WO2012036639A1

WO2012036639A1 - Eeg electrodes with gated electrolyte storage chamber and an adjustable eeg headset assembly

Info

Publication number: WO2012036639A1
Application number: PCT/SG2011/000319
Authority: WO
Inventors: Xiaoping Li; Wu Chun Ng; Wei Long Geoffrey Khao
Original assignee: National University Of Singapore
Priority date: 2010-09-16
Filing date: 2011-09-16
Publication date: 2012-03-22

Abstract

A confined dry scalp EEG sensor design couples an electrode and skin electrically with a confined electrolyte solution. The electrolyte solution is confined inside the EEG sensor when the sensor is not in use. When in use, the electrolyte solution extends from the sensor to contact the skin and form a sensor probe-skin interface. The EEG sensor may be placed in headset assembly for holding the EEG sensor against the skin. The headset assembly may have an adjustable length and adjustable tension to form a comfortable fit on the skin. The EEG sensor may be integrated with an optical apparatus for multimodal neural sensing or stimulation through the skin.

Description

METHODS AND APPARATUSES FOR GATED DRY EEG SENSING

AND NEURAL STIMULATION

FIELD OF THE INVENTION

[0001] This invention relates to electroencephalography (EEG) and more particularly relates to dry electrodes for scalp EEG signal acquisition and neural stimulation.

DESCRIPTION OF THE RELATED ART

[0002] In clinical scalp EEG measurements and scalp EEG-based brain activity monitoring applications, dry EEG sensors are preferred over the wet-type sensors as the latter require laborious hair and scalp preparation prior to the measurement and cleaning up after the measurement. The preparation of the hair and the scalp is to minimize signal instability of the conventional wet sensors caused by electrolyte evaporation, and cross bridging of the EEG sensors caused by excessive electrolyte flowing from one EEG sensor to the other. Ideally, the pre-measurement preparation should be simplified to make the process efficient and comfortable for the patients. In electrical neural stimulation through the scalp, the same electrical connection assembly as the dry EEG sensor is also preferred. For good signal quality, the EEG sensors require low impedance and this can be optimized by means of controlled compression of the scalp by the EEG sensors without compromising the comfort level of the user.

[0003] In addition, an ideal EEG headset should also provide ease to the user for positioning the EEG sensors accurately on specific scalp locations according to the measurement requirements. There are two conventional EEG headset designs - the electrode cap and the electrode harness. One of the key problems associated with these designs is the inaccurate positioning of the sensor on scalp as they cannot be adjusted precisely to suit heads of different shapes and sizes. The variance in size of human heads across different races, sexes, and ages can be huge. Furthermore, for a particular head size, the shape can vary significantly from one individual to another. The difference in head shapes requires slight adjustment of the sensor locations specified by standard systems.

[0004] Some existing harnesses use rigid structures which may not be able to provide good sensors contact with the scalp. In cases when good sensor-skin contacts are required, for example, when dry EEG sensors are used, it is possible that some sensors are incapable of contacting the scalp. To worsen the problem, poor harness design may exert excessive pressure unintentionally on the head, especially when the subject has an irregular head profile. Hence, it is desirable to have an EEG headset that is reconfigurable to suit different subjects. In addition, the headset should have a self-clamping mechanism to ensure that all the sensors are pressed onto the scalp sufficiently in order to provide good sensor-skin contact.

SUMMARY OF THE INVENTION

[0005] Embodiments of apparatus for dry EEG sensing are presented. In one embodiment, the apparatus comprises a housing configured to hold an electrolyte solution. The apparatus may also include a depressible sensor probe coupled to the housing and configured to be depressed within a portion of the housing. Additionally, the apparatus may include a gate coupled to the housing and the depressible sensor probe, the gate configured to retain the electrolyte solution within the housing until an actuation force is received by the gate from the depressible sensor probe causing the gate to open and a portion of the electrolyte solution to flow from the housing through the gate. In a further embodiment, the apparatus is configured to confine the electrolyte solution within a volume defined by an interior portion of the housing and a probe-skin interface region during use.

[0006] According to one aspect, an EEG sensor includes an electrolyte casing storing an electrolyte solution and having a first side and an opposing second side. The EEG sensor also includes an electrode extending through an opening in the first side and making contact with the electrolyte solution. The EEG sensor further includes a gate on the second side for releasing the electrolyte solution from the housing. The EEG sensor also includes a sensor probe casing coupled to the electrolyte casing on the second side of the electrolyte casing. The EEG sensor further includes a sensor probe in the sensor probe casing.

