(14) Cerebral Hemisphere and Cortex

Question 1

(Cerebral Hemisphere)

1. Right and left cerebral hemispheres are derived from embryonic what? Each hemisphere is composed of what type of matter?

Answer 1

1. telencephalon; gray and white matter

Question 2

(Cerebral Hemisphere)

(Gray Matter)

1. What is the coating of gray matter on the surface of the cerebral hemisphere?

Three phylogenetic categories of cerebral cortex are (name them):

2. (hippocampus) oldest, composed of three layers
3. (piriform lobe) old, three layers, olfaction related
4. new, six layers, detailed perception, learning, intelligence

Answer 2

1. cerebral cortex
2. archicortex
3. paleocortex
4. neocortex

Question 3

(Cerebral Hemisphere)

(Gray matter)

1. gray matter located deep within the white matter of the cerebral hemisphere is called what?
2. What do basal nuclei (basal ganglia) include (5 things)

Answer 3

1. basal nuclei
2. accumbens nucleus, caudate nucleus, putamen, globus pallidus (pallidum), and amygdala

Question 4

(Cerebral Hemisphere)

(White Matter)

Consists of myelinated axons that connect cerebral cortex with other brain regions. Three categories of white matter are recognized:

1. These join the internal capsule. There are two categories of prejection fibers, relative to cerebral cortex:
   1a. exit to terminate in basal nuclei, brainstem, or spinal cord
   1b. typically originate in thalamus & terminate in cerebral cortex
2. Fibers that connect cortices of right and left cerebral hemispheres
   2b. What is the name of the largest bundle and what does it connect?
3. Fibers that connect regions of the cerebral cortex within one hemisphere? Two categories are recognized:
   3a. connect adjacent gyri
   3b. connect distanct gyri (different lobes)

Answer 4

1. projection fibers
   1a. corticofugal
   1b. corticopedal
2. commissural fibers
   2b. corpus callosum, connects neocortex
3. association fibers
   3a. short association fibers
   3b. long associated fibers

Question 5

1. The ventromedial portion of each cerebral hemisphere is designated what? why?
2. What type of behavior is rhinencephalon involved with?
3. What kind of cortex does rhinencephalon contain?

Answer 5

1. rhinencephalon (nose brain); assocaition with olfaction (most primitive sensory modality)
2. emotionally driven (the most primitive)
3. archicortex and paleocortex

Question 6

(Cerebral Cortical (Neocortex))

1. Is neocortex the most phylogenetically recent cortex? What is it found in?
2. What does neocortex specialize in (5 things)?
3. What percentage of dog cerebral cortex does it form? What form the remaining?

Answer 6

1. yes; only mammals
2. derailed sensory perception; higher cognitive interpretation; rapid fine movements; learning; goal oriented intelligence
3. 85%; archicortex and paleocortex

Question 7

(Neocortical Cells and Afferent Fibers)

(Two Neuron types predominate in the neocortex)

1. concial cell body with apical and basal dendrites and an axon that leaves the base of the cell to enter white matter. name it. Do they vary in size? They are the _____ cells of the cerebral cortex?
2. Small, round cell body. Serves as an interneuron. name it. receives input from what and synapses on what?

Answer 7

1. pyramidal cell; yes; output
2. granule cell; receives input from cortical afferent axons and synapses on pyramidal output neurons

Question 8

(Neocortical Cells and Afferent Fibers)

Two Types of afferent projection fibers from the thalamus enter the neocortex:

1. modality specific input. name it. terminate where?
2. backgound excitation. name it. terminate where?

Answer 8

1. specific afferents; inner granule cell layer
2. non-specific afferents; molecular layer

Question 9

(Horizontal Layers of the Cerebral Cortical)

The cerebral neocortex is organized into six horizontal layers (although layer boundaries are not very obvious in routine sections). The individual layers have different roles and they vary in relative thickness among cortical regions (e.g., sensory regions have a thick internal granule layer; the motor area has a thick internal pyramidal cell layer).

