Detecting and measuring the electrical activity of the brain with Electron Spin Resonance (ESR)
> Use of electromagnetic radiation wavelengths that make the electrons resonate.
> The intensity of the signal is modulated.
> The electrical discharges of the brain cells influence the magnetic field and the spins of the electrons.
> Broadening of resonance lines.
> By measuring the broadening width of the spectrum lines the intensity of neural activation is measured.
Abstract: “Electrical activity of the brain can be detected and measured by measuring the broadening of the width of NMR spectral lines. A discharging neuron in the
brain introduces an inhomogeneity in the magnetic field which reveals itself as a broadening of resonance lines which can be measured to determine the neuron discharge current flux.”
“Recently, Holder proposed to use ESR at about 1 GHZ to obtain images of the human head, using a technique derived from NMR imaging; referring to Holder, The
Potential Use of ESR or Impedance Measurement to Image Neuronal Activity in the Human Brain” [http://discovery.ucl.ac.uk/1436280/]
“from the viewpoint of neurology, even more useful information can be obtained from the reconstructed images of the electrical firing of nerve cells in the human
brain, since this would allow analysis of functional activity of neuroatomical pathways which cannot be achieved with the current techniques. Holder investigated the possibility that neuronal firing
can be detected by a form of electromagnetic radiation which can then be reconstructed to form three-dimensional images of this functional activity. Holder teaches the use of ESR and impedance
imaging as giving the best results. Holder states that NMR, being well established for spectroscopy and imaging, could be employed to detect neuronal firing, but that current flux from ions moving
across the neuronal membrane would be too small to be detectable by NMR.”
“In one embodiment of the present invention, an imaging technique termed Nuclear Electron Double Resonance (NEDOR) starts with a conventional NMR imaging apparatus
and includes a high frequency resonator or radiator such as is used in ESR techniques. A sample, such as a human body, is placed inside the main magnetic field coils of the NMR imager. A radio
frequency (RF) pulse is applied via RF coils to excite to resonance a plurality of nuclear spins producing an NMR signal. A microwave (MW) pulse is applied via a high frequency resonator or radiator
to excite to resonance a plurality of electron spins within the sample. The RF and MW pulses simultaneously resonate the nuclear and electron spins within the sample. The intensity of the MW signal
is modulated, which translates into a modulation of the intensity of the NMR signal. The modulation is extracted from the NMR signal to produce an image representative of the local ESR and thereby
the concentration of paramagnetic species in the sample. In a preferred embodiment, the RF coil is also used as the MW resonator.”
“In a further embodiment, a plurality of NMR spectral lines having a defined width are derived from the modulated NMR signal. It has been determined by the
applicant, that the width of the spectral lines is broadened due to the electric activity in the brain. The discharge of a neuron in the brain introduces an inhomogeneity into the main magnetic
field. The contribution of the spectral line width due to the electric activity is measured, which can provide a measurement of the intensity of neuron discharges".
"The Potential Use of Electron Spin Resonance Impedance Measurement to Image Neuronal Electrical Activity in the Human Brain"
Holder, DS; (1985) http://discovery.ucl.ac.uk/1436280/
Cited at above U.S. Patent 4719425 A (https://www.google.com/patents/US4719425) which refers to the detection and measurement of the electrical activity of the brain with Electron Spin Resonance (ESR)
"Feasibility of developing a method of imaging neuronal activity in the human brain: a theoretical review"
D. S. Holder
"It is proposed that, for the rapid changes related to the action potential, electron spin resonance using a potential-sensitive spin, label, impedance imaging and NMR are suitable in principle
but that only ESR and impedance methods may have sufficient sensitivity and these merit further assessment."