Cerebral Cortex II

Question 1

Describe layer 4 of cortex specifically

Answer 1

Internal granule layer
Main recipient of afferent inputs from thalamus
Many little cells, main input layer as go up pathway, axons of relay nuclei of thalamus end in layer 4

Question 2

describe what happens after inputs in layer 4

Answer 2

Inputs in layer 4 —> axons to layers 2 and 3 —> other regions of cortex

Question 3

Describe role of pyramidal neurons in layer II and iii

Answer 3

Make feedforward projections to other regions fo cortex
Sends axons from one region to another - like if neurons communicating

Question 4

describe layer 2 = role

Answer 4

pyramidal cells in layer 2 = smaller

Question 5

describe layer 3 = role

Answer 5

pyramidal cells larger = external pyramidal layer

Question 6

describe collective roles of layer 2 and 3

Answer 6

Comprised of pyramidal cells—> excitatory neurons = release glutamate —> connect parts of cortex and project to other regions of cortex (larger cells for projection)
= feedforward connections

Question 7

what do neurons in layer V and vi do

Answer 7

Project to subcortical targets
Output neutrons of cortex = leaving cortex
Very complex connections

Question 8

describe layer V = output neurons = where do they go

Answer 8

large pyramidal neurons in layer V project to basal ganglia, thalamus, brainstem and spinal cord
= projections go to association nuclei, drivers come from cortex = pyramidal neurons in layer 5
Like if motor cortex = axons from large pyramidal neurons —> go to spinal cord and control voluntary movement
Also projections to subcortical structures = leave from pyramidal neurons in layer 5

Question 9

does the thickness of the diff layers of cortex stay the same all throughout Brain

Answer 9

Thickness of various layers varies in diff regions of cortex = variability, depends on region of cortex
Regions involved with more cognitive processes = varying amounts of each layer

Question 10

describe thickness of layers = primary motor cortex

Answer 10

Fusion = layers 3 and 5
Bc many outputs = many large pyramidal neurons
Layer 4 very small

Question 11

describe thickness of layers = primary visual cortex

Answer 11

receiving many inputs
= so layer 4 larger
Output layers more modest

Question 12

Describe neurons in cortex

Answer 12

Excitatory neurons in cortex have highly complex axonal and dendritic projections
Complexity = vast, many connections and communications

Question 13

describe neurons in layer 1

Answer 13

Dendrites from large pyramidal neurons in layer 5 = extends to layer 1, many branches

Question 14

describe neurons in layer 2,3

Answer 14

many synapses onto many neurons
Many axon terminals

Question 15

describe neurons in layer 4a b

Answer 15

Complex terminal of axons = divergence, precise connection but onto many neurons
Much divergence
Axon coming from Lgn
Gets inputs from all layers of cortex

Question 16

describe neurons in layer 4c

Answer 16

Stellate neuron

Question 17

describe neurons in layer 5

Answer 17

Large pryamidal neuron
Neuron not just dong stuff in layer when its cell body is
Extends = axon branches, main output = to spinal cord but sends message to many neurons in layer 6

Question 18

Describe neurons in layer 6

Answer 18

Axon extension from layer 5

Question 18

what is cortex organized into

Answer 18

Vertical columns - perpendicular to surface of cortex
100-500uM diameter
Cortex = sheet divided into functional modules that extend through all 6 layers
Neurons in column = highly inter connected and show similar response properties

Question 19

describe columns of cortex

Answer 19

Primary Somatic sensory cortex - patch corresponds to hand finger tip
All neurons in this column = functional module that responds to pressure on finger tip region
Expand # of columns = expand computational properties = evolution, why humans have huge cortex

Question 20

describe columns of cortex = electrode recording

Answer 20

Stimulate finger tip with constant pressure= neuron fires ap, if push further = ap in next layer = all of teh red column activated
Column next to it = maybe does not respond to same thing = not for constant pressure, maybe for vibration

