Structure and function: different parts of the brain

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17 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

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Structure and function: different parts of the brain
control different functions.

The frontal Lobe

The frontal Lobe




Primary motor cortex


movement


Broca’s

area

speech production


Forward area association judging planning initiative


Expression of characteristics associated with
personality and emotional behaviour





(The motor is in the front of the car
Broca
’ is driving)



The frontal Lobe as a car?

Phineas

gage


frontal lobe damage


September 13, 1848, 25
-
year
-
old Railway foreman


Packing gun powder into a hole with a steel pole to
blow up rock


Sparks from the pole ignite the gun powder and send
the pole under gage’s cheek and out the top of his head



Before the accident he was well liked, organised, calm
and polite

Phineas

gage


frontal lobe damage


After the accident
Phineas

suffered severe personality changes


Became impulsive, aggressive, disorganised


Could not continue his work as foreman


Appeared for a time at Barnum's American Museum in New York


February 1860, Gage had the first in a series of increasingly
severe convulsions


died in or near

San Francisco on May 21


just under twelve
years after his accident



Gage’s case along with others suggest the frontal lobes important
role in emotion and personality, planning and initiative

The Parietal lobe

The Parietal lobe


Primary
Somatosensory

cortex


Receives info from senses


Somatosensory

cortex at front of temporal lobe next to
primary motor cortex which is at the back of the
frontal lobe



(The party lobe, your senses are going wild at a party)


The Parietal lobe


on fire at a party?

Motor and Sensory Cortex organisation

The homunculus man

The temporal Lobe

The temporal Lobe


Primary auditory area


Wernicke’s

area speech comprehension


Primarily associated with hearing


Also important role in memory


Decisions made about which features of environment
we will remember


Facial recognition also performed in temporal lobe



(Temporal sounds like tempo, the tempo of the music)



The Primary Auditory Cortex


Resides in each temporal lobe


Receives and processes sounds from both ears


Each primary auditory cortex has specialised areas of
sound and thus play vital roles in the identification of
sounds


Two main features of sound:
frequency
(perceived as
pitch) and
amplitude or intensity

(perceived as
loudness).


Each primary auditory cortex is also specialised to process
different types of sound. Verbal sounds (e.g. words) in the
left hemisphere and non
-
verbal sounds (e.g. Music)
processed in the right hemisphere. BUT there is some
overlap, this is not exclusive!

Temporal Lobe Association Areas


Located in each temporal lobe


Different association areas appear to be involved in memory
(including linking emotions with memory and determining
appropriate emotional responses to sensory info and memories)


Amnesia
(partial or complete loss of memory) often occurs in
people with damage to either or both temporal lobes.


Receiving, processing and storing of facts
(semantic memories)
how to do things
(procedural memories)

and personal
experiences such as birthdays or holidays
(episodic memories)

appear to occur in areas of the temporal lobes.


Object identification and facial recognition are also involved,
thus perception and memory to make decisions about our
environmental features is an important role of the temporal
lobe.. However, perception and memory are not exclusive to one
area of the brain but involve many interconnected areas.

WERNICKE’S AREA


Located towards the rear of the temporal lobe


In left hemisphere only (next to primary auditory cortex)
and connected to
Broca’s

area by a bundle of nerves.


Has crucial role in comprehension of speech, but is also
involved in speech production, more specifically,
interpreting the sounds of human speech.



Word is heard, then the auditory sensation is processed by
the primary auditory cortex of the left temporal lobe, but
the word cannot be understood until the information has
been processed by Wernicke’s area.

WERNICKE’S AREA


Also vital for not just understanding words, but also for locating
appropriate words from memory to express intended meanings
when we speak or write.



When a word is to be spoken, a “representation” of it is
transmitted to
Broca’s

area in the frontal lobe which co
-
ordinates
the muscles needed to produce the sound of the word and
supplies this information to the face area located where the
temporal and occipital lobes intersect.



Damage to Wernicke’s area causes impairment in understanding
speech
and

to speaking.



Read Box 4.5 on page 194

The temporal Lobe as a drummer?