From superficial to deep, the six layers are:

1. predominantly fibers; apical dendrites and non-specific afferents
2. interneurons for non-specific afferent input
3. small and medium cells; short association fiber output
4. interneurons for specific afferent input
5. large cells; corticofugal projection and long assocation fiber output
6. variably shaped cells that project to the thalamus

Answer 9

1. molecular layer
2. outer granule cell layer
3. outer pyramidal cell layer
4. inner granule cell layer
5. inner pyramidal layer
6. multiform layer

Question 10

(Cortical Colum (Vertical) Organization of Cerebral Cortex)

1. The entire cerebral cortex is organized into functional units consisting of what? extend the entire thickness of what?
2. Each vertical column constitutes a functional unit because all cells within an individual column are activated by what?
3. The vertical organization is the result of what within a cortical column?
   3a. non-specific thalamic input to the column terminates where in the column? what does it provide to the column?
   3b. Specific thalamic input terminates where? exciting interneurons that do what?
   3c. Small pyramidal cells send their axons where to do what?
   3d. Large pyramidal cells (and multiform cells) send their axons where to do what via what?

Answer 10

1. cortical columns; the cortex
2. the same particular feature of a stimulus
3. neuronal connections
   3a. superficially - on distal dendrites of pyramidal cells; background excitation
   3b. internal granule cell layer; spread excitation to other neurons of the column
   3c. into white matter to excite nearby cell columns
   3d. white matter to excite distant sites via long assocation fibers, commisural fibers, and corticofugal projection fibers

Question 11

LOOk at diagram at the bottom of page 112

Question 12

(Functional Areas (regions) of cerebral neocortex)

A. Motor Area

1. Located within the what?
2. somatotopically organized by what?
3. Motor cortex is the main driver of what and what?
4. Primary source of pyramidal tract fibers to what and what?

Answer 12

1. cruciate sulcus
2. movement (its neurons drive joints vs individual muscles)
3. red nucleus and reticular formation (extrapyramidal tracts)
4. cranial nerve nuclei (corticobulbar tracts) and spinal cord (corticospinal tracts)

Question 13

1. Somatotopic organization = organization that what?
2. The organization can be represented by a what?

Answer 13

1. corresponds to regions of the body (neck is near the head, hindlimb is near the tail)
2. animunculus (which appears distorted because area of cortex is proportional to density of innervation no amount of body surface)

Question 14

(Functional Areas (REgions) of cerebral neocortex)

(B. Primary Sensory areas)

• Receive specific afferents of a given modality first, from the thalamus or geniculate bodies
  1. receives specific tactile input as well as info related to pain, temp, and pressure sensation. How organized and around what?
  2. Receives elements of an image (contrast-edges, shape, color, size). How organized and where?
  3. Receives auditory input (temporal and pitch changes). How is this area organzied?
  4. receives vestibular (acceleration) input; rostral to what area?
  5. Taste is represented where?
  6. Olfaction is conciously detected where?

Answer 14

1. somatosensory (somesthetic) area; somatotopically organized around the coronal sulcus
2. Visual area; retinotopiically organized in the occipital lobe
3. auditory area; cochleotopically organized
4. vestibular area; rostral to auditory area
5. somesthetic area near the tongue region
6. the piriform lobe (paleocortex)

Question 15

(Functional Areas (regions) of cerebral neocortex)

(C. Association areas)

1. Assocation cortex is associated with what seven things?
2. Association cortex receive input from where?

Answer 15

1. sensory integration, cognitive interpretation, abstracting complex significance, thinking, goal planning, cretivity, and intelligent behavior
2. other cortical areas and from thalamic nuclei and limbic structures

Question 16

(Functional Areas (regions) of cerebral neocortex)

(C. Association areas)

1. Sensory assocation area immediately surround what, from which they receive what?
2. They extract cognitive significance from what?

There are hierarchies of association cortex:

3. the lowest areas (closest to primary sensory areas) extract what? Surrounding assocation areas extract what?

Answer 16

1. primary sensory areas, active input
2. primitive elements of sensory perception
3. initial meaning; higher levels of significance

Question 17

(Functional Areas (regions) of cerebral neocortex)

(C. Association areas)

1. Prefrontal Association cortex occupies what pole?
2. It directs what kind of behavior? and sends it projections to premotor cortex for what?
3. The prefrontal cortex processes emotional status and cognitive perception as a prelude to what?
4. Attention to goal-oriented behavoir involves short-term working behavior and suppression of what?
5. The medial portion of the prefrontal cortex has abundant what? the lateral portion has strong what?

