Transcript 16-Channel Brain Tissue Stimulator

16-Channel Brain Tissue
Stimulator
Friday, October 27, 2006
Design Team

Team Members
o
o
o
o

Client
o

Ashley Phillips -Team Leader
Nina Lewis - Communications
Steven Skroch - BSAC
Steve Noel - BWIG
Matthew Jones, PhD – Department of
Physiology
Advisor
o
Willis Tompkins, PhD – Department of
Biomedical Engineering
Overview





Problem Statement
Motivation
Background
Design
Future Work
Problem Statement

Our objective is to develop a multi-channel brain tissue
stimulator. This device must generate stimulation
current of 1 mA on 16 separate channels, filter out
external noise, and allow each channel to be
independently gated on and off as well as adjust the
current amplitude on each channel.
Motivation



To learn the circuitry of the hippocampus to
better understand the processes behind
learning and memory
To improve upon the current process, as it is
not physiologically accurate
Provide a low cost multi-channel stimulator
Background

Hippocampus
o
o
o
Site for learning and memory
Receives inhibitory and excitatory potentials from neurons in the
cortex
Contains tightly packed granule cells, called dentate gyrus, which
form one unit of circuitry
(1)
Background

Michigan Electrode
16 electrodes
o Each channel of device will stimulate one electrode
o Each electrode has high impedance of 1 MΩ
o AC current only
o
(2)
Client Requirements
The stimulator should:
•
•
•
•
Trigger each pad independently with a 5V TTL
pulse
Deliver 1 mA of current
Deliver the same amount of current to each
pad
Deliver the pulse in 100s with no lag
Problems Encountered

Lag time cannot be completely eliminated

High voltage must be supplied

Safety
Proposed Design
(3), (4), 5), (6)
Rectifier
Switch
Future Work




Order parts
Build and test circuit
Scale-up circuit
Build at least 2 channels
References/Acknowledgments
1)
2)
3)
4)
5)
6)
www.BrainConnection.com
Jones, Matthew. Personal interview. 15 Sept. 2006.
Kaczmarek, Kurt A., Kevin M. Kramer, John G. Webster, and Robert G.
Radwin. "A 16-Channel 8-Parameter Waveform Electrotactile Stimulation
System." IEEE Transactions on Biomedical Engineering 38 (1991): 933-943.
Yusko, Erik, Danielle Ebben, Marty Grasse, and Tony Wampole. 16-Channel
Brain Tissue Stimulator. UW-Madison. 1-26.
Victorey, Paul. Department of Biomedical Engineering. Personal Interviews.
O’Neal, Burke L. Department of Biomedical Engineering. Personal Interviews.
Any Questions?
Modifications to Original Design




Replaced 50kΩ ½ W Filter resistors with
5MΩ 2.5 W Resistors
470 µF capacitors only rated to 300 V. Will
have to replace when we scale up
22 µF capacitor for charge storage (may
eliminate)
All components must be high power
Switch


5V pulse sent through Schmitt Trigger for
normalization
Pulse sent through optical isolator
–


Want to keep entire gate side of circuit floating
12V Floating Source, rated to 700 V
FET rated up to 1000Vds
Switch




Potentiometer used to modify output voltage
(may move to before gate)
Only the FET must be high power
All components must have minimal
attenuation at 100kHz
No leakage current due to probe acting as a
capacitor (cannot pass DC current)