(A) Two sample episodes where the network carried out sequence duplication (left) and reversal (right). Top to bottom: spike inputs to the network (subset), sequence of symbols they encode, spike activity of 10 sample leaky integrate-and-fire (LIF) neurons (without and with SFA) in the SNN, firing threshold dynamics for these 10 LIF neurons with SFA, activation of linear readout neurons, output sequence produced by applying argmax to them, and target output sequence. (B–F) Emergent neural coding of 279 neurons in the SNN (after removal of neurons detected as outliers) and peri-condition time histogram (PCTH) plots of two sample neurons. Neurons are sorted by time of peak activity. (B) A substantial number of neurons were sensitive to the overall timing of the tasks, especially for the second half of trials when the output sequence is produced. (C) Neurons separately sorted for duplication episodes (top row) and reversal episodes (bottom row). Many neurons responded to input symbols according to their serial position, but differently for different tasks. (D) Histogram of neurons categorized according to conditions with statistically significant effect (three-way ANOVA). Firing activity of a sample neuron that fired primarily when (E) the symbol ‘g’ was to be written at the beginning of the output sequence. The activity of this neuron depended on the task context during the input period; (F) the symbol ‘C’ occurred in position 5 in the input, irrespective of the task context.
Figure 4—source data 1. Raw data to generate Figure 4DEF.