Exam Neurobiology I
Automne 2013 (January 2014)
All sentences are true or false.
1 Central Visual pathway
The formation of ocular dominance columns during cortex development is independent from
spontaneous retinal activity.
In the Lateral Geniculate Nucleus, cells in the Magno (M) & Parvo (P) pathways process different
stimulus feature: P cells are sensitive to colours and spatial frequency, whereas M cells respond to
luminance contrast and temporal frequency.
In monoculary deprived cats, the vast majority of cortical neurones respond to the open eye only,
whereas the ocular dominance histogram obtained from binocularly deprived resembles that of
normal animal. These results reflect competition between right and left eyes.
In cat primary visual cortex, neurones have orientation selectivity but there is no discernible local
structure; neighbouring neurones often respond to different orientations.
2 Neuronal and glia phenotypes
The Nissil staining could reveal the specific cytoarchitectonic organization of brain areas.
The Golgi staining could visualize the entire dendritic arborisation of a neuron.
Immunocytochemistry reveals the distribution of a tissue constituent in situ by detecting specific
antibody-antigen interaction where the antibody has been tagged with a visible label.
In situ hybridation is a molecular biology technic that can specifically label protein and peptides on
tissue section.
The term cytoarchitecture refers to the arrangement of dendritic arbors in the cerebral cortex.
Retrograde tracing is based on the membrane diffusion of tracing molecule.
3 Cells migration in cortical development
Radial glia is the Central Nervous System stem cell that can give rise to pyramidal neurones, GABA
neurones and glia cells.
Protrusion such as filapodia and lamellipodia can be stabilized by cadherin-mediated adhesion to the
extracellular matrix.
Loss of semaphoring signalling may perturb the migration of GABA interneurons in the cortex.
Reelin secreted by striatal neurones establish a permissive corridor and regulates the tangential
migration of GABA neurones.
4 Embryonic neurogenesis
The self-organization optic-cup morphogenesis in 3D culture of mouse embryonic stem cells has
revealed that the lens is required for the formation of the eye cup.
Myosin inhibitors may help to figure out the mechanism that underlies optic-cup folding.
Experiments have shown that the Wnt signalling pathway is required for the development of both
the Retinal Pigmented epithelium and the Neuroretina.
Formation of the optic stalk though wich Retinal Ganglion axons (i.e. optic nerves) can grow involved
a secondary folding and fusion of the ventral regions of the optic vesicle. This movement does not
occur in the self-organizing optic-cup morphogenesis in 3D culture of mouse embryonic stem cells.
5 Axon growth, pathfinding and cell-cell recognition
In the rodent cortex areal patterning of thalamic axons is initiated at birth.
Thalamocortical patterning involves the sorting of rostral versus caudal thalamic axons at subpalliumpallium border.
Migrating interneurons can guide the growth of thalamo-cortical axons by secreting chemoattractive
cues.
Glutamate and serotonin are both involved in the proper segregation of thalamocortical axon in layer
4 of the barrel cortex.
6 Organisation of functional system
The neocortex is an evolutionary ancient forebrain structure.
The neural tube forms by invagination of the mesodermal tissue.
Neocortical interneurons in layers 2/3 mostly have long projection to the opposite hemisphere.
Dorsoventral patterning of the neural tube specifies motor and sensory progenitor domains in the
spinal cord.
7 Synaptic network and critical periods
A synapse can act as an anchor point during dendritic and axonal development.
An excitatory or inhibitory synapse can after be distinguished at ultrastuctural level: excitatory are
asymmetric whereas inhibitory are usually symmetric.
In the binocular visual cortex of adults cats the contralateral eye usually activate more cells than the
ipsilateral eye.
The role of inhibitory neurones in network function and plasticity is negligible during critical period.
8 Control visual pathways
The on and off retinal ganglionic cells are best responding to light spot.
Cat reared with artificial strabism: 1 eye was surgically deflected, such that visual stimuli activated
different topographic positions on each eye. This experiment lead to the disappearance of binocular
neuron outside the layer 4 on the primary visual cortex.
The primary visual cortex has both monocular and binocular neurones.
The fact that cortical neurons are responding to light bars indicate that they are stimulated by
neighbouring retinal ganglionic cells.
9 Basal ganglia
In Parkinson’s disease, rigidity and bradykinesia are associated with an increase in beta activity in the
GPi.
In Parkinson’s disease, rigidity and bradykinesia are associated withan enhanced drive of the direct
pathway upon motor cortex.
The striatum, composed of caudate neurones and putamen, is the main imput of the basal ganglia
and is exclusively involved in motor function.
The striatum, composed of caudate neurones and putamen contains not only dopaminergic but also
cholinergic, glutaminergic and GABAergic neurones.
10 Adult neurogenesis and brain repair
Adult neurogenesis in the brain is restricted to the neocortex and the hypothalamus.
Embryonic stem cells lines can be grown indefinitely in vitro if the correct conditions are met.
Following an injury of fibres tracts in the spinal cord, blocking NOGO signalling would improve axonal
regeneration.
Following an injury in the CNS, transplantation of Schwann cell in the lesion site could improve
axonal regeneration.
11 Coding olfaction information
A lesion of the vomeronasal organ disrupts the response to alarm pheromone.
A knockout mouse of the Trpc2 gene is completely anosmic.
Olfactory sensory neurones express several odorant receptors genes, allowing a combinatorial code.
The number of olfactory bulb glomeruli activated by an odorant is constant when the odorant
concentration varies.
12 Cortical functions
Motor equivalence mean that the same muscle system can execute very different movements.
Pyramidal tract passes though medullary pyramids and contains axons from pyramidal neurones
projecting from motor, premotor and parietal cortices to the spinal cord.
Motor cortex is not necessary for basic locomotion in cats and many other mammals.
A majority of descending axons in the corticospinal tract stem from Betz cells in primates.