Fig 1.
Phase contrast image of a typical culture on MEA at DIV 2.
Distance between electrodes (visible in the lower right corner) is 200 μm.
Fig 2.
A typical signal recording from a culture at 10 DIV obtained from MEA showing synchronization across the 60 channels.
The scales of each window are ±200 μV (y-axis) and 1 second (x-axis).
Fig 3.
Raster plot and its firing-rate-time-histogram (FRTH) of a synchronized burst.
a) Raster plots of spiking events (a dot) in the 60 channels of the MEA as a function of time. b) FRTH in a 5 ms time window constructed from a) together with the definition of burst duration (τB). The 2 kHz threshold used for the detection of burst is also shown. The same data set of Fig 2 is used here.
Fig 4.
The phenomenon of SBs at a larger time scale.
Three SBs are shown together with the definition of inter-burst interval (τIBI) for a sample at 10 DIV. The inset shows the much smaller firing events outside of the SBs. The same data set of Fig 2 is used here.
Fig 5.
Three different types of SBs at different DIVs.
Structures of FRTH at (a) 6 DIV, (b) 9 DIV and (c) 22 DIV. The mean inter-burst interval () are also shown in the figures. The insets are the FRTHs of another SB in the same recording.
Fig 6.
Statistical properties of SBs at different DIVs.
Measured quantities of SBs as a function of DIV (N = 18): a) Mean firing rate (f) within 10 min. b) Mean inter-burst interval (). c) Average number of spikes within SBs (n). d) Mean burst duration
. e) Mean number of spikes within a burst. The error bars are one standard deviation from 18 samples. The classification of three types of SBs are also shown as I, II and III. Note that for a), the firing rate is computed from all the detected spikes not just limited to those within a SB.
Fig 7.
Induction of sub-bursts by removal of [Mg2+].
Effect of [Mg2+] on the FRTH for a sample at 34 DIV: (a) In culture medium with 0.8 mM [Mg2+]. (b) In BSS with 0 mM [Mg2+].
Fig 8.
Statistical analysis of the effects of [Mg2+] on properties of SBs for early and late DIVs.
The firing rate (f), inter-burst interval () and the number of sub-burst measured with different [Mg2+] concentrations for old (a1:a3, DIV>15, N = 9, bursts = 395 and 967 in 0.8 mM and 0 mM [Mg2+]) and young (b1:b3, DIV<15, n = 3) cultures. P<0.05 (*); P<0.005 (***).
Fig 9.
Measurement of as a function of concentration of DHK for cultures at 33 to 34 DIVs (N = 3).
The error bars are one standard deviation from 3 samples. The inset shows a comparison to simulation results from the TMX model described in the text. Note that τx controls the recycling time of neurotransmitters; playing similar role of DHK. Parameters for the TMX model are X0 = 0.95, J = 5.8, U = 0.3, I0 = −1.3, β = 0.01, τ = 0.013 s, τD = 0.15 s, τF = 1.5 s and α = 1.5.
Fig 10.
Phase diagram of oscillation state of the TMX model.
Minimal X0 for eliciting an oscillatory firing for a given value of J for U = 0.3 and τD = 0.15 s. Other parameters are τX = 20 s, I0 = −1.3, β = 0.01, τ = 0.013 s, τF = 1.5 s and α = 1.5. The insets show the characteristic of E(t) (in Hz) in the steady and the oscillatory states.
Fig 11.
Time courses of E(t) (in Hz) of the TMX model to mimic the FRTH at different DIV.
(a) J = 4.8, τD = 0.2 s and U = 0.28. (b) J = 5.8, τD = 0.15 s and U = 0.3. (d) J = 6.8, τD = 0.1 s and U = 0.32. (c) Corresponding time courses of x (blue dash-dot), u (red dot) and χ0 (green) for time course (b). Other parameters are the same as Fig 10.
Fig 12.
Time courses of E(t) (in Hz) of the TMX model to mimic different magnesium treatment.
E(t) (in Hz) from the TMX model for situations of a) normal [Mg2+]: J = 6.8 and τD = 0.1 s and b) low [Mg2+]: J = 7.8 and τD = 0.15 s. Other parameters are τX = 20 s, I0 = −1.3, β = 0.01, τ = 0.013 s, τF = 1.5 s and α = 1.5.