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SCien i iC REPOR S | 7: 17673 | DOI:10.1038/s41598-017-17896-9
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Pe ipe sonal space ep esen a ion
de elops independen ly om isual
expe ience
Emiliano Riccia di1, Da io Menicagli1, And ea Leo1,2, Ma cello Cos an ini3,4,5, Pie o Pie ini1 &
Co ado Sinigaglia6,7
Ou daily-li e ac ions a e ypically d i en by ision. When ac ing upon an objec , we need o ep esen
i s isual ea u es (e.g. shape, o ien a ion, e c.) and o map hem in o ou own pe ipe sonal space.
Bu wha happens wi h people who ha e ne e had any isual expe ience? How can hey map objec
ea u es in o hei own pe ipe sonal space? Do hey do i di e en ly om sigh ed agen s? To ackle
hese ques ions, we ca ied ou a se ies o beha io al expe imen s in sigh ed and congeni ally
blind subjec s. We ook ad an age o a spa ial alignmen e ec pa adigm, which ypically e e s o
a dec ease o eac ion imes when subjec s pe o m an ac ion (e.g., a each- o-g asp pan omime)
cong uen wi h ha a o ded by a p esen ed objec . To sys ema ically examine pe ipe sonal space
mapping, we p esen ed isual o audi o y a o ding objec s bo h wi hin and ou side subjec s’ each.
The esul s showed ha sigh ed and congeni ally blind subjec s did no di e in mapping objec s in o
hei own pe ipe sonal space. S ikingly, his mapping occu ed also when objec s we e p esen ed
ou side subjec s’ each, bu wi hin he pe ipe sonal space o ano he agen . This sugges s ha ( he
lack o ) isual expe ience does no signi ican ly a ec he de elopmen o bo h one’s own and o he s’
pe ipe sonal space ep esen a ion.
In ou daily li e, ac ions a e ypically d i en by ision. When ac ing upon an objec we need o ep esen i s isual
ea u es, such as shape, size, and o ien a ion1–4, and o map hem on o ou own pe ipe sonal space, ha is, he
space immedia ely su ounding ou own bodies and eachable by ou limbs5. Al hough his space mapping has
been la gely in es iga ed o e he las wo decades6, i is s ill a om clea whe he and how isual expe ience
a ec s pe ipe sonal space ep esen a ion. Indeed, wha happens o people who ha e ne e had any isual expe-
ience? How can hey map objec ea u es in o hei own pe ipe sonal space? Do hey ep esen his space di e -
en ly om sigh ed agen s? O a e hei pe ipe sonal space ep esen a ions simila ?
Se e al s udies in non-human p ima es and humans demons a ed ha pe ipe sonal space ep esen a ion
could be d i en by s imuli o he han he isual ones. Fo ins ance, en al p emo o 7 and pos e io pa ie al8
neu ons, which a e ypically in ol ed in ac ions upon eachable a ge s, may selec i ely espond o bo h isual
and audi o y s imuli when p esen ed wi hin monkey’s each. Analogously, he p esence o an audi o y-d i en
pe ipe sonal space ep esen a ion has been also demons a ed in sigh ed humans. A se ies o TMS s udies on
mo o and p emo o co ices showed ha audi o y s imuli may modula e co ical exci abili y when p esen ed
close o speci ic agen ’s body pa only9–12.
These indings indica e ha audi o y inpu s can ica ia e he isual ones in space mapping. This could explain,
pa ially a leas , why congeni ally blind people show le el o pe o mance in objec localiza ion and manipula ion
compa able o sigh ed agen s13–16. Howe e , some s udies a gued and p o ided e idence ha isual expe ience
may exe a dominan ole in he ep esen a ion o space, e en a ec ing he audi o y spa ial maps, which migh be
in ol ed in ac ion planning and con ol17,18. These s udies would seem o suppo he hypo hesis ha congeni ally
blind people ep esen hei space di e en ly om sigh ed agen s18–21.
1MOMILab, IMT School o Ad anced S udies Lucca, I-55100, Lucca, I aly. 2Resea ch Cen e “E. Piaggio”, Uni e si y
o Pisa, Pisa, I-56100, I aly. 3Depa men o Neu oscience and Imaging and Clinical Science, Uni e si y G. d’Annunzio,
Chie i, I-66100, I aly. 4Ins i u e o Ad anced Biomedical Technologies - ITAB, Founda ion Uni e si y G. d’Annunzio,
Chie i, I-66100, I aly. 5Cen e o B ain Science, Depa men o Psychology, Uni e si y o Essex, Colches e , UK.
