Microwire Recording Arrays
Biographic Inc. offers recordings arrays with
different configurations.
Eight–Wire Recording Arrays with Stainless Steel
Ground Lead:
AVAILABLE COMPONENTS:
Arrays with 50 micron Teflon Insulated Stainless Steel
Wires with 50mil strip connectors
Item One: MWA-MI-1x8-S-1B-00-S
This part includes a
group of eight 2-mil Teflon-coated stainless steel wires connected to a ten
position strip connector at 0.05 inch spacing.
The ninth pin includes 10 cm of 5 mil stainless wire for grounding. The tenth pin position is left vacant. The tips of the wires are arranged in a
linear array spaced 250 microns apart in a one by eight pattern. Two holes at the ends of the strip connectors
to allow use of guide pins are included at the ends of the strip connectors.
Item Two:
MWA-MI-2x3x3-S-1B-00-S
This part includes a group of eight 2 mil Teflon-coated stainless steel wires connected to a ten position strip connector at 0.05 inch spacing. The ninth pin includes 10 cm of 5 mil stainless wire for grounding. The tenth pin position is vacant. The tips of the wires are arranged in a linear array spaced 250 microns apart in a two by four pattern.
Item Three:
MWA-MI-2x4-S-1B-00-S
This part includes a group of eight 2 mil Teflon-coated stainless steel wires connected to a ten position strip connector at 0.05 inch spacing. The ninth pin includes 10 cm of 5 mil stainless wire for grounding. The tenth pin position is vacant. The tips of the wires are arranged in a linear array spaced 250 microns apart in a two by four pattern.
Item Four: Surgical Alignment Plug Module – The eight microwire arrays are intended to be used in pairs when mounted on ten-position strip connectors. Each group of eight micro wires is inserted into different regions of the brain and the placed together, when encased with dental acrylic, so that the sixteen channel unity gain head stage/cable fits accurately when plugged in during the recording session. The alignment module includes a dummy plus with two or four strip connectors and holds the two strip connectors together while dental acrylic is applied around the strip connectors at the end of the surgery procedure.
Item Five: Micro Wire Array Tune Up Kit - Micro wire arrays must be handle carefully. The water soluble wax is fragile and may bend or crack if bumped. Also, recording of single neuron activity is found to be improved it the tips of micro wires are cut shortly before insertion into brain tissue. Teflon is flexible and normally handling may cause stretching
Special Orders:
Standard devices can be used in most experiments. However, customers may specify spacing and length of wires subject to $100 set up charge.
Arrays can be fabricated using 1.5 mil Tungsten or 2 mil Pt/Ir wire.
---Arrays with EMG Recording Wires --
Item Six: MWA-MI-8EMG Recording Wire Arrays - Eight twisted pair wires (three 2 mil stainless steel Teflon coated are standard) are provided to allow chronic recording of muscle EMG. These units are based on the standard 10 position strip connectors as employed for microwire recording but provide connections to twisted multi stranded wire, Teflon coated stainless steel, to allow chronic recording of EMG. Wires are intended to be cut to suitable length stripped at the end and inserted into muscle for chronic recording. Amplifier channels of the PA-01 can be specified with filter settings optimal for muscle EMG recording.
Item Seven: MWA-MI-EMG/MWA -6MW-2EMG - Mixed EMG/Microwire arrays for combination of neuron single neuron and muscle recording. This unit provides 6 microwire electrodes (2x3) with two three-strand twisted pair electrodes.
Special Order Items:
Biographics Inc
attempts to maintain availability of legacy items until conversion is possible
to new components. Depending
on availability of ten-position strip connectors from Microtech
Inc. (with
0.07 inch pitch), a similar set of arrays
can be provided with similar spacing of the microwire tips. Parts comparable to items 1-3 are specified
with Microtech strips connectors as –
Special
Order - MWA-07-1x8-S-1B-00-S Microtech connector with 1x8 array and 2 mil SS wire and
single ground wire on pin nine.
Special
Order - MWA-07-2x4-S-1B-00-S Microtech connector with 2x4 array and 2 mil SS wire and
single ground wire on pin nine.
Special Order - MWA-07-2x3x3-S-1B-00-S Microtech connector with 2x3x3 array and 2 mil SS wire and single ground wire on pin nine.
History and Use of Microwire Recording Arrays: It has been known for many years that a simple wire cut off blunt can be implanted into brain tissue and record single neuronal activity. However, the technique did not prove practical at early times since movable microelectrodes seemed to offer a high yield during a typical recording session. Moving an electrode allowed the flexibility of aiming at and spearing specific brain regions and at first the available recording instrumentation consisted only of single channel spike sorters. All experiments were designed with these built in limitations and long term recordings at fixed location did not seem to offer advantages.
With the advent of multiple-channel recording instrumentation it became conceivable to implant large numbers of recording wires and to leave them in place over many days or weeks. Locations of the tips of stainless steel microwires can be done much more precisely than with the reconstructed paths of movable electrodes since passing negative current through the tips electrochemically deposits iron which can be stained during histology. Study of brain activity over changes in learning and adaptive processes has now become possible. Fundamentally different types of experimental questions became feasible to investigate.
Different experimental designs have
begun to emerge that take advantage of long term recording from large numbers
of probes, an approach that has grown in parallel with new technology to allow
insertion and positioning of multiple traditional single neuron probes as well
as groups of movable tetrode recording
assemblies. Also, the early implanted
micro wires were of a large diameter,
These arrays have been proven over a decade of recording from neurons in rat and other mammals. Each array includes a group (8) of eight small but stiff wires connected to a ten position strip connector. The array is imbedded in a water soluble wax, except for the initial 3 mm of wire, to hold the group together so that they may be inserted many millimeters deep into the brain tissue. These electrode arrays are first inserted into brain tissue with each wire separated from its neighbor. Early studies showed that bundle of microwires that clumped together did not record well since they behaved more like one large wire. The wires are fabricated to be spaced 250 micrometers apart in different patterns. These are inserted into brain and follow parallel but independent paths through brain tissue.
Experience of many researchers since 1990 has revealed that such electrodes obtain stable recordings of spikes from single neurons in rats and other mammals for periods of many months. The arrays are typically implanted in pairs within different regions of brain tissue. The two strip connectors are embedded in dental acrylic in parallel with use of a mounting jig so that the mating head stage plug/cable assembly will be aligned to fit.
These arrays are now are available in the configurations: 1x8, 2x4, and 2x3x3 in a pattern approximating a grid of parallel wires. The tips of wires are cut clean to allow only a small 50-millimicron diameter disk of metal to be exposed to brain tissue. Tungsten carbide scissors are used with stainless steel to allow clean cuts to be repeated.
Insertion force is a problem is since many commercially available plugs are designed to be plugged in only once, and these offer so much resistance that the animal skull and brain would be jolted should such connectors be used. The ideal connector is designed to be used daily without changes in the force used to plug and unplug.
All Biographics Inc. strip connectors and plug assemblies have been specially engineered so that the insertion force remains optimal over repeated use. The recording plug/cable assemblies can be plugged in repeatedly quite smoothly so that jarring of the head is minimal and so that the plug remains firmly connected during long duration recordings. This feature is critical if one intends to obtain recordings over many days or weeks. The 0.05 inch Omnetics Micro Strip Connector is rugged and can be used on a daily basis for long duration studies.
Biographics, Inc.
3811 Guinevere Suite 100
Ph 336.499.3773 Fax 336.499.5624