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HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY 11 



which have yielded some clues for the understanding 

 of the extrapyramidal system. It is certainly no acci- 

 dent that the favorite animals for behavior studies are 

 birds which have a highly developed striatum but a 

 negligible cortex. Not only the original observations 

 on instincts by Whitman, Craig and Heinroth but 

 also all important discoveries made recently in this 

 field, such as motivation activities and innate releas- 

 ing mechanisms or angeborenes Schema of Lorenz, im- 

 printing or Prdgung of Lorenz (168-170), and the dis- 

 placement activity or Uhersprung of Kordandt (153) 

 and Tinbergen (253), were first described in birds in 

 which the striatum is the main forebrain structure. 



The study of innate Ijehavior now called 'ethology' 

 is best descriijcd in Tinbergen's book (253). Some 

 correlations with neurophysiological findings have 

 been proposed by Prechd (212, 213). However, the 

 coordination between ethology and neurophysiology 

 is still in its earliest stages. 



EXPERIMENTS ON B.-^S.^L G.^NGLIA OF BIRDS. The first 



worker to take advantage of the unique opportunities 

 for study of basal ganglia function aflforded by birds 

 was Kalischer (140, 141). Using parrots because of 

 their complex foot movements and capacity for 

 speech, he carried out stimulation and extirpation 

 experiments on the relation of the cortex and striatum 

 to instinctive behavior. He found that in these birds 

 the mesostriatum is the main sensorimotor coordina- 

 tion center, especially for feeding mechanisms. Bi- 

 lateral incomplete lesions of the mesostriatum caused 

 severe disturbances of speech and feeding mechanisms 

 whereas unilateral lesions resulted in slight disturb- 

 ances. Lesions of the hyperstriatum (which in his 

 opinion is equivalent to the caudate nucleus in mam- 

 mals) resulted in defects of contralateral turning 

 movements. The motor coordination of these move- 

 ments was laelieved to be dependent on the meso- 

 striatum. Kalischer believed the hyperstriatum to be 

 a higher center of sensorimotor functions for 'orienta- 

 tion,' the sensory influences coming mainly from the 

 mesostriatum and epistriatum. Lesions in the ecto- 

 striatum may cause disorders similar to those in the 

 hyperstriatum. The epistriatum has relations to visual 

 functions since it is the highest optic center superim- 

 posed on the mesencephalic (tectal) visual structures. 

 The higher coordination of vision, especially of foveal 

 function in birds, is not a function of the cortex but 

 of the striatum. The negligible parts of cerebral cor- 

 tex present in parrots do not have much importance 

 for motility and speech and' can be extirpated without 

 serious impairment of these functions. The birds' 



forebrain mechanisms are mainly coordinated by the 

 striatum, with the exception of the rhinencephalic 

 functions. 



In Roger's (219) important early brain-stem studies 

 in pigeons, the effects of ablation of cortex and 

 striatum on instinctive behavior were observed. He 

 concluded that the ectostriatum and mesostriatum 

 were essential to the behavior of feeding, drinking, 

 fighting and courting and that more complex in- 

 stinctive actions as mating, nesting, incubation and 

 rearing the young require the hyperstriatum. Loss of 

 the cerebral cortex with the hyperstriatum intact was 

 followed by no characteristic behavior deficiencies. 

 These decorticated birds fed and protected themselves 

 normally. When cortex and hyperstriatum were elim- 

 inated the birds, after a period of helplessness, again 

 became able to feed themselves but never regained 

 mating and nesting behavior. Rogers concluded that 

 simple association or learning processes in correlation 

 with behavior cycles can be carried out without cortex 

 by lower brain structures, including the hyperstriatum 

 and possibly also the hypopallial area. Rogers be- 

 lieved that the epistriatum is a visual coordinating 

 center and the ecto- and mesostriatum are primary 

 centers for spontaneous feeding, confirming Edinger's 

 view that the basal parts of the corpus striatum are 

 essential for feeding reflexes. 



In recent experiments on the chicken brain, von 

 Hoist (unpublished observations) studied the eflfects 

 of simultaneous stimulation with implanted electrodes 

 at two separate points in the brain stem which ac- 

 tivate difTerent types of instinctive i^ehavior. He found 

 that some of these overlap and occur simultaneously 

 whereas others were mutually exclusive (for example, 

 feeding and nesting behavior), in that when stimula- 

 tion evoked one drive, the other was suppressed. When 

 two loci in the brain producing exclusive drives were 

 simultaneously stimulated, the suppressed behavior 

 reappeared explosively as a rebound after stimulation 

 was stopped. 



INSTINCTIVE BEHAVIOR AND BASAL GANGLIA IN FISHES. 



In fishes (sticklebacks), all special instinctive actions 

 are preserved after extirpation of the forebrain in- 

 cluding the basal ganglia, but coordination of in- 

 stinctive acts is disturbed. Male fishes without fore- 

 brain carry out all instinctive acts of reproduction 

 including nest iiuilding movements but do not com- 

 plete the nesting actions at the same place, so that 

 no nest is built [Schonherr (228)]. Olfactory lesions 

 alone do not interfere with nesting behavior. Male 

 sticklebacks without forebrain are less inclined toward 



