081205 journal club
DESCRIPTION
Journal Club of Rodent Somatosensory Cortex SIITRANSCRIPT
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Journal Club Mouse Somatosensory Cortex SII
Andrew Hires
12.5.2008
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Mouse Somatosensory Cortex SII
• Where is it?
• What is its structure?
• What is its response characteristics?
• What is its function?
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Location of SII
"Gran Torino"
4mm2
4mm2
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Carvell & Simons 1986 Sens & Motor Res
• Sodium pentobarbital
• Tungsten microelectrodes– Normal to pia, 300-450um (III, IV) most vigor
• Poking, brushing, tapping glass
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Somatosensory response map in SIIWhole body somatotopic mapLarger receptive fields“head up” orientation map
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• Only contralateral input in whisker areaSI to SII transition and whisker area
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Subdivisions of SII
Carvell & Simons 1986
Whiskers are most medialFace is 54% of SII, Whiskers are 16% of SIIAuditory overlap in lateral and caudal areas (not in whisker)
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SII cytoarchitecture• No barrels
• Thickening of cortex
• Diffuse IV, less uniform lamination of V
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SII inputs• Thalamic Input
– POm (latency coding), VPMvl– Paralemniscal pathway– Parallel stream
• Cortical Input– Major from SI– Also surrounding cortical areas
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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
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Promiscuous SII Inputs• Big injection
• SI Input from barrel and septa
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MI has septa preference, SII does not
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Broadly somatotopic input to SII
• Same pattern in various layers
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SII has few inputs from layer IV SI
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SII and MI injections• MI prefers border of septal and barrel
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Do individual SI cells project to both?
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Yes.
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Thalamic input of SII and MI somewhat intermingled
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VPMvl projections
• Pierret et al. 20 (19): 7455. (2000)
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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
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SII vs. SI spiking properties• SII latency = across layers, SI-IV
• ~9ms
• Rate < SI
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Stimulus dependent firing in SII
90% 10%
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Large receptive fields in SII
• 5-12 whiskers per recording site
Layer V neuron
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“Primary” vs. “Accessory” whiskers?
• Top 3 ave whisker amp sig dif from rest
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SII angular tuning examples
Cat 6 selective Cat 0 selective
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SII more angularly selective than SI
• VI more selective than other layers– But not significant
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Summary of SII response properties
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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?
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What is SII’s 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)