PHYS224 Lecture Notes - Lecture 20: Pyramidal Cell, Squid, Submersed
Document Summary
Magnetoencephalography (meg) is a neuroimaging technique for mapping brain activity by recording the magnetic fields from the electric currents in the brain [1]. The idea behind meg is that the signals derive from the net effect of ionic currents flowing in the dendrites of neurons during synaptic transmission [1]. Any current will produce a magnetic field, in theory, and can be measured. The (cid:373)ag(cid:374)eti(cid:272) field does(cid:374)"t affe(cid:272)t the (cid:271)rai(cid:374) or skull, (cid:449)hi(cid:272)h (cid:373)akes re(cid:272)ordi(cid:374)g the magnetic field outside the head possible [1]. To have a signal which is detectable, thousands of neurons are needed [1]. Pyramidal cells are often perpendicular to the cortical surface and give rise to the magnetic field [1]. Bundles of neurons are oriented along the scalp and are projected, allowing them to have measurable portions of their magnetic field [1]. Action potentials do not produce observable fields because the current produced flow in opposite directions and the fields cancel out [1].