Plasticity of the sensory system and intro to sensory

Question 1

What are Hebb’s postulate?

Answer 1

Co-activated synaptic contacts will be strengthend/perserved, and other synapses weakend (eliminated)

Question 2

Describe the critical period in central projections of retinal ganglion cells.

Answer 2

• 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

Question 3

What are the critical period?

Answer 3

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)

Question 4

Describe the sensory plasticity that takes place after the critical period.

Answer 4

“Dormant” plasticity
Reorganization of sensory maps (functional remapping) after loss of input
E.g., limb amputation —> functional changes in the somatosensory cortex

Question 5

Describe the plasticity associated with learning during early life compared to adults.

Answer 5

“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

Question 6

Desccribe the molecular mechanisms behind sensory plasticity.

Answer 6

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

Question 7

How do the Ca2+ influx during synaptic plasticity also affect the cells?

Answer 7

Stimulating the cytoskeleton –> trafficking of post-synaptic proteins (e.g., AMPA-Rs) to the PSD

Question 8

How does sensory deprivation and chronic depol respectively affect the AIS?

Answer 8

Deprivation –> move closer to soma/longer –> increased excitability
Chronic depol –> move farther from some/shorter –> decreased excitability

Question 9

Describe how the AIS changes during development in the visual cortex.

Answer 9

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

Question 10

Describe how myelination may play a role in NS plasticity.

Answer 10

Conduction velocity could play a modifiable role through changes in myelin to optimize the timing of info transmission through neuronal circuits

Question 11

What is amblyopia?

Answer 11

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

Question 12

What can maladaptive plasticity lead to in people losing a limb?

Answer 12

Phantom limbs and phantom pain

Question 13

What’s the difference between afferent and efferent?

Answer 13

Afferent: up the spinal cord - from periphery –> CNS
Efferent: down the spinal cord - from CNS –> periphery

Question 14

What are the two main sensory pathways?

Answer 14

Dorsal column-medial lemniscus
Spinothalamic tract/antereolateral system

Question 15

Describe how the touch/proprioception pathway differs from the pain/temp pathway.

Answer 15

Touch/proprio: ipsilaterally in spinal cord (same side)
Pain/temp: contralaterally (opposite side)

Question 16

Describe how the sensory organ surface often is represented in central nuclei.

Answer 16

Topographically

Question 17

How are sensory input modulated in the central nuclei?

Answer 17

Adapted, amplified, contrast enhanced

Question 18

What are sensory input modulated by?

Answer 18

Attention, memory and internal states (etc)

Question 19

Describe sensory cells/receptors.

Answer 19

Biological transducers: transforming one type of stimuli into electrical energy
Found in specialized epithelial structures called sensory organs
Specialized and detects one type of energy only

Question 20

Describe sensory receptor neurons.

Answer 20

• have dendrites
• transmit via APs
• e.g., somatosensory and olfactory receptors

Question 21

Describe sensory receptor cells.

Answer 21

• modified epithelial cells
• no axon
• receptor potential modulates the release of NTs
• e.g., visual, auditory, taste receptors

Question 22

What is psycometric function?

Answer 22

The relationship between the amplitude of a stimulus and the intensity of the sensation felt by the subject

Question 23

Describe adaption of sensory receptors.

Answer 23

• a reduction in sensitivity after constant exposure
• important to filter out constant stimuli