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081205 Journal Club

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Andrew Hires
Andrew Hires

The document summarizes research on the mouse somatosensory cortex SII. SII is located 4mm posterior to SI and has a whole body somatotopic map with larger receptive fields than SI. It receives major input from SI as well as surrounding cortical areas and thalamic regions. Studies in rats find that SII neurons have larger receptive fields than SI neurons and show selectivity for angular whisker deflection. While the core function of SII is still unclear, it may integrate context and spatial information to analyze features of objects touched by multiple whiskers.

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Journal Club Mouse Somatosensory Cortex SII Andrew Hires 12.5.2008
Mouse Somatosensory Cortex SII Where is it? What is its structure? What is its response characteristics? What is its function?
Location of SII 4mm 2 "Gran Torino" 4mm 2
Carvell & Simons 1986 Sens & Motor Res Sodium pentobarbital Tungsten microelectrodes Normal to pia, 300-450um (III, IV) most vigor Poking, brushing, tapping glass
Somatosensory response map in SII Whole body somatotopic map Larger receptive fields head up orientation map
Only contralateral input in whisker area SI to SII transition and whisker area
Subdivisions of SII Carvell & Simons 1986 Whiskers are most medial Face is 54% of SII, Whiskers are 16% of SII Auditory overlap in lateral and caudal areas (not in whisker)
SII cytoarchitecture No barrels Thickening of cortex Diffuse IV, less uniform lamination of V
SII inputs Thalamic Input POm (latency coding), VPMvl Paralemniscal pathway Parallel stream Cortical Input Major from SI Also surrounding cortical areas
Chakrabarti & Alloway 2006- SII Injections Retrograde tracers into SII (and MI) Diamidino yellow, true blue CTb, BDA, Fluoro Gold 50 degree from midline 1200-1400, 1000, 800um below pia
Promiscuous SII Inputs Big injection SI Input from barrel and septa
MI has septa preference, SII does not
Broadly somatotopic input to SII Same pattern in various layers
SII has few inputs from layer IV SI
SII and MI injections MI prefers border of septal and barrel
Do individual SI cells project to both?
Yes.
Thalamic input of SII and MI somewhat intermingled
VPMvl projections Pierret et al. 20 (19): 7455. (2000)
Kwegyir-Afful & Keller - Rat SII physiology Halothane -> fentanyl, or urethane Extracellular platinum, quartz ins, trodes Manual whisker stim 8 dir piezo stim, 50x angle 1cm from base 200ms ramp and hold 1Hz Kwegyir-Afful & Keller - 2004
SII vs. SI spiking properties SII latency = across layers, SI-IV ~9ms Rate < SI
Stimulus dependent firing in SII 90% 10%
Large receptive fields in SII 5-12 whiskers per recording site Layer V neuron
Primary vs. Accessory whiskers? Top 3 ave whisker amp sig dif from rest
SII angular tuning examples Cat 6 selective Cat 0 selective
SII more angularly selective than SI VI more selective than other layers But not significant
Summary of SII response properties
Additional SII findings Evoked activity in SII is lower Preference for multiple whisker stimulation? Preference for active whisking? (Paralemniscial) RSU = FSU magnitude Less feed forward inhibition Nearly all are rapidly adapting neurons Inactivation of SI in cat does not block SII Does block in primate (hierarchal or subdivisions) Driving input is from thalamus? SI input modulates?
What is SIIs function? Receives lemniscal and paralemniscal input Whisking frequency and external stimulus Context integration in stimulus detection? Spatial distributed feature analysis? Size of objects (# of whiskers struck)

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081205 Journal Club

  • 1. Journal Club Mouse Somatosensory Cortex SII Andrew Hires 12.5.2008
  • 2. Mouse Somatosensory Cortex SII Where is it? What is its structure? What is its response characteristics? What is its function?
  • 3. Location of SII 4mm 2 &quot;Gran Torino&quot; 4mm 2
  • 4. Carvell & Simons 1986 Sens & Motor Res Sodium pentobarbital Tungsten microelectrodes Normal to pia, 300-450um (III, IV) most vigor Poking, brushing, tapping glass
  • 5. Somatosensory response map in SII Whole body somatotopic map Larger receptive fields head up orientation map
  • 6. Only contralateral input in whisker area SI to SII transition and whisker area
  • 7. Subdivisions of SII Carvell & Simons 1986 Whiskers are most medial Face is 54% of SII, Whiskers are 16% of SII Auditory overlap in lateral and caudal areas (not in whisker)
  • 8. SII cytoarchitecture No barrels Thickening of cortex Diffuse IV, less uniform lamination of V
  • 9. SII inputs Thalamic Input POm (latency coding), VPMvl Paralemniscal pathway Parallel stream Cortical Input Major from SI Also surrounding cortical areas
  • 10. Chakrabarti & Alloway 2006- SII Injections Retrograde tracers into SII (and MI) Diamidino yellow, true blue CTb, BDA, Fluoro Gold 50 degree from midline 1200-1400, 1000, 800um below pia
  • 11. Promiscuous SII Inputs Big injection SI Input from barrel and septa
  • 12. MI has septa preference, SII does not
  • 13. Broadly somatotopic input to SII Same pattern in various layers
  • 14. SII has few inputs from layer IV SI
  • 15. SII and MI injections MI prefers border of septal and barrel
  • 16. Do individual SI cells project to both?
  • 17. Yes.
  • 18. Thalamic input of SII and MI somewhat intermingled
  • 19. VPMvl projections Pierret et al. 20 (19): 7455. (2000)
  • 20. Kwegyir-Afful & Keller - Rat SII physiology Halothane -> fentanyl, or urethane Extracellular platinum, quartz ins, trodes Manual whisker stim 8 dir piezo stim, 50x angle 1cm from base 200ms ramp and hold 1Hz Kwegyir-Afful & Keller - 2004
  • 21. SII vs. SI spiking properties SII latency = across layers, SI-IV ~9ms Rate < SI
  • 22. Stimulus dependent firing in SII 90% 10%
  • 23. Large receptive fields in SII 5-12 whiskers per recording site Layer V neuron
  • 24. Primary vs. Accessory whiskers? Top 3 ave whisker amp sig dif from rest
  • 25. SII angular tuning examples Cat 6 selective Cat 0 selective
  • 26. SII more angularly selective than SI VI more selective than other layers But not significant
  • 27. Summary of SII response properties
  • 28. Additional SII findings Evoked activity in SII is lower Preference for multiple whisker stimulation? Preference for active whisking? (Paralemniscial) RSU = FSU magnitude Less feed forward inhibition Nearly all are rapidly adapting neurons Inactivation of SI in cat does not block SII Does block in primate (hierarchal or subdivisions) Driving input is from thalamus? SI input modulates?
  • 29. What is SIIs function? Receives lemniscal and paralemniscal input Whisking frequency and external stimulus Context integration in stimulus detection? Spatial distributed feature analysis? Size of objects (# of whiskers struck)