Brain Topography - Benifla

Question 1

How many grey matter/cortex layers are there?

What are they?

Which connect to outside of grey matter?

Answer 1

6 layers of cortex:

Molecular (most external)
External granular
External pyrmidal
Internal granular
Internal pyramidal
multiform (most internal)

Internal granular and pyramidal send neurons to other parts of brain

Question 2

What and where is the central sulcus?

Answer 2

Posterior border of frontal lobe and anterior border of parietal lobe

Question 3

What and where is the lateral sulcus?

Answer 3

Another sulcus running from frontal area
A to P at 45 degrees
Or called Silvian fissure
Inferior border of frontal and parietal lobes and upper border of temporal lobes

Question 4

What is the insula?

Answer 4

Another lobe that is more fxnal than anatomical
Part of limbic system
So each hemisphere has 6 lobes (The 4 and insular and limbic system)

In each hemisphere of the mammalian brain the insular cortex (often called insula, insulary cortex or insular lobe) is a portion of the cerebral cortex folded deep within the lateral sulcus between the temporal lobe and the frontal lobe. The cortical area overlying it towards the lateral surface of the brain is the operculum (meaning “lid”). The opercula are formed from parts of the enclosing frontal, temporal and parietal lobes. It is believed to be involved in consciousness.
The insular cortex is divided into two parts: the larger anterior insula and the smaller posterior insula in which more than a dozen field areas have been identified.

Circular sulcus surrounds it and it is divided into the short and long gyrus.

Question 5

Picture of the Brodmann map

Answer 5

Question 6

What and where is the precentral gyrus?

What is its function?

Answer 6

A to central sulcus
1st gyrus which is A to central sulcus is precentral gyrus

Motor function

Brodmann 4- simple movements (M1)-precentral gyrus - movement of 1 or 2 joints in contralateral side
Brodmann 6- response to stimuli and more complex movements - On precentral gyrus in front of broadman 4 - Responsible for complex movements and responding for diff stimuli
Supplementary motor area (in the medial aspect of motor cortex) muscle tone, coordination, initalization of movements? (M2)

Question 7

The motor cortex:

Response to injury

Input

Targets

Answer 7

Injury- contralateral hemiparesis/plegia
Input- peripheral sensory receptors through the thalamus, Cerebellum, Basal ganglia, sensory cortex.
Other output targets- reticular formation, tectum, red nucleus, basal ganglia

Motor cortex receives input from diff areas of brain in order to regulate and control the movement
In order to make movement accurate and delicate
Motor cortex sends info to the striated muscle on other part of body and also sends info to reticular formation and parts listed
All part of control of muscles and relay areas to other muscles
Neurons out of motor cortex start in pyramidal cells
Glutamate is universal excitatory neurotransmitter in brain

Question 8

Motor Homunculus in coronal cut

Motor pathway of these nerves

Answer 8

Complexity of movement of this organ
For ex, 400-700 facial expressions
Brain gives more neurons to innervate facial muscles
Area below knee is in the medial aspect of hemisphere
If body was built according to map of brain this is what it would look like this

Neurons out of brain going thru the basal ganglia to the brain stem and decussate (cross to other side) in lower part of brain stem (Lower part of medulla oblongata)
From there going to muscles in other parts of body - contralateral side
From cortex to lower part of the brainstem the neurons are running ipsilaterally and lower part crossing to other side of brain stem and innervating contralateral muscles

Question 9

Frontal Eye field: where is it and what does it do?

Answer 9

Brodmann Area 8
Coordination of eye movement to the contralateral direction
Rapid eye movement

Input- primary visual cortex, thalamus, brainstem

Frontal eye field and middle frontal gyrus for left side is responsible for contralateral in R eye
R field and middle responsible for L eye

Lesion- both eyes deviate in the direction of the injury
Damage to L cortex –> eyes pushed to L side
Injury to frontal eye field cause eye deviation to ipsilateral side
Stimulus to this area like in a seizure will cause eye deviation to contralateral side because stimulating this area
Lesion - ispilateral
Stimulate - contralateral

Question 10

Prefrontal cortex: where is it and what does it do?

What does injury cause?

What type of input?