Answer 17

1. the frontal pole
2. goal-oriented behavior; movment selection
3. deciding, planning, and temporally organizing behavior directed toward acheiveing goals
4. distracting influences, including innapropriate emotional behavior
5. limbic connections; somatic (premotor) connections

Question 18

(Functional Areas (regions) of cerebral neocortex)

(C. Association areas)

1. Premotor cortex (motor assocation cortex) is located between what and what? receives projections from what and projects to what?
2. Premotor cortex is active particularly during what?
3. What elese are encoded in premotor regions?

Just read this (it is little type)

(The premotor cortex is actually a collection of related cortical regions including a frontal eye field and
supplemental motor area. The frontal eye field is involved in visual attention and visually tracking objects of
interest. The supplementary motor area extends onto the medial surface of the hemisphere and is active when
movements are being contemplated or observed, prior to movement execution. The supplemental cortex receives
projections from prefrontal cortex and projects to motor cortex.)

Answer 18

1. prefrontal cortex and motor cortex; receives projections from prefrontal cortex and projects to motor cortex
2. complex movement selection and while learning new movements
3. patterns of sequential rapid movements

Question 19

1. Do primate brains have relatively more assocation cortex thatn common domestic mamamals?

(little type again) (seems like the interesting stuff is always little type)

Association areas comprise 85% of the human brain but only 20% of the canine brain. In primates . . .
• parietal association cortex is involved in body awareness; damage results in neglect syndromes (denial of body parts)
• temporal association cortex is responsible for recognizing/identifying categories of objects; damage produces agnosia, e.g., lost ability to recognized faces or familiar objects
• frontal association cortex (prefrontal cortex) is concerned with appreciation of self, goal-directed planning, and appropriate behaviors. Damage impairs goal oriented behavior and personality. Animals are constantly distracted by every incidental stimuli and are unable to pursue purposeful execution for a delayed reward.

Answer 19

1. yes

Question 20

1. In humans, language processing (written, vocal, signing, reading) and math calcuation capability resides in one or both cerebral hemispheres?
2. What is dominant in the other hemisphere?
3. Is handeness a representation of hemispheric dominance?

Answer 20

1. one
2. visual-spatial processing
3. yes

Question 21

LOOk at DiagrARM on bottom of 114

Question 22

(IV. Methods of Determining Cortical Function)

1. Info obtained by producing experimental lesions or by observing patients whose lesions can be confirmed at necropsy

Findings Include (this is little type):

Somesthetic area — loss of the fine aspects of discrimination (e.g., cats lose the ability to discriminate various degrees of texture roughness).

Auditory Area — bilateral lesions cause difficulty in localizing sounds and the meaning (temporal & pitch pattern) of sound is lost.

Answer 22

1. Destructive lesions

Question 23

(IV. Methods of Determining Cortical Function)

1. Stimulate with electrodes and observe the resulting response.

(This is little type)

Motor area — stimulation of the area surrounding the cruciate sulcus causes contralateral joint movement in a somatotopic pattern. Premotor cortical stimulation requires a higher threshold to evoke movement

Answer 23

1. Electrical Stimulation

Question 24

(Methods of Determining Cortical Function)

1. Following a stimulus the corresponding primary sensory areas become excited first. This is employed clinically to evalutate what?

(this is little type)

Primary auditory area — (tonotopic organization)
high frequency tones activate neurons in the caudal sylvian gyrus; low frequency tones activate neurons rostrally.

Primary Visual Area—different cell columns respond to edges, flashes, colors, and intensities (the elements that comprise an image).

Answer 24

1. Electrical recording; pathway integrity

Question 25

(Methods of Determing Cortical Function)

(Metabolic Mapping)

(this is all little type)

Mapping studies utilize a radiolabeled glucose analogue, 2-deoxyglucose, which competes with glucose for neuronal uptake. During a particular brain function, neurons which are active utilize more glucose and thus take up more 2-deoxyglucose. These active neurons become radioactive and can be localized with autoradiographic techniques (Positive Emission Tomography gamma rays).

More recently, Functional Magnetic Resonance is now the method of choice for detecting localized increased blood flow to brain regions during mental tasks. Increased blood flow results in hyperoxygenated hemoglobin and increase MRI signal.