Cortical organisation and function Flashcards
what does the cerebral cortex cover?
entire surface of the brain
what does the cerebral cortex contain?
together with deep nuclei, contain grey matter
how is the cerebral cortex organised?
highly folded with gyri and sulci
organised into lobes
microscopically organised into layers and columns (1-VI)
classification based on cytoarchitecture (52 regions)
(1,2,3= primary somatosensory, 4= primary motor cortex)
what is cytoarchitecture?
cell size, spacing or packing density and layers
what are the lobes of the brain?
what are the functions of the frontal lobe?
regulation and initiation motor function
language
cognitive function (executive function- plans)
attention
memory
what are the functions of the parietal lobe?
- Sensation
- Sensory aspect of language
- Spatial orientation and self-perception
what are the functions of the occipital lobe?
visual input
what are the functions of the temporal lobe?
auditory information
emotions
memories
what anatomy is part of the limbic lobe?
amygdala
hippocampus
mamillary body
cingulate gyrus
what is the function of the limbic lobe?
concerned with learning, memory, emotion, motivation and reward
where is the insular cortex?
deep within the latral fissure
what are the functions of the insular cortex?
visual sensations
autonomic control
interoception
auditory processing
visual-vestibular integration
what is the internal structure of cortex?
grey matter
white matter
association fibres
projection fibres
commissural fibres
what is grey matter made up of?
neuronal cell bodies and glial cells
what is white matter made up of?
myelinated neuronal axons arranged in tracts
what does white matter do?
connect cortical areas using fibres
what are the fibres in the white matter?
association fibres
commissural fibres
projection fibres
what do association fibres connect?
areas within same hemisphere
what do commissural fibres connect?
homologous structure in left and right hemispheres
what do projection fibres connect?
connect cortex with lower brian structures (thalamus, brain stem, spinal cord)
what are the types of association fibres?
short fibres (u-fibres)
long fibres
what do short association fibres do?
connect adjacent cortical regions
what are the examples of long fibres?
- superior longitudinal fasciculus connect frontal and occipital lobes
- arcuate fasciculus- connects frontal and temporal lobes
- inferior longitudinal fasciculus- connects temporal and occipital lobes
- uncinate fasciculus- connects anterior frontal and temporal lobes
what are the direction of projection fibres?
afferent- toward cortex
efferent- away from cortex
where do projection fibres converge?
through internal capsule between thalamus and basal ganglia
what are the most prominent projection fibres?
corona radiata- deeper to cortex
what are the features of functions of primary cortices?
function predictable
organized topographically
symmetry between right and left
what are the features of function of secondary/association cortices?
function less predictable
not organised topographically
left-right symmetry absent/ weak
what are the motor cortices of the frontal lobe and their function?
what are the primary and association cortices of the parietal lobe and functions?
Primary somatosensory- processes somatic sensations arising from receptors in the body (fine touch, vibration, 2 point discrimination, proprioception, pain & temperature
Somatosensory association- interpret significance of sensory information (recognizing an object placed in the hand, awareness of self and personal space)
what are the processes of the occipital lobe anad its functions?
Primary visual-processes visual stimuli
Visual Association- gives meaning and interpretation of visual input
what are the cortices of the temporal lobe and their functions?
Primary auditory-processes auditory stimuli- topographically arranged
Auditory association-gives meaning and interpretation of auditory input.
what association area is responsible for the production of language?
Broca’s area
what association area is responsible for understanding of language?
Wernicke’s area
what are the functions of the prefrontal cortex?
attention
adjusting social behavior
planning
personality expression
decision making
what are the effects of frontal lobe lesions?
- Changes in personality
- Inappropriate behaviour
what are the effects of parietal lobe lesions?
- Contralateral neglect
- E.g. lesion in right hemisphere causes issues on left side
- Lack of awareness of self on left side
- Lack of awareness of left side of extra personal space (e.g. only put food on one side of plate)
what are the effects of temporal lobe lesions?
- Agnosia, inability to recognise
- Patient HM-bilateral resection anterior medial temporal lobe= anterograde amnesia. Cant form new memories
What are the effects of Broca’s area lesions?
- Expressive aphasia-poor production of speech, comprehension intact
what are the effects of Wernicke’s area lesions?
receptive aphasia- poor comprehension of speech, production is fine
what are the effects of primary visual cortex lesions?
Blindness in corresponding part of visual field
what are the effects of visual association lesions?
Deficits in interpretation of visual information
E.g. prosopagnosia (inability to recognise familiar faces or learn new faces-face blindness
what can be used to assess cortical function?
imaging
encephalography
brain stimulation
what imaging can be used to assess cortical function?
- Positron emission tomography (PET)- blood flow directly to brain region when asked to undertake a task
- Note involves radioactive isotopes so some risk in process
- Functional magnetic resonance imaging (fMRI)- amount of blood oxygen in a brain region when asked to undertake a task.
what is spatial resolution?
how detailed the level of individual cells vs tracts vs regions etc
what is temporal resolution?
how quickly are certain that things are changing
what is encephalography?
activity produced by regions
- Electroencephalography (EEG)- measures electrical signals produced by the brain
- Frequency for sleep disorders and epilepsy
- Magnetoencephalography (MEG)- measures magnetic signals produced by the brain
- Somatosensory evoked potentials-assess integrity of sensory pathway. Stimulus to median nerve via peripheral nerve and create a series of waves that reflect sequential activation of neural structures along the somatosensory pathway. Determine where relay of information disturbed
what are the types of brain stimulation?
transcranial magnetic stimulation (TMS)
transcranial direct current stimulation (tDCS)
what is TMS?
- Assess the functional integrity of neural circuits
- Uses electromagnetic induction to stimulate neurons
- Allows to interrogate pathway from beginning to end
- Carry out tasks and cause stimulation of brain interrupting ability to do activity or exciting regions of brain thus causing activity.
what is tDCS?
Uses low direct current over scalp to increase or decrease neuronal firing rates
how can structure of brain be assessed?
imaging
what imaging can be used to assess structure?
- Diffusion Tensor Imaging (DTI)- based on diffusion of water molecules
- DTI with tractography- 3D reconstruction to assess neural tracts
