The alternative is to suppose 
that a given object leads to the 
firing of a particular 
constellation of cells, any 
member of which could also 
belong to other constellations. 
Knowing as we do that 
destroying a small region of 
brain does not generally destroy 
specific memories, we have to 
suppose that the cells in a 
constellation are not localized 
to a single cortical area, but 
extend over many areas. 
Grandmother sewing then 
becomes a bigger constellation 
comprising grandmother-by-
definition, grandmother's face, 
and sewing.

    It is admittedly not easy to 
think of a way to get at such 
ideas experimentally. To record 
from one cell alone and make 
sense of the results even in the 
striate cortex is not easy: it is 
hard even to imagine coming to 
terms with a cell that may be a 
member of a hundred 
constellations, each consisting 
of a thousand cells. Having 
tried to record from three cells 
simultaneously and understand 
what they all are doing in the 
animal's daily life, I can only 
admire the efforts of those who 
hope to build electrode arrays to 
record simultaneously from 
hundreds. But by now we should 
be used to seeing problems 
solved that only yesterday 
seemed insuperable.

    Running counter to wooly 
ideas about constellations of 
cells is long-standing and still 
accumulating evidence for the 
existence of cortical regions 
specialized for face perception. 
Charles Gross's group at 
Princeton has recorded from 
cells in the monkey, in a visual 
area of the temporal lobe, that 
seem to respond selectively to 
faces. And humans with strokes 
in one particular part of the 
inferior occipital lobe often 
lose the ability to recognize 
faces, even those of close 
relatives. Antonio Damasio, at 
the University of Iowa, has 
suggested that these patients 
have lost the ability to 
distinguish not just faces but a 
broader class of objects that 
includes faces. He describes a 
woman who could recognize 
neither faces nor individual 
cars. She could tell a car from a 
truck, but to find her own car 
in a parking lot she had to walk 
along reading off the license 
plate numbers, which suggests 
that her vision and her ability 
to read numbers were both 
intact.

    Speculating can be fun, but 
when can we hope to have 
answers to some of these 
questions about perception? 
Some thirty-seven years have 
passed since Kuffler worked out 
the properties of retinal 
ganglion cells. In the interval 
the way we view both the 
complexity of the visual 
pathway and the range of 
problems posed by perception 
has radically changed. We 
realize that discoveries such as 
center-surround receptive 
fields and orientation 
selectivity represent merely 
two steps in unraveling a puzzle 
that contains hundreds of such 
steps. The brain has many tasks 
to perform, even in vision, and 
millions of years of evolution 
have produced solutions of 
great ingenuity. With hard work 
we may come to understand any 
small subset of these, but it 
seems unlikely that we will be 
able to tackle them all. It would 
be just as unrealistic to suppose 
that we could ever understand 
the intricate workings of each 
of the millions of proteins 
floating around in our bodies. 
Philosophically, however, it is 
important to have at least a few 
examples--of neural circuits or 
proteins--that we do 
understand well: our ability to 
unravel even a few of the 
processes responsible for life--
or for perception, thought, or 
emotions--tells us that total 
understanding is in principle 
possible, that we do not need to 
appeal to mystical life forces--
or to the mind.