BIOMED SCIE L ECTURE 28 neuromodulations

• Neural Engineering


  Emerging new discipline that describes the area where engineering and neuroscience interact
• Questions addressed by Neural Engineering

  • Applying engineering to understand the function of the brain and nervous system and the mechanisms of disease; develop new diagnostic and therapeutic techniques
  • Developing technologies to interact with the nervous system and to replace lost function (prosthesis, brain machine interfaces)
  • Understanding how the brain and nervous system store and process information to transform future computing ( Neuromorphic Computing /Biomimetics)

  
• Neuromodulation


  The modification of neural activity to achieve a therapeutic effect
• Types of Neuromodulation


  • Pharmacological
  • Electrical
  • Optical, thermal, mechanical etc.
• Neural Prostheses


  Applications for which neural stimulation is used to replace a lost or damaged neural function
• Categories of Neural Prostheses


  • Motor prostheses: electrical stimulation of the neuromuscular system is used to substitute for normal control by the brain or spinal cord
  • Sensory prostheses: an artificial sensor replaces neural input that would come from a peripheral biological source
• Applications of neural stimulation


  • Stimulation of the retina to restore vision
  • Memory prostheses to bypass damaged circuits within the brain to improve memory storage and recall
  • Vagal nerve stimulation and deep brain stimulation to reduce seizures in treatment of epilepsy

  
• Cochlear implants


  Devices that comprise an external device worn behind the ear that converts acoustic energy into an analog signal, which is then digitized, compressed, filtered and encoded into a signal that will be used to drive spiral ganglion nerve stimulation
• Cochlear implants


  • The information is transmitted through the skin using radio frequency (RF) signals to an implanted intracochlear stimulator
  • A variable number of electrodes are encased within an "electrode array" to directly stimulate the spiral ganglion nerves
• Retinal Prostheses


  Devices that aim to replace degenerated photoreceptors and provide analog signal to the adjacent intact neural layers, which map the visual pattern into pulse trains
• Types of Retinal Prostheses


  • Subretinal implants consisting of photodiodes and electrodes
  • Epiretinal implants that stimulate ganglion cells directly
• Functional Electrical Stimulation (FES)


  The electrical stimulation of peripheral nervous tissue to produce muscular activity
• Functional Electrical Stimulation (FES)


  • When a motoneuron is stimulated with an external electrode an action potential propagates to the innervated muscle fibres and they contract as if under naturally occurring stimulation
  • FES can be used to stimulate muscle activity when the normal neural drive to the muscle is impaired

  
• Advantages of Functional Electrical Stimulation (FES)


  • Prevent muscle atrophy (wasting) & associated deterioration of joints and skin
  • Reverse loss of muscle mass improve cosmesis & cushioning
  • Reverse muscle loss enable standing in some cases, improve blood flow, skin condition & bone density
  • Improve cardiovascular fitness
• Deep Brain Stimulation (DBS)


  High frequency (100-1140 Hz) electrical stimulation of neural centres within the brain using chronically implanted electrodes for the treatment of symptoms of Parkinson's disease, also being investigated for treating epilepsy, depression & obesity

  
• Deep Brain Stimulation (DBS)


  • Pulse amplitude (1-5 V), duration (~60 ms), frequency (>100 Hz)
  • Stimulation parameters are set empirically and can take up to 6 months to optimize
  • 37% of patients with suboptimal DBS improved with reprogramming
  • 3-4 year battery life with conventional batteries; 15-25 yrs for rechargeable
• Deep Brain Stimulation (DBS) is effective in 85% of patients for control over tremor, improves UPDRS III scores by 65%, and decreases dyskinesias by 70%
• Electroceuticals


  Neuromodulation alternative to pharmaceutical therapies, using adaptive systems based on simultaneous sensing and stimulation
• Electroceuticals need to overcome technical challenges related to electric field distribution, neural interface, cellular and system effects, and require miniaturised, implantable, low power devices