1. |
ANN–CNN described in Table 2
|
N-MNIST, N-Caltech101, DvsGesture |
Spikes are summed over the presentation duration and collapsed into images. Then they are trained using an ANN. |
The ANN obtains comparable to state-of-the-art results on N-MNIST (99.23%) and N-Caltech101 (78.01%). However, ANN performs significantly worse than state-of-the-art on DvsGesture (71.01%), as it cannot handle the spatiotemporal information. Hence, we conclude that N-MNIST and N-Caltech101 does not have additional information contained in the timing of spikes necessary to classify the dataset. |
2. |
RD-STDP and STDP-tempotron |
N-MNIST and DvsGesture |
Comparison of rate-based and temporal STDP algorithms on the two datasets |
While the rate-dependent RD-STDP obtains very good performance on N-MNIST (83.89%), it is unable to do as well in DvsGesture (76.13%). In contrast, STDP-tempotron performs better in DvsGesture (59.11%), but worse for N-MNIST (53.18%). We conclude that while DvsGesture has spatio-temporal information, and therefore needs STDP-tempotron, N-MNIST does not have additional information in the time domain necessary to classify it. |
3. |
RD-STDP |
N-MNIST |
Fixing the output spike time |
Despite fixing the output spike time, the system performs well (84.10%), demonstrating that precise timing of spikes are not useful at all in N-MNIST |
4. |
Populate rate dependent plasticity (new rule) |
N-MNIST |
A new STDP curve was devised based on summing up spikes over the population—the instantaneous population firing rate (The second definition of firing rate—see section 1, Paragraph 2) |
Despite using an STDP curve based on the population spike rates alone, the system is able to give good performance on N-MNIST (85.45%). This demonstrates that spike timing is not important in classifying N-MNIST. |