HUF 2-62 Association function and executive processing

Question 1

Association cortices

Answer 1

4 major lobes: frontal, parietal, temporal, occipital
Corpus callosum

1° areas: close links with specific motor structures or sensory receptors
2° areas: direct connections with 1° areas

Association areas: no direct connect with sensory and motor structures (“silent” areas)
* Receive info from higher-order sensory areas

Question 2

Subdivision of association cortices

Answer 2

Higher functions: thought, perception, consciousness, emotion, memory, languages

1. Prefrontal (ant.) association cortex
2. Limbic “
3. Parietal-temporal-occipital (pos.) “

Question 3

Prefrontal cortex: behavioral control

Answer 3

• Frontal lobe ant. to premotor and motor cortices
• Excluding limbic cortical areas

1. 1° motor cortex: simple movements
2. Premotor cortex: complex movements
3. DL/VL prefrontal cortex: cognition, rule-guided behaviour, decision-making
4. Frontopolar cortex: long-term goals, multitasking

• Somatotopic map gradually lost in more ant. area

Prefrontal cortex: integrate diff. sensory input (esp. from pos. parietal cortex)
=> Select most appropriate motor responses
Frontopolar cortex: no direct sensory input at all

*Phineas Gage: normal intelligence; change in personality

Question 4

Limbic association cortices

Answer 4

Cortical components of complex limbic system:

1. Orbito-frontal cortex: medial and ventral surface of frontal cortex
2. Cingulate gyrus: mid surfaces of cerebral cortex
3. Insular cortex
4. Parahippocampal gyrus of temporal lobe

Close relationship with other subcortical components of limbic system:

1. Amygdala: fear response
2. Hypothalamas: homeostatic drive
3. Hippocampus: emotional memory
4. Ventral striatum / septum: reward, pleasure

• More complex emotions (sadness, anger…) and related behaviours (e.g. aggression, defense)

Question 5

Schizophrenia affects prefrontal and limbic system

Answer 5

Prefrontal cortex: prominent dopaminergic
Schizophrenics:
1. Smaller frontal lobe
2. No normal increase in BF in tasks involving the area

Prefrontal and limbic system malfunctions:
+ve symptoms: delusions, hallucinations
-ve symptoms: withdrawal

Antipsychotic drugs: DA receptor antag.

Question 6

Parietal-temporal-occipital association cortex

Answer 6

• Parietal cortex pos. to somatosensory cortex
• Temporal cortex apart from auditory areas
  ∴ Junction between higher-order somatic, visual and auditory areas
• Higher sensory area
  1. Link and interpret info from diff. sensory modalities
  2. Sensory perception, language and motor planning

Question 7

Regional functional specialisation of parietal-temporal-occipital association cortex

Answer 7

Posterior parietal cortex:

• Locomotion of body parts and surroundings of body
• Project to motor cortex

Angular gyrus
- Visual processing of wards: reading and writing

Temporal association cortex:
- Input from visual areas => analyse visual info.

Wernicke’s area:
- Interpretation of languages (spoken and written)

Question 8

Neural circuit of language

Answer 8

Wernicke-Geschwing model

1. Auditory inputs (spoken words) from auditory cortex to Wernicke’s area
2. Visual inputs (written words) from occipital cortex to angular gyrus to Wernicke’s area
3. Language info to Broca’s area (in frontal lobe) via arcuate fasciculus
4. Language response to motor cortices
5. 1° motor cortex command ms. to produce language (speech, writing, sign language)

Question 9

Higher order disorders of brain

Answer 9

• Lesions in ant. and pos. association cortices
  => Complex, subtle changes in sensory perception and motor functions (incl. language)

Broca’s (expressive) aphasia:
- Difficulty to construct language

Wernicke’s (receptive) aphasia:
- Cannot understand spoken words

Dyslexia:
- Cannot read and write (angular gyrus)

Apraxia:
- Disorders in high-level motor coordination (e.g. lesion in parietal and prefrontal cortex)

Agnosia:
- Lesions of pos. parietal lobe
=> Inability to recognise objects by touch or vision (neglect syndromes)

Question 10

Cortex: collective properties and EEG

Answer 10

• Tendency to synchronise neuron activities in cortex because of interconnection
  => Collective (emergent) properties
• Electroencephalogram (EEG): non-invasive, painless
  => Records activity of large population of cortical neurons simultaneously by macroelectrodes
• EEG patterns occur differentially in diff. cortical areas; vary dramatically with particular states of behaviour and sensory influences

Question 11

EEG and epilepsy

Answer 11

Normal vs. partial seizure vs. generalised seizure EEG

Epilepsy:
- Stereotyped and involuntary alterations in behaviour
- Simple jerking, convulsion, loss of consciousness
- ↓ synaptic inhibition through GABA
=> Cortical neurons firing simultaneously

• Drugs: ↓ excitability of cortical neurons
  e. g. inactivation of Na-channels; ↑ GABA transmission

Question 12

Depression

Answer 12

• Unpleasant mood, intense mental anguish, generalised loss of interest in world
• Disturbed sleep, diminished appetite…
• ↓ availability of biogenic amines (5-HT/NA/…) (?)

Drugs:

• Selective 5-HT reuptake blockers
• MAO inhibitors (↓ degradation of NT)