[0007] According to another aspect, an apparatus includes at least two self-clamping agents having a configurable length. Each self-clamping agent has an opening for receiving an EEG sensor. The apparatus also includes a hinge coupling a first self-clamping agent to a second self- clamping agent. The apparatus further includes an elastic body having an adjustable tension coupling the first self-clamping agent to the second self-clamping agent.

[0008] According to yet another aspect, a method includes contacting a sensor probe of an electroencephalography (EEG) sensor to a subject's head. The method also includes applying force to the EEG sensor to displase a gate retaining electrolyte solution to release electrolyte solution from the EEG sensor to form an interface between the subject's head and the sensor probe. The method further includes receiving signals from the EEG sensor corresponding to electrical activity in the subject's head.

[0009] A biomedical sensor for receiving bio-electrical signals on the skin surface of a subject includes an electrode, one or more probes, electrolyte and a casing housing the electrode, probes, and electrolyte, in which the casing is configured to have one or more extended tubes and with an electrolyte reservoir, with or without an absorbent material, the electrode is connected to a lead, the probes are inserted into the extended tubes of the casing, and the electrolyte is totally confined in the casing when the sensor is not in use and is totally confined in the casing and probe-skin interface when sensor is in use.

[0010] A sensor probe casing may be configured to have one or more extended tubes; an electrolyte reservoir, with or without an absorbent material, contained in the sensor probe casing, is in contact with the electrode which is connected to a lead. One or a number of the sensor probes may be inserted into the extended tubes of the sensor probe casing. A small portion of the sensor probes may be exposed at the end of the extended tube to contact the skin surface. The sensor has a control valve feature for separating the sensor probe and the electrolyte by a gate in contact with the sensor probe casing when the sensor is not in use. When the sensor is pressing on the skin during use, the gate opens and a portion of the sensor probes make contact with the electrolyte solution in the electrolyte reservoir, with or without an absorbent material. Then, the transfer of an amount of electrolyte to the sensor probe occurs creating a conductive pathway between the skin and the electrode through contact with the electrolyte. An upper casing may cover the sensor probe casing at the end of electrolyte reservoir, with or without an absorbent material, and include a hole on the upper casing to allow for injection of electrolyte into the electrolyte reservoir, with or without an absorbent material. The sensor maybe fixed on a strap or peripheral of a headset that holds the sensor assembly in position for sensing and/or stimulation of a subject.

[0011] The sensor probe may be a solid absorbent material that is either electrically conductive or non-conductive such that the electrolyte is confined in the probe. The sensor probe may be a solid material that is either made of electrically conductive or non-conductive material such that a certain amount of electrolyte stays on the surface of the probe when released by means of capillary action and confined at the probe-skin interface when the probe is in contact with a subject's skin. The electrolyte may be an electrically conductive solution with or without additives. The electrode may be a conductive material such as, for example, silver or silver-silver chloride. The extended tube may be configured to facilitate hair penetration to provide clearance for the sensor probe to reach the skin surface. The sensor may also include a control valve having a probe, an elastic body or spring or cantilever pushing the probe, and a gate closing the electrolyte in the casing and releasing the electrolyte out of the casing.

[00 2] The sensor may also include a movable probe cover formed by a probe cover and a spring held inside the sensor casing. The sensor probe may be formed by an absorbent material inserted into the electrolyte reservoir, with or without an absorbent material, confined inside the probe cover. An electrolyte reservoir, with or without an absorbent material, contained in the collapsible probe cover containing the electrolyte is in contact with the electrode connected to a lead. When the probe cover presses on the skin surface, with sufficient force to act on the probe cover, the probe cover moves upward and sensor probe exposed to make contact with the skin surface.

[0013] The sensor may further include an active circuit board that is coupled to the lead so as to allow for onboard amplification of the EEG signal. Additionally, the sensor may include a central tube to hold an optical apparatus which may be in a form of optical fiber. The probes of the EEG sensor act as the support for the optical apparatus, which can be used to adjust the height of optical apparatus.

