A Collection of Electrophysiological Human Datasets

Dataset of electrophysiological recordings from human neurons Executive summary Animal models have long been indispensable for advancing our understanding of the mechanisms underlying neurodevelopmental disorders. However, despite the conservation of many biological processes across species, the human brain exhibits unique structural and functional complexities that limit the translational relevance of animal studies. To overcome these limitations, an alternative strategy involves the use of human brain tissue obtained during neurosurgical procedures, such as those performed to treat drug-resistant epilepsy or brain tumours. Leveraging resected human brain tissue as an ex vivo platform offers significant translational advantages for modelling disease mechanisms and studying human-specific neural activity. A major challenge in this approach is the limited viability of human brain tissue. To address this, we employ organotypic slice cultures, which allow the maintenance of human cortical tissue in vitro for several weeks, while preserving both cytoarchitecture and functional integrity. Compared to acutely prepared slices, organotypic cultures offer longer experimental windows and are amenable to genetic manipulation. We performed patch-clamp electrophysiology on both acute and organotypic human cortical slices derived from paediatric patients with intractable epilepsy. We assessed the passive and active membrane properties of individual neurons using current-clamp recordings to characterize their firing behaviour and membrane potential dynamics. In parallel, voltage-clamp experiments were conducted to examine spontaneous postsynaptic inhibitory currents, providing insights into synaptic activity. This approach lays the foundation for a human-relevant platform to study neurophysiological mechanisms and to test therapeutic interventions with high translational potential. Introduction Animal models have been instrumental in elucidating the mechanisms underlying neurodevelopmental and neurodegenerative disorders. However, despite the conservation of many biological processes across species, the human brain exhibits unique structural and functional complexities that limit the translational relevance of animal studies. To bridge this gap, the use of human brain tissue obtained during neurosurgical procedures, such as those performed for drug-resistant epilepsy or tumor resection, offers a valuable alternative. In recent years, both acute and organotypic brain slice preparations from resected human tissue have emerged as powerful ex vivo platforms for studying human neural circuits, disease mechanisms, and potential therapeutic interventions. Acute human cortical slices, typically prepared and studied within hours of surgical resection, have proven particularly effective for high-resolution electrophysiological recordings, enabling detailed analysis of membrane properties, synaptic transmission, and cellular excitability. Several studies have demonstrated the feasibility of patch-clamp recordings in acute human neocortical slices, revealing preserved functional properties of pyramidal neurons and interneurons (Molnár et al., 2008; Verhoog et al., 2016; Testa-Silva et al., 2014). Complementing acute slices, organotypic slice cultures offer the advantage of long-term viability, allowing extended investigation of dynamic processes such as epileptogenesis, gliosis, or neurodegeneration. These cultures retain the original cytoarchitecture and synaptic organization of the human cortex and support experimental techniques such as viral gene delivery, calcium imaging, and chronic drug testing (Bak et al 2024). Together, human brain slice models help us better study how the human brain works and develop treatments that are more relevant to patients. Content section Electrophysiological recordings Immediately after resection, brain samples were placed in cold oxygenated ACSF containing (in mM): 110 choline chloride, 26 NaHCO3, 10 D-glucose, 11.6 Na-ascorbate, 7 MgCl2, 3.1 Na-pyruvate, 2.5 KCl, 1.25 NaH2PO4, und 0.5 CaCl2) equilibrated with carbogen (95% O2, 5% CO2) and immediately transported to the laboratory. Tissue was kept submerged in cool and carbogenated aCSF at all times. 