CN109171726B

CN109171726B - Infrared nerve stimulation induced whole brain function magnetic resonance high resolution imaging method

Info

Publication number: CN109171726B
Application number: CN201810935858.5A
Authority: CN
Inventors: 王菁; 陈岗; 徐国华
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2018-08-16
Filing date: 2018-08-16
Publication date: 2020-07-07
Anticipated expiration: 2038-08-16
Also published as: CN109171726A

Abstract

The invention discloses an infrared nerve stimulation induced whole brain function magnetic resonance high resolution imaging method. The experimental subject is placed in a magnetic resonance instrument, the optical fiber is fixedly connected with the cortex, the infrared laser stimulation is conducted to the cortex through the optical fiber for stimulation, the infrared laser stimulation is carried out, and meanwhile, the magnetic resonance instrument is utilized for functional magnetic resonance scanning to realize imaging and obtain image data; analyzing and processing to obtain a brain nerve activation network map of the stimulated cortex part; the stimulation conditions were: laser wavelength 1875nm and laser radiation energy 0.1-1.0J/cm2, each stimulus consisting of a pulse train with a single pulse duration of 0.25 ms, frequency of 200 Hz, and total duration of 0.5s-1 s. The invention combines an INS system with a functional magnetic resonance imaging system to realize neural network connection imaging in the whole brain range, and obtains a brain network map in functional connection with a specific focal position of the cortex through the INS of the position.

Description

Infrared nerve stimulation induced whole brain function magnetic resonance high resolution imaging method

Technical Field

The invention relates to a method for stimulating and activating cerebral cortex function imaging, in particular to a magnetic resonance high-resolution imaging method for inducing whole brain function by Infrared Nerve Stimulation (INS).

Background

The study of connectivity pattern maps in the brain is crucial to understanding the brain neural network and its relationship to behavior and disease. There are many ways to study brain network connectivity maps in the brain. However, there is currently no method that can rapidly and systematically render brain network connectivity maps at millimeter resolution over the entire brain of a living subject. Anatomical mapping methods based on tracer injection of 1-5 mm size are limited to a small number of injection sites (typically 3-5 tracers), require 2-3 weeks for tracer transport, animal sacrifice slices and time consuming image reconstruction. In fMRI, resting state connectivity network maps based on low frequency correlations in the brain are commonly used to study brain neural network connectivity; however, the relationship between these correlations and the anatomical connections remains uncertain.

Diffusion-method imaging (DTI) can achieve high spatial resolution, but use in the whole brain is still limited to large nerve fiber bundles. fMRI combined with optogenetic stimulation is a brand-new whole brain network connection imaging method; however, in animals such as primates, this requires viral injection expression for several weeks waiting and is limited to only a few sites. While combining fMRI with electrical stimulation has not so far provided high resolution brain network maps at the full brain scale.

Disclosure of Invention

In order to solve the problems in the background art, the invention provides a whole brain functional neural network connection imaging method combining pulse near-Infrared Neural Stimulation (INS) induced neuron activity and functional magnetic resonance, and infrared laser stimulation is used in functional magnetic resonance imaging (fMRI) to research the whole brain high-resolution cortical neural network connection activity.

The technical scheme adopted by the invention for solving the technical problem comprises the following steps:

the process of the invention for high-field magnetic resonance functional imaging of living animals is shown in figure 1, an experimental object is pretreated and then placed in a magnetic resonance instrument for infrared laser stimulation and functional magnetic resonance scanning by the magnetic resonance instrument to realize imaging: setting parameters of infrared laser stimulation, fixedly connecting an optical fiber with a cerebral cortex, conducting the infrared laser stimulation (INS) to the cerebral cortex through the optical fiber for stimulation, and performing magnetic resonance scanning while infrared nerve stimulation is performed to obtain image data; carrying out data analysis processing on the image data to obtain a cerebral nerve activation network map of a fixed stimulated cortex part, and further researching the high-resolution cerebral cortex neural network connection activity of the whole brain; the infrared nerve stimulation adopts infrared laser to emit to an experimental object for stimulation, and the stimulation conditions are as follows: laser wavelength 1875nm, laser radiation energy 0.1-1.0J/cm2, each stimulus consisting of a pulse sequence with single pulse duration of 0.25 ms, frequency of 200 Hz, and total duration of 0.5s-1 s; the switching phase of magnetic resonance is repeated 10-20 times for 36 seconds with one stimulation initially in the 18 second on phase of magnetic resonance and no stimulation at rest in the 18 second off phase of magnetic resonance.