[0014] An EEG headset apparatus may be used to secure the EEG sensors reliably and be reconfigurable to suit different head shapes and sizes so as to enable accurate positioning of the EEG sensor. The EEG headset may also have a self-clamping mechanism which is capable of applying the required pressure on every EEG sensor. [0015] According to another aspect, an apparatus includes two or more reconfigurable self- clamping agents. Each agent may be reconfigurable in length to allow the headset to suit different head shapes and sizes. The shape of the reconfigurable self-clamping agent is not limited to thin rectangular or square sheet form, and may be configured to have at least one of the edges bent at a certain angle. The end of the bent part is coupled to the end of similar bent part of another reconfigurable self-clamping agent by a hinge joint so as to allow the reconfigurable self- clamping agents to conform to any head shape by rotating within a certain range in relation to the each other. On the bend of the reconfigurable self-clamping agent, an elastic body may couple the two reconfigurable self-clamping agents and can be tightened sufficiently to pull the two reconfigurable self-clamping agents toward each other at a certain angle in the initial form. The elastic body may also be replaced by a spring mechanism at the hinge joint, which can provide the same clamping effect. The self-clamping mechanism may be realized by the tension between the reconfigurable self-clamping agents, which may have an opening and a clip for the accurate positioning and mounting of the EEG sensor assembly and show different embodiments of the reconfigurable self-clamping assembly.

[0016] A tension adjustable headset apparatus may be used to secure the EEG headset or/and EEG sensor firmly and comfortably on subjects' heads of different sizes. After the apparatus is placed on the subject's head, the tension on the head may be adjusted by adjusting the length of the tension belt around the head. The appratus may also include soft cushions between the tension belt and the head to provide comfort to the subject. Some soft cushions may be included in between the appratus and the EEG sensor to provide adequate pressure on the EEG sensor, which is essential for obatining a good EEG signal quality and for reducing the motion artifact.

[0017] According to a further aspect, an apparatus includes a headset frame with a tension control mechanism that includes, but is not limited to, tension belts with track, gears, gear guides and tension control knobs on both sides and the top of the EEG headset. The mechanism may allow the length of the tension belts to be adjustable by turning the tension control knobs. The soft cushions may cover the tension belts providing moderate tension and comfort to the subject. The soft cushion may be an air-pump activated cushion. After the apparatus is placed on a subject's head, the air-pump may be activated to provide tension and, at the same time, provide comfort to the subject. defined as connected, although not necessarily directly, and not

[0019] The terms "a" and "an" are defined as one or more unless this disclosure explicitly requires otherwise.

[0020] The term "substantially" and its variations are defined as being largely but not necessarily wholly what is specified as understood by one of ordinary skill in the art, and in one non-limiting embodiment "substantially" refers to ranges within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5% of what is specified.

[0021] The terms "comprise" (and any form of comprise, such as "comprises" and "comprising"), "have" (and any form of have, such as "has" and "having"), "include" (and any form of include, such as "includes" and "including") and "contain" (and any form of contain, such as "contains" and "containing") are open-ended linking verbs. As a result, a method or device that "comprises," "has," "includes" or "contains" one or more steps or elements possesses those one or more steps or elements, but is not limited to possessing only those one or more elements. Likewise, a step of a method or an element of a device that "comprises," "has," "includes" or "contains" one or more features possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways that are not listed.

[0022] Other features and associated advantages will become apparent with reference to the following detailed description of specific embodiments in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

[0024] FIG. 1 is a graphical illustration of a correlation between scalp-electrode impedance and compression load for one embodiment of an EEG sensor. [0025] FIG. 2A is a cross-sectional view illustrating an EEG sensor according to one embodiment.

[0026] FIG. 2B is a cross-sectional view illustrating an EEG sensor in an initial state according to the first embodiment.

[0027] FIG. 2C is a cross-sectional view illustration an EEG sensor in a contact state according to the first embodiment.

[0028] FIG. 3 is a cross-sectional view illustrating an EEG sensor according to a second embodiment.

[0029] FIG. 4A is a cross-sectional view illustrating an EEG sensor according to a third embodiment.

[0030] FIG. 4B is a cross-sectional view illustrating an EEG sensor in an initial state according to the third embodiment.

[0031] FIG. 4C is a cross-sectional view illustration an EEG sensor in a contact state according to the third embodiment.

