Limits...
Rapid Bidirectional Reorganization of Cortical Microcircuits.

Albieri G, Barnes SJ, de Celis Alonso B, Cheetham CE, Edwards CE, Lowe AS, Karunaratne H, Dear JP, Lee KC, Finnerty GT - Cereb. Cortex (2014)

Bottom Line: We found that there was rapid expansion followed by retraction of whisker cortical maps.Despite the rapid increase in local excitatory connectivity, the average strength and synaptic dynamics did not change, which suggests that new excitatory connections rapidly acquire the properties of established excitatory connections.Hence, the changes in local excitatory connectivity did not occur in all circuits involving pyramidal neurons.

View Article: PubMed Central - PubMed

Affiliation: MRC Centre for Neurodegeneration Research, King's College London, Institute of Psychiatry (Box44), London SE5 8AF, UK Current address: Division of Neurobiology, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.

No MeSH data available.


Related in: MedlinePlus

Inhibitory transmission onto pyramidal neurons in L2/3 of deprived cortex is unaltered by short periods of whisker deprivation. (A) Schematic showing an FS interneuron synaptically connected to a pyramidal cell (top); train of 8 action potentials in the presynaptic FS interneuron generates 8 short latency uIPSPs in the postsynaptic pyramidal neuron (average of 50 trials). Scale bars (top to bottom): 20 mV, 0.1 mV, 100 ms. (B) Percentage of tested FS interneuron to pyramidal cell pairs (FS → Pyr) that were synaptically connected in control (black, 62%) and deprived (red, 64%) cortex. (C) Empirical distribution plots of the amplitudes of mean uIPSP1 (absolute value) in deprived (red) and control (black) cortex. Median [IQR] of mean uIPSP1 amplitudes: deprived: −0.24 [−0.35 to −0.18] mV, n = 16 FS → Pyr connections; control, −0.27 [−0.69 to −0.20] mV, n = 19 FS → Pyr connections. (D) Mean uIPSP amplitude during 20 Hz trains in deprived (red, n = 8 FS → Pyr connections) and control (black, n = 13 FS → Pyr connections) cortex. Error bars, SEM. (E) uIPSP amplitudes during a 20-Hz train normalized to uIPSP1 for each L2/3 FS → Pyr connection in 3-day deprived cortex (red, n = 8) and in control cortex (black, n = 13). Error bars are within the majority of circles. (F) Relationship between mean uEPSP1 amplitude and mean uIPSP1 amplitude (absolute values) for pairs of reciprocally connected FS interneurons and pyramidal cells in control (black) and deprived (red) cortex (correlation: deprived, r = −0.40, n = 14 reciprocally connected FS → Pyr pairs; control, r = −0.06, n = 17 reciprocally connected FS → Pyr pairs).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4537443&req=5

BHU098F7: Inhibitory transmission onto pyramidal neurons in L2/3 of deprived cortex is unaltered by short periods of whisker deprivation. (A) Schematic showing an FS interneuron synaptically connected to a pyramidal cell (top); train of 8 action potentials in the presynaptic FS interneuron generates 8 short latency uIPSPs in the postsynaptic pyramidal neuron (average of 50 trials). Scale bars (top to bottom): 20 mV, 0.1 mV, 100 ms. (B) Percentage of tested FS interneuron to pyramidal cell pairs (FS → Pyr) that were synaptically connected in control (black, 62%) and deprived (red, 64%) cortex. (C) Empirical distribution plots of the amplitudes of mean uIPSP1 (absolute value) in deprived (red) and control (black) cortex. Median [IQR] of mean uIPSP1 amplitudes: deprived: −0.24 [−0.35 to −0.18] mV, n = 16 FS → Pyr connections; control, −0.27 [−0.69 to −0.20] mV, n = 19 FS → Pyr connections. (D) Mean uIPSP amplitude during 20 Hz trains in deprived (red, n = 8 FS → Pyr connections) and control (black, n = 13 FS → Pyr connections) cortex. Error bars, SEM. (E) uIPSP amplitudes during a 20-Hz train normalized to uIPSP1 for each L2/3 FS → Pyr connection in 3-day deprived cortex (red, n = 8) and in control cortex (black, n = 13). Error bars are within the majority of circles. (F) Relationship between mean uEPSP1 amplitude and mean uIPSP1 amplitude (absolute values) for pairs of reciprocally connected FS interneurons and pyramidal cells in control (black) and deprived (red) cortex (correlation: deprived, r = −0.40, n = 14 reciprocally connected FS → Pyr pairs; control, r = −0.06, n = 17 reciprocally connected FS → Pyr pairs).

