Magnetic Field Due to Brain Activity

MAGNETIC FIELD DUE TO BRAIN ACTIVITY

One of the best ways to determine which regions are activated is to detect the magnetic field produced by the activation.

The apparatus in the photograph can detect the magnetic field set up by a persons brain so that a map of brain activity can be correlated to what the person does.

Heres the icing effect- there are NO MAGNETIC MATERIALS IN THE BRAIN.SO HOW CAN BRAIN PRODUCE A MAGNETIC FIELD????

MAGNETIC FIELD DUE TO BRAIN ACTIVITYScientists , researchers,& physiologists have a new tool to understand how the human brain works- MAGNETOENCEPHALOGRAPHY{MEG}

Magnetoencephalography (MEG) is an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via extremely sensitive devices such as superconducting quantum interference devices (SQUIDs). These measurements are commonly used in both research and clinical settings. There are many uses for the MEG, including assisting surgeons in localizing a pathology, assisting researchers in determining the function of various parts of the brain, neurofeedback, and others.

What is it?It is a procedure in which the magnetic fields of a persons are monitored as the person performs a task .

The task activates part of the brain thats involved ,causing weak electrical impulses to be sent along conducting paths between brain cells.

As with any current,each pulse produces magnetic field.

The magnetic field produced detected by MEG are probably produced by the walls of the fissures on the brain surface.

What is the magnitude?Magnitude of the field at a point P located at a distance r=2 cm from the pulse.Let the path of the pulse be tangent to the brain surface so that angle in the eqn is 90In a typical pulse ,the current i=10microampere and the conduting path length is about 1mm.Let us assume that this length is short enough for us to substitute 1mm for element length ds in the eqn

This would come to approximately 3pT

VERY SMALL magnetic feildMillion times weaker than the earths magnetic field.

So cannot use a compass to detect this field.

Extremely sensitive instruments called SQUIDS [superconducting quantum interference devices.]

Superconducting Quantum Interference Devices (SQUID) are very sensitive magnetometers used to measure extremely small magnetic fields, based on superconducting loops containing Josephson junctions. They are sensitive enough to measure fields as low as 5 aT (510-18T) within a few days of averaged measuremen

The extreme sensitivity of SQUIDs makes them ideal for studies in biology. Magnetoencephalography (MEG), for example, uses measurements from an array of SQUIDs to make inferences about neural activity inside brains.

These devices can measure the fields of magnitude less than 1pT.Care must be taken to eliminate sources of varying magnetic fields in the detection area.

Can be used to study inner activities of brain in detail.

Two essential problems of biomagnetism arise: weakness of the signal and strength of the competing environmental noise.