Module 6: Cerebral Cortex Flashcards
What is the posterior and inferior boundary of the dorsolateral surface of the frontal lobe?
- Posterior boundary: central sulcus
- Inferior boundary: lateral sulcus
What is the posterior and inferior boundary of the medial surface of the frontal lobe?
• Posterior boundary: arbitrary line directed inferiorly from central
sulcus to corpus callosum
• Inferior boundary: corpus callosum
What are the anterior, posterior and inferior boundaries of the medial surface of the parietal lobe?
• anterior boundary: frontal lobe
• posterior and inferior boundaries: parieto-occipital sulcus and corpus
callosum
What are the anterior, posterior and inferior boundaries of the dorsolateral surface of the parietal lobe?
• Anterior boundary: central sulcus
• Inferior boundary: lateral sulcus and an arbitrary line directed
posteriorly from the lateral sulcus
• Posterior boundary: upper half of an arbitrary line connecting the
parieto-occipital sulcus with the pre-occipital notch
What are the posterior and superior boundaries of the lateral surface of the temporal lobe?
• Superior boundary: lateral sulcus and its posterior projection
• Posterior boundary: lower portion of arbitrary line connecting the
parieto-occipital sulcus and the pre-occipital notch
What is the posterior boundary of the medial surface of the temporal lobe?
• Posterior boundary: imaginary line joining the pre-occipital notch and
the anterior end of the calcarine sulcus
What is the anterior boundary of the lateral surface of the occipital lobe?
• Anterior boundary: line joining the parieto-occipital sulcus and the
pre-occipital notch
What is the anterior boundary of the medial surface of the occipital lobe?
• Anterior boundary: the posterior borders of the parietal and temporal
lobes
What three areas of cortex are included in the limbic lobe?
• Cingulate gyrus
• Parahippocampal gyrus - connected to cingulate gyrus by narrow
strip of cortex beneath the splenium of the corpus callosum - the
isthmus
• Hippocampal formation
What is the most common classification system used to describe the functional areas of the cortex?
Brodmann’s areas - uses numbers to indicate different functional areas based on their cytoarchitecture
What Brodmann areas are encompassed as motor areas?
4, 6, 8
What is the Brodmann area of primary motor area?
Primary motor area = precentral gyrus, precentral sulcus, central sulcus
4
What is the Brodmann area of premotor or motor association area (secondary motor area)?
Secondary motor area = anterior part of precentral gyrus and parts of superior, middle and inferior frontal gyri
6
What is the Brodmann area of the frontal eye fields?
FEF = control of lateral gaze
8
What connects Broca’s area to Wernicke’s area?
The arcuate fasciculus
What are the frontal association areas concerned with?
Complex aspects of behaviour (i.e., affect, personality, attention. They have extensive connections with dorsomedial (DM) nucleus of thalamus.
What comes anterior to the central sulcus?
Motor areas
What comes posterior to the central sulcus?
sensory areas
On this image of the medial brain, locate the:
- superior frontal gyrus
- Cingulate gyrus
- lingual gyrus
- fusiform gyrus
- parahippocampal gyrus
- uncus
On this image of the medial brain, locate the:
- cingulate sulcus
- parieto-occipital sulcus
- calcarine sulcus
What Brodmann numbers are associated with somatosensory areas?
primary somatosensory area: 1, 2, 3
somatosensory association area: 5, 7, 40
What Brodmann numbers are associated with auditory areas?
Primary autory area: 41, 42
Auditory association (secondary autditory area: 22
Where is the auditory association area (22)?
superior temporal gyrus and area posterior to primary auditory area in lateral
sulcus
Where is the primary auditory area (41,42)?
superior surface of superior temporal gyrus - Heschl’s gyri (convolutions); also called transverse temporal gyri
What Brodmann areas are associated with visual parts of the cortex?
Primary visual area: 17
Visual association (secondary visual) area: 18, 19
Note: areas 17, 18, 19 project to areas of parietal and temporal cortex for higher order vidual processing
Where is the primary visual area (17)?
In the walls of the posterior part of the calcarine sulcus, extending onto the lateral surface
Where is the secondary visual (visual association) area (18, 19)?
Surrounds the primary visual area on medial and lateral surfaces
What Brodmann numbers are associated with taste?
43 - primary taste area
Where is the primary taste area (43) located?
on insula and adjacent medial surface of parietal-frontal operculum - at base of central sulcus (Operculum = lid or cover)
Where are the secondary taste areas located?
Orbital cortex of frontal lobe and amygdala. Here taste information is integrated with olfactory information.
What Brodmann areas are associated with language?
Motor (expressive) area of Broca: 44, 45
Sensory (receptive) speech area of Wernicke: 22, 49, 40
Where is Broca’s area (44, 45) located?
part of inferior frontal gyrus of dominant hemisphere (usually left)
Where is Wernicke’s area (22, 39, 40) located?
includes posterior part of area 22 (superior temporal gyrus), with extensions around the posterior end of the lateral sulcus into the parietal region (areas 39 and 40) - dominant hemisphere
What is the cerebral cortex?
The cortex covers the entire surface of the brain, overlying the deep nuclei.
