Neuroanatomy final
Terms
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- Oldest part of cortex
- allocortex
- Most recently evolved part of cortex
- isocortex
- How many layers are in isocortex
- 6
- How many layers in meso and allocortex
- 3-5
- 2 major cell types of cortex
- pyramidal and non-pyramidal
- Describe pyramidal cells
- spiny, excitatory, contain glutamate, projection neurons, axons enter white matter
- Where do cells in deep layers project to?
- subcortical areas
- Where do cells in superficial layers project to
- other parts of cortex
- Where do cells in layer 6 project to?
- thalamus, mostly specific relay nuclei
- Where do cells in layer 5 project to?
- subcortical areas such as striatum, brainstem, spinal cord
- What function is common to layers 2 and 3?
- association projections - same hemisphere
- What layer projects across corpus callosum to the opposite hemisphere
- layer 3
- What projections are called homotopic
- projections that innervate same structure in the opposite hemisphere
- What projections are called heterotopic
- projections that innervate different structure at the opposite hemisphere
- Describe non pyramidal cells
- Axons project locally, do not enter white matter, mostly local circuit neurons or interneurons
- Stellate cell
- densely spinous interneuron, excitatory, uses glutamate
- Are most local circuit neurons excitatory or inhibitory
- inhibitory, use GABA as NT, smooth aspiny dendrites
- Categories of local circuit neurons
-
1. Main axons branching close to soma, so influence limited to cells in close vicinity
2.vertically projecting axons that can influence cells in layers above and below the interneuron
3. mainly horizontal projections, can influence cells in the distance but within the same layer - Give example of first category local circuit neurons
- Chandelier cell - axon resembles chandelier, synaptic targets of each terminal are segments of pyramidal cells
- Give example of second category local circuit neurons
- double bouquet, vertically directed axons target distal dendrites of pyramidal cells across layers
- Give example of third category local circuit neurons
- wide arbor and basket cells, axons maintain strong projections to pyramidal cells soma within same layer
- Where do excitatory inputs to pyramidal cells tend to terminate
- distally, must converge temporally and spatially to make pyramidal cells fire
- Where do inhibitory inputs to pyramidal cells tend to terminate
- proximally
- What is the main excitatory input ?
- from thalamus, terminate in layer 4 on stellate cells
- Where do monoamine inputs from reticular formation hypothalamus and basal forebrain terminate
- diffusely across many levels and regulate overall cell excitability
- What is the main premise for cortical regulation of complex behavior?
- It involves both parallel processing of separate stimulus features and hierarchial or serial processing of complex aspects of these features
- How does serial processing work?
- It involves projections of primary sensory regions to higher order areas devoted to single sensory modality, information is then routed to multimodal association cortices that receive convergent inut from other areas.
- What is ventral stream responsile for
- route of information from visual cortex to temporal lobe and is known as what pathway
- Which area of brain responsible for ability to recognize and describe objects?
- Temporal lobe specifically occipitotemporal cortex
- What is agnosia
- inability to place meaning onto object
- Prosopagnosia
- inability to recognize people by looking at their faces
- What is the location of the how pathway
- parieto-occipital cortex, responsible for telling how to manipulate an object and in locating objects in space
- Which part of the brain responsible for spatial cognition
- parietal lobe, not verbal ability, more developed in humans then in animals
- Describe Balints syndrome
- caused by damage to dorsolateral parieto-occipital cortex, triad of clinical conditions- simultanagnosia, optic ataxia and ocular apraxia
- Simultanagnosia
- inability to perceive parts of the visual field as a whole, probably due to inability to pay attention to more than one stimulus at a time
- Optic ataxia
- impaired ability to reach for or point to objects under visual guidance
- Ocular apraxia
- difficulty in voluntarily directing one's gaze toward objects in peripheral vision
- 2 major components of attention
-
1)global attention includes functions such as vigilance, concentration and generalized behavioral arousal
2) selective (directed) attention which involves focusing attention on a particular domain above others - What brain structures involved in attention
- brainstem reticular formation, diencephalic structures such as thalamus and hypothalamus, monoamines, higher order associational cortices especially parietal lobe
- Neglect
- condition in which person ignores sensory information that should be considered important, occurs most often in people who suffered from stroke to parietal lobe
- Why does neglect occur
- because parietal lobe is involved in ability to orient objects in space
- Why does damage to right parietal lobe induce neglect to greater extent then left parietal lobe?
