Neural Implants

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Neural Implants

• EEG Analysis
• and Neural Prosthetics

Shawn George BMME 111
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What are they?

• Tiny wires of microscopic diameter
• Plugs into the all of the messy wiring upstairs,
  receives and sends electrical signals
• Inserted into the brain via tiny drilled hole and
  some guesswork
• Interfaced with electronic gadgetry outside
• BCI

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Block diagram
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Kinds of implants

• Micro wires
• Small diameter, less than human hair, single wire
  with sharp end
• Makes contact with 1 or 2 neurons
• Polyethylene glycol (PEG) for mechanical
  stiffening

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Microelectrode arrays

• Bunch of micro wires on single chip, 40
• Can make contact with more than 20 at once

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Insertion

• Head placed in harness
• Burr hole drilled
• X-ray taken at intervals as implant is guided in

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Preparation

• General anesthetic applied
• Headrest mounted

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Insertion

• Burr hole site marked and drilled
• Introducing needle with microelectrode is
  inserted to predetermined distance

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• X-rays taken
• Additional electrodes added, as needed

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Is there an easier way?

• EEGs as an alternative
• Imaging of a large group of neurons, rather than
  a single one
• Inability to probe deeper into the gray matter
• Interference from surrounding neurons
• BUT non-invasive much less complicated setup

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Brain computer interface (BCI)

• 1 - Regular EEG (electrodes attached to scalp)
• 2 Neural implants

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BCI via implants

• Implanted methods signals from single or small
  groups of neurons in order to control a BCI
• Ideal placement motor cortex region
• Direct relevance to motor tasks
• Relative accessibility compared to motor areas
  deeper in the brain
• Ease of recording from its large pyramidal cells
• Much higher signal-to-noise ratio, since
  connected to specific cell
• Cost invasive.

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Epilepsy treatment

• 4 million in U.S. and Europe with epilepsy,
  approx. 1.2 million have recurrent seizures that
  do not respond to antiepileptic drugs
• Answer DBS
• Rationale deep brain stimulation (DBS) disrupts
  regulatory feedback loops in the brain that allow
  seizures to develop and spread
• Ambulatory EEG, then implantation
• Target thalamus
• Widespread connections to cerebral cortex, outer
  layer where seizures originate.
• 14 patients treated with stimulation of the
  anterior nucleus (AN) of the thalamus
• During the first 3 months, the median seizure
  frequency reduction at 64.
• 57 - a 50 or greater decrease in seizure
  frequency (responders).
• 9 patients 80 reduction in seizure frequency

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Neural Prosthetics

• Monkey see, monkey do
• The monkeys real arms are restrained
• 96 electrodes attached to the monkeys motor
  cortex
• exact placement of the electrodes not crucial due
  to brains plasticity
• Monkey tries to grab food, electrical signals
  recorded by scientists
• Signals converted into movements of robotic arm

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Neural Prosthetics quadriplegics

• BrainGate, developed by Cybernetics
  Neurotechnology Systems.
• Silicon wafer about a sixth-inch square, with 100
  hair-thin electrodes that extend a sixteenth of
  an inch into the brain.
• Matthew Nagle, 25, quadriplegic
• Thinks about moving arm, electrodes pick up his
  brain signals, computer translates brain signals
  into a code that moves a cursor
• Able to control the television, to get on to the
  computer and open his e-mailwithout hands.

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The future living computers??

• Neuro-chips
• 16,000 electronic transistors and hundreds of
  capacitors onto a silicon chip just 1 millimeter
  square in size
• Special proteins found in the brain to glue brain
  cells onto the chip
• Electrical signals from neurons were recorded
  using the chip's transistors, while the chip's
  capacitors were used to stimulate the neurons.

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A new fad??