The invention uses infrared laser stimulation to research the cerebral cortex neural network in functional magnetic resonance, and obtains high-resolution and targeted imaging images.

The experimental subjects in the specific embodiment are rats, mice, cats, experimental monkeys and humans, but are not limited thereto.

The optical fiber is fixed by reinforcing a quartz capillary tube through a skull drill hole as an optical fiber guide tube, so that an optical fiber head is arranged on the surface of a cortex layer.

The optical fiber has three diameters of 100, 200 and 400um, the numerical aperture is 0.22, and the distance between the emergent end of the optical fiber and the surface of the skin layer is 0 mm.

The infrared nerve stimulation locally stimulates the cerebral cortex, and the generated activation area on the cerebral cortex is in the range of 100-500 mu m in diameter.

The magnetic resonance scan is a high-field magnetic resonance imaging using a 7T-9.4T magnetic resonance instrument.

The magnetic resonance scanning is to obtain an EPI functional image through functional magnetic resonance single Echo Planar Imaging (EPI), then sequentially perform slice timing correction and motion correction on the EPI functional image, remove baseline offset and baseline restoration by using a third-order polynomial function, thereby completing preprocessing, and then analyze and obtain an activation site with significant difference (activation significance level P <0.05) in a Matlab software tool to obtain a brain nerve activation network map.

The invention further utilizes the image data to analyze the data to obtain the brain nerve activation network map which can represent the relation between the infrared nerve stimulation and the functional magnetic resonance on the cerebral cortex neural network.

The present invention uses focal Infrared Neurostimulation (INS) for functional tracking in the brain in functional magnetic resonance imaging (fMRI). The specificity and focal nature of the activated target sites illustrate a true reflection of the anatomical connectivity between the activation sites. Furthermore, the interneuronal signals generated by Infrared Neurostimulation (INS) activation can be mapped to completely different conditions (two different sensory cortical areas, two different species and two different ultra-high field MRI machines), indicating the universality of the method.

The INS-fMRI combination used in the present invention has advantages over anatomical mapping maps, in that it is applied in vivo (reduces the number of animals required), the brain neural activation network map appears directly in 3D in an anatomical brain scan (eliminates time consuming reconstructions), and is rapid (can be obtained in 1-2 hour fMRI). The use of high-field functional magnetic resonance (fMRI) provides sufficient signal-to-noise ratio for high spatial resolution mapping, enabling in vivo mesoscale brain neural network studies.

The invention has the beneficial effects that:

the invention utilizes the thermal effect of Infrared Nerve Stimulation (INS) conducted by the optical fiber to activate cortical nervous tissue, is particularly suitable for imaging in a high-field magnetic resonance system because of no electromagnetic effect compared with the traditional electrophysiological stimulation, and is characterized in that the focal cortical neuron in a stimulation area range has no electromagnetic effect, and can effectively induce the excitation of the focal cortical neuron through specific sequence stimulation, thereby further activating the activation of the brain area which is functionally connected with the focal position of the cortical neuron.

The activation effect of the invention is safe to cortical nervous tissue, has high repeatability, and the activation effect of the nervous tissue and the laser intensity are linearly related in a certain laser intensity range.

The invention adopts near Infrared Nerve Stimulation (INS) combined with functional magnetic resonance imaging (fMRI) to realize neural network connection imaging in the whole brain range, can obtain a brain network map in functional connection with a specific focal position of the cortex by near Infrared Nerve Stimulation (INS) of the focal position, and then integrates imaging networks of different focal positions, thereby further quickly and efficiently obtaining the neural network connection map of the whole brain.

Drawings

Fig. 1 is a process diagram of an imaging method combining infrared nerve stimulation and functional magnetic resonance.

Fig. 2 is a diagram of an example of an imaging system combining infrared nerve stimulation and functional magnetic resonance.

Fig. 3 is a brain network connection activation map for cat visual cortex focal infrared nerve stimulation imaging.

FIG. 4 is a graph of the dependence of the intensity of infrared nerve stimulation on BOLD signal.

Fig. 5 is a cat brain region activation tracer imaging map.