Deep within the temporal lobe
-

the
amygdala

Deep within the Temporal lobe


the hippocampus



Memory formation


not memory storage



Damage leaves patient unable to form new long term
memories



The hippocampus lives on memory lane


Deep within the temporal lobe
-

the
amygdala


Mediation of fear



Seizures involving the
amygdala

involve intense fear


Damage leaves a person unable to learn a fear response
through classical conditioning



Involved in remembering the emotional significance of an
event



Damage leaves us unable to judge emotional component of
facial expressions in others


i.e. angry person perceived as
calm or even happy

The Occipital Lobe

The Occipital Lobe



Primary visual area


Visual cortex located at base of each occipital lobe


is
the major destination of visual
inforamtion

from the
two eyes.


Other areas visual association areas


identifying
objects etc.




(Occipital sounds like optical, optical relates to vision)


OCCIPITAL LOBE


Located at rearmost area of each cerebral hemisphere


Almost exclusively devoted to the sense of vision


Damage can produce blindness even if eyes and neural
connections to brain are normal


Some areas in other 3 lobes also have important visual
functions


Divided into many different visual areas
-

the largest
being the
primary visual cortex (at the base of the
occipital lobe).



OCCIPITAL LOBE


Information arrives at PVC via visual sensory receptors
(
“photoreceptors”
) on the retina at the back of each eye.



Each hemisphere receives and processes half of visual
information. Left half of each eye receives visual sensory
information from right half of visual field and sends info to
left occipital lobe and vice versa. See Box 4.12 on page 224



Neurons in the PVC and surrounding “secondary” visual
areas specialise in responding to different visual features
e.g. Orientation (direction) of a line, edges, shapes
(forms), motion and colour. Some neurons respond to one
feature only, others to two or more features.

OCCIPITAL LOBE ASSOCIATION
AREAS


Have important roles in vision.


They interact with PVC to select, organise and integrate
visual information.


They interact with association areas of other lobes to
integrate visual information with other information (e.g.
Memory, language, sounds), so that visual information can
be organised and interpreted in a meaningful way.


E
.g.
T
he frontal lobe (together with parietal lobe) is involved
in spatial reasoning such as trying to work out whether a
specific piece of a jigsaw puzzle will fit into a particular place
in the puzzle.

The Occipital Lobe as an eye?

THE EYES IN THE
BACK OF YOUR HEAD!

MAKE A BRAIN BALL!

PATHWAYS FROM THE VISUAL
CORTEX


Areas other than the visual cortex are also involved in
processing visual information to enable visual
perception.



Research evidence suggests there are 2 major pathways
from the visual cortex in the occipital lobe to areas of
the temporal and parietal lobes


they are the
dorsal
stream

and the
ventral stream.

Dorsal and ventral streams


Dorsal (“upper”) stream

includes areas of the occipital
lobe and leads to parietal lobe.


Specialises

in locating objects or spatial perception (where an
object is and relating it to other objects in a scene).


the
“where” pathway



Ventral (“lower”) stream
includes areas of the occipital
lobe and leads to the temporal lobe.


Specialises

in object perception and recognition (identifying
objects)


the “what” pathway


See Figure 4.29 on page 197

CASE STUDIES OF BRAIN DAMAGED
PATIENTS


Case studies of patients with brain damage to specific areas
of the visual cortex provide evidence in support of the
differing roles of the ventral and dorsal streams.



Patient D.F. suffered carbon monoxide poisoning at 34
years of age which damaged brain areas involved in the
“what” pathway.



D.F. could no longer
recognise

the faces of her friends and
family, common objects or even a drawing of a square or
circle. Her condition was diagnosed as
“object
agnosia

(the inability to
recognise

objects).

D.F.


D.F. could
recognise

people by their voices and could usually say
what objects placed in her hands were, through memory of
voices and past experiences with objects using touch and other
senses.



When presented with a drawing of an apple, D.F. cannot identify
or redraw it. But if asked to draw an apple, she can do it from
memory.



D.F. can use visual information about the size, shape and
orientation of objects to control visually guided movements,
suggesting her “where” pathway has not been damaged. E.g. she
can walk across a room and step around things without difficulty
and can also reach out and shake hands as easily as we all do.

D.F.


D.F. can reach out and grasp a block, with the exact
correct distance between her fingers, but she cannot
tell you what she is going to pick up or how big it is.



Her conscious perception of objects is impaired, she
has no awareness of taking in any visual information
about objects she sees.