Session 11 - Higher functions of the brain Flashcards
What are the cortical associations areas?
The association areas make up 70 – 80% of the surface of the cortex. These regions receive, integrate and analyse signals from multiple cortical and subcortical regions and their output produces the complex human behaviours which make up our individuality.
How do gyri and adjacent lobes of the cortex exchange information?
through short-range fibres called Arcuate Fibres.
Give four occiptofrontal connections
o Superior Longitudinal Fasciculus
o Arcuate Fasciculus (Wernicke’s Broca’s area – see below)
o Uncinate Fasciculus
o Cingulum
How thin is the cortex?
The cortex is thin (2-4mm thick), but has lots of convolutions to increase surface area.
What are the six hitological areas of the cortex?
I. Cortical Association Areas II. Cortical Association Areas III. Cortical Association Areas IV. Inputs Motor and sensory cortex Thalamus Brainstem V. Outputs VI. Outputs Hippocampus Basal Ganglia Cerebellum Thalamus
What occurs in the frontal lobe? (7)
Dominant hemisphere (normally the left) o Higher intellect o Personality o Mood o Social conduct o Language o Broca’s area o Motor cortex (primary function)
What occurs in frontal lobe lesions (2)
o Personality and behavioural changes
o Inability to solve problems
What four things occur in parietal lobe (3 in dominant, 1 in non-dominant)
Dominant Hemisphere
o Language
o Calculation
o Primary somatosensory (auditory signals)
Non-Dominant Hemisphere
o Visiospatial function (Shapes and images)
What occurs in parietal lobe lesions?
o Attention deficits
o Contralateral Neglect Syndrome
Right hemisphere damage
Don’t notice things on the left hand side
Hair not brushed on left hand side
Don’t notice food on left side of plate
When asked to draw a clock only draw 1-6 or cram all numbers into the right hand side
What occurs in the temporal lobe (3)
o Memory
o Language
o Contains Wernicke’s Area
o Primary Auditory
What occurs in temporal lobe lesions?
o Recognition deficits (Agnosias)
E.g. Prosognosia – Failure to recognise faces
What is occipital lobe?
Primary visual
What occurs in occipital lobe lesions
Vision loss
What do global lesions cause?
Dementia
How is speech and language organised?
Input - Wernicke’s Area
Output - Broca’s Area
What three things occur in wernicke’s area?
Primary Auditory Cortex
Primary Visual Cortex
Interpretation of written and spoken words`
What two things occur in brocas area?
Formulation of language components
Sends information to motor cortex
Where is language lateralised?
Left hemisphere
What is Wernicke’s aphasia? 3
o Disorder of comprehension
o Fluent, but unintelligible speech (Jargon aphasia)
o Loss of mathematical skills
What is Broca’s Aphasia?3
o Poorly constructed sentences
o Dis-jointed speech
o Comprehension fine
What is the dominant hemisphere of most people?
o 95% Left Hemisphere
What does the dominant hemisphere do? 5
o Processes information in sequence o Language Spoken/Heard Written/Read Gestured/Seen (Deaf person can lose ability to use sign language) o Maths o Logic o Motor skills (Most people R. Handed)
What does non-dominant hemisphere do? 5
o Looks at the whole picture o Emotion of language o Music/Art o Visiospatial Recognition of shapes o Body awareness
What are the main connections between hemispheres?
o Corpus Callosum (Anterior Commissure)
Lesion greats two separate conscious portions – the dominant side could elicit a response from written word without non-dominant knowing why
What are memories a consequence of?
Neuronal plasticity
Where is memory stored?
Throughout cortex in appropriate areas
What are two types of memory?
Procedural and declarative memory
What does declarative memory do?
What’s your name/age?
Where do you come from?
What is procedural memory?
Tying shoelaces
Riding a bike
Give two temporal categories of memory
Short Term Memory
o Seconds to minutes
o Working memory
Long Term Memory
o Up to a lifetime
o Consolidation of short term memory
What four factors mean a short term memory enters long term memory?
Emotion
Rehearsal
Association
Automatic memory
What receptors have a role in synaptic plasticity?