FIG. 6 is a functional tracing imaging spectrum of the cortex of the squirrel monkey.

FIG. 7 is a graph showing the INS-induced time course of blood flow change and the correlation between the intensity of blood flow change and the intensity of IR nerve stimulation.

Detailed Description

The invention is described in further detail below with reference to the figures and the embodiments.

An imaging system adopted in the specific implementation of the invention is shown in fig. 2 and comprises a main control computer, a laser controller, a magnetic resonance instrument and a laser, wherein the output end of the laser is connected with one end of an optical fiber, the other end of the optical fiber is in zero-distance contact with the surface of a cerebral cortex, and the laser emits infrared laser which is transmitted to the cerebral cortex through the optical fiber to perform infrared nerve stimulation. The laser control end is connected with the laser controller, the laser controller is connected with the master control computer, the master control computer is connected with the magnetic resonance instrument, and the human brain is arranged below the magnetic resonance instrument. The laser controller sends a laser control signal to the laser and simultaneously sends a synchronous signal to the master control computer, and the master control computer controls the magnetic resonance instrument to carry out magnetic resonance scanning when the laser sends laser.

The process of carrying out high-field magnetic resonance functional imaging on the living animal by adopting the invention is shown in figure 1, the experimental animal is placed in a magnetic resonance instrument after being pretreated, functional magnetic resonance scanning is carried out while infrared laser stimulation is carried out, and the brain nerve activation network map of a specific stimulated cortex part is obtained after data analysis and processing are carried out after image data are obtained.

Example 1 of the invention:

infrared Nerve Stimulation (INS) (non-destructive radiant energy: 0.1-1.0J/cm 2) was delivered to the visual cortex of cats by generating an infrared laser through a 200 μm fiber and obtaining images with a resolution of 1.0 or 1.5 mm in a 7T magnetic resonance apparatus. The results are shown in fig. 3, where 0.1-1.0 in each of the top-to-bottom plots in fig. 3 represents the infrared nerve stimulation intensity. As can be seen in fig. 3, the stimulation sites (asterisks in fig. 3) correspond to visual cortex locations near the boundary of brain region 17/18 extending into brain regions 17 and 18 (shown by arrows in fig. 3). The different INS stimulation intensities activate regions of activation of brain regions that are anatomically connected to the stimulation site that increase with increasing stimulation intensity.

At the same time, hemodynamic blood oxygen saturation level (BOLD) signals at the site of Infrared Neurostimulation (INS) induced stimulation were detected, as shown in fig. 4. In fig. 4, panel a shows the BOLD signal response of the time axis of the infrared nerve stimulation with different intensities (corresponding to fig. 3), and panel B, panel C and panel D show the correlation between the BOLD signal of the lateral 17/18 brain region and the INS intensity, respectively, of the infrared nerve stimulation region, the ipsilateral 18 region activation region.

The Infrared Neurostimulation (INS) induced hemodynamic time course has a faster rise time (panel a of fig. 4) than the sensation induced hemodynamic blood oxygen saturation level (BOLD) signal and these hemodynamic responses are intensity dependent (fig. 3 whole panel and fig. 4 stimulation site and activation region analysis), it can be seen that Infrared Neurostimulation (INS) induces hemodynamic blood oxygen saturation level (BOLD) signal changes in an intensity dependent manner. The experimental result situation is consistent with the objective fact of the existing optical imaging.

Figure 5 was obtained from the INS stimulation experiment specifically activating the visual cortex 17 region of cats. In FIG. 5, the visual projection path of the cat is shown in sub-diagram A, and the projection path of region 17; the 7T magnetic resonance imaging thalamus activation map is shown in a B sub-map when the visual cortex 17 region is stimulated; the cortex activation map of 7T magnetic resonance imaging when the visual cortex 17 region is stimulated is shown in a C subgraph.

Anatomical summary of the cat's visual system (fig. 5A) shows that these projection regions include the ipsilateral thalamus, which includes the Lateral Geniculate Nucleus (LGN) and the thalamus pillow (pulvinar, abbreviated pul), as well as the ipsilateral and contralateral 17/18/19 regions, 20/21 regions. As shown in fig. 5B and 5C, the activation site consists of voxels up to several millimeters in volume diameter and exhibits focality and specificity. Laser stimulation delivered at low intensity (0.3J/cm2) produced activation primarily in ipsilateral LGN (left panel of fig. 5B).

