Figure 8. Effect of aggregate formation on neural network activity.

Calcium imaging on hippocampal neurons loaded with the calcium-sensitive fluorescent dye, Fluo4-AM was performed. A. PBS-treated WT neurons showed flickering events and simultaneous bursting. The spontaneous activity in α-syn-hWT pff treated WT neurons showed reduced coordination and frequency of oscillations. B. The level of coordinated spontaneous activity was quantified as the synchronization index. α-syn-hWT pff-treated neurons (red) showed a significant decrease in synchronicity by day 4, relative to PBS-treated neurons (blue) and the deficit continued for longer treatment duration. Primary neurons from α-syn −/− mice treated with α-syn-hWT pffs (purple) did not show reductions in the synchronization index relative to PBS-treated neurons (green). C. Excitatory tone in the network was determined by recording spontaneous activity and then by forcing synchronous oscillations via network disinhibition with bicuculline. Incremental concentrations of NBQX were added until coordinated activity stopped and the excitatory tone was reported as [NBQX]/K_d. D. Excitatory tone in PBS (blue) and α-syn-hWT pff (red) treated neurons, showed significant decreases by 10 as well as 14 days post-pff treatment. Addition of α-syn-hWT pffs to α-syn −/− neurons did not affect excitatory tone. E. Functional network connectivity, derived from the rasters in (A), is depicted as nodes (neurons) of varying sizes, where the size of a given node is scaled to reflect the total number of connections to that particular node. F. The average number of connections per neuron was determined from functional connectivity map. Compared to PBS, α-syn-hWT pff treated neurons had fewer numbers of functional connections. Connectivity of α-syn-hWT pff treated α-syn −/− neurons were similar to PBS-treated neurons. PBS-treated: day 4, N=9; day 7, N=11; day 10, N=10; day 14, N=9. PFF-treated: day 4, N=9; day 7, N=12; day 10, N=11; day 14, N=9.