Localisation Flashcards
What are the cerebral hemispheres?
Dense core of white matter with an overlying thin layer of grey matter (cortex)
What is the thickness of the cerebral cortex?
What is the surface of it like?
It varies in thickness from 2-4 mm
it is heavily folded to increase surface area
over half of the total surface area is hidden by the walls of the sulci
What is the arrangement of the cerebral cortex like?
It has a laminar arrangement (I - VI)
it consists of 6 layers of cells, with different types of cells being present in each layer
specific sulci are used to divide the cerebral hemispheres into lobes and specific gyri
What is the main difference between the precentral and postcentral gyrus?
Precentral gyrus:
- this is the primary motor cortex
- it is involved sending out efferent fibres
postcentral gyrus:
- this is the somatic sensory cortex
- it receives afferent (sensory) information
Label the following sulci and gyri
Label the following sulci and gyri
- The collateral sulcus is found in the temporal lobe
- the parahippocampal gyrus hooks upon itself to form the uncus
- the cingulate sulcus and surrounding gyrus are above the corpus callosum
What is significant about the cingulate gyrus and parahippocampal gyrus?
The parahippocampal gyrus, cingulate gyrus and uncus form the limbic lobe
this is a C-shaped rim of grey matter surrounding the diencephalon
What is the role of the limbic lobe?
It is part of the limbic system
this is involved in emotion and memory
What is the role of the olfactory bulb?
It is the primary olfactory area
It connects with the olfactory tract
it eventually brings information into the area around the uncus
this is the only sensation that does not pass through the thalamus
Label the lobes of the brain
What is meant by Brodmann’s areas?
It involves a cortical map that divides the cortex into 46 areas
What does the mapping of Brodmann’s areas show about the different regions within the brain?
It is based on the cellular organisation of the cerebral cortex
specific areas of the cortex are believed to carry out specific functions
What are the primary projection areas?
What do they do?
They receive sensory information or send out motor information FIRST
sensory areas:
- specific sensory pathways terminate here
motor areas:
- specific motor pathways originate here
In which primary projection area are the following sensations located?
What are the primary projection areas involved in motor functions?
The primary motor cortex is found in the pre-central gyrus
this sends signals that initiate movement
Label the following primary projection areas
What is the role of the association (secondary) areas?
They interpret information and give it meaning and an understanding
What are the roles of the secondary sensory and motor areas?
Secondary sensory areas:
- receive input from primary sensory area
- involved in interpretation and understanding
secondary motor areas:
- send output to primary motor area
- organise patterns of movement
Where are the following secondary sensory areas located?
Where are the following secondary motor areas located?
Label the following association (secondary) areas
Where is the primary motor cortex located?
What is its role?
Pre-central gyrus
it controls voluntary contraction of specific muscles
it sends out descending motor information
What is meant by the primary motor cortex being somatotopically organised?
Specific areas of the gyrus control muscle contraction in specific areas of the body
What are the 3 association motor areas?
- Supplementary motor (sm) and pre-motor (pm) areas
- Frontal eye field
- Broca’s area
Which association motor areas are indicated by the Brodmann’s numbers?
6 (pm) and 6 (sm):
- represents the supplementary motor (sm) and pre-motor (pm) areas
8:
- frontal eye field
44 and 45:
- Broca’s area
Where are the supplementary motor and pre-motor areas located?
What are their functions?
They are located anterior to the primary motor cortex
they are involved in learned complex motor activities and storage of those activities
e.g. They allow us to know and remember a specific action
Where is the frontal eye field located?
What is its function?
Located in the frontal lobe
it controls the voluntary scanning movements of the eyes
Where is Broca’s area located?
What is its functions?
Located in the inferior frontal gyrus in the dominant hemisphere
it regulates the pattern of breathing and vocalisation needed for normal speech
Which hemisphere is dominant?
It tends to be, but is not always, the left hemisphere
What happens if there is a lesion that affects Broca’s area?
A lesion leads to higher order deficits and motor activities cannot be controlled
this leads to apraxia
What is apraxia?
a motor disorder in which an individual has difficulty with the motor planning to perform tasks or movements when asked
the request or command is understood and the individual is willing to perform the task
Where is the primary somatosensory cortex located?
What is its function?
