Chapter 26 - Association Cortex and Cognition

Question 1

Studies on the association cortex indicate that it is possible to divide the association cortex in three parts that are specialized for certain cognitive tasks. Which cortexes and which tasks?

Answer 1

1. Parietal association cortex
   - Attending to stimuli in the external and internal environment.
2. Temportal association cortex
   - Identifying the nature of such stimuli
3. Frontal association cortex
   - Selecting and planning appropriate behavioral responses.

Question 2

Most of the cortex that covers the cerebral hemispheres is of a certain classification or type. This type is called…

Answer 2

Neocortex.

Question 3

What is neocortex?

Answer 3

Neocortex is defined as cortex that has six cellular layers, also called laminae.

Question 4

Despite an overall uniformity of the laminae in the neocortex, regional differences based on these laminar features have long been apparent. These regional differences have allowed investigators to identify numerous subdivisions of the cerebral cortex. These histologically defined subdivisions are referred to as…

Answer 4

cytoarchitectonic areas.

Question 5

What are cytoarchitectonic areas?

Answer 5

Histologically defined subdivisions of the cerebral cortex defined by their deviance in laminar uniformity.

Question 6

There are four common features of different cytoarchitectonic areas. What is feature #1?

Answer 6

1. Each cortical layer has a primary source of inputs and a primary output target.

Question 7

There are four common features of different cytoarchitectonic areas. What is feature #2?

Answer 7

2. Each area has connections in the vertical axis and connections in the horizontal axis.

Question 8

There are four common features of different cytoarchitectonic areas. What is feature #3?

Answer 8

3. Cells with similar functions tend to be arrayed in radially aligned groups that span all the cortical layers and recieve inputs that are often segregated into radial bands or columns.

Question 9

There are four common features of different cytoarchitectonic areas. What is feature #4?

Answer 9

4. Interneurons within specific cortical layers give rise to extensive local axons that extend horizontally in the cortex, often linking functionally similar groups of cells.

Question 10

What forms the majority of the input to the association cortices?

Answer 10

Other cortical areas. These projections are called cortiococortical connections.

Question 11

Corticocortical connections also arise from both corresponding and noncorresponding cortical areas in the opposite hemisphere via …

Answer 11

the corpus callosum and the anterior comissure.

Question 12

Corticocortical connections also arise from both corresponding and noncorresponding cortical areas in the opposite hemisphere via the corpus callosum and the anterior comissure, which together are referred to as …

Answer 12

Interhemispheric connections.

Question 13

Most of our evidence about the interconnectivity of the association cortex comes from ..

Answer 13

Most of the evidence comes from anatomical tracing studies in non-human primates, supplemented by the limited pathway tracing that can be done in human brain tissue postmortem.

Question 14

Most of our inferences about the interconnectivity of the association cortex comes from ..

Answer 14

Observations of patients with cortical lesions.

Question 15

The first account of the link between parietal lobe lesions and deficits in attention or perceptual awareness came from whom?

Answer 15

The British neurologist W.R. Brain reported three patients with unilateral parietal lobe lesions in whom the primary problem was varying degrees of difficulty paying attention to objects and events contralateral to the lesion. The patients were able to see things in the contralateral field of view, but nevertheless seemed to ignore their presence.

Question 16

The British neurologist W.R. Brain reported three patients with unilateral parietal lobe lesions in whom the primary problem was varying degrees of difficulty paying attention to objects and events contralateral to the lesion. Based on a large number of patients studied since Brain’s pioneering work, these deficits are now referred to as …

Answer 16

contralateral neglect syndrome.

Question 17

How has case-studies on contralateral neglect syndrome helped our knowledge of the association cortex?

Answer 17

Since Brain’s original description of contralateral neglect and its relationship to lesions of the parietal lobe, it has been generally accepted that the parietal cortex, particularly the inferior parietal lobe, is the primary cortical regions governing attention.

Question 18

Contralateral neglect syndrome is typically associated with damage to the left/right parietal cortex.

Answer 18

Right

Question 19

Contralateral neglect syndrome is typically associated with damage to the right parietal cortex. Why?

Answer 19

This is because the right parietal cortex mediates attention primarily to both the right and left halves of the body and extrapersonal space, whereas the left hemisphere mediates attention primarily to the right. This hemispheric bias is thought to arise from specialization of the left hemisphere for language, thereby driving attentive functions into the right hemisphere.

