Bi-phasic paired pulse transcranial magnetic stimulation
It is an aspect of the present invention to provide a method for recording a response to Transcranial Magnetic Stimulation (TMS) utilizing a bi-phasic double pulse pair from a TMS coil device to stimulate a subject wherein the second pulse has a lower amplitude compared to the first pulse in the bi-phasic double pulse pair. Significant advantages are achieved using bi-phasic double pulse pairs, particularly where the second pulse in a pair has an intensity lower than the first. Obtaining measurements is simpler and more accurate as the number and intensity of stimulation can be reduced compared to standard single pulse stimulation.
1. A method of recording a response to Transcranial Magnetic Stimulation (TMS) comprising the steps of:
inducing a bi-phasic double pulse pair from a single stimulation coil of a TMS coil device to stimulate a subject wherein the second bi-phasic pulse of the bi-phasic double pulse pair has a lower amplitude compared to the first bi-phasic pulse in the bi-phasic double pulse pair, and
measuring the subject's response to the bi-phasic double pulse pair,
wherein no magnetic field is generated by the TMS coil device between the conclusion of the second bi-phasic pulse of the bi-phasic double pulse pair and prior to the measurement of at least a first portion of the subject's response to said bi-phasic double pulse pair.
2. A method in accordance with claim 1 , wherein said measuring step takes place at a point in time when the TMS coil device is not actively producing magnetic stimulation.
3. A method according to claim 1 , wherein said second bi-phasic pulse of the bi-phasic double pulse pair is generated less than 1 ms after said first bi-phasic pulse of the bi-phasic double pulse pair has completed.
4. A method according to claim 1 , wherein there is no magnetic stimulation generated by the TMS coil device within 2 ms of the conclusion of the second bi-phasic pulse of the bi-phasic double pulse pair.
5. A method according to claim 1 , wherein the at least first portion of the subject's response is sufficient to determine an effect of the stimulation on the subject.
6. A method according to claim 1 , wherein the measuring step is carried out by an EEG, microphone, video recorder or combination thereof.
7. A method according to claim 1 , further comprising activating a measuring device for measuring the subject's response once the second bi-phasic pulse of the bi-phasic double pulse pair has completed.
8. A method according to claim 1 , further comprising deactivating a measuring device for measuring the subject's response prior to the first bi-phasic pulse of the bi-phasic double pulse pair.
9. A method according to claim 1 , wherein a task is presented to the subject prior to the first bi-phasic pulse of the bi-phasic double pulse pair and measuring the response of the subject includes determining their response to the task.
10. A method according to claim 1 , wherein the amplitude of the second bi-phasic pulse of the bi-phasic double pulse pair is between 5-50% lower than the amplitude of the first bi-phasic pulse of the bi-phasic double pulse pair.
11. A method according to claim 1 , wherein the amplitude of the first bi-phasic pulse of the bi-phasic double pulse pair is 5-40% lower than the normal motor threshold for the subject.
12. A method according to claim 1 , wherein the bi-phasic double pulses are discharged from a single capacitor.
13. A method according to claim 1 , wherein the bi-phasic pulses are discharged from a single capacitor and wherein a stimulator circuit connected to the TMS coil device is capable of discharging the second bi-phasic pulse within 0.5-100 ms from the first bi-phasic pulse.
14. A method according to claim 1 wherein the amplitude of the first bi-phasic pulse of the bi-phasic double pulse pair is 15-30% lower than the normal motor threshold for the subject.
15. A method according to claim 1 wherein each bi-phasic pulse of the bi-phasic double pulse pair begins at neutral.