Stimulation at higher intensity (0.7j.cm2) produced increased activation in the ipsilateral lateral geniculate nucleus LGN and the ipsilateral thalamus pulvinar (fig. 5B right panel). Activation was also observed in the contralateral posteronuclear LP and thalamus pulvinar (fig. 5B right panel), with results only from the cortex activating the callus junction, most likely the contralateral 17/18 region (fig. 5C left panel). Focal cortical ir nerve stimulation may result in activation of multiple synapses (ipsilateral 17/18 region versus ipsilateral 17/18 region activation posterior thalamic image contrast), with other directly activated cortical sites (fig. 5C) including ipsilateral 18/19/20/21 region, medial snowy region and contralateral 19/20/21 region, medial snowy region. The amplitude of the response activation at these locations is much weaker than the amplitude of the response activation at the laser tip (approximately 10 times, compare the a subgraph of fig. 4). Despite the reduced amplitude, some sites (e.g., ipsilateral 18 and contralateral 17/18 regions, lower panel of fig. 3) still exhibited intensity dependence. This is unlikely to be due to local thermal effects, given the rapid energy dissipation of the INS.

Other connection activations were also observed at the same time including: (1) (ii) corresponding activated position correlations on the topology of ipsilateral and contralateral sides 17/18/19; (2) the callus projections at region 17/18 were similar to previous studies and were not mirror symmetric. These activations are consistent with anatomical objective connections.

INS also activates cortical sites that are indirectly linked to the stimulation site. Which comprises

(1) The multisensory anterolateral vickers (AES) region, which receives visual input through the thalamic LP region and the lateral cortical sulcus (LS) region (fig. 5C right panel),

(2) cingulate Visual Area (CVA), receives input from 17/18 through pulvinar (fig. 5C left panel, and (3) areas 7 and 19/20/21 and the lateral snowy area.

In summary, the entire brain neural activation network map is consistent with the known anatomical connectivity of the 17-zone and 18-zone stimulation focus locations. These activations are not random and also not similar to the resting state connection pattern; instead, they may be functional connections mediated by activated anatomical connections.

Example 2 of the invention:

fig. 6 was obtained from the experiment of INS-activated stimulation of specific sites in the somatic cortex of squirrel monkeys. In fig. 6, a is a schematic drawing showing the connection of the somatosensory cortex subregions of a squirrel monkey. And the B drawing is a schematic diagram of feedforward and feedback connection of subregions of the cortex of the monkey of the squirrel. And the C sub-graph is a schematic plane diagram of the 3b subregion in the nuclear magnetic imaging excited by infrared nerve stimulation. And when the D subgraph is the C subgraph and is stimulated, the orthogonal plane activation imaging atlas has depth information.

The squirrel monkey somatosensory cortex (SI) partitions were organized on two orthogonal axes: medial-lateral inter-phalangeal axes (D1-D5) and anterior-posterior numerically specified inter-facial axes (3a, 3b, 1, 2) (fig. 6A). The SI area also has a specific inter-partition information flow pattern including: features of the feedforward (middle layer labeling) and feedback (surface and deep) linkage modes (fig. 6B).

A 400 μm INS fiber was placed over the optical window on the SI region of the squirrel monkey and laser stimulation was localized to the cortical subregion (approximately 1mm in size) determined by optical imaging. Imaging slices were acquired in a planar section (fig. 6C) or its orthogonal plane (fig. 6D) to the cortical surface using local surface coils in a 9.4T MRI scanner and signal enhancement contrast agent (MION). As can be seen from fig. 7A and 7B, focal infrared nerve stimulation produces intensity-dependent Cerebral Blood Volume (CBV) -related activation at the laser tip site. It is explained that the INS is able to reveal such local connectivity patterns.

FIG. 6C (tangential plane section) illustrates an example where the fiber tip is targeted to a specific SI region subregion location (for digital localization by optical imaging). The INS produced-2 mm activation at the fiber tip and 200-300 μm activation away from the stimulation focus. The D3 numerical representation of the activation sites matching in region 3a and region 1 (black arrows) coincides with the location of the connection between the anatomical fingerprints (white arrows) within region 3b, coinciding with the two orthogonal axes (fig. 6A) described previously. Since the fiber tip points to the digital tip location, activation drops to near the 3a/3b boundary and not near the 3b/1 boundary, consistent with the tip-to-tip representation at the 3a/3b boundary and the palm-to-hand representation at the 3b/1 boundary.

