Cerebral Cortex & Limbic System Flashcards
What is the pre and post central gyrus?
Pre: primary motor cortex
Post: primary sensory cortex
What separates the 2 hemispheres of the cerebrum?
Longitudinal fissure
What separates the frontal and temporal lobes?
Lateral fissure
What is the central sulcus?
A deep sulcus running from one ear to the other separating the pre- and post-central gyrus
What are the regions that the cerebral cortex is arranged into with specific functions?
Brodmann Areas - based on cyto-architecture/histological structure of cortex
What are association areas?
Cortical areas outside the primary areas where high level processing for interpretation and integration occur of the primary functional areas
What is stereognosis?
Figuring out utilising all sensory systems but vision what is in hand i.e. using touch
What is an association area of the primary auditory cortex?
Superior temporal gyrus which allows you to recognise and understand sounds
What does the posterior parietal cortex do? What happens if its injured?
Integrates sensory inputs and controls perception of the contralateral body/environment
SO damage leads to hemispatial neglect (most commonly in R sided damage)
What does the medial occipital/temporal lobe allow us to recognise? What happens if it goes wrong?
Face, shape and colour
SO damage leads to prosopagnosia and achromatopsia
What can occur if there is damage to the primary visual cortex?
Inability to recognise objects when stationary
Associative agnosia
Apperceptive agnosia
What occurs if there is damage to the frontal eye field?
Eyes deviate towards damaged side
Define dysphasia/aphasia.
Defect in power of expression by speech or of comprehending spoken and written language - occur with damage to zone of aphasia/dysphagia (L-side) e.g. Broca’s, Wernicke’s, angular gyrus or 1o auditory cortex
Speech and language are normally ____ dominant functions.
Left-sided
What is Broca’s speech like?
Content correct but slow or missing words if lesioned as this area is responsible for speech motor
What is Wernicke’s speech like?
Receptive aphasia i.e. content incorrect (random words that dont make sense) but speech fluent if lesion leaves motor in tact but they dont know what they are saying is insensical because this area is for auditory and reading functions
What is angular gyrus lesion speech like?
Alexia/agraphia (inability to read/write)
What is primary auditory cortex lesion speech like?
Reduction of hearing sensitivity in both ears (mostly contralateral) and loss of stereo perception of sound origin
What cerebral artery supplies hearing/speech/language areas?
MCA
What is fasciculus?
Bundle of fibres sharing a similar function and route of travel e.g. arcuate fasciculus between Wernicke’s and Broca’s area
What is Broca and Wernicke’s area for?
Wernicke’s: understanding/interpreting head, spoken and written word
Broca’s: motor planning involved in speech to talk about it/talk back
What is the corpus callosum? What happens if its damaged?
Commissural fibres connecting the R and L hemispheres
So damage can disconnect hemispheres causing:
- Inability to name objects held in L hand with eyes closed as R side senses what L is feeling but language centre in L cant put it into words
- Inability to read via L half of visual fields (L half of visual field cannot be accessed by L eye)
How can arterial supply to the CNS be compromised?
Vessel occlusion via embolus or thrombus
ICA aneurysm (often at sites of arterial branching)
Haemorrhage due to burst aneurysm or vessel wall degeneration
Within ___ after an occlusion, you can go unconscious.
10 seconds
What are the 2 major vessels that supply the brain and brainstem?
- ICA (x2)
2. Vertebral arteries (x2)
How does the internal carotid arteries (ICA) get in to supply the brain?
Branch off common carotid arteries and enter skull via carotid canal wrapped in sympathetic plexus then supplying the majority of cerebral hemispheres and eye
How does the vertebral arteries get in to supply the brain?
Branches off subclavian arteries passing up the transverse foramen and entering skull via foramen magnum to then supply the cerebellum, proximal spinal cord and inferior/posterior cerebral hemisphere
What is the Circle of the Willis?
A circle of vessels at the base of the brain joining the ICA and vertebral supplies:
- 2 x vertebral arteries: basilar -> pontine -> PCA + posterior communicating
- ICA: MCA, ophthalmic + ACA and anterior communicating
What is beneficial about communicating vessels?
Act as potential routes for collateral if there is blockage elsewhere
If the posterior cerebral artery (PCA) passes over the tentorium cerebelli, what might raised ICP cause?
