Implant and Alignment Devises for Neurological Research

In the past, when working with single cells on chronically implanted primates, it has been difficult to establish that a given microelectrode penetration corresponds to particular electrode track on histological sections, or indeed, whether they were parallel. As a result of work done by Charles Crist, and Doctors Yamasaki, Komatsu and Robert Wurtz, a Grid System was developed to work in conjunction with microelectrodes, Guide Tubes and a Recording Microsyringe for chemical injections. The success of this system has resulted in it is becoming a standard for use in the research environment when accurate mapping or lesion placement is required. Crist Instrument had the Grid System (6-YGD-D1, 6-YGD-J1, 6-YGD-D2 and 6-YGD-J2) with Guide Tubes and Grids available for this type of study since early testing proved the efficiency of this apparatus. We worked on a method for commercially producing the Recording Microsyringe that was brought to the marketplace in June 1992. Since that time, it has been proven a highly effective device for simultaneous recording and injection of various substances in a single cell site. This brief describes the use of the Grid System and the Recording Microsyringe (3-MRM-S02). The Crist Grid System uses a Grid Cup that fits within the grid holder (Chamber Adapter) and an implanted Recording Cylinder. The Grid is made from Delrin or CILUX to keep it light in weight and also invisible to the MRI. It has an outside diameter of 19.05 mm and an inside diameter of 16.80 mm. The grid area consists of a format of 221 holes spaced 1 mm apart on the X-Y plane. It is in a well deep enough to stabilize a thin walled Guide Tube (6-YGTS-xx, for Guide Tubes up to 60 mm, or 6-YGTSA-xx for Guide Tubes over 60 mm) holding it virtually rigid. The Guide Tube is sufficiently large to allow the passage of a thin tungsten microelectrode or the Recording Microsyringe. The holes in the grid also accommodate thin platinum-iridium microelectrodes used for exploration. We recommend when using the grid that it be aligned stereotaxically to the Recording Chamber. This allows the grid assembly to be removed and replaced repeatedly, still maintaining it is anterior - posterior position. The Adapter (Smokestack) has three slots for the key pin located on the Recording Chamber. This allows a rotation of 30-degree steps of the grid with three times the penetration sites. Chamber Adapters and Head Holders are made from high quality 316 Stainless Steel or from CILUX. Guide Tubes are all custom cut to length with a squared off end and a flared top to facilitate insertion of the microelectrode. The Recording Microsyringe (3-MRM-S02) uses a modified Hamilton Syringe with an extended recording barrel. The wire is thin enough to allow the flow of relatively high viscosity solutions through the barrel. The wire extends .750 mm beyond the tip of the tube to prevent tissue displacement from interfering with recordings. Wire impedance measure in a range of 0.3 and 1.0 micro ohm at 1000 Hz. The Recording Microsyringe permits the occurrences of simultaneous single unit recordings and injections of various substances. It is possible to create a temporary or permanent lesion at or near a single neuron and observe the changes, which occur. Lesion effectiveness is measured with immediate response as the active neuron signal changes or ceases to fire. For convenience and cost, we are packaging the Recording Microsyringe in units that consist of three recording barrels and one modified Hamilton syringe.

ADAPTING THE SINGLE CELL RECORDING SYSTEM FOR USE WITH THE MRI

Because of increasing interest in the use of MRI to locate exact areas of the brain for study and to verify the location of head holders and cylinders after attachment, we have designed and are now producing a line of non-magnetic products expressly for use with MRI equipment. These items include our “0” degree and angle chambers, which are similar in style to the Evarts’ cylinder (6-ICO-J0, 6-ICO-J2A, 6-IAM-J0 & 6-IAM-JA); the Head Holder on the Head (6-FHP-J1, J6 & J4), the Head Post (6-FHP-X2 & B2), the Head Positioner on the Chair (FHD-J9) and the matching Head Holder on the Head (6-FHP-J9), as well as the Chamber to Microdrive Adapter, “Smokestack” (6-YNP-S3 & 6-YNP-J3). These are all comparable to our Stainless Steel devices for the same purpose, although some minor design changes were necessary.

In addition to the standard size line of cylinders and head holders we have also developed a new line of head holders in 316 Stainless Steel (not for MRI use), Titanium and CILUX for small animals (6-FHP-J6 and 6-FHP-J4) such as rats, rabbits, cats and new world monkeys. We have also designed a new Head Holder on the Chair (6-FHC-S6 and 6-FHC-S4) for smaller and lighter animals and the 6-FHC-S5 to work with the Mini Chairs (1-CM).

The latest addition to our repertoire of useful products is the Adjustable Head Positioner (6-FAC-SB series). It swivels, it pivots and turns to the position you need. With this unit the Head Holders for the Head can be placed in almost any position or location you require for your investigations.

For your convenience, store your microdrive adjacent to your work center in a Microdrive Storage Box (3-MMD-P1). The box hangs on a wall near your work center or hangs underneath a shelf. It has a specifically designed hanger for your Microdrive. Leave it connected, hang it up. The box is constructed of plastic with Stainless Steel hinges and a Brass door latch.

When it is freedom to work as you need you need to think of Crist Instrument Co., Inc.

Crist Instrument has been a major provider of Recording Chambers, Caps, Adaptors and Grids for many years. They have been designed to permit a wide variety of choices when studying the brain. Recording Cylinders recommended by Crist Instrument are available for “Single Cell” and “Multi Cell” recordings in either the near term or the chronic environment. Caps provide a protective cover to the dura when placed atop the Recording Chamber. The Adaptor is the holder for the Grid and serves as the interface between the Chamber and the Microdrive. The Grid is the device that provides accurate spacing (1mm) and alignment (A/P) of the penetration sites when performing single and multi cell recordings.

Recording Chambers (Cylinders) can be placed on the skull in a number of different locations. This is achieved by varying the angle at the base of the cylinder from “0” degrees to “45” degrees. “0” degree Chambers can be placed on the flat area of the skull to achieve vertical positioning or can be placed on the side of the skull for compound angle or straight in penetrations. Angle Chambers are used principally to provide a pattern with a common plane, i.e. horizontal; even when working to the periphery of the skull. These devices are attached during surgery using the Cylinder Alignment Tool (6-YSC-S2J or 6-YSC-S2S) the materials they are available in include 316 Stainless Steel or CILUX. Bases of the Chambers are knurled to provide grip when attaching to the skull with acrylic. Stainless Steel units have an overall diameter of 7/8 inch (22.2 mm) with an inside diameter (id) of 3/4 inch (19 mm). The overall height of the “0”