Cerebral Cortex Flashcards
Layers of brain
Molecular - superficial External granular External pyramidal Internal granular Internal pyramidal Multiform - deep
Regions of brain
52
By cytoarchitecture
Brodmann
Frontal lobe
Motor function Language Cognitive function Attention Memory
Parietal lobe
Sensation
Sensory of language
Spatial orientation and self perception
Occipital lobe
Visual
Temporal lobe
Auditory
Emotions
Memories
Limbic lobe
Amygdala, hippocampus, mamillary body, cingulate gyrus
Learning, memory, emotion, motivation and reward
Insular cortex
Deep within lateral fissure
Visceral sensation, autonomic control, interoception, auditory processing, visual vestibular integration
Internal structures
Grey matter - neuronal cell bodies and glial cells
White matter - Myelinated neuronal axons
White matter tracts
Connect cortical areas
Association fibres - same hemisphere
Commissural fibres - right and left hemisphere
Projection fibres - Cortex with lower brain structures
Association fibres
Superior longitudinal fasciculus - frontal and occipital
Arcuate fasciculus - frontal and temporal
Inferior longitudinal fasciculus - temporal and occipital
Uncinate fasciculus - frontal and temporal
Commissural fibres
Corpus callosum - surgically disconnected for intractable or untreatable epilepsy
Anterior commissure
Projection fibres
Afferent - toward cortex
Efferent - away from cortex
Radiate as corona radiata deeper to cortex
Converge through internal capsule between thalamus and basal ganaglia
Localisation of function
Primary cortices - function predictable, organised topographically, symmetrical
Secondary corices - function less predictable, not organised topographically, not symmetrical
Frontal lobe regions
Primary motor cortex - fine, precise, voluntary movement - provide descending signal to execute movements
Supplementary motor cortex - planning complex movements - internally cued
Premotor area - planning externally cued
Parietal lobe regions
Primary somatosensory - somatic sensation from receptors in body, fine touch, vibration, pain
Somatosensory association - interpret significance of sensory info, aware of self and space
Occipital lobe regions
Primary visual - process visual stimuli
Visual association - interpret visual input
Temporal lobe regions
Primary auditory - process auditory stimuli
Auditory association - interpret aduditory input
Other areas
Broca’s - produce speech
Wernicke’s - understanding language
Profrontal cortex - attention, social behaviour, decision making
Frontal lobe lesions
Changes in personality
Inappropriate behaviour
Parietal lobe lesions
e.g. lesion in right hemisphere
Contralateral neglect
Lack of awareness of self on left side
Lack of awareness of left side of extrapersonal space
Temporal lobe lesions
Leads to agnosia, inability to recognise
Could not form new memories - anterograde amnesia
Lesions to Broca’s or Wernicke’s areas
Broca’s area - Expressive aphasia – poor production of speech, comprehension intact
Wernicke’s area - Receptive aphasia – poor comprehension of speech, production is fine
Primary visual cortex lesion
blindness in the corresponding part of the visual field
Visual association lesion
deficits in interpretation of visual information e.g. prosopagnosia: inability to recognise familiar faces or learn new faces (face blindness)
Assessing cortical function – imaging
Positron emission tomography (PET) - blood flow directly to a brain region
Functional magnetic resonance imaging (fMRI) - amount of blood oxygen in a brain region
Electroencephalography (EEG) - Measures electrical signals produces by the brain
Magnetoencephalography – (MEG) - Measures magnetic signals produces by the brain
Assessing cortical function – brain stimulation
Transcranial magnetic stimulation (TMS) - assessthefunctionalintegrity of neural circuits, uses electromagnetic induction to stimulate neurons
Transcranial direct current stimulation (tDCS) - Uses low direct current over the scalp to increase or decrease neuronal firing rates
Assessing structure – imaging
Diffusion tensor imaging (DTI) - Based on diffusionof water molecules
DTI with tractography - 3D reconstruction to assess neural tracts
Multiple sclerosis
Autoimmune
Loss of myelin from neurons of CNS
MS symptoms
Blurred vision Fatigue Difficulty walking Paraesthesia Muscle stiffness
Peripheral nerve stimulation
Activation of motor axon cause muscle contraction (a twitch) recorded by EMG - M wave
Same stimulus may cause activation of sensory axons - travel to spinal cord and cause twitch - H reflex
Large stimulus cause activation to occur antidromatically - travel to spinal cord in opposite direction and cause motor neurons to activate - F wave
Total motor conduction time
Time from brain to muscle
PMCT = (M+F-1)/2 - -1 time taken for action potential to turn around
CMCT = TMCT-PMCT
In MS - TMCT decrease but PMCT normal
