BRAIN MAPPING SYSTEM AND METHOD THEREOF

Abstract

A brain mapping system includes a brain signal acquisition device for collecting brain signals corresponding to different locations of the brain, a stimulator for generating a stimulus based upon a pseudorandom sequence, and a processor for segmenting the brain signals into a plurality of epochs and correlating features extracted from the epochs with the pseudorandom sequence to generate correlation functions, wherein a brain map is constructed by the correlation functions.

Claims

1. A brain mapping system, comprising: a brain signal acquisition device, comprising sensors that collect a plurality of brain signals corresponding to different locations of the brain; a stimulator, generating a stimulus based upon a pseudorandom sequence; and a processor, segmenting the brain signals into a plurality of epochs and correlating at least one of a plurality of features extracted from the epochs with the pseudorandom sequence to generate a plurality of correlation functions that last more than two runs of the pseudorandom sequence.

2. The brain mapping system of claim 1, wherein a brain map is constructed by the correlation functions.

3. The brain mapping system of claim 2, wherein the brain map is time-varying.

4. The brain mapping system of claim 1, wherein the time interval between consecutive peaks of at least one of the correlation functions is substantially equal to the period of one run of the pseudorandom sequence.

5. The brain mapping system of claim 1, wherein the brain signal acquisition device collects electroencephalography (EEG) signals.

6. The brain mapping system of claim 1, wherein the brain signal acquisition device collects magnetoencephalography (MEG) signals.

7. The brain mapping system of claim 1, wherein the stimulus is visual, audio, mechanical, optical, or electrical.

8. The brain mapping system of claim 1, wherein the stimulus is perceptual.

9. The brain mapping system of claim 1, wherein the stimulus cues a motor response.

10. The brain mapping system of claim 1, wherein the pseudorandom sequence is a maximum-length sequence with a period of 2.sup.m−1, m≧3.

11. The brain mapping system of claim 1, wherein the duration of the epochs are substantially equal.

12. The brain mapping system of claim 1, wherein the processor is comprised of a plurality of specialized circuits.

13. The brain mapping system of claim 1, wherein the features comprise power, power spectral density, and maximal voltage.

14. The brain mapping system of claim 2, further comprising a brain stimulation device that stimulates the brain according to a montage provided by the brain map.

15. A brain mapping method, comprising the steps of: utilizing sensors to collect a plurality of brain signals corresponding to different locations of the brain; generating a stimulus based upon a pseudorandom sequence; segmenting the brain signals into a plurality of epochs; and correlating at least one of a plurality of features extracted from the epochs with the pseudorandom sequence to generate a plurality of correlation functions that last more than two runs of the pseudorandom sequence.

16. The brain mapping method of claim 15, wherein a brain map is constructed by the correlation functions.

17. The brain mapping method of claim 16, wherein the brain map is time-varying.

18. The brain mapping method of claim 15, wherein the time interval between consecutive peaks of at least one of the correlation functions is substantially equal to the period of one run of the pseudorandom sequence.

19. The brain mapping method of claim 15, wherein the stimulus cues a motor response.

20. The brain mapping method of claim 15, further comprising the step of stimulating the brain according to a montage provided by the brain map.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 shows a schematic diagram of a brain mapping system illustrated according to an embodiment of the present invention.

[0010] FIG. 2 shows how correlation functions are generated from features extracted from brain signal epochs and a pseudorandom sequence.

[0011] FIG. 3 shows how a brain map is constructed or updated

[0012] FIG. 4 shows a flow chart of a brain mapping method illustrated according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 shows a schematic diagram of a brain mapping system 100 illustrated according to an embodiment of the present invention. The brain mapping system 100 includes a brain signal acquisition device 110, a variety of stimulators 120, and a processor 130. The signal acquisition device 110 includes sensors that collect brain signals 140 corresponding to different locations of the brain. The brain signals 140 can be electroencephalography (EEG) signals and magnetoencephalography (MEG) signals. The stimulators 120 generate a stimulus based upon a pseudorandom sequence 150 (e.g., maximum-length sequence) and is applied via visual, audio, mechanical, optical, or electrical medium. These can be computer screens, computerized goggles, a headphone, speakers, a vibrator, lights, an electrical stimulator or any other device that activates perceptual brain regions. The processor 130 can be a computer, a microprocessor, or application specific integrated circuits that are designed to process brain signals. In a preferred embodiment, the processor 130 processes the brain signals 140 by first filtering and removing artifacts. The processor 130 then segments the brain signals 140 into appropriate epochs and generate specific features from the epochs to correlate with the pseudorandom sequence 150 that generated the stimulus. Examples of the specific features include power, power spectral density, and maximum/minimum values of the epochs. Accordingly, a brain map 160 can be generated by the aforementioned process.

[0014] An embodiment of the process that takes place in the processor 130 is illustrated in FIG. 2. The pseudorandom sequence 150 shifts along the time axis to correlate with the 1's or 0's derived from the epochs. The epochs are segmented from the brain signals 140 to be substantially equal to the duration of the codes (1's or 0's) in the pseudorandom sequence 150 and the duration of each of the individual codes are also substantially equal. The 1's or 0's derived from the epochs can be determined by comparing the feature of the current epoch with that of earlier epochs. For example, if the power of the current epoch is greater than the mean power of a specific number of prior epochs, a “1” will be assigned to the epoch, otherwise a “0” will be assigned. Please note that the 0's will be converted to −1's for the mathematical procedure of calculating correlation.

[0015] FIG. 3 is how a correlation function may look like. The correlation function without spikes 170 corresponds to no correlation while correlation function with spikes 180 corresponds to at least some correlation. The more obvious the spikes the greater the correlation. In addition, the spikes are separated by an interval that is substantially equal to the period T of the pseudorandom sequence 150. For example, in the case of a maximum-length sequence, the period T is a single run of the sequence (2.sup.m−1 multiplied by the time duration of each code, where m≧3). The extent of correlation can be mapped into the brain map 160.

[0016] The stimulus may also cue a motor response (e.g., a muscle contraction or walking gait) and then generate correlation functions that reflect the motor response. Other applications can include navigated brain stimulation that operates with the incorporation of the time-varying brain map. The changes of the brain signals corresponding to the motor or sensory responses will assist in providing the target for brain stimulation, i.e., the brain will be stimulated according to a montage provided by the brain map.

[0017] An embodiment of the present invention is a brain mapping method presented in FIG. 4, which includes the following steps:

[0018] Step S410: utilizing sensors to collect brain signals corresponding to different locations of the brain;

[0019] Step S420: generating a stimulus based upon a pseudorandom sequence;

[0020] Step S430: segmenting the brain signals into epochs;

[0021] Step S440: correlating at least one of various features that can be extracted from the epochs with the pseudorandom sequence to generate correlation functions; and

[0022] Step S450: constructing/updating a time-varying brain map with the correlation functions.

[0023] Please note that the time interval between consecutive peaks of at least one of the correlation functions is substantially equal to the period of one run of the pseudorandom sequence.

[0024] In some applications of the embodiment, the stimulus may cue a motor response and then generate correlation functions that reflect the motor response. Moreover, the method may be utilized to guide brain stimulation in real time.

[0025] While the invention has been described by way of examples and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.