344 Self and the Phenomenon of Lifeb2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”neurotransmitters (neuromodulators) are likewise identified. Chemical
makeup of neurons and glia (supporting cells in the brain) and their
metabolism and intracellular signal transduction, along with gene regu-
lation, are all obtained by chemical studies.
Injection of chemicals into the blood stream or cerebrospinal fluid
helps with the discovery of neuro-active drugs.
Micro-injection of chemicals into specific regions of the mouse
brain helps to discover drugs affecting the nervous system. Micro-dialy-
sis collects small molecules secreted from specific brain regions, provid-
ing a window into their metabolism and helping to identify neurotrans-
mitters and neuromodulators.Lesion and ablation studies
Surgical removal of brain parts or severance of fiber tracts, coupled with
observation of the physiological and behavioral consequences, helps
with functional delineation of brain areas. For example, removal of the
hippocampus in a patient led to the identification of its pivotal role in
memory storage.
Disease states such as stroke, tumor, and developmental deficiency
provide a natural setting for the study of function (actually loss of func-
tion) pertaining to the defective part of the human brain. For example,
observation of stroke patients who have lost the ability to speak led to the
identification of the motor speech center in the frontal lobe.
Transient inhibition of function can be achieved in humans by focal
cooling of a brain area while awake and observing the deficit in function,
such as speech.Electrical recordings
Electro-encephalography (EEG) is a procedure that records electri-
cal activity of the brain using multiple electrodes placed on the head
(scalp). It is a noninvasive procedure as it does not require opening ofb2726_Appendix-D.indd 344 6/12/2017 7:51:55 PM