6Depa men o Philosophy, Uni e si y o Milan, ia Fes a del Pe dono 7, I-20122, Milano, I aly. 7CSSA, Cen e o he
S udy o Social Ac ion, Uni e si y o Milan, Milan, I-20122, I aly. Co espondence and eques s o ma e ials should
be add essed o C.S. (email: [email p o ec ed])
Recei ed: 14 Augus 2017
Accep ed: 1 Decembe 2017
Published: xx xx xxxx
OPEN
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SCien i iC REPOR S | 7: 17673 | DOI:10.1038/s41598-017-17896-9
To ackle he ques ion as o whe he pe ipe sonal space ep esen a ion can de elop independen ly om ( he
lack o ) isual expe ience, we ca ied ou a se ies o beha io al expe imen s by aking ad an age o a spa ial align-
men pa adigm and sc u inizing he space ep esen a ion o bo h sigh ed and congeni ally blind people. The spa-
ial alignmen e ec e e s o a dec ease o eac ion imes when subjec s pe o m an ac ion (e.g., a each- o-g asp
pan omime) cong uen wi h ha a o ded by a p esen ed objec (e.g., a mug)22. Ou g oup p e iously demon-
s a ed ha his e ec could be sys ema ically used o in es iga e pe ipe sonal space ep esen a ion, in he isual
domain a leas . Indeed, he spa ial alignmen e ec has been shown o occu when he a o ding objec s we e
isually p esen ed wi hin he agen ’s each only23–25. Fu he mo e, his e ec u ned ou o be also modula ed by
manipula ions o he pe ipe sonal space, such as hose induced ei he by he in oduc ion o a ba ie p e en ing
subjec s om eaching o he wise close objec s, o by he use o a ool allowing hem o each and g asp o he wise
a objec s25. These manipula ions ha e been demons a ed o iden i y he na u e and he ange o pe ipe sonal
space ep esen a ion26–29.
Ac oss Expe imen s 1, pa icipan s had o pan omime a each- o-g asp ac ion owa ds a isually cued (in
sigh ed only) o audi o ily cued (in sigh ed and blind subjec s) g aspable objec (e.g. a small ball), p esen ed ei he
wi hin o ou side hei each. Acco ding o he hypo hesis ha he pe ipe sonal space ep esen a ion can de elop
independen ly om ( he lack o ) isual expe ience, one could expec no di e en ial spa ial alignmen e ec in
sigh ed and blind people. On he con a y, he hypo hesis o a isual dominance on space ep esen a ion would
lean owa ds a di e ence in he spa ial alignmen e ec be ween sigh ed and blind people.
Ac oss Expe imen s 2, we examined he spa ial alignmen e ec when he same g aspable objec (a small ball)
was audi o ily p esen ed close ei he o he sigh ed and blind pa icipan s o o ano he indi idual. In a p e ious
s udy, we showed ha he spa ial alignmen e ec occu ed in he isual domain whene e he objec s we e
p esen ed wi hin he pe ipe sonal space o a po en ial agen , ega dless o whe he his agen was he pa icipan
o ano he po en ial ac o 30,31. Is his a esul o he isual expe ience only? O does some hing simila occu in
he audi o y domain oo? I he la e we e he case, one should expec ha bo h sigh ed and blind people do no
e eal signi ican di e ences in mapping no only hei own, bu also ano he ’s pe ipe sonal space. This would
u he suppo he iew ha he pe ipe sonal space ep esen a ion can be independen om a speci ic senso y
expe ience. And his would be no wi hou consequences also o unde s anding how blind indi iduals may
in e ac e icien ly wi h o he people in a wo ld hey ha e ne e seen, o so we a gued.
Resul s
Expe imen 1. When pa icipan s had o pan omime a each- o-g asp mo emen owa ds a isually cued o
audi o ily cued g aspable objec p esen ed ei he wi hin o ou side agen s’ pe ipe sonal space, simila esul s o a
spa ial alignmen e ec we e ob ained ac oss modali ies (i.e., isual and audi o y) and g oups (i.e., sigh ed and blind).