The cortex, together with these deep gray matter nuclei, comprise the forebrain
Of what two areas is the forebrain comprised?
- telencephalon
- diencephalon
Of what is the telencephalon comprised?
- cerebral hemispheres
- deep structures
Of what is the diencephalon comprised?
- thalamus
- hypothalmus
- subthalmus
What is another name for the precentral gyrus?
The primary motor area
On this medial image of the brain, locate the central sulcus
Why does describing the cortex based on lobes not generally provide an understanding of function?
Because the lobes of the brain are named after the bones of the skull
The cortex can be divided into two area, what are they?
Primary cortical areas
Association areas
What is the function of primary cortical areas?
To receive information from peripheral receptors (e.g., the thalamus), with little interpretation of the meaning of the information. These areas are concerned with receiving sensory information or executing motor tasks
What is the function of secondary cortical areas?
These areas receive input from the primary area and are involved in higher order processing, integrating, and interpreting information. These areas are located adjacent to primary areas.
Outflow from the primary motor area makes up what?
The corticospinal tract
Where is the primary motor area and what is it responsible for>
- Located in the precentral gyrys of the frontal lobe
- It is responsible for motor output to the contralateral side of the body
Where are the supplementray motor area and premotor association area located?
They are both located anterior to the primary motor area in the frontal lobe. The supplementary motor area lies superior to the premotor area.
What is the function of the supplementary motor area?
- contains motor maps for posture
- efferents innervate limbs and the truncal musculature
What is the function of the premotor association area?
Involved in higher order processing and integration of motor information
What is the pathway to the primary somatosensory area?
Sensory afferents from contralateral peripheral receptors travel to the thalamus and ultimately project to the primary somatosensory area.
What is the primary somatosensory area located?
In the postcentral gyrus of the parietal lobe
Where is the somatosensory association area located?
Adjacent to the primary somatosensory area in the parietal lobe
What is the function of the somatosensory association area?
Allows for interpretation of the significance of sensory information, such as touch, pressure, and proprioceptive information
What is the pathway fromt he retina to the primary visual cortex?
Fibers from the retina project to the lateral geniculate nucleus of the thalamus, and from there to the primary visual cortex.
How is the primary visual cortex organized?
retinotopically
Where are the frontal eye fields located? What is their role?
The frontal eye fields are located in the supplementary motor area and extend anteriorly
They are involved in eye movements
Where is the motor-hand area located? What is it’s function
- Hook-shaped segment of the precentral gyrus located just posterior to the frontal eye fields
- responsible for motor hand function
What is the pathway to the primary auditory cortex?
Auditory information reaches the cochlea, projects to the medial geniculate nucleus of the thalamus, and then project to the primary auditory area cortex.
Does information from the cochlea to the primary auditory cortex travel contralaterally or ipsilaterally?
Information from the cochlea travels both ipsilaterally and contralaterally, such that each ear is represented in a bilateral manner on the cortex
What is the primary auditory cortex composed of?
- The transverse Heschl’s gyri deep within the lateral sulcus
- A strip of cortex on the superior surface of the superior temporal gyrus of the temporal lobe
Where is the auditory association area located? What is its function?
Adjacent to the primary auditory area on the lateral surface of the superior temporal gyrus. It allows us to interpret sounds and give them meaning.
What is the function of the insular cortex?
It has a wide array of functions including being involved in consciousness, emotion, self-awareness, and cognitive function
Where is the primary gustatory area located?
In the insular cortex, within the lateral fissure
Where is Broca’s area located? What is its function?
In the frontal lobe, anterior to the premotor association area
Broca’s area allows for the production of all forms of language
Where is Wernicke’s area located? What is its function?
- Spans the parietal and temporal lobes around the lateral fissure and primary auditory area
- Wernicke’s area allows for the comprehension of language
What is another name for the prefrontal cortex?
The frontal association areas
With what areas does the prefrontal cortex have extensive connections?
- The sensory cortices
- The motor cortices
- The basal ganglia
- The cerebellum
- The amygdala
- The hypothalamus
- The brainstem
What is the role of the prefrontal cortex?
It is important for executive function, including memory, problem solving, attention, planning, and cognitive flexibility
What is the function of the parietal association areas? Where is it located?
It is involved in orienting our attention in time and space, and his highly connected with the prefrontal cortex
Located posterior to the primary somatosensory area (postcentral gyrus)
Where are the temporal association areas located? What are their function?
Located widespread across the temporal lobe
Critical for making the link between the visual stimulus of a face or object and its meaning or identity
What are unimodal areas?
Unimodal areas include association areas responsible for higher-order porcess of a single sensory or motor modality. These areas include the visual, auditory, and somatosensory association areas, as well as the supplementary motor, premotor and language areas
What are hetermodal areas?
Heteromodal areas include association areas responsible for integration from multiple sensory and/or motor modalities. These include frontal, parietal, and temporal association areas.
What do subcortical fiber bundles do? What are their three designations?
Subcortical fiber bundles relay information to and from specific areas of the brain.
3 designations:
- commissural fibers
- association fibers
- projection fibers
What do association fibers do?
