VOL. 4 (1950) FUNCTIONAL ORGANIZATION OF THE BRAIN II9 



be expected if successive surgical sections were made at different levels of the brain. 



In order to explain the changes observed in hypoglycemia it must be recalled that 

 glucose is no longer available to the brain. Since glucose is the chief foodstuff of the 

 brain^' '» ^ the metabolic fires falter because of the decrease in the coal to be burned*. 

 A decrease to 52 %^° and 40 %^^ respectively of the normal rate have been reported 

 in hypoglycemia. With the most profound metaboHc depression {i.e., in the 5th phase, 

 see below) cerebral metabolic rate may be reduced to 25 % of the normaP^. But not all 

 parts of the brain are effected to an equal degree. Though the brain possesses a high 

 rate of metabolism, the rate is not the same in all regions but in general exhibits a 

 quantitative gradient along the neuraxis, most intense anteriorally and superiorally in 

 the cerebral hemispheres and less so posteriorally and inferiorally until it reaches its 

 lowest level in the medulla oblongata. This conception is borne out by the observation 

 of excised cerebral tissues which show a decreasing rate of oxygen intake as the neuraxis 

 is descended^^' ^^. The oxygen consumption of various parts in the human brain in 

 vivo will not be considered at this time because of conflicting results^*' ^^. Pending 

 the solution of this discrepancy we may point to another 

 bit of evidence of a hierarchy in metabolic rate. In order 

 to combat hypoglycemic coma carbohydrate must be admi- 

 nistered and it has been observed that a larger amount of 

 glucose is required to restore the functions of the cerebral 

 hemispheres than for the subcortical areas^^. Presumably 

 a greater amount of foodstuff is necessary to support a 

 higher rate of metabolism. 



If we accept the concept of dissimilar metabolic rates 



it must follow that all parts of the brain will not be equally ^'S- i- Representation (trans- 



rr , 1 , T 1 -li,!,,! • -,1 versc sectlon) of the brain 



affected by hypoglycemia but that those regions with disclosing the five phyletic 



fastest rates would succumb first and those with the areas: i. cerebral cortex; 2. 



slowest, for example the medulla, last. Then in accord subcorticodiencephalon ; 3. 



. ^ midbrain; 4. pons and upper 



With HUGHLINGS Jackson's idea^ that the brain is so medulla; 5. medullary centers 



constructed that the higher anatomic and newer phyletic 



portions contain areas which regulate and control the lower anatomic and older phyletic 



regions we might expect a series of release phenomena as each area in turn succumbs 



to an increasingly severe degree of carbohydrate deprivation^^. Such a series is seen 



in the insulin h5Apoglycemia repeatedly produced in the pharmacologic treatment of 



schizophrenia^^. 



Following the injection of insulin the first phase involves the depression of the 

 cerebral cortex (area i, Fig. i). Sensations become dull and abnormal, understanding is 

 impaired and motor activity poor in execution. Contact with the environment is gra- 

 dually lost as the patient becomes unconscious, the beginning of the second stage. The 

 second group of signs proves to be due to a release of the functions in area 2, the sub- 

 corticodiencephalon. Three types of phenomena are observed in this stage. First are 

 changes in motility reminiscent of those seen in a newborn baby with motor restlessness 

 and primitive movements of many types such as involuntary sucking and involuntary 

 grasping. Second there is increased sensitivity so that responses to stimuli become in- 

 tense, excessive and at the same time lose direction. Finally, alterations in the autonomic 

 system are seen with sympathetic predominance indicated by dilatation of the pupils, 

 bulging of the eyeballs from their sockets, acceleration of the heart rate and rise of blood 

 References p. 125. 