[0032] FIG. 5A is a cross-sectional view illustrating an EEG sensor according to a fourth embodiment.

[0033] FIG. 5B is a cross-sectional view illustrating an EEG sensor in an initial state according to the fourth embodiment.

[0034] FIG. 5C is a cross-sectional view illustration an EEG sensor in a contact state according to the fourth embodiment.

[0035] FIG. 6A is a cross-sectional view illustrating an EEG sensor according to a fifth embodiment.

[0036] FIG. 6B is a cross-sectional view illustrating an EEG sensor in an initial state according to the fifth embodiment.

[0037] FIG. 6C is a cross-sectional view illustration an EEG sensor in a contact state according to the fifth embodiment. [0038] FIG. 7A is a cross-sectional view illustrating an EEG sensor according to a sixth embodiment.

[0039] FIG. 7B is a cross-sectional view illustrating an EEG sensor in an initial state according to the sixth embodiment.

[0040] FIG. 7C is a cross-sectional view illustration an EEG sensor in a contact state according to the sixth embodiment.

[0041] FIG. 8 is a angled view illustrating an EEG sensor assembly according to one embodiment.

[0042] FIG. 9 is a cross-section view of one embodiment of a confined dry EEG sensor assembly.

[0043] FIG. 10 is a transparent cross-section view of one embodiment of a confined dry EEG sensor assembly.

[0044] FIG. 11 is a transparent cross-section view of one embodiment of a confined dry EEG sensor assembly.

[0045] FIG. 12 is a cross-section view of one embodiment of a confined dry EEG sensor assembly.

[0046] FIG. 13 is an angled view illustrating a reconfigurable self-clamping assembly according to one embodiment.

[0047] FIG. 14 is an angled view illustrating a reconfigurable self-clamping assembly according to one embodiment.

[0048] FIG. 15 A is a side view illustrating a reconfigurable self-clamping assembly in a short configuration according to one embodiment.

[0049] FIG. 15B is a side view illustrating a reconfigurable self-clamping assembly in a long configuration according to one embodiment.

[0050] FIG. 16 is a drawing illustrating a tension-adjustable headset apparatus for securing an EEG headset assembly according to one embodiment. [0051 ] FIG. 17 is a drawing illustrating a tension-adjustable headset apparatus for securing an EEG headset assembly according to one embodiment.

[0052] FIG. 18A is a drawing illustrating a reconfigurable self-clamping EEG headset according to one embodiment.

[0053] FIG. 18B is a drawing illustrating a reconfigurable self-clamping EEG headset according to one embodiment.

[0054] FIG. 19 is a side view illustrating a tension control mechanism for an EEG headset according to one embodiment.

DETAILED DESCRIPTION

[0055] Various features and advantageous details are explained more fully with reference to the nonlimiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well known starting materials, processing techniques, components, and equipment are omitted so as not to unnecessarily obscure the invention in detail. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, and not by way of limitation. Various substitutions, modifications, additions, and/or rearrangements within the spirit and/or scope of the underlying inventive concept will become apparent to those skilled in the art from this disclosure.

[0056] Embodiments of a confined dry scalp EEG sensor that bridges the electrode and skin electrically with confined electrolyte are presented. In one embodiment, the electrolyte is confined such that it is kept totally inside the sensor when the sensor is not in bridging electrically the electrode and skin, and is totally confined within the sensor and sensor probe-skin interface when the sensor is in bridging electrically the electrode and skin.

[0057] In a further embodiments, the dry scalp EEG sensor allows for controlled scalp compression in order to reduce skin-electrode impedance hence obtaining good signal quality. In particular, various means of controlled compression of the scalp by the EEG sensors without compromising the comfort level of the user are presented. FIG. 1 is a graphical representation illustrating a correlation between scalp-electrode impedance with respect to compression load on between the scalp and an embodiment of a sensor in dry conditions. [0058] Additionally, embodiments of dry electrodes for electrical neural stimulation are discussed. In particular embodiments, the dry electrodes for neural stimulation may share a common assembly with the confined dry scalp EEG sensor.

[0059] In a further embodiment, the confined dry scalp EEG sensor may include or be integrated with an optical apparatus for multimodal neural sensing or stimulation.