Glutamate receptors
Outline the process of long term potenitation
o Activation of NMDA receptors and mGluRs can lead to up regulation of AMPA
o Strong, high frequency stimulation can cause Long Term Potentiation (LTP)
This is thought to be the basis of long time synapse strengthening and learning
What is long term depression?
Opposite of LTP, weakening of infrequently used synapses. E.g. what did you have for lunch a month ago?
How is memory formed (4 steps)
- Information from senses, e.g. auditory, visual passes to cortical sensory areas
- Information passes to Amygdala and Hippocampus
Forms memories
Does not store or find memories
Destruction of Hippocampus cause Anterograde Amnesia – failure to form new memories - Thalamus, Hypothalamus, Basal forebrain
- Pre-Frontal Cortex
Finds formed memories
When does memory function peak?
Age 25
How many individuals over 85 have alzheimers?
50%
What is anterograde amnesia?
Failure to form new memories
Give 6 causes of anterograde amnesia
Vascular interruption Tumours Trauma Infections Vitamin B1 deficiency (Korsakoff’s syndrome – Chronic alcohol abuse) Destruction of the Hypothalamus
What is retrograde amnesia and what is a cause?
Failure to retrieve old memories
Alzheimer’s Disease
What causes transient global amnesia?
TIA
What two things can cortex be broken down into?
o The Behavioural Cortex (Anterior to Central Sulcus)
o The Sensory Cortex (Posterior to Central Sulcus)
Give six causes of damage between areas of the brain?
o Trauma o Stroke o Deprivation of metabolism substrates o E.g. CO inhalation o Neurotransmitter synthesis and release o E.g. Parkinson’s Disease o Degeneration of Neurones o Congenital failures
Describe strokes effcting primary motor cortical strips (precentral gyri)
o Impairment is proportional to the size of lesion
o Impairments are directly related to the ischaemic parts of the motor homunculus
What does infarct of anterior cerebral artery cause?
Leg
What does infarct of middle cerebral artery cause in terms of paralysis
The rest of the body
What does a stroke affecting sensory cortical strips cause
o Lesions caused by ischaemia
o Impairment is proportional to size of lesion
o Impairments are directly related to the ischaemic parts of the sensory homunculus
What type of infarct damages sensory cortical strips?
MCA
Define dementia
Dementia is an acquired loss of cognitive ability sufficiently severe to interfere with daily function and quality of life.
Give three overarching causes of dementia
Direct neuronal damage
Age related brain tissue degeneration
Vascular damage to brain tissue
Outline the prevalence of dementia
o Prevalence is age specific
1% of dementia cases below 60 years old
30-50% of dementia cases by 85 years old
What is presenile dementia
<65 years
Give four causes of age related brain tissue degeneration
o Alzhiemer’s Disease
o Pick’s Disease
o Huntington’s
o Parkinson’s
Give four other causes of dementia
o Infection Creutzfeldt-Jakob Disease (CJD) HIV Infection Viral encephalitis o Metabolic Hepatic, Thyroid or Parathyroid Disease Cushing’s Syndrome o Nutritional Thiamine, B12 or Folate deficiency o Tumour E.g. Subfrontal meningioma o Chronic Inflammatory Vasculitis Multiple Sclerosis o Trauma Head injury o Hydrocephalus
What is cortical dementia?
o Global-type personality changes in suffers
o Complex disabilities
What is the extreme presentation of anterior cortical dementa?
o Frontal lobe / Premotor Cortex
o Behavioural changes, loss of inhibition, antisocial behaviour, irresponsibility
o Huntington’s Chorea
o Metabolic Disease
What is the extreme presentation of posterior cortiacal dementia?
o Parietal and Temporal lobes
o Disturbances of memory and language
o No marked changes in behaviour or personality
o Alzheimer’s Disease
What occurs in subcortical dementia?
o Slowness and forgetfulness
o Gross changes in movement
o Increase in muscle tone
Give three early features of dementia
Loss of memory of recent events
Global disruption of personality
Gradual development of abnormal behaviour
Give three intermediate features of dementia
Loss of intellect
Mood changes, blunting of emotions
Cognitive impairment with failure to learn
Give three late features of dementia
Reduction in self-care
Restless wandering
Incontinence
What causes ventriculomegaly in dementia?
Cortical atrophy
CSF pressure normal
