Chapter 26 - Association Cortex and Cognition Flashcards
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?
- Parietal association cortex
- Attending to stimuli in the external and internal environment. - Temportal association cortex
- Identifying the nature of such stimuli - Frontal association cortex
- Selecting and planning appropriate behavioral responses.
Most of the cortex that covers the cerebral hemispheres is of a certain classification or type. This type is called…
Neocortex.
What is neocortex?
Neocortex is defined as cortex that has six cellular layers, also called laminae.
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…
cytoarchitectonic areas.
What are cytoarchitectonic areas?
Histologically defined subdivisions of the cerebral cortex defined by their deviance in laminar uniformity.
There are four common features of different cytoarchitectonic areas. What is feature #1?
- Each cortical layer has a primary source of inputs and a primary output target.
There are four common features of different cytoarchitectonic areas. What is feature #2?
- Each area has connections in the vertical axis and connections in the horizontal axis.
There are four common features of different cytoarchitectonic areas. What is feature #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.
There are four common features of different cytoarchitectonic areas. What is feature #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.
What forms the majority of the input to the association cortices?
Other cortical areas. These projections are called cortiococortical connections.
Corticocortical connections also arise from both corresponding and noncorresponding cortical areas in the opposite hemisphere via …
the corpus callosum and the anterior comissure.
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 …
Interhemispheric connections.
Most of our evidence about the interconnectivity of the association cortex comes from ..
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.
Most of our inferences about the interconnectivity of the association cortex comes from ..
Observations of patients with cortical lesions.
The first account of the link between parietal lobe lesions and deficits in attention or perceptual awareness came from whom?
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.
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 …
contralateral neglect syndrome.
How has case-studies on contralateral neglect syndrome helped our knowledge of the association cortex?
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.
Contralateral neglect syndrome is typically associated with damage to the left/right parietal cortex.
Right
Contralateral neglect syndrome is typically associated with damage to the right parietal cortex. Why?
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.
A right hemisphere lesion causes contralateral neglect syndrome. How severe would this neglect be, and in what direction?
A right hemispheric lesion would cause severe left neglect.
A left hemisphere lesion causes contralateral neglect syndrome. How severe would this neglect be, and in what direction?
A left hemispheric lesion would cause minimal right neglect, because the right hemisphere also mediates attention to the right.
A parietal billateral lesion causes contralateral neglect syndrome. How severe would this neglect be, and in what direction?
A bilateral lesion would cause severe right neglect, and a moderate to severe neglect to the left.
Studies of rhesus monkey’s using single-neuron recordings in the parietal cortex reveal what?
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).
What are agnosias?
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 (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?
A mismatching of verbal or other cognitive symbols with the sensory stimuli.
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?
A failure to recall stimuli when confronted with them again.
One of the most studied agnosias following damage to the temporal association cortex in humans is prosopagnosia. What is prosopagnosia?
Prosopagnosia (Greek posopon, “face” or “person”) is the inability to recognize and identify faces.
Prosopagnosia is associated with damage to the ..
Temporal lobe. Temporal association cortex.
To what extend does a toilet brush look like a monkey’s face?
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.
What is the Wisconsin Card Sorting Task?
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.
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)
Phineas Gage.
What happened to Phineas Gage?
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’.”
What are the main cognitive disabilities associated with frontal lobe damage?
- Impaired restraint
- Disordered thought
- Perseveration (repetition of the same behavior)
- Inability to plan appropriate action.
What behavioral test has been used to study cells in the monkey frontal cortex?
The delayed response task.
What is the setup of the delayed response task, a behavioral test used to study cells in the monkey frontal cortex?
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.
