Invented by Karl Deisseroth, Jin Hyung Lee, Leland Stanford Junior University
The Leland Stanford Junior University invention works as followsDisclosed are systems and techniques involving magnetic resonance imaging and optical neural stimulation. The disclosure includes aspects such as modifying a neural cell population of a target in a first brain region to express light responsive molecules. The light-responsive molecules of the target cell population can be stimulated using a light pulse. Magnetic resonance imaging is used to scan multiple brain regions. The scans enable the observation of a neuronal reaction to stimulation in one or more of the multiple brain regions.
Background for Optogenetic Magnetic Resonance Imaging
Blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD-fMRI)” is a widely-used technology for noninvasive whole-brain imaging. BOLD signals are complex variations in cerebral blood flow, cerebral blood volume and cerebral metabolic rate oxygen consumption following neuronal activation. The neural circuits responsible for triggering BOLD signals is not fully understood. This may cause confusion in fMRI interpretation. Circuit elements that may trigger different types of BOLD signals are excitatory neuronal populations and mixed neuronal population, as well as astroglia or fibers of transmission. Understanding the neural circuits responsible for BOLD signals could help diagnose neurological disorders affecting specific circuits and screen therapeutic agents that can treat these disorders.
The present disclosure is aimed at apparatuses and techniques that use magnetic resonance imaging. The disclosure includes aspects such as modifying a neural cell population of a first brain region to express light responsive molecules. The light-responsive molecules of the target cell population can be stimulated using a light pulse. Magnetic resonance imaging is used to scan multiple brain regions. The scans enable the observation of a response in the neural system to stimulation in one or more of the multiple brain regions. The observations are used to determine whether the neural projections in a second brain region are connected to some of the modified target cells in the first brain region.
The present disclosure relates to a general method of stimulating and/or inhibiting neurons in vivo by using light, and mapping the neural response. This is done through magnetic resonance imaging (MRI) and methods related to optogenetic modification. In a specific embodiment, blood oxygenation-dependent signals (BOLDs) are used in functional magnetic resonance imaging to map neural responses.
Certain aspects of this disclosure relate to the integration of high-field fMRI with optogenetic stimulation. Light-activated and light-responsive molecules, such as an opsin are introduced into specific cell types or circuit elements by using cell-type-specific promoters. This allows millisecond-scale targeted activity modulation. The transmembrane conductance is regulated by an opsin that is light-activated. It can be a microbial single-component light-activated conductance controller. The genetic material for a desired optin is altered to include promoters that are specific to cell types as well as those that allow optimal expression in an animal. “The opsin could be modified to express, for instance, in mammalian cell.
Other aspects” of the disclosure relate to devices and methods that modify a neural cell population of a first brain region to express light-responsive molecule. After modification, light pulses are used to stimulate the light-responsive molecules in the target cell population. While the target cell population is stimulated, the fMRI scans multiple brain regions. The fMRI scanner is used to monitor the neural response in at least one region of the brain in response to stimulation.
Other aspects of this disclosure concern apparatuses and techniques for verifying BOLD response. The method involves modifying a neural cell population in order to express light responsive molecules in a region of the brain. Light-responsive molecules stimulate the target cell populations in response to light. A light pulse is used to stimulate the light-responsive molecules of the target cell population. The first brain region is scanned using an fMRI device during the light stimulation of target neural cells. “Based at least in part, on a BOLD response in the targeted neural cell populations due to light stimulation. A BOLD response is assessed when an electronic stimulation of the target cell population is used.
In some embodiments, the modification of neural cells can be achieved by delivering a light responsive molecule (e.g. ChR2) into neural cells in a first region of the brain. By positioning an optical fibre at the first region of the brain and applying light pulses, neural cells in the first region can be stimulated. By acquiring magnetic resonance imaging of first and secondary brain regions, multiple regions of the human brain can be scanned to identify neural cells in the second brain area that are connected with the neural cell of the first.
In other embodiments the neural cells in the first brain area may be stimulated through the application of light pulses by placing optical fibers at the second brain area. By acquiring magnetic resonant images of first- and second-brain regions, multiple regions of the human brain can be scanned to identify neural cells that are connected between the two brain regions.
