Plasticity of the sensory system and intro to sensory Flashcards
What are Hebb’s postulate?
Co-activated synaptic contacts will be strengthend/perserved, and other synapses weakend (eliminated)
Describe the critical period in central projections of retinal ganglion cells.
- each retina in a newborn independently generates a pattern of waves of electrical activity –> the waves are initiated in local retinal cells (amacrine cells), and this subthreshold activity leads to AP firing by ganglion cells that is then relayed to the lateral geniculate nucleus (LGN)
- this activity are asynchronous –> binocular competition during the critical period aligns orientation tuning in binocularly innervated cortical neurons
What are the critical period?
The post-natal period where stimulation is critical for the right development (e.g., cats where one eye are deprived of simuli during the critical period —> that eye being blind)
Describe the sensory plasticity that takes place after the critical period.
“Dormant” plasticity
Reorganization of sensory maps (functional remapping) after loss of input
E.g., limb amputation —> functional changes in the somatosensory cortex
Describe the plasticity associated with learning during early life compared to adults.
“Perceptual”/sensory learning
Passive exposure to relevant info is sufficient to drive robust plasticity in early life, but higher-order attentional mechanisms are necessary to drive plasticity in adults
Desccribe the molecular mechanisms behind sensory plasticity.
Glut release –> AMPA-R activation –> Mg2+ block from NMDA-R dissociated –> NMDA-R activated –> rapid Ca2+ influx –> PKs activation –> voltage-gated Ca2+ channels are gated –> Ca2+ influx –> cAMP increase –> PKA activation –> transciptional regulators activated (CaMKII, ERK –> CREB) –> –> transcription of synapse growth proteins (e.g., BDNF, ARC and –> –> synapse growth
How do the Ca2+ influx during synaptic plasticity also affect the cells?
Stimulating the cytoskeleton –> trafficking of post-synaptic proteins (e.g., AMPA-Rs) to the PSD
How does sensory deprivation and chronic depol respectively affect the AIS?
Deprivation –> move closer to soma/longer –> increased excitability
Chronic depol –> move farther from some/shorter –> decreased excitability
Describe how the AIS changes during development in the visual cortex.
Lack of sensory inputs very early –> growth of AIS length –> increased excitability
Onset of sensory input –> shortening of AIS (to optimal physiological range in adulthood) –> decreased excitability
Describe how myelination may play a role in NS plasticity.
Conduction velocity could play a modifiable role through changes in myelin to optimize the timing of info transmission through neuronal circuits
What is amblyopia?
When the sensory system favors one eye over the other, which leads to unequal development of the eyes/atrophy of the optic nerve –> strabimus aka lazy eye
What can maladaptive plasticity lead to in people losing a limb?
Phantom limbs and phantom pain
What’s the difference between afferent and efferent?
Afferent: up the spinal cord - from periphery –> CNS
Efferent: down the spinal cord - from CNS –> periphery
What are the two main sensory pathways?
Dorsal column-medial lemniscus
Spinothalamic tract/antereolateral system
Describe how the touch/proprioception pathway differs from the pain/temp pathway.
Touch/proprio: ipsilaterally in spinal cord (same side)
Pain/temp: contralaterally (opposite side)
