Cerebral Cortex & Limbic System Flashcards
What parts of the brain are included/not included in the cerebrum?
Cerebrum = telencephalon so does not include thalamus, hypothalamus, cerebellum or brainstem
What meningeal structure lies within the longitudinal fissure?
Falx cerebri
What connects the two hemisphere of the brain and what type of fibres do they contain?
The two hemispheres are connected via the corpus callosum which contains commissural fibres
What are the different regions which the cerebral cortex can be divided into called? (Functional regions)
Brodmann Areas
What is the mapping of body region to specific cortical region called?
Somatotopy
What are the symptoms of a primary motor cortex lesion?
Injury leads to contralateral weakness/paralysis (UMN type)
What are the symptoms of a primary somatosensory cortex lesion?
Injury causes contralateral paraesthesia; can’t assess or perceive stimulus; astereognosis.
Can’t integrate information to understand what they’re holding.
What are the symptoms of a primary visual cortex lesion?
Injury causes visual field defects
What are the symptoms of a primary auditory cortex lesion?
Injury causes reduction in hearing acuity on contralateral side
What are the symptoms of a superior temporal gyrus lesion?
Injury leads to inability to recognise sounds eg. is it sound speech vs. a door opening?
What are the symptoms of a lesion in prefrontal cortex?
Injury can cause changes in emotional behaviour/processes; ‘flat’ personality; memory problems
What are the symptoms of a premotor & supplementary motor cortex lesion?
Injury leads to ideomotor apraxias (patient can’t act out a movement)
What does the posterior parietal cortex do?
The posterior parietal cortex integrates sensory inputs and controls perception of the contralateral body/environment
What can happen if the posterior parietal cortex is damaged?
Damage can cause hemispatial neglect, especially in right-sided damage.
Patients may:
-Ignore contralateral side of their body/world
-Walk into objects
-Experience contralateral astereognosis
Which areas of the brain do facial, shape and colour recognition involve?
Facial, shape and colour recognition involve association cortex in the medial occipital/temporal lobe
What is cerebral achromatopsia?
Inability to name/point to/match colours
What is prosopagnosia?
Inability to recognise faces
What can happen if there is damage to the frontal eye field?
Eye deviation towards damaged side
What is associative visual agnosia?
See object but do not recognise/distinguish
What is appercerptive visual agnosia?
Fail to perceive/see an object
What is dysphasia/aphasia?
Dysphasia/aphasia is a defect in power of expression by speech or of comprehending spoken and written language
Are speech and language normally right or left-sided functions?
Speech and language are normally left-sided dominant functions
What are the symptoms of a lesion in Broca’s area?
Expressive aphasia -
Content correct, but slow or missing words. Like trying to speak a language you’ve just started to learn.
What are the symptoms of a lesion in Wernicke’s area?
Receptive aphasia (both auditory and reading) Content incorrect, but speech fluent. Can speak fluently but it is nonsense but they don’t realise it’s nonsense.
What are the symptoms of a lesion in the Angular gyrus?
Alexia and agraphia (inability to read or write)
What are the symptoms of a lesion in 1st Auditory Cortex?
Reduction of hearing sensitivity in both ears (mostly contralateral) & loss of stereo perception of sound origin
What cerebral artery supplies hearing/speech/language areas? What other symptoms might a patient exhibit if this artery becomes blocked?
Middle Cerebral Artery.
Other symptoms of occlusion include:
- hemiparesis/hemiplegia of lower half of contralateral face
- Hemiparesis/hemiplegia of the contralateral upper and lower extremities
- Sensory loss of contralateral face, arm and leg
- Ataxia of contralateral extremities
- Speech impairments/aphasia
- Perceptual deficits: hemispatial neglect, anosognosia, apraxia
- Visual disorders: déviation conjuguée, a gaze preference towards the side of the lesion; contralateral homonymous hemianopsia
What do white matter association fibres do?
White matter association fibres between cortical areas enable complex functions to interlink
Define fasciculus
Fasciculus = bundle of fibres sharing a similar function and route of travel
What is damaged in conductive aphasia?
The arcuate fasciculus which connects Broca’s area to Wernicke’s area
What is conductive aphasia?
Patient can express themselves well and comprehend things well but will have difficulty repeating phrases.
What does Broca’s area do?
Motor planning involved in speech
What does Wernicke’s area do?
Understanding/interpreting heard, spoken and written word
What does Angular Gyrus do?
Understanding writing and letters
What causes split-brain symptoms?
Damage to corpus callosum
What are split-brain symptoms?