Compression of PCA so almost all the blood supply to a big chunk of the cerebellum and cerebral cortex will be disturbed
What arteries branch off of the anterior/middle cerebral arteries (ACA/MCA) to perfuse basal ganglia and thalamus areas?
Medial striate artery (from ACA)
Lateral striate artery (from MCA)
Other vessels too
What will infarction of the internal capsule (IC) cause?
Widespread contralateral symptoms of descending fibres (frontopontine, spinothalamic), motor (head, arm + leg), sensory and vision/hearing
What is the thalamic and choroid plexus blood supply?
Anterior choroidal artery (branch of ICA at CoW)
Posterior choroidal artery (branch of PCA at CoW)
What structures does the anterior choroidal artery supply?
Thalamus Choroid plexus Lateral geniculate body (vision) Posterior limb of IC Limbic system
What does the anterior cerebral artery supply (ACA)? What will occur if there is an infarction?
Supplies pre-central gyrus ~ face and arm region on contralateral side
Infarction would cause facial palsy with forehead sparing (CBT) and UMN symptoms of upper limbs on contralateral side (CST)
What does the middle cerebral artery (MCA)supply? What will occur if there is an infarction?
Zone of aphasia/dysphagia e.g. superior temporal gyrus (Wernicke’s area)
Infarction would affect speech on both sides causing receptive aphasia
What is the limbic system?
Many structures that form a ring (limbus) around the diencephalon (thalamus + hypothalamus) involved in sensations of emotions, visceral responses to emotion and memories
What is the limbic system composed of?
- Rim of cortex (hippocampus and insula)
- Subcortical nuclei (amygdala group, accumbens, septal + hypothalamic)
- Multiple input/output tracts
What connects to the limbic system to allow you to link smells to memory?
Olfactory bulb
What is the Papez Circuit?
Main part of limbic system giving us memory, associations and relevant emotions, made up of:
Cingulate gyrus -> hippocampus -> fornix -> mamillary bodies -> anterior thalamic nucleus -> radiates back up to cingulate gyrus
What is the hippocampus?
A structure involved in memory FORMATION, RECALL and also memories involving spatial/visual tasks + language (not procedural memory) located in the inferomedial temporal lobe (also has blood supply from PCA)
What happens if there is damage to the hippocampus?
Anterograde amnesia = no NEW memory formation but 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 e.g. writing, motor skills and language
What is Korsakoff’s psychosis?
Mamillary body deterioration and thalamic damage due/2ndary to thiamine (Vit B1) deficiency (metabolic damage) or alcohol abuse causing symptoms such as anterograde/retrograde amnesia, confabulation and hallucinations
What is Wernicke-Korsakoff syndrome?
Korsakoff’s psychosis with ataxia, opthalmoplegia and confusion/dementia
What is the cingulate gyrus? What is it made up of?
Cortical part of Papez Circuit involved in multiple functions and made up of:
- Anterior gyrus: autonomic area (cardiorespiratory, digestion + visceral response to emotion), bladder control + emotional modulation of pain
- Posterior gyrus: vocal area controlling appropriate sentence construction and memory/cognition
What is the amygdala?
Nuclear group with multiple inputs controlling multiple emotions, responses and systems embedded in inferior temporal lobe
How does the amygdala work?
- Multiple inputs/activators: visual, auditory, sensory from body, solitary tract, olfactory, limbic system + hypothalamic
- Multiple outputs: hypothalamus, hippocampus + multiple areas of cortex
- Brings about reaction of fear, anger, behavioural emotions, impulsivity + sexual behaviour/emotions
What are behavioural emotions involved in?
Recognising emotional content of faces
What is the solitary tract involved in?
CN VII and IX go into this tract and up to amygdala so taste can trigger a memory/emotion
What can stimulation of the amygdala cause?
Increased BP/HR Reduced saliva Increased GI motility Cause irritability Startle easily Increase muscle tension Pupil dilation
What can bilateral damage to the amygdala cause?
- Kluver-Bucy syndrome: docile, lack of fear/anger, increased appetite, hypersexual, excessive exploratory behaviour w/ mouth and hands, visual agnosia + memory disorders (lack of facial recognition)
- Overactive: anxiety, stress, anger?
What are the septal and accumbens nuclei involved in?
Pleasure (sexual/orgasm sensations)
Dopamine-activated reward centre (addiction)
Intense sense of wellbeing
What substances activate the septal and accumbens nuclei?
Amphetamine and cocaine
