Cerebral Cortex

Question 1

In which lobe are the supramarginal and angular gyri found?

Answer 1

Parietal lobe

Question 2

What is the posterior aspect of the frontal lobe?

Answer 2

Central sulcus

Question 3

Which structure separates the frontal and parietal lobes above from the temporal lobe below?

Answer 3

Lateral sulculs/fissure

Question 4

Which two gyri are separated by the calcarine sulcus?

Answer 4

The Cuneus (superior) and Lingual (inferior) gyri of the occipital lobe

Question 5

What is the main function of the precentral gyrus?

Answer 5

Primary motor cortex

Question 6

What is the main function of the postcentral gyrus?

Answer 6

Somatorsensory function

Question 7

Where is the supramarginal gyrus found?

Answer 7

In the parietal lobe (it is partially responsible for language processing and perception)

Question 8

Where is the angular gyrus found and what is it responsible for?

Answer 8

In the parietal lobe: it is partially responsible for language, # processing, spatial cognition, memory and attention

Question 9

Where is the lingual gyrus found and what is it responsible for?

Answer 9

The inferior gyrus of the occipital lobe: it helps in processing vision, especially letters

Question 10

Where is the cuneus gyrus found and what is it responsible for?

Answer 10

Superior gyrus of the occipital lobe: it helps in visual processing

Question 11

Where is the uncus found and what is it responsible for?

Answer 11

Anterior extremity of the parahippocampal gyrus: it involves olfactory (part of the medial temporal lobe) and memory functions

Question 12

What are the 6 layers of the grey matter (3-4 mm thick) of the cortices?

Answer 12

Layer I – Molecular Layer (most external)
Layer II – External Granular Layer
Layer III – External Pyramidal Layer
Layer IV – Internal Granular Layer
Layer V – Internal Pyramidal layer
Layer VI – Multiform layer (most internal)

Question 13

What are the main types of neurons contained in the six layers of cortical gray matter?

Answer 13

1. pyramidal cells (somas mostly in Layers III and V)
2. stellate cells
3. fusiform cells
4. horizontal cells of Cajal
5. cells of Martinotti

Question 14

Approximately how many nuerons are contained within the gray matter of the cortices?

Answer 14

10 billion neurons

Question 15

Where do tangential axons terminate?

Answer 15

Tangential fibers terminate within the gray matter providing cortico-cortical connections within layers.

Question 16

Where do radial axon fibers terminate?

Answer 16

Radial fibers also terminate with the gray matter, between layers, but also project out of the cortex becoming projection, association, and commisural fibers of the white matter.

Question 17

In addition to the gray matter being divided into layers, the cortex can be divided into what features (300-600mm wide) of functional activity?

Answer 17

vertical columns (gray matter layers–>vertical columns–>functionally specialized areas–>lobes or cortices–>functional circuits)

Question 18

What are the three functional circuit pathways categories?

Answer 18

1. Association fibers from other regions within the same hemisphere.
2. Commissural fibers from regions in the contralateral hemisphere.
3. Projection fibers from the thalamus (thalamocortical projections).

Question 19

Describe somatic sensation: primary somatosensory cortex

Answer 19

Primary Somatosensory Cortex

a. Primary somatosensory cortex (the post-central gyrus), contains somatotopic representation of the body (sensory homunculus)
b. Receives input from the thalamus regarding discriminative general senses as well as pain and temperature sense from the body and face.

Question 20

A lesion to the somatosensory cortex (post-central gyrus) will cause what types of deficits?

Answer 20

Hemi anesthesia on the side of the body opposite to the cortex: Deficits include discrimitive touch and position sense

Question 21

A lesion to the somatosensory association cortex (superior parietal lobule and supramarginal gyrus) may cause what types of deficits?

Answer 21

Hemineglect syndrome (often left hemineglect syndrome): denial that the left side of the body belongs to the patient, patients may shave and dress only left side of the body or draw the right side of an image.

Question 22

How will a lesion to the non-dominant (usually right) somatosensory association cortex affect language?

Answer 22

A lesion of the non-dominant (usually right) cortex causes NO disturbance in language because in most people, language function is located in the left hemisphere, but does cause a lack of appreciation of spatial aspects of all sensory input from the left side of the body (hemineglect syndrome)

Question 23

Describe somatic sensation: primary somatosensory association cortex

Answer 23

Found in: Superior parietal lobule and supramarginal gyrus

Used for: perception of shape, size, texture and identification of objects by feel (stereognosis)

Question 24

Describe the primary visual cortex (where is it and what does it do?)

Answer 24

Found in: Primary Visual Cortex (cuneus and lingual gyri)

a. This is the termination of the retinogeniculostriate pathway (optic radiations)
b. This area fuses the inputs from both eyes into one image.
c. Analyzes the visual world with respect to orientation of visual stimuli, with special attention paid to lines and edges of images.

Question 25

Describe the visual association cortex

Answer 25

(Medial and lateral occipital gyri, angular gyrus)

a. Essential for comprehension of a visual image.
b. Mediates slow pursuit (tracking) movements of the eyes through connections with the superior colliculus of the midbrain tectum and cranial nerve nuclei of the extraocular muscles.
c. Mediates vergence eye movements (e.g., convergence and divergence when focusing near & far, respectively).
d. Mediates conjugate eye movements

Question 26

Describe the primary auditory cortex

Answer 26

Primary Auditory Cortex located in superior temporal gyrus and the transverse temporal gyri of Heschl in the temporal lobe.
a. Neurons in these regions respond to different frequencies of sound (tonotopic organization).

