Some results that agree very strongly with the specific details of HTM theory.
“Using 2-photon calcium imaging to record from layer 2/3 neurons in the primary visual cortex, we found that novel images evoked excess activity in the majority of neurons. When a new stimulus sequence was repeatedly presented, a majority of neurons had similarly elevated activity for the first few presentations, which then decayed to almost zero activity. The decay time of these transient responses was not fixed, but instead scaled with the length of the stimulus sequence. However, at the same time, we also found a small fraction of the neurons within the population (~2%) that continued to respond strongly and periodically to the repeated stimulus. Decoding analysis demonstrated that both the transient and sustained responses encoded information about stimulus identity. We conclude that the layer 2/3 population uses a two-channel predictive code: a dense transient code for novel stimuli and a sparse sustained code for familiar stimuli.”
I’m particularly interested in the italicized part. Do we observe a relationship between sequence length and time to learn that sequence in HTM? With perfect input sequences I don’t think we do. But maybe with slightly noisy sequences? It could also be due to distal segments requiring repeated presentations to form new connections, or unlearn old ones.