Question 21

describe columns of cortex = organization

Answer 21

Each neuron = response to specific region of patch and specific modality
Cortex organized = sheet = connection of functional modules all arranged together

Question 22

describe ocular dominance and orientation columns in v1

Answer 22

Ocular dominance columns = either response to contralateral or ipsilateral eye
Monkey cortex = ipsilateral column is black and contralateral column is white = map of ocular dominance columns in v1

Question 23

describe what happens within a column

Answer 23

Neurons in layer iv project to layers II and iii
Neurons in these superficial layers then project to layers V and vi and to other cortical areas
WITHIN COLUMN
Neurons connected to each other

Question 24

describe general pattern of flow of info within column

Answer 24

To layer 4–> up to superficial layers II —> down to deep layers

Question 25

describe general pattern of flow of info within column = thalamocortical projections

Answer 25

End in layer 4 = excitatory End at Stellate cells = very small, also excitatory —> extend to layers 2 and 3 = pryamidal cells Axons then go down into cortical white matter

Question 26

describe general pattern of flow of info within column = feedforward cortical projections

Answer 26

axons from pryamidal cells in layers 2 and 3

Question 27

describe general pattern of flow of info within column = sub cortical and cortical feedback projections

Answer 27

Axons from layers 2 and 3 = connect cortex to other parts of cortex Neurons Also make synapses in layers deeper = 5-6

Question 28

what are diff regions of cortex specialized for

Answer 28

do diff things = specialized for diff functions Primary = get info first

Question 29

describe primary motor cortex

Answer 29

Have maps of body that are aligned = m1 and v1 Final output for motor control Pre central gyrus

Question 30

describe primary somatic sensory cortex

Answer 30

Have maps of body that are aligned = m1 and v1 Receive inputs from thalamus Post central gyrus

Question 31

describe primary auditory cortex

Answer 31

Behind lateral sulcus

Question 32

describe primary visual cortex

Answer 32

Mostly on medial surface

Question 33

where is primary somatic sensory cortex located

Answer 33

In postcentral gyrus

Question 34

What is preserved up to level of primary somatic sensory cortex

Answer 34

Somatotopic organization = map preserved

Question 35

describe somatotopic organization

Answer 35

How body mapped onto primary somatic sensory cortex 1/2 of brain = hand (use to touch, rfs small and densely innervated) and face (speaking, facial expression) take up more than legs/back (Have many neurons dedicated to fingers = preserved across every level in sensory processing up to primary somatic sensory cortex)

Question 36

what happens after primary cortex

Answer 36

Primary —> Send info to higher order processing —> higher area

Question 37

where do neurons in SI project

Answer 37

Project to higher order processing areas in cortex = including SII and area 5 = referrers to as somatic sensory association cortex Specialized for more complex somatic sensory processing (SI=priamry somatic sensory processing, SII = next level = 2nd area, then area 5) HIERARCHICALLY ORGANZIED

Question 38

what is involved in higher order processing of individual sensory modalities

Answer 38

Unimodal association regions = defined areas Applies to all sensory systems Sensory perceptions built up a step at a time

Question 39

describe somatic sensory association cortex

Answer 39

= area 5 and SII

Question 40

describe visual association cortex

Answer 40

V1,v2,v3,v4 Rest = higher order visual processing

Question 41

describe motor association cortex

Answer 41

Higher order cortical regions help organize movements = supplemental motor area and premotor cortex (opposite direction = start out with goal and broken down into steps) THEN = primary motor cortex

Question 42

describe auditory association cortex

Answer 42

Primary auditory cortex then auditory association cortex

Question 43

describe layer vi = output neurons = where do they go

Answer 43

Feedback projections to thalamus come from layer 6

Question 44

What is the Fundamental functional module of cortex

Answer 44

Column is fundamental functional module of cortex

Question 45

Are columns actually column shaped

Answer 45

noooo Not just squares = do look like round things Segregated regions of neurons within region extending vertically down from surface of cortex