
case the flipping occurred spontaneously, while in the other it was predeter-
mined. Any differences in activity between the two should then reveal which
areas of the brain are involved in causing the flip to occur. Such differences
were found in many areas, including parts of the parietal and frontal cortex
that had previously been implicated in selective attention (Lumer, 2000). These
results add to the impression that conscious visual experiences are correlated
not with activity in V1 or other early parts of the sensory pathways but with
more central areas.
FIGURE 4.5 • (a) Brain areas showing greater fMRI activity during perceptual dominance of the face compared with periods
during which the face was unseen are shown as see-through projections onto lateral (left) and horizontal (right)
representations of standard stereotactic space (precise 3D positioning). (b) Activity maps during face perception in
selected coronal sections, overlaid onto normalised anatomical MRIs. Activity is shown in the fusiform gyri (left),
middle and inferior frontal gyri (centre), and dorsolateral prefrontal cortex (right). Distance from the anterior
commissure is indicated below each coronal section (Lumer, 2000).