In another case (fig. 6D), the fiber tip is placed in region 2 and the slice is scanned in the orthogonal plane. Near the INS tip site, the stimulation leads to-2 mm activation and anterior and posterior focal activation (arrows). The activation regions are located in the area of the primary motor cortex (M1), in the area before the 3a, 3b and 1 zones and in the area after the 5 zones. Note that the active voxels in region 3a and M1 fall on the middle cortex (grey triangular arrows), while the active voxels in region 3b and region 1 exhibit a bi-layer distribution (white and grey triangular arrows, respectively). In region 5, which is known to receive feed-forward input from region 2, the location of the activated lamina is less clear because it falls on the lateral sulcus crown of the brain region where the great vessels are located (white arrows).

In general, these activation maps are similar to the previously described feed-forward (to regions 3a and M1) and feedback (to regions 3B and 1) connectivity patterns (fig. 6B). The size of the fiber tip activation site is also similar to the size of the marker site (-200 and 300 μm) for post-dissection. It is illustrated that INS can be used to reveal high resolution connections within and between local areas. These ligation patterns were more pronounced at higher stimulation intensities (0.38J/cm2), with a reduction in intensity of about half (0.17J/cm2) being weaker, supporting the hypothesis that activation at non-stimulated sites is related to INS.

The foregoing detailed description is intended to illustrate and not limit the invention, which is intended to be within the spirit and scope of the appended claims, and any changes and modifications that fall within the true spirit and scope of the invention are intended to be covered by the following claims.

Claims

1. An infrared nerve stimulation induced whole brain function magnetic resonance high resolution imaging method is characterized by comprising the following steps: the experimental subject is placed in a magnetic resonance instrument, infrared laser stimulation is carried out, and meanwhile, the magnetic resonance instrument is utilized to carry out functional magnetic resonance scanning to realize imaging: setting parameters of infrared laser stimulation, fixedly connecting optical fibers with a cerebral cortex, conducting the infrared laser stimulation to the cerebral cortex through the optical fibers for stimulation, and performing magnetic resonance scanning while stimulating infrared nerves to obtain image data; carrying out data analysis processing on the image data to obtain a cranial nerve activation network map of the fixed stimulation cortex part; the infrared nerve stimulation adopts infrared laser to emit to an experimental object for stimulation, and the stimulation conditions are as follows: laser wavelength 1875nm, laser radiation energy 0.1-1.0J/cm2, each stimulus consisting of a pulse sequence with single pulse duration of 0.25 ms, frequency of 200 Hz, and total duration of 0.5s-1 s; the magnetic resonance on-off phase 36 is repeated 10-20 times with one stimulation during the 18 second on-phase of magnetic resonance and a rest during the 18 second off-phase of magnetic resonance.

2. The method of claim 1, wherein the method comprises the following steps: the optical fiber is fixed by reinforcing a quartz capillary tube through a skull drill hole as an optical fiber guide tube, so that an optical fiber head is arranged on the surface of a cortex layer.

3. The method of claim 1, wherein the method comprises the following steps: the optical fiber has three diameters of 100, 200 and 400um, the numerical aperture is 0.22, and the distance between the emergent end of the optical fiber and the surface of the skin layer is 0 mm.

4. The method of claim 1, wherein the method comprises the following steps: the infrared nerve stimulation locally stimulates the cerebral cortex, and the generated activation area on the cerebral cortex is in the range of 100-500 mu m in diameter.

5. The method of claim 1, wherein the method comprises the following steps: the magnetic resonance scan is a high-field magnetic resonance imaging using a 7T-9.4T magnetic resonance instrument.

6. The method of claim 1, wherein the method comprises the following steps: the magnetic resonance scanning is to obtain an EPI functional image through functional magnetic resonance single Echo Planar Imaging (EPI), then to sequentially carry out slice timing correction and motion correction on the EPI functional image, then to remove baseline offset and baseline restoration by using a third-order polynomial function, and then to analyze and obtain activation sites with obvious differences to obtain a brain nerve activation network map.