Cerebral Cortex Flashcards
What is the cerebral cortex responsible for?
the qualities that distinguish humans from other animals
How does the cerebral cortex fit within the volume of the brain?
it has many folds i.e. gyri and sulci
What is the primary excitatory cell type of the cerebral cortex?
pyramidal neurons
What is the neurotransmitter of pyramidal neurons?
glutamate
Where do small and medium pyramidal cells project to?
areas of the ipsilateral cortex
Where do large and giant pyramidal cells project to?
ipsilateral and contralateral cortex subcortical areas, brainstem and spinal cord
What is the neurotransmitter for non-pyramidal neurons?
GABA
What does layer III of the cerebral cortex contain?
medium pyramidal cells whose axons project to the ipsilateral cortex
What is layer IV of the cerebral cortex?
the major input layer that receives input from the thalamus
What is layer V of the cerebral cortex?
the major output layer that contains medium, large and giant pyramidal cells
What does each vertical column contain?
about 200 neurons that form functional units
How many Brodmann areas are there?
52
What do short association fibres do?
connect adjacent gyri within one hemisphere
What do long association fibres do?
connect different cortical regions within one hemisphere e.g. arcuate fasciculus
What does the corpus callosum do?
connect homologous regions of the two hemispheres
What do projection fibres do?
connect the cerebral cortex with the subcortical brainstem and spinal cord regions
What are corticopetal fibres?
input fibres that run towards the cerebral cortex
What are corticofugal fibres?
output fibres that exit the cerebral cortex
When may aminergic axons be altered?
in psychiatric disorders
Where is the primary visual cortex (area 17)?
on both sides of the calcarine sulcus, on the medial aspect of the occipital lobe
Where does the primary visual cortex receive visual information from?
the contralateral visual field
What does stimulation of the primary visual cortex cause?
crude sensations of bright flashes of light
What would damage to the primary visual cortex result in?
loss of vision in the contralateral visual field
What are the occipital visual areas (18 and 19) responsible for?
the “what” stream of visual processing
What do the occipital visual areas do?
interpret the visual impulses that reach the primary visual cortex (area 17)
What is agnosia?
the inability to recognise things even though one sees them
What does stimulation of the occipital visual areas cause?
hallucination of formed images
What does damage to the occipital visual areas cause?
visual agnosia
Where is the primary auditory cortex?
on the superior part of the temporal lobe, in areas 41 and 42 called Heschl’s gyri
What is the function of the primary auditory cortex?
hearing
What does stimulation of the primary auditory cortex cause?
tinnitus
What does damage to the primary auditory cortex cause?
slight hearing loss
Where is the auditory association area (Wernicke’s speech area)?
beind the primary auditory cortex in the dominant hemisphere (left superior temporal lobe) area 22
What happens if the auditory association (Wernicke’s) area is damaged?
word deafness or auditory aphasia i.e. the patient can hear what is being said without knowing what it means
Where is the primary somatosensory cortex?
on the postcentral gyrus of the parietal lobe (areas 1, 2 and 3)
What does the superior parietal lobe (areas 5 and 7) have reciprocal connexions with?
the primary somatosensory cortex and the dorsal tier of lateral thalamic nuclei
What is the superior parietal lobe concerned with?
discriminative aspects of sensation, such as the qualities of shape, roughness, size and texture and also in remembering the positions of objects in space
What could a lesion in the superior parietal lobe cause?
- inability to identify familiar objects manually (tactile agnosia)
- unawareness of the side of the body opposite to the lesion
What does damage to the inferior parietal lobe (areas 39 and 40) cause?
word-blindness (alexia) and inability to copy (agraphia)
What is sensory aphasia?
the inability to understand written and spoken language
Where is the primary motor cortex and what is it responsible for?
in the pre central gyrus (area 4) of the frontal lobe concerned with initiating voluntary movements
What does stimulation of the primary motor cortex cause?
discrete and isolated movement limited to a single joint or muscle
What does damage of the primary motor cortex lead to?
- upper motor neuron lesion
- contralateral side of the body being affected
- initial hypotonia, hyporeflexia or flaccid paralysis followed by chronic hyperreflexia and spasticity
- Babinski sign (extension of the big toe)
What is the premotor area?
area 6 associated with area 4 to help with voluntary movements
Where is Broca’s area (area 44 and 45)?
on the inferior frontal gyrus in the triangular and opercula regions
What can damage to Broca’s area cause?
the individual being unable to talk, even though the vocal muscles are not paralysed; the patient knows what they want to say but all that comes out is garbled sound, or one word repeated over and over again
What is the frontal eyefield (area 8) concerned with?
the voluntary conjugate movements of both eyes
What does stimulation of the frontal eyefield cause?
deviation of both eyes to the contralateral side
What does damage of the frontal eyefield cause?
deviation of both eyes to the ipsilateral side
What are functions of the prefrontal cortex?
- motor planning
- planning for the future
- language production
- holding memory
What can damage to the prefrontal cortex lead to?
- changes in mood, behaviour and personality
- individual neglecting their appearance, laughs or cries inappropriately and demonstrates no appreciation of social norms
What is the dominant hemisphere dominant for?
language
What is the non-dominant hemisphere responsible for?
the appreciation of spatial dimensions, totality of a scene (including recognition of faces) and nonverbal symbolism
What does the right temporal lobe do?
store tone memories
What can damage to the parietal lobe lead to?
hemi-neglect syndrome; reduced awareness of stimuli on one side of space, even though there may be no sensory loss