[0060] Additionally, the dry scalp EEG sensor may include or be coupled to a self-clamping reconfigurable headset locating and securing the confined dry EEG sensors or the integrated confined dry EEG sensors and optical apparatus for neural sensing or neural stimulation, in which the sensors and apparatus are properly placed on human heads of different shapes and sizes.

[0061] FIG. 2A is a cross-sectional view illustrating an EEG sensor assembly according to one embodiment. An EEG sensor assembly 1 may include an electrode 3 coupled to a lead 2. An electrolyte 9 may be stored between an upper casing 4 and a sensor probe casing 5, which holds a sensor probe 8. In an initial state for the EEG sensor assembly 1 of FIG.2B, cantilevers 6 load the sensor probe 8 and confine the electrolyte 9 within the EEG sensor assembly 1 by closing the space between a gate 7 and the sensor probe casing 5, also known as the gate-probe interface. When the sensor probe 8 contacts a subject's skin with sufficient force as shown in FIG. 2C, the sensor probe 8 moves upwards thereby opening the gate 7 which regulates the releasing of the electrolyte 9 to bridge the skin and the electrode.

[0062] FIG. 3 is a cross-sectional view illustrating an EEG sensor assembly according to a second embodiment. A gated sensor probe 17 is placed into a sensor probe casing 15 with an exposed end of the sensor probe 17 configured to contact a subject's skin. The sensor probe 17 is maintained in place by an upper casing 12. Upon contact with subject's skin, the sensor probe 17 displaces a cantilever 19 upwards to open a gate 16 and releases an electrolyte 18 held in place by the sensor probe 17 and the sensor probe casing 15. The released electrolyte 18 flows from the gate-probe interface to contact the subject's skin. The electrode 14 may be coupled to the lead 11 to an active circuit board 13 for onboard amplification of the EEG signal. According to one embodiment, a hole in the active circuit board 13 and the cantilever 19 allows injection of the electrolyte 18 into the EEG sensor assembly 10. A sensor assembly cap 20 may cover the EEG sensor assembly 10 to protect the active circuit board 13. [0063] FIG. 4A is a cross-sectional view illustrating an EEG sensor assembly according to a third embodiment. An EEG sensor assembly 21 may be formed by coupling an electrode 28 to a lead 22, with an electrolyte 24 stored between a cantilever 23 and a sensor probe casing 27, which holds the sensor probe 26. The sensor probe 26 is loaded by the cantilever 23 and a downward force closes the gate 25 and holds the electrolyte 24 within the EEG sensor assembly 21. FIG.4B is a cross-sectional view illustrating an EEG sensor in an initial state according to the third embodiment. FIG. 4C is a cross-sectional view illustration an EEG sensor in a contact state according to the third embodiment. FIG. 4C illustrates the sensor probe 26 with the sensor probe casing 27, which upon contact with the subject's skin, will open the gate 25 and releases the electrolyte 24 from the gate-probe interface to the interface between the skin and the sensor probe 26.

[0064] FIG. 5A is a cross-sectional view illustrating an EEG sensor assembly according to a fourth embodiment. An EEG sensor assembly 29 may include a sensor probe casing 37, having a collapsible probe container, a probe cover 34, and a spring 31. An electrolyte reservoir 35, with or without an absorbent material, in the collapsible probe cover housing the electrolyte 36 may be in contact with an electrode 32 coupled to a lead 30. A sensor probe 33 may be formed by an absorbent material and inserted into the electrolyte reservoir 35, with or without an absorbent material. A portion of the sensor probe 33 may be exposed to contact the subject's scalp. FIG. 5B is a cross-sectional view illustrating an EEG sensor in an initial state according to the fourth embodiment. FIG. 5C is a cross-sectional view illustration an EEG sensor in a contact state according to the fourth embodiment.