Question 27

Describe the auditory association cortex

Answer 27

(superior temporal gyrus)

a. Important in the interpretation of sounds.
b. Lesion to a specialized portion of this are (Wernike’s area) makes spoken language difficult to understand.

Question 28

Describe the primary olfactory cortex

Answer 28

The Primary Olfactory Cortex consists of the uncus, pirirform cortex, the periamygdaloid, and part of the parahippocampal gyrus.
a. Projects to the hypothalamus, hippocampus, amygdala, thalamus, and orbitofrontal olfactory area of the cortex

Question 29

What are some of the effects of lesions to the (somatosensory, visual, auditory) association cortices?

Answer 29

Agnosia (inability to recognize an object; inability to interpret and recognize sensory stimuli)
A. tactile agnosia (also called Asterognosis) (mostly involves a lesion in area 40)
B. visual agnosia (mostly involves a lesion in area 39; inability to recognize objects by sight); prosopagnosia is the inability to recognize faces
C. auditory agnosia (mostly involves a lesion in area 22; inability to recognize familiar sounds and words)

Question 30

Describe the primary motor cortex

Answer 30

A. The precentral gyrus
B. Contains somatotopic representation of the body for motor function (motor homunculus) with disproportionate representation of the areas for the hand, face and tongue

Question 31

What are some indications and effects of a lesion to the primary motor cortex?

Answer 31

A lesion in the motor cortex produces:

a. contralateral paresis
b. increased deep tendon reflexes
c. positive Babinski sign

Question 32

Describe the premotor cortex and frontal eye fields

Answer 32

A. Middle Frontal Gyrus (posterior aspect)
B. Motor planning area
C. Receives input from the cerebellum and is involved in the production of externally referenced movements
D. Stimulation produces postural or tonic movements, and contralateral eye movements and head movements (connections to ocular motor nuclei)

Question 33

What does a lesion to the premotor cortex and frontal eye fields produce?

Answer 33

Lesion produces hypertonus and increased resistance to passive movements

Question 34

Describe the supplemental motor cortex

Answer 34

A. Superior Frontal Gyrus (posterior aspect)
B. Motor planning area
C. Superior to the premotor cortex
D. Receives input from the basal ganglia and is involved in the production of internally referenced movements

Question 35

Describe Broca’s area

Answer 35

A. Inferior Frontal Gyrus (Posterior Aspect)
B. Speech planning area (usually in the left hemisphere).
C. Connected to Wernikes area by the arcuate fasciulus

Question 36

What are some characteristics of Broca’s aphasia or expressive aphasia?

Answer 36

Normal comprehension of language; expression of speech is difficult and crudely articulated; muscles involved in speech are not damaged; patients can express memorized words correctly.

Question 37

Lesions of motor planning areas can cause Apraxia. What is Apraxia?

Answer 37

a disorder of sensory integration interfering with the ability to plan and perform skilled and complex movements. Lesions causing apraxia can be in a variety of cortical areas. Various types of apraxias include: Akinetic, Amnestic, Motor, Ideational and Facial apraxia.

Question 38

Describe akinetic, amnestic, motor, ideational and facial apraxia

Answer 38

A. Akinetic apraxia: loss of ability to carry out spontaneous movement.
B. Amnestic apraxia: inability to carry out movement on command due to inability to remember the command.
C. Motor apraxia: inability to perform complicated motor tasks.
D. Ideational apraxia: inability to demonstrate use of objects (e.g., tools placed in a patient’s hand).
E. Facial apraxia: inability to perform facial-oral movements on command (e.g., lick the lips). This is the most common apraxia.

Question 39

Where are all motor, cognitive and emotional activities planned?

Answer 39

In the frontal lobe-this planning can be referred to as executive function. These areas also regulate the affect associated with sensation (happy, sad, friendly, disagreeable)

Question 40

Describe the limbic association cortex (psychial cortex)

Answer 40

Location: The anterior pole of the temporal lobe.
Involved in: the regulation of emotions, mood, affect, and memory
Electrical stimulation of this area elicits recall of things seen or heard (e.g., music from the past) (closely associated with the olfactory cortex).

Question 41

Visual or auditory hallucinations may be the effect of a tumor or stroke in which association cortex?

Answer 41

The limbic association cortex (psychical cortex)

Question 42

Describe the Parietotemporal Association Cortex

Answer 42

A. Involved in sensory integration, problems solving, speech, and spatial processing.
B. Interpretation and Integration of sensations are localized here
C. Can be considered tertiary sensory association areas

Question 43

What is one exception to the typical symmetry between the cerebral hemispheres?

Answer 43

One exception is the planum temporale (an area located on the upper surface of the temporal lobe and including Wernicke’s speech area) which tends to be larger in the left hemisphere

Question 44

What are functions of the dominant hemisphere?

Answer 44

a. Language
b. Skilled motor formulation (aka. Praxis)
c. Arithmetic: analytical skills
d. Sequential processing

Question 45

What are functions of the non-dominant hemisphere?

Answer 45

a. Prosody (emotion, tone and rhythm of voice)
b. Visual-spatial analysis and spatial attention
c. Arithmetic: spatial skills
d. Spatial orientation and processing

Question 46

What is the difference between externally referenced movements (premotor cortex and frontal eye fields) and internally referenced movements (supplemental motor cortex)?

Answer 46

Externally directed movments may be described as responses to external stimuli while internally directed movements are where you simply decided to do something (without reacting to other stimuli)