8.1 Higher Cortical Function

Question 1

what are the main inputs and outputs of the cortex?

Answer 1

Most INPUTS are from thalamus and other cortical areas via recurrent feedback loops where the cortex provides its own input. Also from the reticular formation
Most OUTPUTS are from pyramidal cells and project to widespread areas

Question 2

what is the cerebral cortex?

Answer 2

Cerebral cortex is a thin layer of grey matter. On the superficial surface of the cerebral hemispheres 5-6mm thick. Most sophisticated part of the CNS. Very dense in neurones.

Question 3

what are pyramidal cells?

Answer 3

Pyramidal cells are large neurones that send long projections down to brain stem/basal ganglia and spinal cord. Carries motor information out. UMN in the primary motor cortex

Question 4

where are the frontal lobes?

Answer 4

sit anterior to the central sulcus. most anterior lobes of the brain

Question 5

what are the main functions of the frontal lobes?

Answer 5

eye movement (frontal eye fields)
motor (primary motor cortex)
expression of speech (usually left hemisphere)
behavioural regulation and judgement (pre-frontal regions)
cognition (math problems)
continence (paracentral lobes regulate micturiton

Question 6

describe how a frontal lobe lesion might present?

Answer 6

change in mood - inappropriate, impulsive and lack of control
complete loss of contralateral motor ability
brocas aphasia / expressive dysphasia
impulsive, disinhibited behaviours e.g. sexual
inappropriateness, aggression
urinary incontinence
difficulty in calculation / problem solving
problems with conjugate gaze (eyes not working well together, causes diplopia)

Question 7

what are the main functions of the parietal lobes?

Answer 7

sensory
comprehension of speech ( usually the left hemisphere)
body image (usually right)
awareness of external environment (attention)
calculation and writing
visual pathways project through the white matter (superior optic radiation)

Question 8

what is neglect?

Answer 8

patients have normal visual fields but dont acknowledge one half of their environment

Question 9

how might a patient with a lesion of the parietal lobe present?

Answer 9

wernicks aphasia / receptive dysphasia (left)
contralateral anaesthesia affecting all modalities
neglect (right)
contralateral homonymous inferior quadrantanopia
body dysmorphia (right)
decreased calculation ability

Question 10

what are the main functions of the temporal lobes?

Answer 10

hearing (primary auditory cortex)
olfaction (primary olfactory cortex)
memory
emotion
inferior optic radiation passes through white matter ( 3rd order visual fibres from the lateral geniculate ganglion to the occipital lobe

Question 11

where is the temporal lobe located?

Answer 11

sit inferior to the parietal lobe, beneath the sylvian fissure.

Question 12

how might a lesion of the temporal lobe present?

Answer 12

change in emotions / psychiatric disorders if damage to the limbic system structures
erratic behaviour as cannot regulate emotion
disruption of smell, taste, hearing (auditory hallucinations/ olfactory hallucinations)
loss of memory / amnesia
trigger memories / feeling of deja vu
contralateral homonymous superior quadrantanopia

Question 13

what is the fine structure of the cortex?

Answer 13

Arranged as 6 layers containing cell bodies and dendrites (i.e. cortex is
grey mater)

Question 14

what are the 3 different types of output fibres from the cortex?

Answer 14

• Outputs can be projection fibres going down to brainstem and cord (e.g. upper motor neurones)
• Outputs can be commissural fibres going between
  hemispheres (e.g. corpus callosum)
• Outputs can be association fibres connecting nearby regions of cortex in the same hemisphere (e.g. arcuate fasciculus)

Question 15

what is meant by cerebral dominance?

Answer 15

Some functions are represented more prominently in one hemisphere

Question 16

what is dysphasia?

Answer 16

Dysphasia is a partial or complete impairment of the ability to communicate resulting from brain injury.

Question 17

what functions is the left hemisphere usually dominant for?

Answer 17

In 95% of people, the left hemisphere is dominant for language and mathematical /logical functions

Question 18

what functions is the right hemisphere usually dominant for?

Answer 18

In 95% of people the right hemisphere is dominant for body image, visuospatial awareness, emotion and musical ability

Question 19

what is the function of the corpus callosum?

Answer 19

The corpus callosum allows the two hemispheres to communicate with one another, meaning we can be thought of as an ‘average’ of the two hemispheres

Question 20

what are some of the symptoms of damage to the corpus callosum?

Answer 20

speech and movement ataxias

alien hand syndrome

Question 21

where is brocas area?

Answer 21

in the infero-lateral frontal lobe, near the mouth/pharynx area of the primary motor cortex.

Question 22

what is the function of brocas area?

Answer 22

responsible for the production of speech

Question 23

what happens if there is damage to brocas area?

