i6i8 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY III 



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17 



fk;. 14. Hidden-figure test (sample page), modified after 

 Gottschaldt (164, 165). The subject is required to find the 

 figure .it the /"/' within each of the lower {embedding) figures. 

 [From Teuber & Weinstein ( 4 7 9 1 - 



the perceptual analysis of such patterns (161 , 386, 

 I7<|i. However, while field defects are sufficient to 

 produce such a deficit, they are not necessary. In- 

 juries in any lobe of the brain, in either or both 

 hemispheres, lead to significant loss on this task 

 (fit;. 15; 479). Neither does it seem necessary that 

 there be other symptoms of cerebral lesion, such as 

 somatosensory or motor changes (see fig. 16), since 

 following brain injury subjects with or without such 

 symptoms perform equally poorly as compared with 

 normal controls. Only aphasic patients, as a group, 

 can be shown to fall significantly below the others 

 with brain injury (see, again, fig. 16), who in turn 

 arc surpassed significantly b\ the controls. M 



Perceptual changes after cerebral lesions in man 

 thus range from those that arc most specific (scoto- 

 mata) to those thai are general, or nonlocalizablc. 

 Which one of these alterations appears seems to 

 depend on the nature and level of the task employed. 

 Such findings recall the belief of Flourens (127) who 

 assigned to all major sectors of the forebrain an 

 action commune, in addition to their action propre. If one 

 considers the wide scope of perceptual selectivity in 

 higher forms, one can perhaps understand its de- 

 pendence on such common action of the hemispheres 

 and its nonspecific decline alter brain injury in man. 



Analogous hierarchical findings can be obtained 



for man's somatosensory systems. Here, alterations 

 in basic sensory thresholds after lesion of the somato- 

 sensory projection system correspond to the scotomata 

 in the visual sphere. By their very nature, these 

 deficits might be expected to interfere with the per- 

 ception of what are traditionally known as 'higher' 

 or complex aspects of objects presented through the 

 sense of touch. However, the classical concept of 

 'astereognosis' (i.e. agnosia for touch) suggests that 

 recognition of object qualities can be impaired in the 

 absence of any "primary' or 'elementary' deficit in 

 that modality. 



Difficulties in tactile perception, then, could reflect 

 either a mere consequence of sensory alterations 

 (such as changes in thresholds) or a separate higher- 



35 



uj 30+ 



o 

 oc 



UJ 



CD 



3 



25-- 



20- ■ 



R L BIL NF F 

 UNI 



NP P NT T NO 



fig. 15. Average number of hidden figures (see fig. 14) 

 correctly traced by normal adults (controls, C) and by subjects 

 with brain injury, grouped according to location of lesion : 

 /., left unilateral lesion, R, right unilateral lesion; /•", /', '/', (>, 

 frontal, parietal, temporal and occipital, respectively; A7-, 

 NP, NT, NO, nonfrontal, nonparietal, etc. [From Teuber & 

 Weinstein 1.479).] 



35 T 



30-- 



cr 25+ 

 O 



o 



20" 



CO 



5 

 3 

 z 



15- • 



1 



n<OI 



1 



p«.0l 



NA A 



N V 

 FD FD 



NF. E N SO 

 SD 



"This mmspeeifii delirii on hidden-figure tasks cannot be 



interpreted as a : form of generalized intellectual decline, 



since intelligence at least as denned by routine tests, e.g. 

 Weinstein & reubei ,28 and reubei (467)] turned out to be 

 unimpaired in all but .1 few members ol the groups to whom 

 the hidden figures were presented. 



in, id Average number of hidden figures (see figs. 14, 151 

 traced correctly by controls it.'i and by subjects with brain 

 injury, grouped according to presence or absence of aphasia 

 [A), visual field delect 'l'//)i. epilepss '/ i and somatosensory 



defect [SD) Absence of a given delect is indicated by N. 

 From Teuber & Weinstein (479 



