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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.


TC input to L4 increases relative to L6 during the first postnatal week. (A) Example traces showing an average of 15 TC EPSCs (upper) and excitatory postsynaptic potentials (EPSPs) (lower) in simultaneously recorded cells from mice aged P3–P5 in L4 (black) and L6 (gray). (B) As for A except mice aged P7–P9. (C) As for A except mice aged P19–P21. (D) Summary graph showing change in EPSC amplitude throughout the first week in L4 (black) and L6 (gray). (E) Summary graph showing change in EPSP amplitude throughout first week rise time throughout first week. *P < 0.5, **P < 0.01, ***P < 0.005.
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BHU031F2: TC input to L4 increases relative to L6 during the first postnatal week. (A) Example traces showing an average of 15 TC EPSCs (upper) and excitatory postsynaptic potentials (EPSPs) (lower) in simultaneously recorded cells from mice aged P3–P5 in L4 (black) and L6 (gray). (B) As for A except mice aged P7–P9. (C) As for A except mice aged P19–P21. (D) Summary graph showing change in EPSC amplitude throughout the first week in L4 (black) and L6 (gray). (E) Summary graph showing change in EPSP amplitude throughout first week rise time throughout first week. *P < 0.5, **P < 0.01, ***P < 0.005.

Mentions: At P3–P5, L6 receives an equally strong TC input to L4 with no difference in the amplitude of EPSCs (L4 33 ± 9 pA and L6 37 ± 9 pA, n = 17, P = 0.3; Fig. 2A,D) or EPSPs (L4 4.8 ± 0.8 mV and L6 3.8 ± 0.9 mv, n = 17, P = 0.2; Fig 2A,E). Although the presence of slow EPSCs in L4 would be expected to result in larger EPSPs (given equal peak EPSC) (Daw et al. 2006), this is balanced by much higher input resistance in L6 cells than in L4 (Table 1). To test if development during the first postnatal week leads to the larger input to L4, we repeated the simultaneous recordings in slices made from P7 to P9 mice. At this age, TC EPSCs in L4 cells were approximately double in amplitude compared with those in L6 cells (L4 74 ± 13 pA and L6 39 ± 9 pA, n = 11, P < 0.01; Fig. 2B,D). LTP at L4 TC synapses results in an increase in the fast EPSC, but a reduction in the slow EPSC, a change that is mirrored in development. These changes do not always result in an increase in peak EPSP amplitude (Daw et al. 2006); therefore, we investigated if the TC EPSP amplitude in L4 increases relative to L6. We found that EPSP amplitude in L4 is more than double that in L6 at P7–P9 (L4 7.2 ± 1.2 mV and L6 2.8 ± 0.6 mV, n = 11, P < 0.001; Fig. 2B,E). This apparent discrepancy is explained by a reduction in input resistance in L6 cells only (Table 1).Table 1


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

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

TC input to L4 increases relative to L6 during the first postnatal week. (A) Example traces showing an average of 15 TC EPSCs (upper) and excitatory postsynaptic potentials (EPSPs) (lower) in simultaneously recorded cells from mice aged P3–P5 in L4 (black) and L6 (gray). (B) As for A except mice aged P7–P9. (C) As for A except mice aged P19–P21. (D) Summary graph showing change in EPSC amplitude throughout the first week in L4 (black) and L6 (gray). (E) Summary graph showing change in EPSP amplitude throughout first week rise time throughout first week. *P < 0.5, **P < 0.01, ***P < 0.005.
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Related In: Results  -  Collection

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BHU031F2: TC input to L4 increases relative to L6 during the first postnatal week. (A) Example traces showing an average of 15 TC EPSCs (upper) and excitatory postsynaptic potentials (EPSPs) (lower) in simultaneously recorded cells from mice aged P3–P5 in L4 (black) and L6 (gray). (B) As for A except mice aged P7–P9. (C) As for A except mice aged P19–P21. (D) Summary graph showing change in EPSC amplitude throughout the first week in L4 (black) and L6 (gray). (E) Summary graph showing change in EPSP amplitude throughout first week rise time throughout first week. *P < 0.5, **P < 0.01, ***P < 0.005.
Mentions: At P3–P5, L6 receives an equally strong TC input to L4 with no difference in the amplitude of EPSCs (L4 33 ± 9 pA and L6 37 ± 9 pA, n = 17, P = 0.3; Fig. 2A,D) or EPSPs (L4 4.8 ± 0.8 mV and L6 3.8 ± 0.9 mv, n = 17, P = 0.2; Fig 2A,E). Although the presence of slow EPSCs in L4 would be expected to result in larger EPSPs (given equal peak EPSC) (Daw et al. 2006), this is balanced by much higher input resistance in L6 cells than in L4 (Table 1). To test if development during the first postnatal week leads to the larger input to L4, we repeated the simultaneous recordings in slices made from P7 to P9 mice. At this age, TC EPSCs in L4 cells were approximately double in amplitude compared with those in L6 cells (L4 74 ± 13 pA and L6 39 ± 9 pA, n = 11, P < 0.01; Fig. 2B,D). LTP at L4 TC synapses results in an increase in the fast EPSC, but a reduction in the slow EPSC, a change that is mirrored in development. These changes do not always result in an increase in peak EPSP amplitude (Daw et al. 2006); therefore, we investigated if the TC EPSP amplitude in L4 increases relative to L6. We found that EPSP amplitude in L4 is more than double that in L6 at P7–P9 (L4 7.2 ± 1.2 mV and L6 2.8 ± 0.6 mV, n = 11, P < 0.001; Fig. 2B,E). This apparent discrepancy is explained by a reduction in input resistance in L6 cells only (Table 1).Table 1

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.