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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

Local excitatory connectivity changes in concert with BOLD whisker representations. (A) Schematic showing orientation of a brain slice with respect to BOLD fMRI images. Electrophysiological recordings were made in L2/3. Dashed line indicates the boundary between spared C-row whiskers and deprived cortex. (B) Synaptically connected pyramidal neurons. Upper trace, train of action potentials in presynaptic neuron. Lower trace, evoked response in postsynaptic neuron. Scale bars: 50 mV (upper), 0.1 mV (lower); 50 ms. (C) Confocal reconstruction of the presynaptic (green) and postsynaptic (orange) pyramidal neurons. Scale bar, 50 μm. (D) Connectivity between deprived L2/3 pyramidal neurons in controls (black, 3.6%), after whisker trimming for 2–4 days (red, 12.0%) and after whisker trimming for 6–8 days (blue, 4.0%).
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BHU098F3: Local excitatory connectivity changes in concert with BOLD whisker representations. (A) Schematic showing orientation of a brain slice with respect to BOLD fMRI images. Electrophysiological recordings were made in L2/3. Dashed line indicates the boundary between spared C-row whiskers and deprived cortex. (B) Synaptically connected pyramidal neurons. Upper trace, train of action potentials in presynaptic neuron. Lower trace, evoked response in postsynaptic neuron. Scale bars: 50 mV (upper), 0.1 mV (lower); 50 ms. (C) Confocal reconstruction of the presynaptic (green) and postsynaptic (orange) pyramidal neurons. Scale bar, 50 μm. (D) Connectivity between deprived L2/3 pyramidal neurons in controls (black, 3.6%), after whisker trimming for 2–4 days (red, 12.0%) and after whisker trimming for 6–8 days (blue, 4.0%).

Mentions: We next investigated the cellular basis for the cortical reorganization. We made electrophysiological recordings in SI that had been deprived of its principal whisker sensory input. Recordings were focused on L2/3 of deprived cortex adjacent to spared cortex because this region lies in the periphery of the expanded PBR where our functional imaging indicated that reorganization was occurring. We prepared brain slices that cut across the whisker barrel rows and made recordings from pairs of pyramidal neurons in L2/3 near the junction between the C and D barrel columns (Cheetham et al. 2007, 2008) (Fig. 3A–C), where spared representations had expanded into deprived cortex. In control cortex, the chance of finding a connection between neighboring L2/3 pyramidal neurons (Pyr → Pyr) was low (21/553 is 3.8%, 21/553 tested Pyr → Pyr pairs). In contrast, there was a dramatic increase (>3-fold) in Pyr → Pyr connectivity in deprived cortex after 2–4 days of whisker trimming (12.0%, 16/133 connections tested, P < 0.001, χ2 test) (Fig. 3D). After trimming for 6–8 days, connectivity in deprived cortex had returned to control levels (4.0%, 8/201 connections tested, P = 0.988, χ2 test) (Fig. 3D). Hence, the reorganization of local excitatory circuitry follows the same temporal pattern as the expansion and retraction of the spared whisker representations imaged with BOLD fMRI.Figure 3.


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)

Local excitatory connectivity changes in concert with BOLD whisker representations. (A) Schematic showing orientation of a brain slice with respect to BOLD fMRI images. Electrophysiological recordings were made in L2/3. Dashed line indicates the boundary between spared C-row whiskers and deprived cortex. (B) Synaptically connected pyramidal neurons. Upper trace, train of action potentials in presynaptic neuron. Lower trace, evoked response in postsynaptic neuron. Scale bars: 50 mV (upper), 0.1 mV (lower); 50 ms. (C) Confocal reconstruction of the presynaptic (green) and postsynaptic (orange) pyramidal neurons. Scale bar, 50 μm. (D) Connectivity between deprived L2/3 pyramidal neurons in controls (black, 3.6%), after whisker trimming for 2–4 days (red, 12.0%) and after whisker trimming for 6–8 days (blue, 4.0%).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

BHU098F3: Local excitatory connectivity changes in concert with BOLD whisker representations. (A) Schematic showing orientation of a brain slice with respect to BOLD fMRI images. Electrophysiological recordings were made in L2/3. Dashed line indicates the boundary between spared C-row whiskers and deprived cortex. (B) Synaptically connected pyramidal neurons. Upper trace, train of action potentials in presynaptic neuron. Lower trace, evoked response in postsynaptic neuron. Scale bars: 50 mV (upper), 0.1 mV (lower); 50 ms. (C) Confocal reconstruction of the presynaptic (green) and postsynaptic (orange) pyramidal neurons. Scale bar, 50 μm. (D) Connectivity between deprived L2/3 pyramidal neurons in controls (black, 3.6%), after whisker trimming for 2–4 days (red, 12.0%) and after whisker trimming for 6–8 days (blue, 4.0%).
Mentions: We next investigated the cellular basis for the cortical reorganization. We made electrophysiological recordings in SI that had been deprived of its principal whisker sensory input. Recordings were focused on L2/3 of deprived cortex adjacent to spared cortex because this region lies in the periphery of the expanded PBR where our functional imaging indicated that reorganization was occurring. We prepared brain slices that cut across the whisker barrel rows and made recordings from pairs of pyramidal neurons in L2/3 near the junction between the C and D barrel columns (Cheetham et al. 2007, 2008) (Fig. 3A–C), where spared representations had expanded into deprived cortex. In control cortex, the chance of finding a connection between neighboring L2/3 pyramidal neurons (Pyr → Pyr) was low (21/553 is 3.8%, 21/553 tested Pyr → Pyr pairs). In contrast, there was a dramatic increase (>3-fold) in Pyr → Pyr connectivity in deprived cortex after 2–4 days of whisker trimming (12.0%, 16/133 connections tested, P < 0.001, χ2 test) (Fig. 3D). After trimming for 6–8 days, connectivity in deprived cortex had returned to control levels (4.0%, 8/201 connections tested, P = 0.988, χ2 test) (Fig. 3D). Hence, the reorganization of local excitatory circuitry follows the same temporal pattern as the expansion and retraction of the spared whisker representations imaged with BOLD fMRI.Figure 3.

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