Lecture 11 - ‘Higher’ cortical function

Question 1

describe the cerebral cortex

Answer 1

• Thin layer of grey matter
• Sitting on the superficial surface of the cerebral hemispheres
• 5-6mm thick
• Arranged in 6 cortical layers

Question 2

complex functions of the cerebral cortex

Answer 2

• Behaviours
• Thoughts
• Emotions

Question 3

Majority of inputs to the cortex:

Answer 3

• From the thalamus
• From other parts of the cortex
  
  • Recurrent feedback loops where cortex provides its own input – e.g. one thought leading to another
• Monamine neurones

Question 4

Majority of outputs from the cortex:

Answer 4

• Other cortical regions
• Pyramidal cells
  
  • Large neurones which send structures down to the:
    
    • basal ganglia
      
      • caudate putamen and pons
    • reticular formation and red nuclues
    • spinal cord, brainstem and cranial nerves

Question 5

Cortex is not homogenous

*

Answer 5

• Phrenologists believed that personality traits and tendencies to crime etc could be correlated with the size of bony prominence’s on the skull
  
  • Now discounted but early inspiration for cortical localisation

Question 6

Cortical localisation

Answer 6

• Various regions of the cortex have different functional properties
  
  • Demonstrated by strokes
• Different histological regions of the cortex

Question 7

Different functional regions of the cortex

Answer 7

Frontal

Parietal

Temporal

occipital

Question 8

location of the frontal lobe

Answer 8

anteriro to central sulcus

Question 9

Major functions of the frontal lobe

Answer 9

• Motor
  
  • Primary motor cortex
  • Motor homunculus
• Expression of speech (usually left hemisphere)
• Behavioural regulation/judgement
• Cognition
  
  • E.g. mathematical ability
• Eye movement
  
  • Region called frontal eye field
  • Projects down onto the brainstem and communicates with CN nuclei relevant to the eyes
• Continence
  
  • Paracentral lobule (near midline)- regulates micturition

Question 10

example of Behavioural regulation/judgement role of the frontal lobe

Answer 10

E.g. Phineas Gage story- iron rod went through frontal lobe. Became impulsive, alcoholic and violent behaviour significantly changed

Question 11

location of the parietal lobe

Answer 11

Posterior to central sulcus

Question 12

major functions of the parietal lobe

Answer 12

• Sensory
• Comprehension of speech (usually left hemisphere)
  
  • Wernicke’s area
• Body image (usually right)
• Awareness of external environment (attention)
  
  • Condition called Neglect – despite the fact pt has normal visual field, they can’t acknowledge the existent of one of half of their environment
• Calculation and writing
• Don’t forget visual pathways projecting through white matter
• Superior optic radiations pass through the parietal lobe

Question 13

what condition regarding awareness of external enbironemnt can occur if the parietal lobe is damaged

Answer 13

Neglect

Question 14

hemispatial neglect

Answer 14

Hemispatial neglect is a neuropsychological condition in which, after damage to one hemisphere of the brain is sustained, a deficit in attention to and awareness of one side of the field of vision is observed. It is defined by the inability of a person to process and perceive stimuli on one side of the body or environment, where that inability is not due to a lack of sensation.[1] Hemispatial neglect is very commonly contralateral to the damaged hemisphere, but instances of ipsilesional neglect (on the same side as the lesion) have been reported.

ie.

• despite the fact pt has normal visual field, they can’t acknowledge the existent of one of half of their environment

Question 15

which side of the brain is most responsible for comprehension of speech

Answer 15

left hemisphere in the wernickes area (parietal)

Question 16

temporal lobe located

Answer 16

inferior to synvian fissure

Question 17

major functions of the temporal lobe

Answer 17

• Sensory (relatively posterior)
  
  • Hearing- primary auditory cortex (superior)
  • Olfaction- primary olfactory cortex (inferior)
• Memory
  
  • Hippocampus sits deep in the temporal love e.g. factual memory
• Emotion
  
  • Thought olfactory centre (smell)is linked to emotional function
• Don’t forget visual pathways projecting through white matter
  
  • Inferior optic radiations pass through the temporal lobe

Question 18

location of the occpital lobe

Answer 18

posterior to the parietal and temporal lobes. Thus, it forms the caudal part of the brain

Question 19

major function of the occipital lobe

Answer 19

visual processing area of the brain. It is associated with visuospatial processing, distance and depth perception, color determination, object and face recognition, and memory formation

Question 20

cerebral dominance/lateralisation

Answer 20

Asymmetry in the functions of the left and right cerebral hemispheres

• Left hemisphere is dominant in 95% of people (think about how it controls the right hand)
• Right hemispheres attends to both halves of spaces but the left hemispheres only attends only to the right half of space
  
  • This links to Neglect disorder

Question 21

Left hemisphere

Answer 21

Sequential processing (processing which occurs in a serial fashion):