Answer 10

Cortical association areas - unimodal,
multimodal
A to I frontal gyrus is composing prefrontal cortex, Brodmann Areas 9,10,11,12
Multimodal association area
Personality, judgment, behavior
Inability to solve problems, emotional deficits, disinhibition, loss of fear, apathy, mood and personality changes

Input from 1 type of sensory input and responds to this stimulus
Visual cortex or auditory cortex are unimodal
As opposed to multimodal association area where area receives many types of sensory input and integrate them and respond to this stimuli
Biggest area of multimodal is prefrontal cortex
Injury to frontal cortex - lose judgement and ability to solve problems
Judgement is like knowing not to pee in class
Injury to prefrontal - cant solve problems and suffer from disinhibition and will scream, may defecate in public, apathy, personality changes

Question 11

What is Broca’s Area?

What sections of the brain compose it?

Where is it?

What does injury cause?

Answer 11

Brodmann Areas 44,45 of dominant hemisphere

pars triangularis, pars opercularis
the motor involvement in speech
Aphasia- impaired or absent comprehension of or communication by speech, writing or signs
Lesion: motor (or expressive)
aphasia (motor = expressive = nonfluent = anterior = Broca’s)

Dysphasia (oppositionally): say diff things like saying sunglasses is a chair
 Pts w aphasia understand everything but cant say anything  Usually lesion from infarct of dominant hemisphere and involving motor area    Motor cortex injury in L hemisphere --\> L motor aphasia and if motor area involved --\> and injury to L motor cortex --\> R hemiplagia/hemiparesis
  When injury to Broca area --\> motor apahsia due to infarct to L hemisphere  If infarct to L hemisphere --\> lesion to motor cortex as well so aphasia and R hemiplagia/pesia
   Eye deviation to L side - ipsilateral  In children younger than year and a half or 2 --\> may be reversible because of brain plasticity  If take lesion out in older pts - irreversible

Question 12

Primary auditory area/cortex:

where is it?

what does a lesion cause?

Answer 12

Brodmann Areas 41,42 (within superior temporal gyrus)
HESCHL gyruses - receives auditory stimulation
Lesion: bilateral auditory deficit mainly contralateral
Deficit in the ability of localizing the sound source (not deafness)

Audtiory cortex responsible for other parts of brain stem to locate the source of sound

Question 13

What and where is Wernicke’s Area?

What is the result of a lesion?

What is global aphasia?

Answer 13

Brodmann Area 22
Auditory unimodal association area
Interpretation of sounds and written words.

Still in temporal - dominant which is usually in L
Speech reception area
This area which is unimodal
R responsible for compresion so injury to area causes inability to understand everything- sensory aphasia
Pts dont understand and can speak but gibberish
Good intonation but if dont understand language no meaning to what they say since dont understand
Happy - as long as not hungry or thirsty or cold or etc
Broca working so Broca can give orders but not related to anything
Wernicke’s and Broca - global aphasia - cant understand words or speak words

Question 14

What is the role of Brodmann area 21? What would a lesion cause?

Answer 14

Brodmann Area 21, below Wernicke’s, slightly posterior and inferior
Dominant hemisphere which is usually the L

Responsible to name things

Visual unimodal association area: Lesion: inability to name visible subjects -visual agnosia or anomia

Cant name sunglasses but knows what to do with it and what its purpose is

Question 15

What is the Brodmann 20 area responsible for?

Where is it?

What is the effect of a lesion?

Answer 15

In the middle temporal gyrus
Process of compound visual input- eg. Features
Impairment in the learning ability of visual tasks
Visual agnosia- inability to name visible subjects
Other defects- impaired long run memory, attention disorders

Everyone shares the same face but in order to differentiate btwn the different compound features, we need to process the features

Bilateral temporal injury - suffer many things but in terms of brodmann 20 –> all the faces are the same
Cant differentiate btwn person to person
Can differentiate by hearing
Injury to temporal lobe may cause impaired long run memory
As oppose to injury to fornix/hippocampus which is depth which cause impairment of short memory

Question 16

Somatosensory cortex:

Where is it? What does it do? What does injury cause?

Answer 16

Primary somasthetic area Brodmann Area 3,1,2
touch, temperature, pain
input- thalamus, motor cortex
Sensory homunculus
Lesion: contralateral sensation deficits. Inability to evaluate temprature, weight and localize body parts in space. Injury to area wont cause inability to feel but inability tactile descrimination

Thalamus is the main sensory coordinating center
Somatosensory in L hemisphere –> see sensory of R side
Lips and tongue have a lot of sensitivity
Receive a large at of input

Question 17

Sensory homunculus

Answer 17

Question 18

Somasthetic association area

where is it?

what does it do?

what does injury cause?