Answer 23

Damage can cause staccato speech, where the patient still understands what is being said to them (Broca’s / expressive dysphasia). difficulty speaking but retains comprehension.

Question 24

where is Wernicke’s area?

Answer 24

at the parieto-temporal junction near the primary auditory cortex in the temporal lobe

Question 25

what is the function of Wernicke’s area?

Answer 25

responsible for the comprehension of speech

Question 26

what occurs if there is damage to Wernicke’s area?

Answer 26

Damage can cause fluent, nonsensical speech where the patient does not appear to understand what is being said to them (Broca’s / receptive dysphasia). have poor comprehension.

Question 27

how can a large middle cerebral artery infarct influence verbal communication?

Answer 27

Large middle cerebral artery infarcts can cause am dense / global aphasia where both areas are destroyed leading to virtually no verbal language

Question 28

what is the arcuate fasciculus?

Answer 28

a white matter pathway connecting brocas area in the frontal lobe to wernickes area in the temporal lobe

Question 29

what occurs if there is damage to the arcuate fasciculus

Answer 29

results in the inability to repeat heard words

Question 30

what are the 4 different types of memory?

Answer 30

declarative / explicit - factual information that tends to be stored in cerebral cortex.
nondeclarative / implicit - motor skills, emotion, tends to be stored in the subcortical structures (basal ganglia) and cerebellum
short term memory - stored for seconds to minutes as a reverberation or echo in cortical circuits
long term memory - stored for long period in the cerebral cortex, cerebellum etc. for up to a lifetime following consolidation

Question 31

what is consolidation?

Answer 31

Converting short term memories into long term memories

Question 32

what factors influence consolidation?

Answer 32

o Emotional context (if an event has strong emotional
content, then it tends to be remembered better)
o Rehearsal (you are all familiar with this idea)
o Association (if you can associate a piece of knowledge with something you already know it tends to be more easily remembered)

Question 33

what structure consolidates declarative memories?

Answer 33

the hippocampus. It has a role as an ‘oscillator’, facilitating consolidation of memories in the cortex via its output pathways (primarily the fornix -> mammillary bodies-> thalamus -> cortex)

Question 34

where is the hippocampus?

Answer 34

The hippocampus sits deep in the temporal lobe (in fact, it is the rolled medial edge of the temporal lobe)

Question 35

what is long term potentiation?

Answer 35

The key molecular mechanism of memory consolidation
- Causes changes in glutamate receptors in synapses leading to
synaptic strengthening
- New physical connections can also form between neurones to further strengthen connections (axonal sprouting)

Question 36

damage to what area of the brain causes neglect?

Answer 36

Damage to the right parietal lobe results in failure to acknowledge the left half of the world. The right hemisphere ‘attends’ to both halves of space but the left hemisphere only ‘attends’ to the right half of space

Question 37

what is the pathway for repeating a heard word?

Answer 37

Auditory information is processed in the cortex within the primary auditory cortex within the temporal lobe.
Information travels to near by to wernickes area. Interprets the auditory information and begins understanding what the sound patterns mean. The wernicks area needs to communicate with Broca’s area if we are to repeat the word (arcuate fasciculus)
Broca’s area sends a set of impulses to the primary motor cortex. These impulses drive the facial and laryngeal muscles to contra t in the correct pattern to reproduce the sound. Results in repetition of a heard word.

Question 38

describe the pathway for speaking a written word

Answer 38

The visual cortex is located in the back of the occipital lobe. The visual pattern information corresponding to a word is sent from the occipital lobe to wernickes area. Wernicks area then examines the pattern of impulses from the visual system and interpret that pattern as language/ a word. Information is sent via an impulse carrying the word from the wernickes area to the Broca’s area along the arcuate fasciculus. Broca’s area communicates with the PMC to instruct it to produce the correct pattern of muscular contraction to produce the word that you have just read

Question 39

describe the pathway for speaking a thought

Answer 39

Thoughts can come from many areas of the Brain and be thought of as converging on the wernickes area. Thought is the collective function of the entirety of the cerebral cortex. Wernickes area interprets the information and converts the thought into language. Then communicates the information forward to the Broca’s area which communicates with the PMC to produce a series of contractions to speak the thought

Question 40

where is declarative memories stored?

Answer 40

stored in a distributive fashion in the cerebral cortex.

Question 41

where are non-declarative memories stored?

Answer 41

in the cerebellum and basal ganglia

Question 42

what occurs at the neuronal level in long term potentiation?

Answer 42

If there is increase in firing of a neurone there are some developments such as:
Presynatic neurones grow more terminals
Terminals release more neurotransmitter
More neurotransmitters expressed within the synapse
these help form stronger connections between the neurones.