even a complete loss of ability to recognize faces. This is a very specific
symptom; other aspects of visual perception remain intact. There is
also substantial individual variation among normal people regarding
the ability to recognize and recall faces. It is speculated that this may
relate to variation in the wiring of the temporal lobe visual areas—
different people, different wiring, different capacities for facial recog-
nition and recall.
Prosopagnosia is a specific type of the more general neurological
syndrome called agnosia (Greek a = without; gnosis = knowledge). A
person suffering from a serious visual agnosia may have difficulty rec-
ognizing all or nearly all visual objects. While their ability to identify
details of a visual scene may be completely normal, integrating the de-
tails into a meaningful whole object or scene may be severely disabled.
Visual agnosias are often associated with lesions in the region where
the occipital, temporal, and parietal lobes come together.
One way of thinking about visual perception is that the eye-brain
system does something like a deconstruction process, representing
the visual scene in terms of edges, colors, and movements, all the
while keeping track, via the maps, of where things are in space. Then
a synthesis or coupling of all this information somehow takes place,
perhaps by way of synchronous neural oscillations over large areas of
cortex. And finally these physiological processes are in some way con-
nected to our mental experience of the visual world, with all its rich-
ness of color and texture. Many mysteries remain at every step.
Ah, photons and waves—
ethereal as can be—
as real as it gets.