P012 Real-Time Temporal Code-driven Stimulation using Victor-Purpura Distance for Studying Spike Sequences in Neural Systems
Alberto Ayala*1, Angel Lareo1, Pablo Varona1, Francisco B. Rodriguez1 1Grupo de Neurocomputación Biológica, Departamento de Ingeniería Informática, Escuela Politécnica Superior, Universidad Autónoma de Madrid, Spain *Email: alberto.ayala@uam.es
Introduction Most neural systems encode information by stereotyped sequences of spikes linked to specific functions (e.g., see [1-4]). However, their inherent variability introduces temporal variations even in spike sequences with the same function (i.e., those produced by the same underlying dynamic state). The temporal code-driven stimulation protocol [5-8] can be used to explore the functional equivalence of these sequences via their controlled detection, and subsequent stimulation. Different sequences are considered functionally equivalent when stimulation upon detection elicits comparable responses [9]. We used this protocol to detect a specific state by its spike sequences in the Hindmarsh-Rose (HR) model [10] and drive it toward a distinct state.
Methods Theprotocolacquiresa neuralsignalin real-time,discretizingittoabinarycode, anddeliversstimulationupondetectingatriggercode[11, 12].Foreachsystem-producedcode,theVictor-Purpuradistance[13]toatargetdetectioniscomputed.Whenthisdistancefallsbelowapredefinedthreshold,stimulationistriggered,allowingforacontrolledlevelofvariability.Theprotocol'sperformancewasassessedforreal-time use, andtwoexperimentswereconducted:i)itdetectedvariablesequencesoftheHRmodelburstingstateanddeliveredstimulationtogeneratebriefbursts(targetdynamicstate), andii)thestimulationinduceda regulardynamicstate(secondcontrolgoal)emergingfromthemodelset in achaoticregime. Results The real-time performance testsindicatedthat the protocolcanoperate at frequencies of up to 20 kHz and detect codes of up to 50 bits for a fixed frequency of 10 kHz, fulfilling the temporal requirements for studying temporal coding in neural systems. The two experiments discussed abovevalidatedthe protocol's ability to detect a specific dynamic state in the activity of the HR model, accounting for the intrinsic variability, and to drive it toward a target state. Finally, the closed-loop stimulation protocol outperformed an open-loop approach (where no specific code precedes the stimulation) in driving the system toward the target states in both experiments.
Discussion The closed-loop stimulation protocol studied in this work wasvalidatedfor real-time use. Two experiments proved that the protocolcandetect variable sequencesemergingfrom the same underlying dynamic states and drive neural activity toward a target state through activity-dependent stimulation. Consequently, it allows for the study of neural codes with an equivalent function in real-time. It does so by detecting temporally variable sequences of spikes that trigger stimulation. If system responses are comparable, it suggests that detected neural codes before stimulation convey the same information. Therefore, this protocol can be employed to study temporal coding in neural systems while accounting for their intrinsic variability.
Acknowledgements This research was supported by grants PID2024-155923NB-I00, CPP2023-010818, PID2023-149669NB-I00, PID2021-122347NB-I00 (MCIN/AEI and ERDF – “A way of making Europe”), and a grant from the Departamento de Ingeniería Informática at the Escuela Politécnica Superior of Universidad Autónoma de Madrid. References 1.https://doi.org/10.3389/fncom.2022.898829 2.https://doi.org/10.1016/S0928-4257(00)01103-7 3.https://doi.org/10.1016/j.neunet.2003.12.003 4.https://doi.org/10.1016/j.anbehav.2003.10.031 5.https://doi.org/10.1007/s10827-022-00841-9 6.https://doi.org/10.1007/978-3-031-34107-6_43 7.https://doi.org/10.1007/978-3-031-63219-8_21 8.https://doi.org/10.1007/s12530-025-09670-4 9.https://doi.org/10.1152/jn.00829.2003 10.https://doi.org/10.1098/rspb.1984.0024 11.https://doi.org/10.3389/fninf.2016.00041 12.https://doi.org/10.1007/978-3-319-59153-7_9 13.https://doi.org/10.1152/jn.1996.76.2.1310
