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crumcasteAI and Robotics

Nov 17, 2013 (3 years and 9 months ago)

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CS4005

Name:

Eamonn Walsh.

Student
I.D
.:
10108343

1
st

Year M.M.P.T

Topic:

Face recognition, Visual Agnosia and
Prosopagnosia.












In this assignment I will explore the

theories surro
unding face recognition
, the

phenomena

of
visual agnos
ia
,

prosopagnosia

and how
face recognition

plays a
major role in our
navigation

of the

highly social world in which we live
.

I aim to
discover the level of proces
sing involved within the h
uman brain that allows us to
recognise objects and in particular fac
es
. I will research case studies to try and
determine

what happens when particular levels of processing
, in relation to face
perception,

are impaired or removed entirely and how this can i
mpact the day to
day life of a h
uman
.


Face recogn
ition can account
for determining age, sex, emotion and so on but
how this works has been debated for years.

Bruce and Young (1986) suggest
that there are seven codes involved in face recognition

pictorial, structural,
identity
-
specific semantic, visually derived semantic,
name, expression and facial
speech codes
. I would not fully agree with this. I would argue that only the first
four are relevant when strictly dealing with face recognition. Name, expression
and
facial speech can only loosely be associated with face recogn
ition. For
example If you were to think of a name, this could bring forth the memory of a
face, however it is still the first four codes in action that associate the name with
the face.





Another theory
, configural processing,

would suggest that face
recognition
develops over time and happens in three stages. First as an infant we learn to
recognise features of the face i
.
e. Eyes, nose, ears and so on. By age seven
months it is thought that the infant starts to glue these features together, they
begin
to see a relationship between the facial features. Studies suggest that the
last stage, whole stage recognition can continue up until and after the age of 14
years (
Catherine
et al,
2002)
. This argument seems to be largely based on
simple observations, for

example an Infant can recognise its mother by smell or
an infant will examine a face for longer than an adult

would, this is suggestive
and although
relevant, not conclusive
. I feel this argument is plausible but I do
not feel as tho
ugh there is enough co
nclusive evidence for

it to be a convincing
argument. The Thatcher effect could be used to argue against this

theory
.


Huble and Wiesel (1977) carried out

a series of experiments of

the primary visual
cortex

of monkeys

to determine how this part of the bra
in worked
. These
experiments reveled that the Primary visual cortex was mapped, broken up into
approximately 2,500 modules. These modules would receive information from a
small part of the retina and would analyze specific parts of the information they
rec
eived,
e.g.

Color,
lines, movement

etc
. In a sense, what their experiments
concluded was that when an image comes through our retina and travels to the
primary visual cortex it is broken down
into tiny pieces of information,

depending
on what
part of the r
etina it came from. It

is then processed by these modules to
identify different characteristics of the image. This information can then be
reconstructed into what we perceive as the visual world around us.




Visual agnosia is a condition caused largely b
y damage to the right hemisphere.
The result o
f such damage can lead to

an inability to recognise objects in the
world around you. Patients that suffer from Visual agnosia can often perceive
what an object is by touch, smell, sound, but not by sight.

These

objects are most
often specific categories such as animals, inanimate objects or animate objects.


Martin, A., Wiggs, C.L., Underleider, G., Haxby, V. (1996) studied healthy brain
activity to try and determine if there was a relationship
between the part
of the
brain

that has been

damaged and the category of objects lost. It was discovered
that cretin areas of the brain were in fact responsive to different categories of
objects

by name

and it was suggested that there is
in fact
a link between the part
of t
he brain damaged and categories of objects that are lost
. I agree with these
suggestions
. I
t

would appear to me that it is not the m
emories of these objects
that are

lost to the patient
,

as they can still identify them by using

their

other
senses, instead
it is damage to a part of the brain required to link the name
of an
object
to

the object or the object to its

name.


Prosopagnosia is a rarer more specific form of agnosia. The sufferer in this case
looses the ability to recognise faces. It is irrelevant h
ow long the patient knows
the person, or how often the
y

see them, they simply cannot recognise any faces.
Yet they can recognise people by the sound of their

voice. So what causes this
loss

of facial recognition?