- reason in lateralization, right side responsible for sensory information coming from left side and some from right side, left information only right side
- What is left hemisphere responsible for
- specialized for many specific functions such as language in addition to processing sensory inofrmation from the right side, so damage to left is compensated by right side
- How does right side of the brain process sensory information
- processes sensory information from the left side mainly but also some information from the right side
- Extinction
- neglect of information from one side of the body if it is presented simultaneously with a similar object on the other side of the body
- Functions of the frontal lobe
-
1.Restraint (inaility to curtail inappropriate behaviors)
2. Initiative (motivation to pursue positive and rewarding activities
3.order (ability to organize and sequence tasks) - Patient G.H
- suffered damage to right posterior parietal cortex, after surgical removal of the tissues had trouble copying drawings, solving puzzles and finding his way around town.
- Patient M.M
- had damage to left posterior parietal cortex, had difficulty in language, copying movements, reading, mathematics and generating names and objects.
- Anosognosia
- Subset of patients with right hemisphere damage are unaware of the fact that they have any damages
- What causes epilepsy
- abnormal brain activity in which neurons fire synchronously and then stop firing completley
- Name 3 main symptoms of epilepsy
-
1. person may have a feeling that seizure is about to begin
2. may lose consciousness or have amnesia for event
3. abnormal movements or loss of postural support - Evidence that right side of the brain responsible for recognizing faces
- faces made out of vegetables flashed to right hemisphere, faces recognized, if to the left hemisphere says that only vegetables/fruits
- Patient PS
- suffered epileptic seizures early in life, damage to left hemisphere, since he was young, right hemisphere developed some language ability. Underwent corpus callosum bisection, had different answers to questions depending on which part of brain asked
- Dementia
- deterioration of intellectual function and other cognitive skills, leading to a decline in ability to perform activities of daily living
- What are possible causes of dementia
- brain tumors, head injury, stroke
- Picks disease
- degeneration of fronral and temporal lobes, also called frontotemporal dementia
- Knife blade atrophy
- atrophy in Picks disease can become so severe that gyri become very thin, there is also degeneration in thalamus and basal ganglia
- What are the neuropathological hallmarks of disease
- Picks cells and inclusions (accumulations in the cytoplasm of cell) or Picks bodies
- Epidemiology of Picks disease
- very rare form of dementia, 1 of 100.000, age of onset between 40-60 (average 54), death 5-10 years after diagnosis
- Symptoms of Picks disease
- because of loss of frontal cortex, problems with executive functions (initiating, organizing, completing tasks), apathy, poor social judgement, aggression
- Vascular dementia
- 2nd most common, from problems with blood circulation in brain, affects men and women, 50-65 y.o. Biggest risk factor - hypertension, also smoking, high cholesterol, diabetes
- What is the most common type of vascular dementia?
- multi-infarct dementia, caused by TIA, symptoms - weakness of limbs, slurred speech, dizziness, do not last more then 20 min
- What feature distinguishes vascular dementia
- step-wise progression
- Is there treatment for vascular dementia
- no, therapy to prevent subsequent strokes, find underlying reason
- What is the most common type of dementia
- Alzheimers
- Most important risk factor of AD
- age
- Neuropathological findings of AD
- plaques and tangles
- How are plaques formed
- abnormal cleavage of amyloid precursor protein, in neurons made up of 695 amino acids
- Name 3 secretases involved in cleavage of amyloid-beta
-
1. alpha secretase cleaves amyloid beta between amino acids 16 and 17
2. beta secretase - cleaves N terminal portion
3. gamma secretase cleaves Cterm portion - What normally happens to amyloid beta
- cleared away by microglia and enzymes
- How do tangles form in AD
- hyperphosphorylation of protein tau, which normally plays role providing structure for neurons
- Where do tangles form
- start forming in entorhinal cortex, spread through hippocampus, temporal cortex and frontal cortex
- Braak scoring system
- scoring system to assess severity of AD based on tangles location
- What type of problems patients with AD have
- episodic memory first, then STM, semantic dementia and procedural memory, in end stage lose reasoning, language, attention
- Is there treatment for AD
- no, there is no treatment, 2 common drugs - acetylcholine esterase inhibitor and NMDA receptor antagonist
- Pittsburgh compound B
- will hopefully lead to improvement in early diagnosis and treatment, radioactive compound that binds to amyloid beta. Patients are injected with that and undergo PET scan, enables to see levels of amyloid beta in vivo and start treatment.