Answer 18

Brodmann Area 5,7
understanding the senses
Identify objects and planning movements, eye-hand coordination

Responsible to understand what we feel
Learns from R somatostatic 5,7 to feel (w L hand) and then opened eyes and did again and named it from L temporal lobe brodman 21
Stimuli from L hand went to brodmann 3, 2, 1 and felt it
Told it was charger and 5, 7 and knows what it is and remembers its a charger and understands what he feels and then in order to give name –> info from R to L temporal lobe to give name
Also eye and hand coordination

Input- thalamus, primary somasthetic area
Injury:
Agnosia- lack of sensory –perceptual ability to recognize objects
Apraxia- what to do with the object?
Astereognosis-loss of the ability to judge the form of an object by touch

If not able to ID subject –> sensory agnosia
Apraxia - say what it is but wont remember what to do with it
Can say battery charger but dont know what to do

Injury to L temporal and cant give name but know to charge battery --\> put in socket

Question 19

What does injury to Brodmann 39,40 (Supramarginal and Angular Gyri) in the cause?

Answer 19

Dominant hemisphere:

Alexia, agraphia
Gerstman syndrome
finger agnosis - inability to give names to fingers
R to L disorientation
Aculculia - cant do mathematical tasks
Agraphia - cant write properly

Adominant hemisphere:

Heminglect
Pts ignore (since non dominant usually R) what there is in the L side
May wake up in the morning and touch own arm but since ignore L side –> they think its someone else’s arm
Ignore L side so if tell them to look left and describe whats around you, only describe R side of them
Whatever way they are facing –> only describe the R side

Question 20

What and where is the primary and secondary visual area?

What does injury cause?

Answer 20

Brodmann Area 17
Primary visual area lesion-homonymous hemianopsia
Since R occipital lobe receives visual input from the left visual field, R injury will cause left hemianopsia
L injury will cause R hemianopsia

Brodmann 18,19
Visual association area- Visual memory. Injury- can’t identify/name a visible subject

Question 21

What and where is the corpus collosum?

Answer 21

Interconnect homologous areas between both hemispheres
Connection between the hemispheres, memory, learning
Form most of the roof of the lateral ventricles

Below the corpus collosum sulcus

Posterior aspect: splenium (temporal and occipital interconnection)

Trunk: interconnects posetrior frontal lobe and parietal lobe

Frontal aspect: Genu (interconnects anterior frontal lobes)

Anterior/Inferior aspect: Rostrum

Question 22

What is split brain syndrome?

Answer 22

Injury of corpus collosum

Inability of a blindfolded patient to match an object held in one hand with that held in the other hand
Inability to correctly name objects placed in the left hand (or people, but will understand who it is. Ex: can’t name picture of Angelina Jolie but can say will date her and visa versa. Goes to right occipital lobe, fibers to dominant temporal lobe through corpus collosum, moved to right side no problem)
Inability to match an object seen in the right half of the visual field with on seen in the left half
Alexia of the left visual field

Question 23

What and where is the cunate gyrus and where does its input come from?

What is the effect of injury?

Answer 23

Brodmann 17,18,19

Upper part of occipital lobe above Calcarine sulcus

Receives input from lower part of visual field

Right cuneate gyrus injury: Block of left lower quadrant of visual field

Left cuneat gyrus injury: block of lower right visual field

Block of both with lingual gyrus: cortical blindness

Question 24

What and where is the Lingual gyrus and where does its input come from?

What does injury cause?

Answer 24

Brodmann 17,18,19

Below the calcarine sulcus

Input from upper side of visual field

Left lingual gyrus injury: block of upper right visual field

Right lingual gyrus injury: block of upper left visual field

Both with cuneate: cortical blindness

Question 25

Summary of naming visual subjects

Answer 25

Blindness despite eyes being fine = cortical blindness (occipital region)

Visual agnosia (from Brodmann 39, 40, 21)

Sensory aphasia (from Wernicke: Brodmann 22)

Conductive Aphasia

Motor aphasia (from Broca’s area B 40, 45)

Dysarthria (motor cortex)