Rhodes, G., Byatt, G.,

Michie, P.T. and Pu
ce, A
. (
2004)
conducted experiments
on the fusiform face area (FFA)

of the brain to see if it was a specific area to
distinguish between different faces.
They conducted a test using faces and
different species of Lepidoptera, they used both people that co
uld distinguish
between the different species and those who could not. There results showed
that
the activity around the FFA

of the brain was low while observing the
Lepidoptera and high while observing the faces. Therefore it has been suggested

that

the F
FA is responsible for discriminating between faces.
I discovered an
article on (
yalescientific.org

(2011) that stated the FFA was often damaged in
patients that suffer from prosopagnosia. For these reasons I believe that the FFA
is linked to prosopanosia

h
owever it is clear that it

is not limited to damage of the
FFA.

It would appear that damage to any part of the

occipital and/or ventral
temporal lobe

can cause a break down in the process of identifying faces,
resulting in prosopangnosia with a higher risk

of prosopangnosia if there is
damage to the FFA.

As research on prosopangosia continues a new theory is
emerging, it is now thought that a person can suffer from prosopagnosia without
having suffered any form of brain damage. This form of prosopagnosia is

called
congenital

prosopagnosia. (prosopagnosia.org (2011)


Prosopagnosia often has a major impac
t on the life of the patient.

Humans are a
highly social species and face recognition is an essential part the social networks
in which we live, having this a
bility removed greatly decreases our ability to
interact with the people around us.
Many sufferers of prosopagnosia have
rep
orted

avoid
ing

social situations, damage to

their

carrier and relationship,
depression and even social anxiety

disorder (prosopagnos
ia.org (2011)
. Here are
a few cases where prosopagnosia restricts the ability

of

a human to socialise.

“I was getting off a bus and somebody got on it and grabbed me, and I pushed
them out of my way and it was only when they opened their mouth that I reali
zed
it was my own mother”

(Yardley
et al.,

2008)


The condition makes me less interested in the social events, the partying, the
getting to know lots of people, because that just gives me a whole set of things I’ll
get wrong” (Yardley
et al

2008)


I have

explored some of the theories surrounding face recognition; I have yet to
find one that convinces me. This is a reflection of the complexity of the brain. It
can be concluded however that in order to recognise a face
it take
s

a high level
of processing ca
rried out at different stages within the brain to create the faces
we perceive around us. I have concluded that visual agnosia is a condition
caused by damage to the right hemisphere that prevents a person from
recognising certain categories of objects, ho
wever it is not the memory of the
objects the patient looses, rather the ability to link the objects with there names.
Prosopagnosia is much the same a visual agnos
ia only more specific. It is the
loss

of
the ability to recognise faces
caused

by damage to
the

occipital and/or
ventral temporal lobe
, with specific infuses on the FFA. Prosopagnosia can also
develop over time naturally. Prosopagnosia is a condition that can destroy a
human’s

ability to socialise effectively, minimizing their ability to function

within
society. This can lead to serious mental illness’s that can be life threatening such
as depression. It can be exceptional difficult to overcome these mental illness’s
as the root problem, the pro
sopagnosia, can not be cured as of yet.























References

Bruce, V., Young, L.A.W, (1986).
Understanding face recognition.
British Journal
of Psychology.


Catherine, J., Mondloc, Richard Le Grand, Daphne Maurer, (2002).
Perception
.
Department of Psychology, McMaster University.


Hubel, D.H.,

Wiesel, T.N. (1977).
Function architecture of macaque monkey
visual cortex.
Proceedings of the Royal Society of London.


Martin, A., Wiggs, C.L., Ungerleider, G., Haxby, V. (1996).
Neural correlates of
category
-
specific knowledge.
Nature.


Rhodes, G., Bya
tt, G., Michie, P.T., Puce, A. (
2004).
Is the fusiform face area
specialised for faces, individuation or expert indivifuation?.
Journal of Cognitive
Neuroscience.


Yardley, L., McDerott, L., Pisarski, S., Duchaine, B., Nakayama, K. (2008).
Psychosocial con
sequences of development prosopagnosia: A problem of
recognition.

Journal of Psychosomatic Research.


yalesscientific.org,
prosopagnosia


whose face is that?

[online] available:

http://www.yalescientific.org/2010/02/prosopagnosia
-
whose
-
face
-
is
-
it/
, accessed
10/11/2011.


Prosopagnosiaresearch.org,
Information about prosopagnosia

[online] available:

http://pr
osopagnosiaresearch.org/index/information
, accessed 8/11/2011.