[0065] FIG. 6A is a cross-sectional view illustrating an EEG sensor assembly according to a fifth embodiment. An EEG sensor assembly 38 may include a sensor probe casing 41 , having a sensor probe 44 and an elastic body 42. An electrolyte 45, contained in the space enclosed by an upper casing 40 and the sensor probe casing 41, is coupled to an electrode 46, which is then coupled to a lead 39. The sensor probe 44, upon contact with a subject's skin, may compress the elastic body 42 to open a gate 43 and release the electrolyte 45 from the gate-probe interface to the probe-skin interface. An opening in the upper casing 40 may allow for injection of the electrolyte 45. A mounting 47 may allow the EEG sensor assembly 38 to attach to a headset for acquisition of an EEG signal. FIG. 6B is a cross-sectional view illustrating an EEG sensor in an initial state according to the fifth embodiment. FIG. 6C is a cross-sectional view illustration an EEG sensor in a contact state according to the fifth embodiment. [0066] FIG. 7A is a cross-sectional view illustrating an EEG sensor assembly according to a sixth embodiment. An EEG sensor assembly 48 may include a sensor probe casing 52, a sensor probe holder 55, a sensor probe 54, and an elastic body 56. An electrolyte 57, which is contained in a space enclosed by an upper casing 50 and the sensor probe casing 52, is coupled to an electrode 51 and coupled to a lead 49. The sensor probe 54, upon contact with the subject's skin, may compress the elastic body 56 to open a gate 53 to release the electrolyte 57 from the gate- probe interface to the sensor probe 54 and create a conductive path between the electrode 51 and the subject's skin. An opening in the upper casing 50 may allow for injection of the electrolyte 57 when the EEG sensor assembly 48 is mounted on a headset (not shown) via the mounting 58. FIG. 7B is a cross-sectional view illustrating an EEG sensor in an initial state according to the sixth embodiment. FIG. 7C is a cross-sectional view illustration an EEG sensor in a contact state according to the sixth embodiment.

[0067] FIG. 8 is an angled view illustrating an EEG sensor assembly according to one embodiment. An EEG sensor assembly 59 may be integrated with functional near infrared (fNIR) detectors and/or emitters 61 for simultaneous EEG-fNIR brain imaging. The EEG sensor assembly 59 may include a central tube 62 to hold the fNIR detector or emitter 61. The central tube 62 may be, for example, an optical fiber. The legged probes of the EEG sensor assembly 59 may provide support for the fNIR detector and/or emitter 61. According to one embodiment, the height of the fNIR detector and/or emitter 61 may be adjusted for comfortable scalp contact. The EEG sensor assembly 69 may include a headband component as the upper casing.

[0068] FIG. 9 illustrates another embodiment of the confined dry EEG sensor assembly 63 that incorporates in itself a housing consisting of a housing upper casing 65, housing lower casing 66, upper spring adapter 64 and lower spring adapter 75 that keeps in place a spring 76. The electrolyte 71 , contained in the space enclosed by the upper casing 74 and the sensor probe casing 68, is connected to the electrode 72 which is then connected to the lead 73. The sensor probe 70 upon contact with the skin will compress the spring 76 and release the electrolyte 71 to the sensor probe 70 and create a conductive path between the electrode 72 and the skin. The external of the housing consisting of the housing upper casing 65 and housing lower casing 66, is tapered so mat the EEG sensor assembly 63 is able to be mounted onto a headset by assembling the housing lower casing 66 to that of the housing adapter 67. [0069] FIG. 10 illustrates another embodiment of the confined dry EEG sensor assembly 77 that may be formed by a sensor probe casing 82, which contained a sensor probe 84. The electrolyte 85, contained in the space enclosed by the upper casing 79 and the gate 83 on the sensor probe casing 82, is connected to the electrode 85 which is then connected to the lead 78. The sensor probe 84 upon contact with the skin releases the electrolyte 85 from the sensor probe casing 82 to the electrode-skin interface. The EEG sensor assembly 77 can be attached to a headset via the fastener 80 onto the headset for the acquisition of EEG signal. To ensure that the EEG sensor assembly 77 remains normal to the scalp, a sensor stand 86 could be attached to the EEG sensor assembly 77. The sensor probe 84 would deform upon the application of pressure so as to provide the user with enhanced comfort. This sensor probe 84 feature is not limited to this embodiment of the confined dry EEG sensor assembly.

[0070] FIG. 11 illustrates another embodiment of the confined dry EEG sensor assembly 88 that may be formed by a sensor probe casing 90, which contained a sensor probe 94. The electrolyte 92, contained in the space enclosed by the upper casing 89 and the gate 95 on the sensor probe casing 90, is connected to the electrode 93. The sensor probe 94 upon contact with the skin releases the electrolyte 92 from the sensor probe casing 90 to the electrode-skin interface. The reservoir enclosed by the upper casing 89 and the sensor probe casing 90 could be replaced should the electrolyte 92 is insufficient.