300 µm thick acute slices were transferred onto culture membranes and kept in six-well culture dishes in an appropriate media and stored in an incubator. For electrophysiological recordings, slice were transferred to the recording chamber. After completing patch-clamp recordings, slices were fixed in 4% paraformaldehyde and processed for immunocytochemistry. Whole-cell patch-clamp recordings were performed using patch electrodes (resistance 3–6 MΩ) filled with an intracellular solution containing (in mM): 70 K-gluconate, 70 KCl, 2 NaCl, 10 HEPES, 10 EGTA, 1 MgCl₂, 4 Mg-ATP, and 0.3 Na-GTP. Signals were amplified using a MultiClamp 700B patch-clamp amplifier (Molecular Devices, Sunnyvale, CA), sampled at 20 kHz, and low-pass filtered at 10 kHz. Data were acquired and analyzed using a Digidata 1550 digitizer and pCLAMP 9 software (Molecular Devices). The pipette solution set the intracellular chloride concentration to yield a calculated chloride reversal potential of –16 mV. In voltage-clamp mode, neurons were held at –70 mV, allowing GABAergic spontaneous inhibitory postsynaptic currents (sIPSCs) to be recorded as inward currents (datasets: B, G, J, O, P, U, V, K). In current-clamp mode, neurons were subjected to depolarizing and hyperpolarizing current steps (10 mV increments from a holding potential of –70 mV) to assess their firing properties (step datasets: A, F, L, N, R, T, W, Y). To monitor spontaneous membrane potential fluctuations, recordings were also performed without current injection (gap-free datasets: C, D, E, I, M, Q, S, Z, X). Outcomes Electrophysiological recordings from human cortical neurons, provide valuable insights into their intrinsic properties, synaptic activity, and network behaviour. Below is a summary of the key outcomes observed: 1. Firing Properties (Current Clamp Mode) • Normal appearing Pyramidal neurons (excitatory): show regular spiking behaviour with frequency adaptation during depolarizing current steps. • Putative balloon cells: show non- spiking behaviour. • Putative immature cells: show calcium spikes • Putative dysmorphic neurons: irregular spiking behaviour with lack of firing frequency adaptation • Interneurons: show non-adapting or fast-spiking behaviour 2. Spontaneous Inhibitory Postsynaptic Currents (sIPSCs) – (Voltage Clamp mode) • sIPSCs are observed at a holding potential of –70 mV as inward currents, due to the Cl⁻ gradient set by the pipette. • sIPSC frequency and amplitude reflect the level of inhibitory synaptic input and can vary between neuron types and disease states. 3. Membrane Potential Fluctuations (Gap-Free Recordings; Current Clamp Mode) • Reflect ongoing synaptic activity and intrinsic membrane dynamics in the absence of stimuli. • Include spontaneous postsynaptic potentials. • Tissue from epileptic cortex may show abnormal membrane potential shifts • These recordings are valuable for assessing network excitability and baseline synaptic input. Conclusions These strategic human electrophysiological data from patients suffering from intractable epilepsy can be integrated in the multiscale data-driven network models of human brain foreseen in EBRAINS. These data can be useful for the Medical Informatics Platform (MIT) which supports the development of disease-oriented federations for hospitals and (medical) research centres that wish to engage in collaborations, share data without transferring them, and perform federated analysis of large-scale distributed clinical datasets. Users of MIT can explore human neurophysiological data without transferring original clinical data. References (and link) a) Molnár G, Rózsa M, Baka J, Holderith N, Barzó P, Nusser Z, Tamás G. Human pyramidal to interneuron synapses are mediated by multi-vesicular release and multiple docked vesicles. Elife. 2016 Aug 18;5:e18167. doi: 10.7554/eLife.18167. PMID: 27536876; PMCID: PMC4999310. b) Verhoog MB, Goriounova NA, Obermayer J, Stroeder J, Hjorth JJ, Testa-Silva G, Baayen JC, de Kock CP, Meredith RM, Mansvelder HD. Mechanisms underlying the rules for associative plasticity at adult human neocortical synapses. J Neurosci. 2013 Oct 23;33(43):17197-208. doi: 10.1523/JNEUROSCI.3158-13.2013. PMID: 24155324; PMCID: PMC6618441. c) Testa-Silva G, Verhoog MB, Linaro D, de Kock CP, Baayen JC, Meredith RM, De Zeeuw CI, Giugliano M, Mansvelder HD. High bandwidth synaptic communication and frequency tracking in human neocortex. PLoS Biol. 2014 Nov 25;12(11):e1002007. doi: 10.1371/journal.pbio.1002007. PMID: 25422947; PMCID: PMC4244038. d) Bak A, Koch H, van Loo KMJ, Schmied K, Gittel B, Weber Y, Ort J, Schwarz N, Tauber SC, Wuttke TV, Delev D. Human organotypic brain slice cultures: a detailed and improved protocol for preparation and long-term maintenance. J Neurosci Methods. 2024 Apr;404:110055. doi: 10.1016/j.jneumeth.2023.110055. Epub 2024 Jan 5. PMID: 38184112.