In some embodiments, a first brain region can be located in the motor cortex, and a second brain area may be located in the thalamus or vice versa. In some variations, the first region of the brain may be either the anterior or posterior thalamus. In certain embodiments, the thalamus may contain the first brain area and the somatosensory cortex may house the second. “Acquiring magnetic resonance images from bilateral regions of somatosensory and/or motor cortices” may be part of scanning multiple brain regions.
The skilled artisan can appreciate various embodiments, especially in light of the figures or the following discussion.
The above overview does not intend to describe every illustrated embodiment or implementation of the disclosure. The disclosure is open to many modifications and alternative forms. Specifics of the disclosure have been illustrated in the drawings as examples and will be described in more detail. However, it should be understood that the intention was not to limit disclosure to these particular embodiments. The intention is to cover any modifications, alternatives, or equivalents that fall within the scope and coverage of the disclosure, including aspects defined in claims.
The following detailed description of different embodiments will help you better understand the aspects of this disclosure. The Examples and ‘Global and Local fMRI Signals Driven by Neurons Defined Optogenetically By Type and Wiring? are used to present this description and various embodiments. Nature, Vol. 465, 10 Jun. 2010 pp. 788-792 which is hereby fully incorporated. The embodiments discussed herein can be used in conjunction with any of the aspects, embodiments, and implementations described above, or those illustrated in the figures. You may also refer to the following background documents: in U.S. Published Patent Application No. Published Patent Application No. 2010/0190229 entitled “System for the Optical Stimulation Cells” to Zhang et al. ; U.S. Published Patent Application No. Published Patent Application No. 2010/0145418, entitled also?System for the Optical Stimulation Cells? to Zhang et al. Published Patent Application No. Published Patent Application No. Published Patent Application No. 2007/0261127 entitled “System for the Optical Stimulation Cells” to Boyden et al. All of these applications are part of the provisional document, and they are all hereby included by reference. These publications show that a variety of opsins are capable of being used to provide optical stimulation and cell control in mammalian cellular systems in vivo or in vitro. When ChR2 is injected into a target cell, activation by light of the ChR2 opsin leads to excitation and firing. When NpHR is injected into a cell and the opsin of NpHR activated by light, the cell will be inhibited. The disclosures in the patent applications cited above may provide useful information for implementing different aspects of this disclosure.
In certain embodiments, a virus vector containing a light-sensitive molecule is injected into cells of the primary motor cortex in an animal. The viral vector only infects the chosen cell type (cortical neurons) and not other cells. The animal’s brain is implanted with a cannula to allow both injection of the viral vector and an optical fiber that provides light to infected cells. Cannulas, optical fibers, and other accessories must be made from materials compatible with magnetic resonance to reduce susceptibility artifacts during MRI scans. The optical fiber delivers light pulses to the infected cells in the motor cortex. The wavelength of light chosen is based on light-sensitive molecules introduced to the cell population. The light pulses are delivered directly to the neurons that express the light-sensitive molecules. A BOLD signal is observed at the injection site and the optical stimulation site in the grey matter of the cortex. In fMRI slices, the BOLD signal can be seen in the motor cortex. During optical stimulation, additional fMRI slices are used to capture the downstream responses. These additional fMRI images are, for instance, centered around the thalamus. Cortico-thalamic fibers are observed when the motor cortex is stimulated by the infected cells. The thalamus shows a reaction despite no cells being infected by light-sensitive molecules.
BOLD fMRI” is a non-invasive technology that allows for whole-brain imaging. Bold signals are complex and poorly understood changes in cerebral circulation (CBF), cerebral blood volume (CBV), or cerebral metabolic rate (CMRO2) after neuronal activity. It is important and useful to know what types of activity can trigger BOLD responses for a number of reasons.
In various embodiments, local stimulation of cortex during fMRI can be used to determine whether unidirectionally-triggered BOLD responses have been observed and measured. This embodiment eliminates the antidromic effect of electrical stimulation and allows global causal connectivity mapping. In response to stimulation of the cortex, robust thalamic signals BOLD are observed. The properties of thalamic responses are different from those in the cortex. The thalamic reaction is slower than the response in the cortex.
