Chronic chamber microdrive

Details Chronic chamber microdrive Chronic chamber microdrive

1999-03-05

2001-06-19

Kamm, William E. (Department: 3762)

Surgery

Diagnostic testing

Structure of body-contacting electrode or electrode inserted...

Reexamination Certificate

active

06249691

ABSTRACT:

TECHNICAL FIELD
The present disclosure relates to neural recording via electrode insertion, and more particularly to neural recording via electrode insertion using an implanted microdrive.
BACKGROUND
Neural recording typically selects different parts of the brain to obtain different information. One approach to neural recording includes extra-cellular electrode insertion. Extra-cellular electrode insertion typically involves the insertion of one or more electrodes into neural tissue. Conventional extra-cellular electrode insertion has traditionally followed one of two paths.
One conventional technique extra-cellular electrode insertion is a chronic technique, i.e. long term, such as more than one day. One or more electrodes are surgically implanted in the brain of a subject, such as an animal. In general, these electrodes are not subsequently repositionable without another surgical procedure. Any available motion is typically only in depth. Thus, the X and Y positions along the surface of the brain are fixed during surgery and the Z position into the brain is potentially adjustable. Using this configuration, experimenters can record from a small group of neurons for an extended time period. However, because this technique uses a surgical procedure to insert electrodes into the animal's brain, the experimenters typically can only record from the one collection of neurons corresponding to the surgical site in the animal. To accomplish additional recordings from different collections of neurons in the animal's brain, additional surgical procedures are required for each desired recording site. Due to the trauma of such surgical procedures, test animals typically cannot withstand more than a limited number of applications.
A second conventional technique for extra-cellular electrode insertion is an acute technique, i.e., short term, such as less than one day. This technique typically involves daily reinsertion of electrodes into an animals brain. A craniotomy is opened surgically, and is them covered by an implanted resealable cylinder. This cylinder is typically called a “recording chamber”. The recording chamber includes a sealing plug. The sealing plug is used to maintain a closed seal so that intracranial tissue is not exposed while neural recording is not being performed. To perform neural recording, such as on a daily basis, the sealing plug from the recording chamber is removed and one or more electrodes are inserted in a target location in the neural tissue accessed by the craniotomy and defined by the recording chamber. An external device called a “microdrive” is typically used to position the electrodes. The microdrive mounts into the recording chamber and is adjustable in all three dimensions (X, Y, and Z). The microdrive is typically first set to an XY position and then scanned in the Z direction. When neural recording is complete, the microdrive and electrodes are removed from the recording chamber and the sealing plug is replaced, thereby sealing the recording chamber. In this acute technique, the experimenter typically has access to a larger total number of cells than in the chronic technique described above. However, the experimenter typically can record from a given group of cells for at most a single recording session, typically one day. This limitation arises from the exposure of intracranial tissue to an external environment caused by removing the sealing plug of the recording chamber. Prolonged external exposure of the target site tissue is potentially detrimental to the health of the tissue, impeding overall neural recording efficiency.
The inventors have determined that it would be desirable to provide the advantages of chronic neural recording as well as the positional advantages of acute neural recording using a microdrive.
SUMMARY
The present disclosure describes methods and apparatus implementing a chronic chamber microdrive (“CCMD”). In one implementation, a CCMD for neural recording from a target site of neural tissue exposed by an opening in a skull of a subject, includes: an outer cylinder, having a longitudinal axis, positioned within the opening and rotatable within the opening; an inner cylinder positioned within the outer cylinder, such that the longitudinal axis of the outer cylinder is within a circumference of the inner cylinder and the inner cylinder rotates within the rotatable outer cylinder; at least one fine leadscrew, positioned longitudinally in the inner cylinder; at least one electrode for neural recording, where at least one of said electrodes is coupled to a corresponding one of said fine leadscrews, where said electrodes are positioned horizontally by rotating the outer cylinder and separately rotating the inner cylinder, and where said electrodes are positioned vertically by rotating said fine leadscrews. In another implementation, at least one of the electrodes is replaced by a non-electrical probe.
Another implementation of neural recording with a CCMD includes: exposing a target site of neural tissue; positioning one or more electrodes at a first target position in the neural tissue using a microdrive device; recording neural activity at the first target position using said electrodes; repositioning said electrodes at a second target position in the neural tissue using the microdrive device, without removing the microdrive device from the target site; and recording neural activity at the second target position using said electrodes.
The CCMD allows experimenters to insert electrodes for a period of many days, and then retract the electrodes and reinsert the electrodes in a new location without repeated surgical intervention. The CCMD allows experimenters to place a group of electrodes at a target site in neural tissue and maintain the position of the electrodes across multiple recording sessions, similar to conventional surgically implanted chronic electrodes. CCMD also allows the electrodes to be withdrawn from the neural tissue and repositioned in the manner of conventional inserted acute electrodes. Thus, the CCMD provides advantages taken from conventional techniques without the accompanying limitations of those conventional techniques. There is no apparent limitation to the number of X, Y, Z locations that can be explored within a target site. The reduced size of the CCMD relative to conventional microdrives allows the CCMD to be positioned within a conventional recording chamber. In addition, since the CCMD is designed to be physically compatible with a conventional recording chamber, initial tissue exploration in a target site can be done either with a CCMD or conventional inserted acute electrodes and then the CCMD can be used for chronic neural recording of the acutely identified target area. This flexibility of application improves the yield and efficiency of neural recording.


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