Synaptic integration Flashcards
(11 cards)
• Pouille and Scanziani (2001)
Recorded CA1 PC isn acute rat hippocampal slices and stimulating from the schaffer collaterals, found that the hippocampal pyramidal cells have time window is very narrow less than 2ms. Feedforward inhibition was much stronger on the soma than In the dendrites resulting in a broader integration window, indicating subcellular partitioning of feedforward inhibition enforces coincidence detection at the soma and broader integration window in the dendrites, (longer window with GABAAR antagonist bicuculline)
• Perez-Garci (2006):
using pharmacological blockafe in wt mice found that activation of metabotropic GABAB mediated gradual long lasting inhibitory effect whereas GABAA mediated short lasting inhibition.
• Schiller et al (2000):
Using laser glutamate uncaging onto basal dendrites and whole cell patch clamp recordings of Layer V pyramidal neurons and recording soma found that increasing stimulus amplitude, there was not a graded increase in EPSP amplitude but there was a threshold in a sort of all or none. If apply DAP5 then get a graded response. These responses are accompanied by large transients in Ca2+.
• Polsky et al (2004):
Whole cell recording layer 5 pyramidal neurons (rat neocortical) with somatic recording of synaptic responses induced by stimulation of 2 synaptic inputs to either the same branch or different dendrites. Low input → linear for both. Medium input→ suprathreshold for same and linear for different, max → sublinear for same but NMDA plateau in the different. Also sensitive to the delay, if looking at same branch then get NMDA spike until over 15ms delay. So if neurons express NMDARs then they are sensitive to spatially and temporally sensitive.
• Branco et al (2010):
Whole cell current clamp recording on layer 2/3 pyramidal neurons in somatosensory and visual cortex and using 2 photon uncaging over multiple spine heads on same dendritic branch (8-10) and found they exhibit sensitivity to the temporal pattern, Dap5 abolished the supralinearity consistent with the amplification via NMDAR dependant regenerative signal boosting and it blocked the direction sensitivity. Bigger on way in than out (due to greater internal resistance further out ) Suggests that pyramidal cells dendrites can thus act as processing compartments for detection of synaptic sequences → implementing a fundamental cortical computation.
• Lavin et al (2012):
in vivo whole cell recording from layer 4 spiny stellate neuron in barrel fields of mice that show tuning to the angular direction of whisker and applied MK-801, over time this reduced the angular tuning to a short lasting nonpreferred deflection so seems like NMDARs contribute to sensory integration and angular tuning
o No control of dialysis alone, also did not show if NMDARs are contributing as synaptic integration or if it is an under these conditions get recruitment of NMDARs following synaptic input (not sure if they have a regenerative effect
• Palmer et al (2014):
): 2 photon activatable version of MK801 onto restricted region o the dendritic tree, to look at whether local NMDAR dependant electrogenesis occurs in the tuft dendrites of L2/3 pyramidal neurons under in vivo conditions and found that in vitro and in vivo revealed tat the tuft dendrites of L2/3 pyramidal neurons can support local NMDA receptor dependant electrogenesis, and that they were regenerative (e.g. dendritic Ca2+ transients were dependant on NMDAR, occurred in the absence of bAPs). Demonstrating that NMDARs have a vital role in coupling the tuft region of layer 2/3 pyramidal neurons to the cell body, enhancing the effectiveness of layer 1 input.
• Stuart et al (1997)
Triple recordings of AIS, soma and dendrites of a neocortical pyramidal neurons. Current injections in soma → AP initiated in AIS and could backpropagate into the dendritic tree, it gets smaller as it propagates and supported by VGNCs (TTX)
• Lurkum et al (1999);
Triple recording of L5 pyramidal neurons in soma apical and distal dendrites Found that small current injected into the distal dendrite attenuated and too small to dive AP firing at soma. However if subthreshold input to distal dendrite is paired with bAP (somatic spike preceded synaptic input) this lead to generation of dendritic Ca2+ spike and then propagates forward and drives burst of Na+ APs. So high speed bidirectional communication enabling detection of complex spatiotemporal patterns of synaptic input across the dendritic arbour. Inhibitory dendritic input can selectively block the initiation of dendritic Ca2+ AP and preenting burst of APs
Takahashi et al (2016)
Rbp4-Cre mice injected with floxed GCaMP6s and 2 photon imaging to monitor responses in apical dendrites of layer 5 neurons during whisker detection task. Found that in 34% of cases there was significant correlation between dendritic Ca2+ activity and behavioural performance used different methods to evaluated. Express ChR2 in the pyramidal neurons then dec threshold detection but chemogenetic activation of inhibitory, GABAB agonist, and coinfection of GCaMP6 with iChloC resulted in increased detection threshold and suppression of Ca2+ activity. Therefore found that Ca2+ activity in the apical dendrites of L5 pyramidal neurons in S1 correlated with threshold for perceptual thresholds
• Gidon et al (2020):
.cute brain slices from resected tissue of patients with epilepsy or tumour and dual patch clamping with 2 photon imaging or L2/3 pyramidal neurons and found that unlike in rodents increasing the current can emit Ca2+ spikes but as increase then spikes are smaller.So all or none but graded responses were decreases with increasing activity. Suggests that this allows XOR computation that was originally thought to be a multilayer computation nd thus acts as anti-correlation detector.
o In vitro, post-mortexm