In certain embodiments, the fMRI scan occurs a few days (in some cases, at least 10) after the virus injection. The fMRI signal is acquired using 0.5mm coronal slices. Slices are taken around the motor cortex to assess the response of the brain at the injection site. To evaluate the neural response in areas distant from the motor cortex, 0.5 mm thick slices are taken at the site of interest. The optical fiber delivers a 473 nm pulse at 20 Hz with a pulse width of 15 ms to the cells that express the light-responsive molecules.
In a second embodiment that is consistent with this disclosure, a virus vector containing a light-sensitive molecule was injected into cells of the primary motor cortex in an animal. The viral vector is designed to deliver a light-responsive molecular to a selected cell type (for example, cortical neuron cells) without infecting other cell types. A cannula implanted in a distant location from the cortical neuron expressing the light responsive molecule. The cannula, which is implanted into the thalamus for example, is implanted after the viral vector has been injected into the motor cortex. The thalamus can be illuminated to confirm the functional patterns of projection in the brain. The light-responsive molecules cause spikes to appear in photosensitive axons, which drive synaptic outputs and propagate back through the axons to stimulated cells. It is possible to map the thalamus using optical fMRI by selectively controlling the motor cortex cells. Locally, both in the thalamus as well as in the motor cortex, BOLD signals appear to be very strong. This is in line with the fact that the cells are recruited both locally and distantly. This study also shows that the stimulation of the axons from neurons expressing light-responsive molecules can elicit BOLD responses even in distant areas. It also demonstrates the feasibility of mapping the global impact of a cell based on the anatomical location and genetic identity of the cell, as well as the topology of its connections. “The projections of infected cells are mapped by the axons’ reaction to light stimulation on areas distant from the cell body.
In certain embodiments that are consistent with this disclosure, a virus vector containing a light-responsive molecular is injected into the cells of the thalamus. Implanting a cannula to deliver light to a target cell population that expresses the light-responsive molecules within the thalamus is the first step. The target cells are illuminated. Functional mapping of thalamic projections into the motor cortex is possible with fMRI scans. Scanners can also detect responses in other areas of the cortex, or even other parts of your brain. The mapping of thalamic pathways is likely to include both ipsilateral as well as contralateral pathways, because motor control and planning require bilateral coordination. “The use of light stimulation to thalamic nuclei allows for functional mapping of thalamocortical projects without showing cortical – thalamic projections.
In certain embodiments it was shown that optical stimulation to posterior thalamic cells resulted in an intense BOLD response both at the stimulation site and in the posterior ipsilateral cortex. The optical stimulation of excitory fibers and cell bodies in anterior nuclei led to a BOLD response both at the site and in the ipsilateral and opposite cortical BOLD. This is consistent with the bilateral involvement of anterior thalamocortical neurons in motor control and coordinated movement.
Turning to FIG. A section of the brain 100 can be seen in Figure 1A. The brain 100 is divided into two distinct regions with different cell populations. The first cell population 102 of the target is modified by adding a light-responsive molecular. A neural projection 116 connects the second cell population 110 to the first cell population 102. A cannula compatible with fMRI is implanted, and an optical fibre 108 is delivered to the target population 102 through the cannula. The optical fiber 108 delivers light 104 to light-responsive molecules within the target cell populations 102. The light-responsive molecules of the target cell 102 are stimulated by the delivery of light. This excitation then spreads along the neural projection 116 and to the cell populations 110 in a secondary region. An fMRI device 112 records the progress of excitation in the target cell populations 102 and remote cell populations 110. The fMRI scans brain 100 in designated areas. “The results 114 from the fMRI show evidence of excitation of the remote cell populations 110.
In certain embodiments, the target cell 102 population is injected at the same time as the cannula with a viral. The injection of a virus includes a virus vector that delivers a light-responsive molecular, such as Channelrhodopsin(ChR2), to the target population. The viral vector contains promoters that drive the expression of ChR2 within the target cell population. The promoters are chosen according to the cell type of the target population 102, so that ChR2 expression is restricted. In adult rats, for example, an adenoassociated viral vector AAV5 CaMKII is used? ::ChR2(H134R)-EYFP can be used to drive expression of a ChR2 specifically in Ca2+/calmodulin-dependent protein kinase II? (CaMKII? (CaMKII? In embodiments in which ChR2 is used as the light-responsive molecular, the optical fibre 108 delivers a 473nm pulse of light at 20Hz. This was found to reliably trigger local neuronal activity in vivo.Click here to view the patent on Google Patents.