• Language
• Mathematic/logic

Question 22

Right hemisphere

Answer 22

Whole picture processing:

• Body image
• Visuospatial awareness
• Emotion
• Music

Question 23

the corpus callosum

Answer 23

Allows the left and right hemispheres to work together

A huge bundle of white matter connecting the two hemispheres. An early surgical treatment for severe epilepsy was to cut the corpus callosum to prevent seizure activity from propagating through the whole brain. This had some interesting neuropsychological consequences for those patients…

Question 24

language pathways are primarily dominant in the

Answer 24

left hemisphere

Question 25

important ares for correct processing of language

Answer 25

Brocas and Wernickes For most people, these areas are functional for language primarily in the left hemisphere.

Question 26

**Broca’s area** ​

Answer 26

* Inferior lateral portion (think face of homunculus) of **frontal** lobe * Production of speech (motor function) * Directs muscles to produce language

Question 27

**Wernicke’s area**

Answer 27

* Superior portion of **temporal** (some say parietal as well) lobe * Near primary auditory region * Interpretation of language (sensory) * Understanding of what is being said

Question 28

Brocas and Wernickes area are connected via

Answer 28

Arcuate fasciculus (green) - white matter pathway * Best though of as a unidirectional pathway (although is technically bilateral)

Question 29

**1) Pathway for repeating a heard word**

Answer 29

1. Word heard 2. Auditory info is processed in the cortex within the primary auditory cortex and then goes to Wernicke’s area- where it is interpreted and translated into language 3. Wernicke’s area then communicates with Broca’s’ area through the **arcuate fasciculus** 4. Broca’s area tells the cortex to produce pattern of muscle contractions which will produce the sound of the word that was previously heard 5. Impulse to primary motor cortex (PMC) area which drives the facial and laryngeal muscles, resulting in repetition of heard word

Question 30

**2) Pathway for speaking a written word**

Answer 30

1. When we read we use primary visual cortex in occipital lobe 2. Visual pattern sent from visual cortex to Wernicke’s area 3. Wernicke’s is then able to examine pattern as impulses and interpret pattern as a word 4. Wernicke’s then sends word via the arcuate fasciculus to Broca’s area 5. Broca’s area then instructs PMC to produce a pattern of muscular contraction in order to produce pattern of musculature contraction to produce the read word

Question 31

**3) Pathway for speaking a thought**

Answer 31

1. Thoughts can arise from many brain regions, but converges at Wernicke’s area 2. Wernicke’s interprets thought patterns and converts into language 3. Sends impulses to Broca’s via the arcuate fasciculus 4. Broca’s sends to PMC instructing to produce pattern of musculature contraction to be able to speak thought

Question 32

Damage specially to arcuate fasciculus results in patients not being able to

Answer 32

repeat the word read allowed a word speak a thought

Question 33

**Wernicke’s aphasia (fluent aphasia)**

Answer 33

A type of aphasia (language disorder after stroke) with poor comprehension. Speech is effortless, but the meaning is impaired. * Speech is very fluent and confident * Intact Broca’s * However what they say doesn’t make any sense at all * Cant understand questions being asked

Question 34

**Broca’s aphasi**

Answer 34

A type of aphasia characterized by partial loss of the ability to produce language (spoken, manual, or written), although comprehension generally remains intact * No problem with understanding questions being asked * Wernicke’s area intact * Frustration with trying to articulate answer * Hesitant and lots of pausing

Question 35

**Types of memory**

Answer 35

* Declarative * Nondeclarative * Stored in a different regions in the brain therefore differentially effected in different types of brain damage

Question 36

Declarative memory

Answer 36

* Explicit * Facts e.g. revising for an exam

Question 37

Nondeclarative memory

Answer 37

* Implicit * Motor skills * Emotions

Question 38

where are declarative memories stored

Answer 38

Hippocampus which sits in the temporal lobe of thecerebral cortex

Question 39

the hippocampus

Answer 39

* Called hippocampus due to its resemblance to a seahorse * Site of association receiving input from multiple regions of the brain * Visual * Auditory * Limbic (emotions) * Somatosensory * Through a reverberatory circuit between itself and the cerebral cortex, it is able to produce long term potentiation within the synapses of the cortex in order for us to lay down long term memories

Question 40

where are non declarative memories stored

Answer 40

in the cerebellum and basal ganglia

Question 41

**How are memories stored?**

Answer 41

* Short term memory (seconds to minutes) * Consolidation of STM to LTM depends on * Emotional cortex * Rehearsal * Association * Long term memory (up to a lifetime)

Question 42

**Neuroplasticity: molecular and cellular mechanisms of memory**

Answer 42

**Long term potentiation** * Presynaptic neurone grows more terminals which impinge on post synaptic neurone * Terminals will release more NT per given stimulus * More NTs receptors expressed within synapse