Combined single neuron unit activity and local field potential oscillations in a human visual recognition memory task

Combined single neuron unit activity and local field potential oscillations in a human visual recognition memory task 170 177 IEEE Transactions on Biomedical Engineering (TBME)


Kucewicz, M.T., Berry, B.M., Bower, M.R., Cimbalnik, J., Svehlik, V., Stead, S.M., Worrell, G.A., Mayo Clinic, USA

Current neurotechnologies typically probe only a limited range of the vast scale of human brain electrophysiological activities, focusing either on the micro-electrode recordings of single neurons and their local assemblies (action potentials and local field potential) or the macro-electrode field potential of large neural populations (e.g. electrocorticogram). This paper compares the two scales through intracranial hybrid electrode recordings from micro-contacts (40 μm diameter) embedded between macro-contacts (1300 μm diameter) in epilepsy patients performing a recognition memory task. High frequency oscillations (HFOs) recorded on the macro-contacts were transformed to point processes and directly compared to single neuron action potentials (SUA) detected on adjacent micro-contacts during epochs of memory encoding and retrieval of emotionally charged images. HFOs showed more robust average response to image presentations than SUA with up to 80% increase in HFO counts compared to 2% increase in SUA firing rates. A large proportion of the macro-contacts also showed significantly different HFO responses to affectively charged vs neutral images (up to 18%) and to previously seen versus new images (up to 32%), compared to approx. 5% of all SUA recorded from all micro-contacts. These results offer a new analytical approach to combined micro- and macro-contact recordings during cognitive processing and support development of new high-density hybrid electrode technologies as envisioned in the BRAIN initiative. Such large-scale electrophysiology will enable simultaneous sampling of the activity of multiple individual neurons on the micro-scale, and their coordinated networks on the macro-scale to provide biomarkers of neuronal assemblies underlying human memory and other brain functions.

Keywords: high frequency oscillations, hybrid electrodes, large-scale electrophysiology, neuronal assemblies, neurons, human brain, memory, cognition, local field potential.