Fi s , Exp. 1A aimed a expanding he p e iously obse ed spa ial alignmen e ec o ou o iginal isual pa a-
digm23,30. Pa icipan s we e eques ed o eplica e a each- o-g asp pan omime, as p omp ed by a i s ins uc ion
s imuli (depic ing he hand o be used), once a ask i ele an go-signal (a ball placed on he side o a able which
was ei he cong uen o incong uen wi h he hand o be used) occu ed. In hal o he ials, he ball was loca ed
wi hin he pa icipan s’ each, while in he o he hal in a non- eachable space (Fig.1-Expe imen al design, uppe
panel). RTs we e en e ed in a linea mixed e ec s (LME) epea ed-measu es model wi h he ‘Loca ion’ o he
objec ( eachable s. non- eachable) and ‘Alignmen ’ (cong uen s. incong uen ) as wi hin-subjec s epea ed
ixed ac o s, ‘Subjec s’ as andom ac o and ‘Age’ as co a ia e. RT analysis e ealed a signi ican Alignmen e ec
(F1,13 = 6.9; p = 0.021; pa ial η2 = 0.37) and a Loca ion by Alignmen in e ac ion (F1,13 = 5.4, p = 0.037; pa ial
η2 = 0.29), bu no signi ican Loca ion e ec (F1,13 = 3.5, p = 0.83). The Alignmen e ec and in e ac ion we e
explained by he ac ha while RTs o cong uen (435 ms) and incong uen (438 ms) ials we e compa able in
he non- eachable space (p = 0.53), hey we e signi ican ly highe o incong uen (455 ms) han cong uen ials
(436 ms, p < 0.001; Bon e oni co ec ed) in he eachable space (Fig.1A).
In Exp. 1B, he audi o y e sion o Exp. 1A was employed in bo h sigh ed and blind indi iduals o sys em-
a ically examine he spa ial alignmen e ec when he each- o-g asp pan omime was p omp ed by audi o ily
ins uc ion s imuli (a beep signal monola e al o he hand o be used) as soon as audi o y ask-i ele an go-signal
( he sound o a bouncing ball p esen ed on he side ei he cong uen o incong uen wi h he hand o be used and
wi hin o ou side he pa icipan s’ each) occu ed (Fig.1-Expe imen al design, lowe panel). The LME - now
including he G oup (sigh ed s. blind) a iable as be ween-subjec s ixed ac o - showed a signi ican Alignmen
e ec (F1,33 = 13.0; p < 0.001; pa ial η2 = 0.28) and a Loca ion × Alignmen in e ac ion (F1,33 = 19.8; p < 0.001;
pa ial η2 = 0.37). Pos -hoc T- es compa isons we e pe o med o assess signi ican e ec s and in e ac ion ound
in he LME analyses. In sigh ed and blind indi iduals, he Alignmen e ec and Loca ion × Alignmen in e ac ion
we e explained by he ac ha while RTs o cong uen (sigh ed: 427 ms; blind: 396 ms) and incong uen (sigh ed:
429 ms; blind: 392 ms) ials we e compa able in he non- eachable space (p = 0.79), hey we e signi ican ly
highe (p < 0.001; Bon e oni co ec ed) o incong uen han cong uen ials (sigh ed: 438 s. 415 ms; blind:
424 s. 391 ms) in he eachable space (Fig.1B). A signi ican Loca ion × G oup in e ac ion was addi ionally
ound signi ican (F1,33 = 4.73; p = 0.037; pa ial η2 = 0.13). Nei he signi ican G oup (F1,33 = 0.2; p = 0.63) and
Loca ion (F1,33 = 3.2; p = 0.80) e ec s, no Alignmen × G oup (F1,33 = 0.1; p = 0.71) no Loca ion × Alignmen
× G oup (F1,33 = 1.4; p = 0.25) in e ac ions we e ound. While no di e ences o main e ec s and in e ac ions
be ween sigh ed and congeni ally blind indi iduals we e ound, he Loca ion × G oup in e ac ion was explained
by he signi ican ly la ge RT di e ences be ween eachable and non- eachable loca ions in he blind (di e -
ence = 14 ms; p < 0.025; Bon e oni co ec ed) as compa ed o he sigh ed (di e ence = −1 ms; p = 0.73) g oup.