Post-central gyrus
it receives sensory pathways for touch, temperature, vibration, pain and proprioception
What is meant by proprioception?
Having an awareness of where the limbs are located in space
e.g. If you lift your arm above your head and close your eyes, you know where the arm is
How is the primary somatosensory cortex organised?
It is somatotopically organised
What sensory nuclei are involved in communication with the primary somatosensory cortex?
Lateral VPL:
- receives input from the leg
- projects to the midline
Medial VPL:
- receives input from the arm
- projects to the lateral region
VPM:
- receives input from the face
- projects to the lateral region
These nuclei are located in the thalamus
all sensation except for CN I (olfaction) stops in the thalamus before travelling to the cortex
What are the two fundamental principles around somatotopic organisation?
Regions:
- specific regions of the brain analyse information from and control specific areas on the body
Size of the regions:
- some areas are more sensitive/have more motor control
- more information is processed in this area of the cortex, so the area is larger
What is meant by the somatosensory and motor homunculi?
The size of each region of the homuniculi is related to its importance in sensory or motor function, resulting in a distorted appearance
Where are the association somatosensory areas located?
What is their function?
Superior parietal lobe
they are involved in interpretation, understanding and recognition
and spatial analysis
What happens if there is a lesion in the association somatosensory area?
Tactile agnosia
this is when someone is touching an object (e.g. key) and they cannot recognise what it is
this is because spatial awareness has been disrupted
Where is the primary auditory cortex located?
What is its role?
Superior temporal gyrus (Heschl’s gyrus)
it is involved in the conscious perception of sound
How is the primary auditory cortex organised?
Tonotopically organised
this means that the spectrum of audible frequencies is mapped onto the primary auditory cortex
low frequency sounds are analysed by the most anterior regions of the gyrus
Where is the association auditory cortex located?
It surrounds the primary auditory area
It also involves Wernicke’s area which is located in the dominant hemisphere
What is the function of the association auditory cortex?
Auditory information is interpreted and given significance
Wernicke’s area:
- this is involved with interpretation of written or spoken word
- important in understanding language
Where is the primary visual cortex located?
Where does it receive information from?
It is the area around the calcarine sulcus and occipital pole
it receives information from the retina
(LG = lateral geniculate nucleus of thalamus)
How is the primary visual cortex organised?
Retinotopically organised
information is projected onto the retina in a specific way
right and left visual fields are sent to specific areas of the cortex
Where is the association visual cortex found?
What is its function?
It surrounds the primary visual cortex
it is involved in interpretation of visual information
e.g. Recognising faces, objects, etc.
What would a lesion in the association visual cortex lead to?
Prosopagnosia
this is the inability to recognise faces
the perception is still there but there is no understanding/meaning
Where is the taste cortex located?
It extends from the inferior margin of the post-central gyrus
It is known as the insula
the lateral fissure must be opened up in order to see the insula
What is the role of the general association cortex?
How is it divided?
It is involved in more complex aspects of behavioural and intellectual functioning
It is divided into the prefrontal cortex and parieto-temporal cortex
What are the roles of the prefrontal cortex?
- Regulates moods and feelings
- involved in higher order cognitive functions
- conceptualisation, planning and judgement - behaviour in response to different stimuli
What are the roles of the parieto-temporal cortex?
- Integrates information of different modalities
e. g. Associating vision, language, taste etc with a certain object - involved in memory
If someone was to have an injury to the prefrontal cortex, how might their behaviour change?
They tend to become impulsive
they lose the ability to make sound judgements and inhibition of impulsive behaviour
What are the 2 language areas within the dominant hemisphere?
What does damage to these areas result in?
Broca’s area and Wernicke’s area - connected by the arcuate fasciculus
Damage to either of these areas leads to aphasia - an impairment of language
What type of aphasia does damage to Broca’s area cause?
Motor / non-fluent aphasia
this is the inability to correctly articulate speech
but the understanding is still intact
What type of aphasia does damage to Wernicke’s area cause?
Sensory / fluent aphasia
there is an inability to understand language
the person speaks words without difficulty, but the language they use does not make sense
What type of aphasia results from damage to the arcuate fasciculus?
Conduction aphasia
comprehension and fluency are intact, but there is impaired repetition
the fibres within the fasciculus carry understanding from Wernicke’s area to Broca’s area
