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Experience-Dependent, Layer-Specific Development of Divergent Thalamocortical Connectivity.

Crocker-Buque A, Brown SM, Kind PC, Isaac JT, Daw MI - Cereb. Cortex (2014)

Bottom Line: Here, we show that, in neonates, the input to layer 6 is as strong as that to layer 4.This strengthening consists of an increase in axon branching and the divergence of connectivity in layer 4 without a change in the strength of individual connections.We propose that experience-driven LTP stabilizes transient TC synapses in layer 4 to increase strength and divergence specifically in layer 4 over layer 6.

View Article: PubMed Central - PubMed

Affiliation: Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK.

No MeSH data available.


A pairing protocol induces LTP in L4 but not in L6 cells. (A) Upper panel: example traces from simultaneously recorded L4 (black) and L6 (gray) cells before (1) and after (2) pairing 50 stimuli at 0.2 Hz with a postsynaptic holding potential of 0 mV. Traces show an average of 3 sweeps. Lower panel: amplitude versus time plot for EPSCs from cells shown in A. Points in graph show peak amplitude from an average of 3 traces. (B) Summary graph showing the average of all experiments as shown in (A). Points show the average of 5 values as shown in (A).
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BHU031F3: A pairing protocol induces LTP in L4 but not in L6 cells. (A) Upper panel: example traces from simultaneously recorded L4 (black) and L6 (gray) cells before (1) and after (2) pairing 50 stimuli at 0.2 Hz with a postsynaptic holding potential of 0 mV. Traces show an average of 3 sweeps. Lower panel: amplitude versus time plot for EPSCs from cells shown in A. Points in graph show peak amplitude from an average of 3 traces. (B) Summary graph showing the average of all experiments as shown in (A). Points show the average of 5 values as shown in (A).

Mentions: Long-term potentiation is thought to underlie the developmental increase in L4 TC EPSC amplitude and speeding of EPSP rise time in L4 cells (Kidd and Isaac 1999; Daw et al. 2006). Given the increase in amplitude and speeding of kinetics of the TC input to L4 cells relative to L6 cells during the first postnatal week, we hypothesized that this form of LTP may not occur in L6 at this developmental stage. Previous studies in other brain areas have shown that LTP can be difficult to induce reliably with whole-cell recordings, but may be revealed by using perforated patch recordings (Lamsa et al. 2005). Therefore, we carried out an LTP pairing protocol (50 stimuli at 0.2 Hz with a postsynaptic holding potential of 0 mV) in simultaneous perforated patch recordings from L4 and L6 cells in slices from P3 to P5 mice. Robust LTP was induced in L4 cells (EPSC 25–30 min after pairing 257 ± 63%, n = 8, P = 0.041, Fig. 3A,B), whereas no LTP was observed in simultaneously recorded L6 cells (EPSC 101 ± 23% baseline, n = 8, P = 0.97, Fig. 3A,B). Additional single recordings made from L6 cells also showed no change in response to the pairing protocol (EPSC all L6 recordings 92 ± 14% baseline, n = 17, P = 0.6, Supplementary Fig. 2A). However, we found that the pairing protocol is sufficient to induce LTP of slow, putative corticocortical EPSCs in L6 cells (EPSC 203 ± 84% baseline, n = 7, P = 0.018, Supplementary Fig. 2A,B). Plotting change in EPSC amplitude in L6 versus EPSC rise time clearly shows that only slow, presumed corticocortical (CC), EPSCs are consistently potentiated. Taken together with the relative change in L4/L6 TC inputs, these data indicate that, although the TC input to L4 is plastic at P3–P5 and is developmentally regulated, L6 TC inputs do not readily express synaptic strengthening at an early postnatal age.Figure 3.


Experience-Dependent, Layer-Specific Development of Divergent Thalamocortical Connectivity.

Crocker-Buque A, Brown SM, Kind PC, Isaac JT, Daw MI - Cereb. Cortex (2014)

A pairing protocol induces LTP in L4 but not in L6 cells. (A) Upper panel: example traces from simultaneously recorded L4 (black) and L6 (gray) cells before (1) and after (2) pairing 50 stimuli at 0.2 Hz with a postsynaptic holding potential of 0 mV. Traces show an average of 3 sweeps. Lower panel: amplitude versus time plot for EPSCs from cells shown in A. Points in graph show peak amplitude from an average of 3 traces. (B) Summary graph showing the average of all experiments as shown in (A). Points show the average of 5 values as shown in (A).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4494033&req=5

BHU031F3: A pairing protocol induces LTP in L4 but not in L6 cells. (A) Upper panel: example traces from simultaneously recorded L4 (black) and L6 (gray) cells before (1) and after (2) pairing 50 stimuli at 0.2 Hz with a postsynaptic holding potential of 0 mV. Traces show an average of 3 sweeps. Lower panel: amplitude versus time plot for EPSCs from cells shown in A. Points in graph show peak amplitude from an average of 3 traces. (B) Summary graph showing the average of all experiments as shown in (A). Points show the average of 5 values as shown in (A).
Mentions: Long-term potentiation is thought to underlie the developmental increase in L4 TC EPSC amplitude and speeding of EPSP rise time in L4 cells (Kidd and Isaac 1999; Daw et al. 2006). Given the increase in amplitude and speeding of kinetics of the TC input to L4 cells relative to L6 cells during the first postnatal week, we hypothesized that this form of LTP may not occur in L6 at this developmental stage. Previous studies in other brain areas have shown that LTP can be difficult to induce reliably with whole-cell recordings, but may be revealed by using perforated patch recordings (Lamsa et al. 2005). Therefore, we carried out an LTP pairing protocol (50 stimuli at 0.2 Hz with a postsynaptic holding potential of 0 mV) in simultaneous perforated patch recordings from L4 and L6 cells in slices from P3 to P5 mice. Robust LTP was induced in L4 cells (EPSC 25–30 min after pairing 257 ± 63%, n = 8, P = 0.041, Fig. 3A,B), whereas no LTP was observed in simultaneously recorded L6 cells (EPSC 101 ± 23% baseline, n = 8, P = 0.97, Fig. 3A,B). Additional single recordings made from L6 cells also showed no change in response to the pairing protocol (EPSC all L6 recordings 92 ± 14% baseline, n = 17, P = 0.6, Supplementary Fig. 2A). However, we found that the pairing protocol is sufficient to induce LTP of slow, putative corticocortical EPSCs in L6 cells (EPSC 203 ± 84% baseline, n = 7, P = 0.018, Supplementary Fig. 2A,B). Plotting change in EPSC amplitude in L6 versus EPSC rise time clearly shows that only slow, presumed corticocortical (CC), EPSCs are consistently potentiated. Taken together with the relative change in L4/L6 TC inputs, these data indicate that, although the TC input to L4 is plastic at P3–P5 and is developmentally regulated, L6 TC inputs do not readily express synaptic strengthening at an early postnatal age.Figure 3.

Bottom Line: Here, we show that, in neonates, the input to layer 6 is as strong as that to layer 4.This strengthening consists of an increase in axon branching and the divergence of connectivity in layer 4 without a change in the strength of individual connections.We propose that experience-driven LTP stabilizes transient TC synapses in layer 4 to increase strength and divergence specifically in layer 4 over layer 6.

View Article: PubMed Central - PubMed

Affiliation: Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK.

No MeSH data available.