Mentions: We next considered inhibition of pyramidal neurons by FS interneurons (FS → Pyr) since strengthening of inhibitory synapses has been predicted to play a role in maintaining the excitatory–inhibitory balance during cortical reorganization (Vogels et al. 2011). uIPSPs were measured by holding the L2/3 pyramidal neuron at −55 mV in current clamp mode while stimulating the presynaptic FS interneuron to fire a train of action potentials (Fig. 7A). The probability of finding an FS → Pyr connection was similar in control and in deprived cortex (deprived: 64%, 16/25 connections tested; control, 62%, 17/28 connections tested; P = 0.97, χ2 test) (Fig. 7B). The mean uIPSP amplitude in deprived L2/3 pyramidal neurons after a 3-day deprivation was not different from controls (deprived: −0.24 [−0.35 to −0.18] mV; n = 16 connections; control, −0.27 [−0.69 to −0.20] mV; n = 19 connections; P = 0.13, t-test after log transformation of the absolute uIPSP amplitude) (Fig. 7C). The synaptic dynamics during a 10-Hz train showed minimal and variable depression of uIPSPs during the train (Supplementary Fig. 7B,C). uIPSPs evoked by 20 Hz trains showed greater synaptic depression than the responses elicited by 10 Hz stimulation (Fig. 7D and Supplementary Fig. 7). However, 3-day whisker deprivation did not affect the short-term synaptic dynamics of uIPSPs evoked by 20 Hz trains (Fig. 7E) (normalized steady-state amplitude: deprived, 0.57 ± 0.05, n = 8 FS → Pyr connections; control, 0.56 ± 0.05, n = 13 FS → Pyr connections; P = 0.842, t-test). Whisker deprivation for 3 days did not change the reversal potential for uIPSPs (Supplementary Material). Taken together, our findings suggest that 3 days of whisker deprivation did not alter the strength of inhibition from L2/3 FS interneurons onto L2/3 pyramidal neurons as a whole.Figure 7.


Rapid Bidirectional Reorganization of Cortical Microcircuits.

Albieri G, Barnes SJ, de Celis Alonso B, Cheetham CE, Edwards CE, Lowe AS, Karunaratne H, Dear JP, Lee KC, Finnerty GT - Cereb. Cortex (2014)

Inhibitory transmission onto pyramidal neurons in L2/3 of deprived cortex is unaltered by short periods of whisker deprivation. (A) Schematic showing an FS interneuron synaptically connected to a pyramidal cell (top); train of 8 action potentials in the presynaptic FS interneuron generates 8 short latency uIPSPs in the postsynaptic pyramidal neuron (average of 50 trials). Scale bars (top to bottom): 20 mV, 0.1 mV, 100 ms. (B) Percentage of tested FS interneuron to pyramidal cell pairs (FS → Pyr) that were synaptically connected in control (black, 62%) and deprived (red, 64%) cortex. (C) Empirical distribution plots of the amplitudes of mean uIPSP1 (absolute value) in deprived (red) and control (black) cortex. Median [IQR] of mean uIPSP1 amplitudes: deprived: −0.24 [−0.35 to −0.18] mV, n = 16 FS → Pyr connections; control, −0.27 [−0.69 to −0.20] mV, n = 19 FS → Pyr connections. (D) Mean uIPSP amplitude during 20 Hz trains in deprived (red, n = 8 FS → Pyr connections) and control (black, n = 13 FS → Pyr connections) cortex. Error bars, SEM. (E) uIPSP amplitudes during a 20-Hz train normalized to uIPSP1 for each L2/3 FS → Pyr connection in 3-day deprived cortex (red, n = 8) and in control cortex (black, n = 13). Error bars are within the majority of circles. (F) Relationship between mean uEPSP1 amplitude and mean uIPSP1 amplitude (absolute values) for pairs of reciprocally connected FS interneurons and pyramidal cells in control (black) and deprived (red) cortex (correlation: deprived, r = −0.40, n = 14 reciprocally connected FS → Pyr pairs; control, r = −0.06, n = 17 reciprocally connected FS → Pyr pairs).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4537443&req=5

