Neuro Flashcards
(40 cards)
Q:What is a bioelectronic medicine or neuroprosthetic device in essence?
A:It is an electronic system that interfaces with physiology closes the loop on a compromised control system to treat disease examples include cardiac pacemakers deep brain stimulators and cochlear implants
Q:Why do engineers describe closed loop neurostimulators with a technology stack?
A:The stack divides the device into material interface sensors classifiers control policy and actuators which clarifies design goals constraints and risks
Q:Why is identifying a biomarker crucial in adaptive neurostimulation?
A:A biomarker is a measurable signal tied to disease state or user intent and without it the device cannot decide when or how to adjust therapy
Q:What are action potentials and why are they all or none?
A:They are rapid neuron voltage spikes produced by coordinated sodium and potassium channel dynamics and once threshold is crossed the spike propagates without attenuation ensuring reliable signalling
Q:List the main steps of Hodgkin Huxley membrane modelling
A:Model membrane as capacitor plus ionic conductances write current balance include voltage dependent gating variables and solve to predict action potentials
Q:What is the neural activation function in stimulation terms?
A:It is a simplified relation between external electric field and transmembrane voltage that predicts which stimulus parameters trigger or block action potentials
Q:How does the cable equation aid extracellular stimulation analysis?
A:It models axial and extracellular current flow with membrane capacitance letting designers compute spatial voltage gradients that set activation thresholds
Q:Define rheobase and chronaxie
A:Rheobase is the minimum current for an infinitely long pulse and chronaxie is the pulse width at twice rheobase indicating energy efficient duration
Q:How does ultrasound neuromodulation differ from electrical pulses?
A:Ultrasound focuses mechanical energy to modulate mechanosensitive channels can reach deep tissue noninvasively and has different dosing and safety profiles
Q:Why must chronic stimulation pulses be charge balanced?
A:Biphasic charge balanced pulses prevent net direct current thereby avoiding electrode corrosion tissue damage and pH shifts
Q:Name common electrode materials for implant interfaces
A:Platinum iridium stainless steel titanium nitride and iridium oxide are chosen for biocompatibility electrochemical stability high charge capacity and conductivity
Q:Contrast action potentials with local field potentials LFPs
A:Spikes occupy three hundred hertz to five kilohertz last about one millisecond and reach hundreds of microvolts while LFPs are below two hundred hertz slower and larger
Q:Compare ECoG with scalp EEG
A:ECoG uses cortical surface electrodes yields higher amplitude and wider bandwidth but is invasive whereas EEG is noninvasive but attenuated and lower resolution
Q:What is a differential amplifier’s role in neural recording?
A:It measures the voltage difference between signal and reference electrodes rejecting common mode noise to reveal microvolt neural signals
Q:State two design challenges for low noise neural amplifiers
A:They need megaohm input impedance with picoamp bias and must minimize thermal and flicker noise so spikes remain visible
Q:How does a physiologic closed loop controller differ from open loop therapy?
A:It senses a biomarker and automatically adjusts therapy improving efficacy reducing side effects and saving energy while open loop stays fixed
Q:Define the classifier block in a BMI for movement intent
A:It converts neural features into predicted movement state such as direction or action which then drives the control policy
Q:Why can pure feedforward control be risky in bioelectronic devices?
A:Physiology changes with time and disturbances so without feedback a feedforward system may deliver unsafe or ineffective therapy
Q:Give one automation risk and the IEC 60601 1 10 mitigation
A:Automation bias could cause unsafe stimulation and the standard mandates fallback modes user override and safety margins to protect patients
Q:What is fallback mode in a closed loop medical device?
A:A predefined safe therapy level or shutdown entered when faults or uncertainties are detected until normal control is restored
Q:How are large common mode artefacts mitigated in neural systems?
A:Use balanced high impedance electrodes differential amplifiers with strong rejection and synchronized filtering or blanking
Q:List benefits of biphasic pulses
A:They maintain zero net charge reduce electrochemical damage enable reversible stimulation and extend electrode life
Q:What does the strength duration curve illustrate?
A:It plots threshold current versus pulse width showing rheobase and chronaxie to guide energy efficient safe stimulus design
Q:Explain electrode surface area trade offs
A:Larger area lowers charge density and damage risk but decreases spatial selectivity and can raise noise whereas small area does the opposite