Question 20

A right hemisphere lesion causes contralateral neglect syndrome. How severe would this neglect be, and in what direction?

Answer 20

A right hemispheric lesion would cause severe left neglect.

Question 21

A left hemisphere lesion causes contralateral neglect syndrome. How severe would this neglect be, and in what direction?

Answer 21

A left hemispheric lesion would cause minimal right neglect, because the right hemisphere also mediates attention to the right.

Question 22

A parietal billateral lesion causes contralateral neglect syndrome. How severe would this neglect be, and in what direction?

Answer 22

A bilateral lesion would cause severe right neglect, and a moderate to severe neglect to the left.

Question 23

Studies of rhesus monkey’s using single-neuron recordings in the parietal cortex reveal what?

Answer 23

Certain neurons increase their firing rate when the monkey’s attention is directed towards a certain object. When the target was ignored, the firing was small. When the target was attended to, the firing rate spiked. When given fruit juice rewards for attending to certain targets, the activity of some neurons in the parietal cortex varied systematically as as function of the amount of juice associated with each target (and therefore probably the amount of attention paid by the monkey to the target).

Question 24

What are agnosias?

Answer 24

Agnosias (Greek, “uknown”) are disorders where patients have difficulty recognizing, identifying and naming different categories of objects. They are typically caused by lesions in the association cortex in the temporal lobe.

Question 25

Agnosias (Greek, “uknown”) are disorders where patients have difficulty recognizing, identifying and naming different categories of objects. They are typically caused by lesions in the association cortex in the temporal lobe. Agnosias have both a lexical aspect and a mnemonic aspect. What is meant by a lexical aspect?

Answer 25

A mismatching of verbal or other cognitive symbols with the sensory stimuli.

Question 26

Agnosias (Greek, “uknown”) are disorders where patients have difficulty recognizing, identifying and naming different categories of objects. They are typically caused by lesions in the association cortex in the temporal lobe. Agnosias have both a lexical aspect and a mnemonic aspect. What is meant by a mnemonic aspect?

Answer 26

A failure to recall stimuli when confronted with them again.

Question 27

One of the most studied agnosias following damage to the temporal association cortex in humans is prosopagnosia. What is prosopagnosia?

Answer 27

Prosopagnosia (Greek posopon, “face” or “person”) is the inability to recognize and identify faces.

Question 28

Prosopagnosia is associated with damage to the ..

Answer 28

Temporal lobe. Temporal association cortex.

Question 29

To what extend does a toilet brush look like a monkey’s face?

Answer 29

According to face recognition neurons in the rhesus monkey (Desimone et al., 1984), it is sufficiently face-like to elicit a response, albeit not as strong as a real monkey face.

Question 30

What is the Wisconsin Card Sorting Task?

Answer 30

The task is a part of a battery of tests developed in the 1940s to evaluate the integrity of cognitive function and to help localize lesions. It features cards with symbols that differ in their color, shape and number on each card. They need to sort after a rule that is not given, receiving their results after each time. The sorting rule changes after 10 correct trials.

Question 31

The functional deficits that result from damage to the human frontal lobe are diverse and devastating. The first case-study that called attention to the consequences of frontal lobe damage was that of … (answer is a name)

Answer 31

Phineas Gage.

Question 32

What happened to Phineas Gage?

Answer 32

Phineas Gage was a railroad laborer in the mid-nineteenth centure Vermont. An accident drove a metal rod through his left orbit (eye socket) and into his frontal brain. Famously, he recovered but his mind was “radically changed, so decidedly that his friends and acquaintances said he was ‘no longer Gage’.”

Question 33

What are the main cognitive disabilities associated with frontal lobe damage?

Answer 33

1. Impaired restraint
2. Disordered thought
3. Perseveration (repetition of the same behavior)
4. Inability to plan appropriate action.

Question 34

What behavioral test has been used to study cells in the monkey frontal cortex?

Answer 34

The delayed response task.

Question 35

What is the setup of the delayed response task, a behavioral test used to study cells in the monkey frontal cortex?

Answer 35

In the simplest version of the delayed response task, the monkey watches an experimenter place a bit of food in one of two wells; both wells are then covered. Subsequently, a screen is lowered for an interval of a few seconds to several minutes (the delay). When the screen is raised, the monkey gets only one chance to uncover the well containing food and receive the reward. The ability to carry out this working memory task is diminished or abolished if the prefrontal cortex is destroyed bilaterally.