1 634 



HANDBOOK OF PHYMi )1 I «.Y 



NEIROI'IIYSIOLOGY III 



I his sensory reorganization seems maximal in those 

 amputees who report that their phantom limb has 

 become telescoped with time, so that it now seems 

 to lie in or near the tip of their stump (177, 178)- 



Recombination [Rearrangement and Disarrangement) Studies 



PERSISTENT SPATIAL DISORIENTATION IN LOWER SPECIES. 



Space perception in lower vertebrates, and in birds 

 and rodents, seems to arise autonomously, irrespective 



of early experience and use, in correspondence to 

 their motor coordination which has been shown to 

 be independent of practice (436, 437, 439, 530, 

 7; 1 ). The same autonomy of central patterns that 

 makes these species immune to early sensory depri- 

 vation leaves them helpless in the face of abnormal 

 changes in sensory input, as after inversion of their 

 visual fields (438) or transplantation of cutaneous 

 nerves (437). After surgical rotation of their eyes or 

 cross-conncction of optic nerves, newts attack a lure 

 in diagonally opposite parts of their visual field where 

 the lure is not, and these mislocations persist in- 

 definitely without correction. Newly hatched Leg- 

 horn chicks do no better when they are fitted, on 

 emerging from the egg, with rubber hoods bearing 

 binocular prisms that displace all visual objects 

 laterally by several degrees; their pecking responses 

 are correspondingly displaced. These responses 

 become less scattered (as in normal chicks during the 

 first few days alter hatching), but this development 

 only diminishes the variations in the distance by 

 which they miss their target (212). The distance 

 itself remains the same, reflecting exactly the visual 

 displacement imposed by the prismatic spectacles. 23 



< (ne form of central compensation has nevertheless been 

 described foi lish and frogs. After unilateral destruction of a 

 labyrinth, the ensuing corkscrew motions in lisli (503) and the 

 characteristic forced attitude (tilt toward the injured carl in 

 frogs (287) gradually disappear. This adaptation which re- 

 sembles the gradual disappearance of Bechterev nystagmus in 

 man (after unilateral section of the eighth nerve) Ins .1 definite 

 lime- course <o to 8 wk. in liana Irm/wraria and 6 to 8 mo. in 



liana exulenta), but the under! v chanism remains obscure. 



Leaving aside the possibility ol regeneration in tin- eighth-nerve 

 system ol fish and amphibian, one must consider the potential 

 role of supersensitivity in the denervated vestibular nuclei 

 which eventually restores the balance between deafferented 



.md iiii.k t halves ol th( central vestibulai i plex (Sharpless, 



personal communication) It should be noted, however, thai 

 the disappearance ol the l>od\ nil 'in liana esculenla) is re- 

 putedly hastened l>\ low spinal transection, and delayed by 

 forebrain removal or section of both optic nerves and this 



even in animals kept in the dark .'It; l 



ADAPTATION IN MAN TO PROLONGED VISUOSPATIAL 



inversion or distortion. Corresponding experiments 

 on man suggest that prolonged wearing of inverting 

 or displacing spectacles leads to more readaptation 

 than in lower forms. Yet, the course and limit of this 

 adaptation still need to be defined. The classic 

 experiments by Stratton ion himself) have been 

 quoted equally as showing complete visuospatial 

 reorganization (53) and complete failure of reorgani- 

 zation in anything but the motor sphere (521). 

 Stratton inverted his visual field b\ wearing a tele- 

 scope over one eye (occluding the other) for 21 and 

 87 hr., respectively. He reports in diary fashion that 

 there was partial adaptation to the inverted scene 

 (455 417). Yet, when he saw the world as upright, 

 he felt as if his head were inverted ! 



Ewert's three subjects (including himself) wore 

 binocular inverting telescopes for 175, [93 and 195 

 hr., respectively, during 2 weeks (116 118). His 

 reports focus on motor readjustment (as assessed, 

 e.g. by card-sorting tests) and give less detail on the 

 appearance of the visual scene; there seems to have 

 been less perceptual adaptation than in Stratton's 

 study. Complete adaptation, however, has been 

 claimed for the one subject (Snyder) in Snyder & 

 Pronko's experiment in which a binocular device 

 was worn for 30 days (431 ). 



As \\';ills (521) has pointed out, the binocular 

 spectacles used in these experiments actual!) repre- 

 sented a pseudoscope, since t ln\ reversed not only 

 up and down but interchanged all binocular dis- 

 parities. The same was true of the device worn by 

 the one monkcv tested b\ I'olcv (128); his animal 

 carried inverting binocular telescopes for one week 

 When one wears such a device, distant objects seem 

 to approach as one walks backwards, and the inonkev 

 developed a propensity lor moving backward through- 

 out the testing period. She also acquired a habit of 

 looking at the world through her leys. 



By far the most thorough studies of this type, 



however, are those undertaken over man) years in 



Innsbruck I >v Erismann and Kohler [reported by 

 kohler (285, -'8(11,. In their work, the devices em- 

 ployed provided either right-left reversals of vision, 



or up-down reversals. Inn not both simultaneously, 

 as in all the earlier studies. Thcv paid equal attention 

 to motor readjustment and 10 possible perceptual 

 changes and tried to measure the course ol both, 

 their ultimate extern, and the aftereffects when the 



spectacles were removed after periods of continuous 

 wearing (extending, in some of their subjects, to as 



