sodium amytal test: anesthetize one hemisphere and check for language function; dichotic listening test: report more digits heard by dominant half; functional brain imaging: fMRI or PET used to see which half is active when performing a language test speech laterality and handedness sex differences in brain lateralization
A typical neuron has characteristic features: a cell body, dendrites and an axon. The axon projects from the cell body and makes contact with a target cell at the synapse. A neuron is stimulated by signals, chemical and electrical, to initiate an action potential (a rapid and reversible change in membrane potential). In the absence of a signal, the resting potential of the neuron is maintained by the potassium leak channels, which allow the flow of potassium ions out of the cell, resulting in a more negative charge in the cell when compared to outside the cell.
Figure 2.4: (a) Recording of an action potential in an axon following stimulation due to changes in the permeability of the cell membrane to sodium and potassium ions. (b) The cell membrane of a resting neuron is more negative on the inside of the cell than on the outside. When the neuron is stimulated, the permeability of the membrane changes, allowing Na+ to rush into the cell. This causes the inside of the cell to become more positive. This local change starts a similar change in the adjoining segment of the neuronâs membrane. In this manner, the electrical impulse moves along the neuron.