Association fibers connect areas on the same side of the brain, providing integration between all lobes on one side of the brain
What do commissural fibers do?
Commissural fibers cross the midline, allowing for interhemispheric connection into one functional human
What do projection fibers do?
Travel between the cortex and the brainstem - allowing for connection of the forebrain with the brainstem and spinal cord
Describe the superior longitudinal fasciculus
The superior longitudinal fasciculus connects the all main cortices for the integration of sensory information
What does the arcuate fasciculus connect?
Broca’s and Wernicke’s area
What do the corona radiata fibers converge to form?
The internal capsule
What is the role of the uncinate fasciculus?
To connect the temporal and frontal lobes
The internal capsule is divided into two regions, what are they?
Anterior limb and posterior limb
What does the anterior limb of the internal capsule separate?
The anterior limb of the internal capsule separates the head of the caudate from the putamen and globus pallidus
What does the posterior limb of the internal capsule separate?
The thalamus from the putamen and globus pallidus
The corpus callosum is divided into four areas, what are they?
- Body
- Splenium
- Genu
- Rostrum
Describe the genu of the corpus callosum?
Anterior end of body. Fibers originating in frontal areas.
Describe the body of the corpus callosum?
Blosely packed fibers in the mid-sagittal region - connects 2 parietal lobes and posterior parts of 2 frontal lobes.
Describe the splenium of the corpus callosum.
Thickened posterior end of the body. Fibers originating in or proceeding to the more posterior parts of hemispheres - connecting occipital lobes and possibly posterior temporal lobes
Describe the rostrum of the corpus callosum.
The thin shelf of fibers projecting backwards from genu. Rostrum is continuous with lamina terminalis.
Describe the radiation of the corpus callosum.
As they enter medullary center, fibers in corpus callosum fan out to all parts of cortex.
- forceps minor - at anterior end
- forceps major - at posterior end
The main bundle of commissural fibers is corpus callosum. What are the other two major bundles?
The anterior commissure and the posterior commissure
What are the four main long association fibers?
- superior longitudinal fasciculus
- inferior occipitofrontal fasciculus
- Superior occipitofrontal fasciculus
- Cingulum
Describe the inferior occupitofrontal fasciculus.
Runs below insula, from frontal through temporal to occipital lobe. Fibers that hook around margin of lateral fissure to interconnect areas of frontal and temporal cortex are called the unicate fasciculus
Where is the superior occipitofrontal fasciculus located?
It runs parallel to corpus callosum along most of its course
What is the path of the cingulum?
It runs beneath the cingulate gyrus and parahippocampal gyrus. Connects raes of limbic cortex with each other.
Projection fibers are primarily…
2-way traffic between the thalamus and the cortex
&
Descending fibers - to striatum, brainstem, and spinal cord
What kind of fibers are the corona radiata?
Projection fibers
The projection fibers of the corona radiata gather to form a compact bundle known as what?
The internal capsule
What fibers are in the anterior limb of the internal capsule? What is their blood supply?
Fibers: corticopontine and thalamocortical fibers
Blood supply: lenticulostriate arteries
What fibers are in the genu of the internal capsule? What is their blood supply?
Corticobulbar fibers
Blood supply: Lenticulostriate arteries & anterior choroidal arteries
What fibers are in the posterior limb of the internal capsule? What is their blood supply?
Fibers:
- corticopontine
- thalamocortical
- corticospinal
Blood supply: lenticulostriate arteries, PCA, and anterior choroidal arteries
Commissural fibers
originate from cell bodies in the cortex of one hemisphere,
cross the midline, and synapse with neurons in the cortex of the other hemisphere
Projection fibers
either originate in the thalamus and project to the cortex, or
originate in the cortex and proceed to subcortical gray centers in the cerebral
hemisphere, brainstem or spinal cord
Association fibers
confined to the same hemisphere
The surface of the cortex is supplied by which three main arteries?
- Posterior cerebral arteries
- Anterior cerebral arteries
- Middle cerebral arteries
Two major arterial systems supply the CNS, what are they?
Posterior supply (vertebral-basilar system)
Anterior supply (internal carotid arteries)
Which surfaces of the cortex are supplied by the
- middle cerebral arteries
- anterior cerebral arteries
- posterior cerebral arteries
- MCA supplies most of lateral surface of hemisphere
- ACA supplies medial surface of frontal and parietal lobes
- PCA supplies medial surface of temporal and occipital lobes
An area where two perfusion areas come together is known as what?
A watershed area
What are two major groups of vains?
- superficial/external
- deep/internal
What is the difference between a vein and an artery
Veins typically bring oxygen-depleted blood to the heart, while arteries transport oxygenated blood from the heart to the rest of the body.
Where do veins in the brain drain?
Into venuous sinuses
The major veins of the brain drain into the venuous sinuses, there are 9 venuous sinuses, what are they?
- Superior sagittal sinus
- Inferior sagittal sinus
- Straight sinus
- Transverse sinus
- Sigmoid sinus
- Cavernous sinus
- Sphenoparietal sinus
- Petrosal sinuses
- Occipital sinus
Where do all venuous sinuses meet?
At the posterior pole of the skull at the confluence of the sinuses
