Cortical Organisation and Function Flashcards
What is the cerebral cortex?
Covers entire surface of the brain
Together with deep nuclei, contains grey matter
Highly folded with gyri and sulci
Organised into lobes
What are the layers of the cerebral cortex?
Molecular layer (I) External granular layer (II) External parietal layer (III) Internal granular layer (IV) Internal pyramidal layer (V) Multiform layer (VI)
How is the brain classified?
It classified based on cytoarchitecture (cell size, spacing or packing density and layers)
What is the role of the frontal lobe?
Regulating and initiating motor function Language Cognitive function (executive function [e.g. planning]) Attention Memory
What is the role of the parietal lobe?
Sensation - touch, pain
sensory aspects of language
spatial orientation and self-perception
What is the role of the occipital lobe?
processing visual information
What is the role of the temporal lobe?
Processing auditory information
Emotions
Memories
What is in the limbic lobe?
Includes the amygdala, hippocampus, mamillary body, and cingulate gyrus
What is the role of the limbic lobe?
Concerned with learning, memory, emotion, motivation and reward
Where is the insular cortex found?
Deep within the lateral fissure
What is the role of the insular cortex?
Concerned with visceral sensations, autonomic control, and interoception, auditory processing, visual-vestibular integration (related to motion suckness)
What is grey matter?
neuronal cell bodies and glial cells – around 85 billion of each
What is white matter?
Myelinated neuronal axons arranged in tracts
What is the role of white matter tracts and what are the 3 different fibres?
Connect cortical areas:
Association fibers
Commissural fibres
Projection fibres
What is the role of association fibres?
connect areas within the same hemisphere
What is the role of commissural fibres?
Connect homologous structure in left and right hemispheres
What is the role of projection fibres?
connect cortex with lower brain structures (e.g. thalamus, brain stem and spinal cord)
What are the different types of association fibers?
Short fibres
Long fibres
Superior Longitudinal Fasciculus connects 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 different types of commissural fibres?
Corpus callosum
Anterior commissure
What are the different types of projection fibres?
Afferent- towards cortex
Efferent- away from cortex
Deeper to cortex radiate as corona radiata
Converge through internal capsule between thalamus and basal ganglia
What are features of primary corticies?
Function predictable Organised topographically (parts of body controlled by particular parts of brain like homunculus) Symmetry between left and right
What are features of secondary/association cortices?
Function less predictable
Not organized topographically
Left-right symmetry weak or absent
What is the role of the primary motor area?
controls fine, discrete, precise voluntary movements.
Provides descending signals to execute movements.
What is the role of the supplementary motor area?
Involved in planning complex movements (e.g. internally cued)
What is the role of the premotor area?
involved in planning movements (e.g. externally cued)
What is the role of the primary somatosensory area?
processes somatic sensations arising from receptors in the body (e.g. fine touch, vibration, two-point discrimination, proprioception, pain and temperature.
What is somatosensory association?
Interpret significance of sensory information, e.g. recognizing an object placed in the hand.
Awareness of self and awareness of personal space
What is the role of the primary visual area?
Process visual stimuli
What is the role of the visual association?
Gives meaning and interpretation of visual input
What is the role of the primary auditory area?
Process auditory stimuli
What is the role of the auditory association?
Gives meaning and interpretation of auditory input
What is the role of Broca’s area?
Production of language
What is the role of Wernicke’s area?
Understanding of language
What is the role of the prefrontal cortex?
Attention Adjusting social behavior Planning Personality expression Decision making
What is the consequence of frontal lobe lesions?
Changes in personality
Inappropriate behavior
What is the consequence of parietal lobe lesions?
e.g. Lesion in the right hemisphere:
Contralateral neglect
Lack of awareness of self on left side
Lack of awareness on left side of extrapersonal space
What are consequences of temporal lobe lesions?
Agnosia and inability to recognise
What are consequences of a lesion to Broca’s area?
Expressive aphasia – poor production of speech, comprehension intact
What are consequences of a lesion to Wernicke’s area?
Receptive aphasia – poor comprehension of speech, production is fine
What are consequences of a lesion to the primary visual cortex?
blindness in the corresponding part of the visual field
What are consequences of a lesion to the visual association?
deficits in interpretation of visual information e.g. prosopagnosia: inability to recognise familiar faces or learn new faces (face blindness)
What are different imaging techniques we can sue to assess cortical function?
Positron emission tomography (PET)- looks at blood flow directly to brain region (tells you what brain is using during task)
Functional magnetic resonance imaging- looks at amount of blood oxygen in brain region
How is encephalography carried out?
Use of:
Visual evoked potentials
Event-related potentials/ evoked potentials
A large stimulus is needed to see any traces. An average of these traces are then taken to show waves
These signal differences can show you where there may be a problem on the path
By using somatosensory evoked potentials we can look at: somatosensory activity, thalamic activity, mid cervical cord activity and impulses arriving at shoulder
A series of waves that reflect sequential activation of neural structures along the somatosensory pathways is produced
What encephalography techniques can be used to assess cortical function?
Electroencephalography (EEG)- measures electrical signals produced by the brain (looks at things such. as seizure activity or sleep disturbances)
Magnetoencephalography (MEG)- measures magnetic signals produced by the brain (immobile and expensive)
What brain stimulation techniques can be used to assess cortical function?
Transcranial magnetic stimulation (TMS)- Asses functional integrity of neural circuits. Uses EM induction to stimulate neurons
Transcranial direct current stimulation (tDCS): Uses low direct current over the scalp to increase or decrease neuronal firing rates
What imaging techniques can be used to asses structure??
Diffusion tensor imaging (DTI): Based on diffusion of water molecules
DTI with tractography: 3D reconstruction to assess neural tracts