- Inability to name objects held in left hand.
- Inability to read left half of visual fields
Input pathways (somatosensory and visual) to right hemisphere still intact, but can’t transfer information to language area.
What things can disrupt blood supply to brain?
1) vessel occlusion (eg. thrombus or embolus)
2) Aneurysm (often at arterial branch points)
3) Haemorrhage (eg. trauma to vessel)
What are the 2 major blood vessels that supply the skull?
1) Internal Carotid Artery x2.
Branch of common carotid. Enters skull via carotid canal wrapped in sympathetic plexus. Supplies majority of cerebral hemispheres. Also supplies eye.
2) Vertebral Artery x2.
Branch of subclavian artery. Passes up within transverse foramina & enters skull via foramen magnum. Supplies brainstem, cerebellum, proximal spinal cord, inferior/posterior cerebral hemispheres.
Where in the Circle of Willis is aneurysm common?
At the two anastomoses: at anterior communicating artery and at posterior communicating artery. Most aneurysms (Berry aneurysms) occur at the junction of anterior cerebral artery and anterior communicating artery. Most common cause of non traumatic subarachnoid haemorrhage.
What blood vessel supplies the part of the cortex that controls the legs?
Anterior Cerebral Artery
What blood vessel supplies the part of the cortex that controls face and hands?
Middle cerebral artery
What does the anterior choroidal artery supply?
Choroid plexus, thalamus, optic tract, lateral geniculate body in thalamus, posterior limb of internal capsule, parts of limbic system
Does infarction of the brainstem cause UMN or LMN symptoms?
Infarction of the brainstem can cause a LMN lesion for the cranial nerves and an UMN lesion for the limbs and trunk.
What is the limbic system involved in?
Sensations of emotions, visceral responses to emotion, memory
Describe the Papez circuit
Hippocampus –> Fornix –> Mammillary bodies –> Anterior Thalamic Nucleus –> Cingulate gyrus –> radiates back to hippocampus…
What does the hippocampus do and where is it formed?
Hippocampus is involved in memory formation and recall. It is located in the inferomedial temporal lobe.
What can happen if there is damage to the hippocampus?
Anterograde amnesia. No new memory formation. Still able to recall long term memories.
What is declarative/explicit memory?
Recall of fact/event/knowledge (takes effort)
What is implicit/procedural memory?
Learned skills - writing, motor skills, language
What is Wernicke-Korsakoff syndrome and what causes it?
Metabolic damage/alcohol abuse. Mammillary and thalamic damage due to thiamine (vitamin B1) deficiency leading to Wernicke’s encephalopathy and Korsakoff syndrome.
What are the symptoms of Wernicke’s encephalopathy?
Ataxia, opthalmoplegia and confusion/dementia
What are the symptoms of Korsakoff syndrome?
- Anterograde amnesia and often retrograde amnesia.
- Confabulation - Patients insert fabricated ‘memories’ of long-term events into current conversation
- Hallucinations
What are the functions of the anterior cingulate gyrus?
- Autonomic area: Cardiorespiratory and digestion, visceral response to emotion
- Bladder control
- Emotional modulation of pain
What are the functions of the posterior cingulate gyrus?
- Vocal area controlling appropriate sentence construction
- Memory, cognition
Name some inputs to the amygdala
Visual and auditory, sensory from body, solitary tract, olfactory and limbic system, hypothalamic
Name some outputs of the amygdala
Hypothalamus, hippocampus, multiple areas of cortex
What emotional reactions can the amygdala bring?
Fear, anger, behavioural emotions (involved in recognising emotional content of faces), impulsivity, sexual behaviour & emotions
What physiological reactions can the amygdala bring?
- Increase BP/HR
- Reduce saliva
- Increase GI motility
- Cause irritability
- Startle easily
- Increase muscle tension
- Cause pupil dilation
What is Kluver-Bucy syndrome and what are it’s symptoms?
Bilateral damage to the amygdala.
- Docile, lack of fear/anger
- Increased appetite
- Hypersexual
- Excessive exploratory behaviour with mouth and hands
- Visual agnosia
- Memory disorders (lack of facial recognition)
What emotions can be caused by an overactive amygdala?
Anxiety/stress and anger
What do the septal and accumbent nuclei do?
Septal and accumbent nuclei are involves in dopamine-activated reward circuitry. Activated during sexual functions/orgasm, eating and anticipation of reward.
Which areas do amphetamine and cocaine activate?
Septal and accumbens nuclei. Addiction has been linked to modulation of this system.
