[November, 1921.] 



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BRAIN 



PART 3, VOL. 44. 



STUDIES OF CEKEBEAL FUNCTION IN LEARNING. 

 No. III.— THE MOTOR AREAS. 



BY K. S. LASHLEY, 

 Department of Psychology of the University of Minnesota. 



In their first study of the electro-stimulable cortex of the dog, 

 Fritsch and Hitzig [5] ascribed to it the function of control of 

 voluntary movement, although they recognized that its destruction 

 resulted in a difficulty rather than a complete loss of ability to make 

 voluntary movements. The latter fact was largely disregarded by the 

 investigators following them and the view that the fibres descending 

 from the stimulable area form the chief efferent path from the cortex 

 was adopted by Ferrier, Carville and Duret, Luciani, Bechterew, and 

 other early workers, so that this theory has come to be accepted as one 

 of the most firmly established facts of cerebral localization. From the 

 first, however, certain facts, derived chiefly from studies of recovery 

 from paralysis following lesion to the motor area, have seemed incom- 

 patible with this view. Fritsch and Hitzig emphasized the importance 

 of other descending tracts, and Carville and Duret [4] showed that 

 recovery from hemiplegia is not due to the vicarious functioning of the 

 uninjured stimulable area. The belief that recovery from paralysis is 

 only a revival of depressed reflex functions and that the power of 

 voluntary movement is permanently abolished by complete destruc- 

 tion of the motor area was disproved by Rothmann [16] who observed 

 the formation of motor habits in monkeys after destruction of the 

 stimulable area of one hemisphere and the pyramidal and rubrospinal 

 tracts of the opposite side. 



Such experiments show that the extra-pyramidal fibres are capable 

 of mediating complex activities of the habitual or voluntary type but 



BRAIN. — VOL. XLIV. 17 



