Electrophysiology

At 4Brain we use electrophysiological data to evaluate neural activity. We work with two main electrophysiological signals, evoked potentials (EPs) and electroencephalography (EEG).

Evoked Potentials (EPs)

Evoked potentials are electrical signals generated by the brain and nervous system in response to specific time-locked stimuli. At 4Brain we use EPs to asses hippocampal excitability. We generate the EPs through electrical stimulation of either the Schaeffer Collaterals (SC) to assess responses in CA1 region of the hippocampus, or at the Perforant Path (PP) to assess responses in the dentate gyrus (DG) region of the hippocampus. To assess the excitability of the hippocampal region we focus on two metrics. First the slope of the field post synaptic potential (fPSP) and second the amplitude of the population spike (PS). These metrics give us information about the synaptic input strength and neuronal output. At 4Brain we have extensive experience in measuring these EPs both ex vivo (hippocampal slice model) and in vivo in rodents. To measure these electrophysiological signals ex vivo we use multielectrode array (MEA) technology and to measure them in vivo we leverage our expertise with stereotactic surgeries and electrode implantations.

Electroencephalography (EEG)

Electroencephalography is a technique used to measure the electrical activity of the brain through different type of electrodes. At 4Brain we perform this technique in vivo in rodents and we use both epidural electrodes, minimally invasive, to record local field potentials (LFPs) at a cortical level and depth electrodes, invasive, to record LFPs in deeper brain regions such as the hippocampus. Through the LFPs we analyze electrical activity at the cortex and hippocampus, which allows for the detection of seizures and abnormal electrical activity. The clear detection of these electrophysiological signals is used to then apply closed-loop neuromodulation approaches, where we assess different kind of neuromodulation approaches as seizure-suppressive therapies.