WTEC Brain Computer Interface (BCI) Workshop:
Sensor Technology
Greg A. Gerhardt
University of Kentucky Health Sciences Center
Departments of Anatomy and Neurobiology,
Neurology and Psychiatry
WTEC Workshop on Brain Computer Interface Research: 21 July 2006 Sponsors: NSF, TATRC, NIBIB, NINDS, DoED
Sensors in BCI – Study Highlights
• Science of BCI in North America and Europe
• The majority of BCI science in North America involves “invasive” technologies , i.e., multi-electrode recordings from arrays of electrodes implanted directly into brain.
• However, certain BCI sites in Europe are capable of providing technologies that could aid in the advancement of “invasive” sensor technologies.
These sites could be an untapped resource!
• The majority of BCI science in Europe involves “noninvasive” technologies , i.e., multi-electrode recordings from arrays of electrodes mounted onto the surface of the skull.

• Invasive Technologies – wire arrays,
Electrocorticographic (ECoG) strips, microfabricated electrode arrays (MEAs)
• Non-invasive Technologies – EEG, “headware devices”
• Enabling Technologies – In Vitro technologies such as MEAs
• Hess (1932) -
• Fischer (1957) -
• Collias (1957) first to implant electrodes in diencephalon of cat various metals/insulators used as single wire electrodes; 1-2 mm injury around tract
Histopathological analysis; evolving response; astrocyte capsule formation by 1 mo.;
FBR to electrode
• Delgado (1961)
• Robinson and
Johnson (1961)
- Reinforced histological findings
**Courtesy of Patrick Tresco

MICROWIRES
• Salcman and Bak (1973) -
• Woodward and Chapin (1980s) -
Record with parylene-coated microwires
Developed multi-wire arrays
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SILICON MICROELECTRODE ARRAYS
• Wise and Angell
•
(1970, 1975)
BeMent (1986)
-
-
Use IC technology to develop microelectrodes
Developed first multi-site electrode from Si (Michigan-style electrode)
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• Campbell (1991) Developed first monolithic multi-shank electrode from Si (Utah Electrode Array)
**Courtesy of Patrick Tresco
Micro-wire Recordings of Single-Unit Activity
ELECTRODE ARRAY
9 1
16
CA3
8
CA1
LA
TE
R
A
L
CA1
DG
T
M
E
D
IA
L
S
5
0
CA3
5
“Micro-wires” – the work horse sensors of many multi-single unit recording labs
0
0 50
Time (sec)
100
Neural Activity = Vector in N-dimensional space
X i,t
X = Firing Rate, i = Neuron, t = time
Courtesy of Drs. Sam Deadwyler and Rob Hampson
L-SAMPLE
R-NONMATCH
R-SAMPLE
L-NONMATCH
NOSEPOKE
1
2
5
6
7
10
CA1
11
12
CA3
13
150
16

Courtesy of
Scientific American and John Chapin
Wise, et al.(2004), Proceedings of the IEEE.
Hetke and. Anderson (2002). Handbook of Neuroprosthetic Methods.

Basic probe assembly for chronic studies in animals
4/11/2003
Vetter, Kipke, et al. (2004) IEEE Trans Biomed Eng
Kipke et al. (2003). IEEE Trans Neural Systems and Rehab. Engin.
~60 functional channels
~90 high-quality spikes
Discriminated spike waveforms
Schwartz et al. (U Pitt.)
Kipke et al., (Univ. of
Michigan)
Spike rasters for acquired robot control

4/11/2003
Microscale drug-delivery
500 µV
0
-500 µV
Chronic unit recordings
(FP5, day 7)
Courtesy of
Daryl Kipke,
Univ. of
Michigan

Direct communication with the CNS:
The ‘Utah Electrode Array’.
• MEM’s built silicon microsystem.
• 100 electrodes.
• Each electrode communicates with
2-3 neurons.
Courtesy of John Donoghue and Cyberkinetics
Courtesy of
John
Donoghue and
Cyberkinetics

DG
Neuron-Silicon Communication:
Conformal Multi-Site Recording Electrode Arrays
CA1
CA3
100 µm
„
„
„
„
Designed to allow recording from DG, CA1, and CA3 simultaneously
Designed for external single site stimulation
Capable of multi-site internal stimulation
Precisely aligned with averaged hippocampal slice cytoarchitectural coordinates
Trisynaptic conformal design aligned with rat acute slices
Courtesy of Ted
Berger, USC
Ceramic-Based Conformal Microelectrodes
Unique Features of Ceramic-based
“Conformal” Microelectrodes
1. Ceramic (Al
2
O
3
) substrates 37.5 to 125 µm
2. Long electrode configurations (1-20 cm)
3. “Multi-purpose” tip and shank designs
135
0
μ m
W3
Side-by-Side
600
μ m
Serial
W2
“Ceramic-based
Microarrays”
15x333 μ m
20x150 μ m
USC, Wake Forest and Univ. of Kentucky

MEAS with Flexible Connectors Analogous to Subdural Designs
Ceramic microelectrode
Spencer-Gerhardt
(SG-1) microelectrodes
Sub-dural strips Spencer-Gerhardt Microarray
(Chemistry and Physiology)
SG-1 prototype
SG-1
Electrode tip
Univ. of Kentucky and Ad-Tech Medical Instruments
• What factors improve longevity of the recordings?
• Failure analysis of components over 1-12 month periods.
• How long do current designs last?
• How do we develop designs that last for ca. 5-10 years?

ECoG: Anatomical localization: Albert-Ludwigs
University, Freiburg, Germany
8
L
FL
7
6
5
4
3
2
1
H
G
F
E
D
C
B
A
TL
Courtesy of Dan Moran, Washington Univ., St. Louis

Multi Channel Systems
In Vitro MEAS (Reutlingen, Germany)
60 channel arrays

Professor Peter Fromherz
Max Planck Institute for Biochemistry, Munich, Germany
Rat neuron on electrolyte-oxide-silicon (EOS) field effect transistor. a) Electron micrographs (colorized) of a hippocampal neuron on a silicon chip array; b)
Schematic cross section of a neuron on a buried-channel field-effect transistor with blow-up (drawn to scale) of the contact area.
Cultured Hippocampal Slices
7.4 μ resolution – 2 KHz Measures

Max Planck Institute for Biochemistry,
Munich, Germany

brain signal
BCI control signal closed loop system visual feedback
Application
Mobile EEG system from g ® .tec (Austria)

• Need for “dry electrode” systems
• More “on electrode” electronics for improved signal-to-noise
• Editors – Ted Berger and Greg Gerhardt
• Manuscripts due by 12/1/06
• 1-2 volumes + overview - Currently 12 tentative manuscripts