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[Narrator] Unlike Graham, Peggy Palmer has normal vision.
She should be able to copy this star easily.
[Peggy] "I'll never get this star I'm hopeless at this."
[Narrator] But something odd is happening.
One whole side of the star is missing.
Peggy has a condition called visual neglect.
Although her eyesight is fine,
half of her visual world no longer seems to matter.
Ten years ago, Peggy suffered a stroke in the parietal lobes of her brain.
[V.S. Ramachandran] "The parietal lobes are concerned mainly
with creating a three-dimensional representation
of the spatial layout of the world allowing a person to walk around
to navigate, to avoid bumping into things.
When the right side is damaged
the patient is unable to deal with the left side of the world.
[Narrator] This condition has fascinated neurologists for more than a century
because it reveals not only how the brain shapes the way we perceive space in the present
it even determines the spatial look our memories.
This became apparent when Peggy was asked to draw a daisy from memory.
"Alright, a daisy it shall be"
[Narrator] For neuropsychologist Peter Halligan Peggy's drawings reveal exactly what's gone wrong.
[Peter] It is like a radar system whereby
the actual radar system on the left hand side is no longer working well.
If someone comes into my left hand side now
or I hear a sound my eyes will immediately move to left hand side
that makes me, for evolutionary purposes very aware of my environment
because I wasn't aware of those things I would have accidents
I'd get hurt or I might get eaten by wild animals and whatever.
Now, in Peggy's case she will not attend to those things
that we would normally be aware of.
[Narrator] Peggy thinks she's drawn her daisies right
until it's pointed out to her.
[Peter] "You've noticed that, have you?"
[Peggy ]"Oh, dear."
[Peter] "So what Peggy's drawn for us is several nice daisies
with the left side missing same this one and this one
look at this one this is a very good example"
[Peggy] "I've done it on all of them"
[V.S. Ramachandran] Which means she's not only neglecting events in the world but when she
conjures up a mental image she's ignoring the left side of that mental image.
[Peggy] "I thought I was going all the way around you see"
[MD] "And the shows you that this is not simply a sensory problem but
a problem of consciousness"
[Peggy] "It's cause I was so concentrated on that side takes everything away, you see
It is attention really is taking this taken away this
there must be two attentions somewhere in your body one side's taking another one away.
I can't make it out at all, very odd"
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