[0071] FIG. 12 illustrates another embodiment of a confined dry EEG sensor assembly. In the depicted embodiment, the assembly includes an upper casing 123 and a sensor probe casing. In such an embodiment, the upper casing 123 may hold the electrolyte fluid 128, and the sensor probe 126 may be disposed within the sensor probe casing 124. The sensor probe casing 124 may also house an electrode 125. The electrode 125 may be placed adjacent a sponge material 127 within the sensor probe casing 124. Further, a plunger 129 and spring 130 assembly may be coupled to the sensor probe 126. The plunger 129 may include a flange or other member forming a gate 133. Additionally, the sensor assembly may include a conduit or tube 132 for receiving electrolyte solution 128 from a remote source.

[0072] In one embodiment, the sensor assembly may be placed on a skin surface during use. For example, pressure may be applied to the sensor assembly, causing the sensor probe 126 to be depressed within the sensor probe casing 124. The plunger 129 may be moved within the sensor assembly in response to the sensor probe 126 being depressed. In such an embodiment, the spring 130 may also be compressed. When the plunger 129 moves within the assembly, the gate 133 may be displaced, allowing a portion of the electrolyte solution 128 to flow into the sensor probe casing 124. The solution 128 may wet the sponge 127 and the sensor probe 126. In a further embodiment, the solution may be contained within the sensor probe casing 125 and the sensor probe 126. Additionally, a small portion of the solution 128 may form an interface layer between the skin and the sensor probe 126 during use. When the pressure is removed, the spring 130 causes the plunger 129 to move to its original position, thereby closing the gate 133 and stopping additional electrolyte solution 128 from flowing out of the upper casing 123.

[0073] In certain embodiments, the sensor probe 126 may be removable. Further, the sensor probe 126 maybe replaceable and/or disposable. In a particular embodiment, the sensor probe 126 may comprise a fibrous plastic material, or other porous material suitable for containing a portion of the electrolyte solution 128.

[0074] FIG. 13 is an angled view illustrating a reconfigurable self-clamping assembly 96 according to one embodiment. A self-clamping assembly 96 may include two or more reconfigurable self-clamping agents 99. Each self-clamping agent 99 may be reconfigurable in length to allow a headset to adapt to different head shapes and sizes. The shape of the reconfigurable self-clamping agent 99 may not be limited to rectangular or square shape and may be configured to include at least one of the edges bent at a certain angle. The end of the bent part may be coupled to the end of a similar bent part of another reconfigurable self-clamping agent by a hinge joint 101. Thus, the reconfigurable self-clamping agents 99 may conform to a variety of head shapes by rotating the self-clamping agents 99.

[0075] On a bend of the reconfigurable self-clamping agent 99, an elastic body 100 couples the two reconfigurable self-clamping agents 99 and may be tightened to decrease a distance between the reconfigurable self-clamping agents 99. In an embodiment, an elastic body 100 may include a spring mechanism at the hinge joint 101 to provide a clamping effect. The self- clamping mechanism may have an opening 97 and a clip 98 for accurate positioning and mounting of the EEG sensor assembly. FIGS. 14 and 15 illustrate embodiments of a reconfigurable self-clamping assembly. FIGS. 16 and 17 illustrate a tension-adjustable headset apparatus for securing an EEG headset assembly and/or an EEG sensor on a subject's head. FIGS. 18A and 18B are drawings illustrating a reconfigurable self-clamping EEG headset according to one embodiment. [0076] FIG. 14 illustrates another embodiment of a reconfigurable self-clamping assembly 102. In one embodiment, the reconfigurable self-clamping assembly 102 includes a wire embedder 103 for allowing lead wires to pass through the assembly 102. Additionally, the embodiment may include one or more hinges 104 for adjusting the position of the assembly 102. Further, the assembly 102 may include one or more elastic bodies 105 coupled to one or more elastic body mounts 106 for, e.g., regulating compression loads and holding the assembly 102 in position. Further, assembly 102 may include a reconfigurable self-clamping agent 107 and a clip 108 to engage an EEG sensor assembly.

