Association cortex and cognition

Question 1

What are the functions of the association cortex? What percent of the cerebral cortex is association?

Answer 1

Has functions more complicated than a simple input and/or output

Combines signals from primary sensory modalities to create psychological properties we know as ‘cogntion’

• Memory
• Planning
• Spatial analysis
• Language and reading
• Emotion and appetite

Most (80%) of cerebral cortex is association cortex!

Question 2

Higher order unimodal association areas (inputs, function, example, outputs)

Answer 2

Primary sensory cortices (vision, audition, touch) project to higher-order unimodal association areas

Integrate afferent information from a single sensory modality

E.g., Visual association cortex integrates information about form, color, and motion that arrives in the brain in separate pathways

Unimodal projection areas send information to multimodal sensory association areas that integrate information about more than one sensory modality

Multimodal sensory association areas project to multimodal motor association areas for acting upon them

Question 3

Broadman’s cytoarchitectural maps

Answer 3

based on types and densities of six cortical layer neurons

allowed for further functional analysis of these areas in research!

Question 4

What are the six cortical layers defined by?

Answer 4

densities, sizes, shapes, inputs, and outputs

Question 5

Describe neocortex

Answer 5

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

Each area has columnar and lateral connections (receptive fields)

Cells with similar functions are aligned in groups that span all cortical layers

Interneurons within specific cortical layers give rise to extensive local axons that extend horizontally, linking functionally similar groups of cells together (lateral processing)

Question 6

When you go from shallow layers to deep layers in the neocortex what changes?

Answer 6

shallow: local connections
deeper: starts to cross or go to the thalamus

Question 7

What layer does thalamic input enter into association neocortex?

Answer 7

Layer 4

Question 8

What two thalamic nuclei are involved in assocation cortex?

Answer 8

pulvinar: projects to parietal association cortex

medial dorsal nuclei: project to frontal association cortex

Question 9

How is the connectivity of association cortices different than primary and secondary motor cortices?

Answer 9

When compared to primary and secondary motor cortices

Two thalamic nuclei NOT involved in relaying primary motor or sensory input provide the majority of subcortical input to association cortices

Pulvinar projects to parietal association cortex

Medial dorsal nuclei project to frontal association cortex

Question 10

Describe the information that the thalamus inputs into association cortex.

Answer 10

Most input to higher-order thalamic nuclei comes from other regions of the cortex

Information reflects sensory and motor information that has already been processed by primary regions of cerebral cortex

Question 11

Describe the unique corticocortical connections of the association cortices

Answer 11

Contain enriched corticocortical connections

Forms the majority of input to association cortices

Includes ipsilateral connections from primary and secondary cortices, as well as other association cortices

Also includes contralateral hemispheric connections via the anterior commissure and corpus callosum

Note: lots of reciprocal connections, not all evenly giving input.

Question 12

Do association cortices talk to each other?

Answer 12

yep. there’s sharing of information amongst association cortices

Question 13

What scenarios have allowed us to study association cortices?

Answer 13

Much of what we know about association areas comes from observing human behavior following injuries to cerebral cortex

• Trauma (TBI)
• Stroke
• Tumor
• Surgery

Especially useful as lesions are well-defined and limited

Non-human primate work (NHPs)

Functional imaging techniques

(More about these in the methods lecture)

Question 14

What information does the posterior association cortex link?

Answer 14

Located at junction of the parietal, temporal and occipital lobes.

info from several sensory modalities for perception and language.

includes visuospatial location and attention

NHP single-cell recordings confirm parietal lobe involvement in visual attention

Question 15

What occurs when the posterior association cortex is lesioned?

Answer 15

Lesions interfere with awareness of one’s body and the space in which it moves

Hemispatial or contralateral neglect syndromes (failure to attend to contralateral half of visual field)

Question 16

What information does the limbic association cortex deal with? also where is it located

Answer 16

Located along the medial edge of the cerebral hemisphere.

emotion and memory storage

recognition

Question 17

What are signs of damage to the limbic association cortex?

Answer 17

Memory: Damage to bilateral medial temporal lobes selectively impairs the conversion of short-term memories to long-term memories

Recognition: Damage to fusiform face area (FFA) linked to failures to identify familiar faces

Question 18

NHP experiments on the limbic association cortex

Answer 18

NHP single-cell recordings confirm limbic association cortex involvement in recognition

increases firing with faces of primates/humans, but not hands and scrambled faces

Question 19

Anterior association cortex location and function

Answer 19

Rostral to postcentral gyrus, is concerned with planning movement

Includes language production (motor) and judgment

NHP studies confirm frontal lobe involvement in planning and regulating behavior

Question 20

What does damage to the anterior association cortex result in?

Answer 20

Damage results in deficits in

Judgment

Planning for the future

Holding and organizing events in memory

executive functioning

Question 21

anterior association cortex psychosurgery or accidents

Answer 21

phineas gage : pole through his anterior association cortex

experimental lesioning of the anterior assocation cortex to fix people with mental illness

modern day surgery that’s really pinpointed to the anterior cingulate: heals depression without lots of the side effects

Question 22

compare the flow of information in the frontal lobe motor control systems compared to sensory systems

Answer 22

Flow of information is reversed in the frontal lobe motor control systems when compared to sensory systems

Question 23

Describe how the components of the brain form cognition.

Answer 23

Dorsolateral prefrontal association cortex and parietal association cortex are some of the most densely interconnected regions of association cortex

The interactions between areas of association cortex give rise to consciousness

Interactions between the posterior and anterior association areas determine whether an action will occur and what the temporal pattern of that action will be

Patients with focal lesions have selected deficits in attending (being conscious of) certain classes of stimuli

Split brain patients (which we will talk about later) may have TWO independent conscious selves as a result of a failure in communication between two hemispheres