9 - Neuroprostheses Overview

• Implant

  materials, inserted in body to restore functionality for a limited time or whole life (also man-made)

• Prothesis

  artificial replacement for missing body part (e.g. arms, legs, bones, arteries, teeth, …)

• Neuroprothese

  interfaces between neuronal system and electronic devices

  -> for clinical applications and research

• Neuroprosthetics (or neural prosthetics)

  field within neuroscience and biomedical engineering

  -> creating devices that replace/enhance neural functions

  contrast: brain-computer interface (connects brain to computer rather than restoring lost functions)

  
  

1. implant electrode array into prefrontal cortex -> touches neurons in layer 2/3 and layer 5

2. electrodes record brain activity and send to microprocessor (under skin at top of head)

3. microprocessor detects a specific pattern (e.g. neural signature of person trying to recall memory) -> array sends electric pulses into surrounding area, stimulating mental processing

1. implant electrode arrays in motor cortex and somatosensory cortex

2. user thinks of kicking ball -> brain sends neural commands from motor cortex -> picked up by array -> transmitted to microprocessor on patients skull

3. microprocessor transmits commands to lower-body exosceleton (with own processor)-> leg moves to ball

4. foot touches ground -> pressure sensors on exoskeleton surface generate tactile signal -> sent back to array in sensory cortex

—> feedback loop: patient can feel ground and kick back

= battery-powered medical device implanted under skin to help regulate heart’s rhythm

—> generates electrical impulses that stimulate heart to beat regularly

stimulate auditory neurons in cochlear to restore hearing

ABI is similar to Cochlear Implant, but outcomes are poorer

1. Subretinal Chip - implanted beneath retina

   light signals -> electrical pulses -> stimulate ganglion cells

2. Subdermal Receiver - implanted beneath skin

   acts as relay btw implant and external components

3. External Transmitter Antenna - behind ear

   transmits signals and energy to implants

4. Power Box & Control Unit - held in hand

   adjustment of brightness and contrast to optimize seeing

• Ultra-large imaging windows - larger than entire rodant brain, enable unprecendented large-scale circuit analyses

• Long-term imaging stability - functional longer than a mouse lifespan, allowing longitudinal studies of circuits over timeframes relevant to human cognitive development

Novel tools and techniques:

• Optogenetics - precise neural activation using light

• Voltage-, Calcium- and Glutamatesensitive dye imaging

• Two-photon and wide-field optical imaging

• Viral delivery and genetic expression systems

• Morbus Parkinson

• Tremor

• Dystonia

• Huntington disease

Pain control, Epilepsy, Depression, Tourette-Syndrom, Addiction, Schizophrenia

1. electrodes surgically implanted in specific brain regions (e.g subthalamic nucleus for Parkinson)

2. Pulse generator under skin in chest delivers electrical impulses to electrodes

3. impulses modulate abnormal brain activity, restoring normal functions

20% of all Europeans

15.000 treated with implants

electrodes delivers low-voltage electrical impulses to spinal cord

—> interfere with pain signals traveling to brain

non-invasive BCI - uses external devices without surgery

e.g. controlling wheelchair using brain-activity with EEG cap

+ safe, easier setup

- limited signal resolution, slower response

invasive BCI - surgical implantation of electrodes in brain

e.g. restoring mobility for individuals with paralysis (robotic arm)

+ high accuracy, can do complex tasks

- brain surgery with risks, long-term biocompatibility issues

Vagus Nerve Stimulation - implant delivers pulses to vagus

invasive

+ approved in US, Canada and EU for depression

+ works for years

- works perfectly in 1/6 patients

- requires surgery

delivers low-intensity electrical current through electrodes on scalp

non-invasive: electrodes placed externally

+ simple, cheap

- few studies, little known how it works

magnetic coil to generate focused magnetic field that induces electrical currents in brain

non-invasive: magnetic stimulation through scalp

+ few side effects

- long-term risks and effectivness unknown

similar to TMS, with higher magnetic stimulation

non-invasive

+ could be more effective than other

- requires daily anaesthesia for weeks

- few patients undergone this treatment

- little known about side effects

blocks signals between gut and brain (vagus nerve)

-> treat diabetes

• Neuromodulation

  pain control, epilepsy, deep brain stimulation, stimulation of bladder, vagus nerve

• Functional electrical stimulation

  neuronal and muscle stimulation

• Transcranial magnetic stimulation

  stroke, depression

• Motorprostheses

  walking support, hand motion

• Sensory neuroprostheses

  Cochlear Implants, retina implant

• Bidirectional neuroprostheses

  Motor control puls, somatosensory feedback

• Brain-Computer-Interface

  Locked-In-Syndrome, user interface, exosceleton control

• Brain-Brain-Interface

  dementia

Brain implants allow paralysed monkeys to walk

Moving robotic arm with BCI reading motion planning

Paralyzed moving hand with FES

Pioneering brain implant restores paralysed man's sense of

touch