BHU098F7: Inhibitory transmission onto pyramidal neurons in L2/3 of deprived cortex is unaltered by short periods of whisker deprivation. (A) Schematic showing an FS interneuron synaptically connected to a pyramidal cell (top); train of 8 action potentials in the presynaptic FS interneuron generates 8 short latency uIPSPs in the postsynaptic pyramidal neuron (average of 50 trials). Scale bars (top to bottom): 20 mV, 0.1 mV, 100 ms. (B) Percentage of tested FS interneuron to pyramidal cell pairs (FS → Pyr) that were synaptically connected in control (black, 62%) and deprived (red, 64%) cortex. (C) Empirical distribution plots of the amplitudes of mean uIPSP1 (absolute value) in deprived (red) and control (black) cortex. Median [IQR] of mean uIPSP1 amplitudes: deprived: −0.24 [−0.35 to −0.18] mV, n = 16 FS → Pyr connections; control, −0.27 [−0.69 to −0.20] mV, n = 19 FS → Pyr connections. (D) Mean uIPSP amplitude during 20 Hz trains in deprived (red, n = 8 FS → Pyr connections) and control (black, n = 13 FS → Pyr connections) cortex. Error bars, SEM. (E) uIPSP amplitudes during a 20-Hz train normalized to uIPSP1 for each L2/3 FS → Pyr connection in 3-day deprived cortex (red, n = 8) and in control cortex (black, n = 13). Error bars are within the majority of circles. (F) Relationship between mean uEPSP1 amplitude and mean uIPSP1 amplitude (absolute values) for pairs of reciprocally connected FS interneurons and pyramidal cells in control (black) and deprived (red) cortex (correlation: deprived, r = −0.40, n = 14 reciprocally connected FS → Pyr pairs; control, r = −0.06, n = 17 reciprocally connected FS → Pyr pairs).
Mentions: We next considered inhibition of pyramidal neurons by FS interneurons (FS → Pyr) since strengthening of inhibitory synapses has been predicted to play a role in maintaining the excitatory–inhibitory balance during cortical reorganization (Vogels et al. 2011). uIPSPs were measured by holding the L2/3 pyramidal neuron at −55 mV in current clamp mode while stimulating the presynaptic FS interneuron to fire a train of action potentials (Fig. 7A). The probability of finding an FS → Pyr connection was similar in control and in deprived cortex (deprived: 64%, 16/25 connections tested; control, 62%, 17/28 connections tested; P = 0.97, χ2 test) (Fig. 7B). The mean uIPSP amplitude in deprived L2/3 pyramidal neurons after a 3-day deprivation was not different from controls (deprived: −0.24 [−0.35 to −0.18] mV; n = 16 connections; control, −0.27 [−0.69 to −0.20] mV; n = 19 connections; P = 0.13, t-test after log transformation of the absolute uIPSP amplitude) (Fig. 7C). The synaptic dynamics during a 10-Hz train showed minimal and variable depression of uIPSPs during the train (Supplementary Fig. 7B,C). uIPSPs evoked by 20 Hz trains showed greater synaptic depression than the responses elicited by 10 Hz stimulation (Fig. 7D and Supplementary Fig. 7). However, 3-day whisker deprivation did not affect the short-term synaptic dynamics of uIPSPs evoked by 20 Hz trains (Fig. 7E) (normalized steady-state amplitude: deprived, 0.57 ± 0.05, n = 8 FS → Pyr connections; control, 0.56 ± 0.05, n = 13 FS → Pyr connections; P = 0.842, t-test). Whisker deprivation for 3 days did not change the reversal potential for uIPSPs (Supplementary Material). Taken together, our findings suggest that 3 days of whisker deprivation did not alter the strength of inhibition from L2/3 FS interneurons onto L2/3 pyramidal neurons as a whole.Figure 7.

Bottom Line: We found that there was rapid expansion followed by retraction of whisker cortical maps.Despite the rapid increase in local excitatory connectivity, the average strength and synaptic dynamics did not change, which suggests that new excitatory connections rapidly acquire the properties of established excitatory connections.Hence, the changes in local excitatory connectivity did not occur in all circuits involving pyramidal neurons.

View Article: PubMed Central - PubMed

Affiliation: MRC Centre for Neurodegeneration Research, King's College London, Institute of Psychiatry (Box44), London SE5 8AF, UK Current address: Division of Neurobiology, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.

No MeSH data available.


Related in: MedlinePlus