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Neuroanatomy final


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Oldest part of cortex
Most recently evolved part of cortex
How many layers are in isocortex
How many layers in meso and allocortex
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
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
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
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
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
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.
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
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
Most important risk factor of AD
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.

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