[0077] The headset apparatus may include a headset frame 114 having a tension-control mechanism illustrated in FIG. 19 that includes tension belts with track 119, tension control knobs 122, gears 120, and track guides 117. The tension-control mechanism may allow the length of the tension belts to be adjustable by turning the tension control knobs 122. Soft cushions 118 that cover the tension belts may provide moderate tension and comfort to the subject. A soft cushion 114 may be, for example, an air-pump activated cushion. The air-pump may be activated to provide tension and comfort to the subject.

[0078] All of the methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the apparatus and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. In addition, modifications may be made to the disclosed apparatus and components may be eliminated or substituted for the components described herein where the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope, and concept of the invention as defined by the appended claims.

Claims

1. An apparatus comprising:

a housing configured to hold an electrolyte solution;

a depressible sensor probe coupled to the housing and configured to be depressed within a portion of the housing; and

a gate coupled to the housing and the depressible sensor probe, the gate configured to retain the electrolyte solution within the housing until an actuation force is received by the gate from the depressible sensor probe causing the gate to open and a portion of the electrolyte solution to flow from the housing through the gate.

2. The apparatus of claim 1, wherein the apparatus is configured to confine the electrolyte solution within a volume defined by an interior portion of the housing and a probe- skin interface region during use.

3. An electroencephalography (EEG) sensor, comprising:

an electrolyte casing storing an electrolyte solution and having a first side and an opposing second side;

an electrode extending through an opening in the first side and making contact with the electrolyte solution;

a gate on the second side for releasing the electrolyte solution from the housing;

a sensor probe casing coupled to the electrolyte casing on the second side of the electrolyte casing; and

a sensor probe in the sensor probe casing.

4. The EEG sensor of claim 3, in which the sensor probe activates the gate to release the electrolyte solution from the housing to couple the sensor probe to the electrode.

5. The EEG sensor of claim 4, in which the gate activates to release electrolyte solution through capillary action.

6. The EEG sensor of claim 3, in which the sensor probe comprises a solid absorbent material.

7. The EEG sensor of claim 3, in which the electrode comprises at least one of silver and silver chloride.

8. The EEG sensor of claim 3, further comprising:

a lead coupled to the electrode; and

an active circuit coupled to the lead, the active circuit configured to amplify signals received from the electrode.

9. The EEG sensor of claim 8, further comprising a sensor assembly cap covering the active circuit.

10. The EEG sensor of claim 3, further comprising:

a probe cover covering an exposed end of the sensor probe; and

a spring holding the probe cover in place over the exposed end of the sensor probe.

11. The EEG sensor of claim 3, further comprising a mounting for placing the EEG sensor in a headset.

12. The EEG sensor of claim 3, further comprising an opening in the electrolyte casing to inject electrolyte solution.

13. An apparatus, comprising:

at least two self-clamping agents having a configurable length, each self-clamping agent having an opening for receiving an electroencephalography (EEG) sensor; a hinge configured to couple a first self-clamping agent to a second self-clamping agent; and

an elastic body having an adjustable tension configured to couple the first self-clamping agent to the second self-clamping agent.

The apparatus of claim 13, in which the self-clamping agents have a rectangular shape.

15. The apparatus of claim 13, in which the at least two self-clamping agents are coupled together to fit a subject' s head.

16. The apparatus of claim 13, in which the elastic body comprises a tension belt.

17. The apparatus of claim 13, further comprising a soft cushion coupled to the self clamping agent.

18. The apparatus of claim 13, further comprising a control knob for adjusting a tension level imposed by the elastic body to fit a subject's head.

19. A method, comprising:

contacting a sensor probe of an electroencephalography (EEG) sensor to a subject's head; applying force to the EEG sensor to displace a gate coupled to the EEG sensor, the gate configured to retain an electrolyte solution within a body of the EEG sensor and configured to release electrolyte solution from the EEG sensor to form an interface between the subject's head and the sensor probe when the gate is displaced during use; and

receiving signals from the EEG sensor corresponding to electrical activity in the subject' s head.

20. The method of claim 19, in which contacting the sensor probe of the EEG sensor to the subject's head comprises:

placing the EEG sensor in an adjustable headset assembly;

placing the headset assembly on the subject's head; and

adjusting a tension level of the adjustable headset assembly to contact the sensor probe of the EEG sensor to the subject's head.

21. The method of claim 19, further comprising integrating functional near field infrared (fNIR) detectors or emitters with the EEG sensor.

22. The method of claim 19, further comprising stimulating the subject's head through the skin with the EEG sensor.