Finally, a neu al, ac ion-un ela ed en i onmen al sound was p esen ed in Exp. 1C as audi o y ask-i ele an
go-signal o ule ou he possibili y ha he di e ences in spa ial alignmen e ec ound in he Exp. 1B could be
me ely accoun ed by he le - igh loca ion o he audi o y s imuli, as well as by pe cep ual/a en ional di e ences
in he audi o y salience o he p esen ed objec s. The LME showed no G oup o Loca ion e ec s, no signi ican
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in e ac ions (Fig.1C). Only an Alignmen e ec was ound signi ican (F1,33 = 4.4; p = 0.043; pa ial η2 = 0.12),
ela ed o he longe RTs o non- eachable (481 ms) as compa ed o eachable (465 ms) loca ions ac oss bo h
expe imen al g oups.
Figu e 1. Expe imen al p ocedu es and esul s o Expe imen s 1. Exempla go s imuli and exempla ial o
he isually-cued Exp. 1A and o he audi o ily-cued Exp. 1B and 1C (uppe panel). G aphs show es ima ed
ma ginal mean RTs (±s anda d e o s) o cong uen (blue) and incong uen ( ed) ials o Exp. 1A (A), Exp.
1B (B) and Exp. 1C (C) ac oss sigh ed and congeni ally blind pa icipan s; a ull ci cle and an emp y ci cle
indica e es ima ed ma ginal mean RTs o he sigh ed and congeni ally blind samples, espec i ely; as e isks
highligh signi ican Loca ion × Cong uency in e ac ions and pos -hoc T- es compa isons.
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SCien i iC REPOR S | 7: 17673 | DOI:10.1038/s41598-017-17896-9
Expe imen 2. Th ee sessions wi hin Exp. 2 sys ema ically examined he same spa ial alignmen e ec when
an audi o ily p esen ed objec was loca ed close ei he o he pa icipan s (bo h sigh ed and congeni ally blind
– Exp. 2A) o o ano he indi idual (whose p esence was simula ed by p onouncing he exclama ion ‘hey’– Exp.
2B) o assess whe he he spa ial alignmen e ec occu ed whene e he objec was p esen ed wi hin he pe ip-
e sonal space o a po en ial agen , ega dless o whe he i was he pa icipan ’s own o ano he ’s space (Fig.2,
uppe panel), consis en ly wi h ou p e ious indings in he isual domain30,31. Finally, an a i icial neu al sound
subs i u ed he agen e ealing exclama ion in a con ol condi ion (Exp. 2C), o exclude ha any di e ence in
spa ial alignmen e ec s in he Exp. 2B could be accoun ed by pe cep ual/a en ional di e ences in he audi o y
salience o he p esen ed s imuli.
When no o he indi idual was p esen (Exp. 2A - ‘No agen ’ – Fig.2A), he LME showed o e lapping esul s
wi h Exp. 1B. A signi ican Alignmen e ec (F1,32 = 10,7; p < 0.003; pa ial η2 = 0.25) and a Loca ion × Alignmen
in e ac ion (F1,32 = 5.5; p < 0.025; pa ial η2 = 0.15) we e assessed. As in Exp. 1B, he Alignmen e ec was
es ic ed o he eachable space (sigh ed: 431 s. 472; blind: 278 s. 304; p < 0.002), and no in he non- eachable
spaces, in line wi h he Alignmen × Loca ion in e ac ion. Only a signi ican G oup e ec was addi ionally ound
(F1,32 = 10.3; p = 0.003; pa ial η2 = 0.24), bu nei he Loca ion (F1,32 = 0.9; p = 0.34) e ec , Alignmen × G oup
(F1,32 = 0.0; p = 1.0), Loca ion × G oup (F1,32 = 0.01; p = 0.91), no Loca ion × Alignmen × G oup (F1,32 = 1.4;
p = 0.24) in e ac ions we e ound signi ican .
When ano he indi idual was p esen on he scene (Exp. 2B - ‘P esen agen ' – Fig.2B), he LME showed a
signi ican Alignmen e ec (F1,32 = 36.2; p < 0.0001; pa ial η2 = 0.54) and a G oup e ec (F1,32 = 8.4; p = 0.007;
pa ial η2 = 0.21). Speci ically, in sigh ed and blind indi iduals, pos -hoc analyses showed ha when ano he
indi idual was p esen on he scene, he Alignmen e ec in e ms o cong uence gain was obse ed bo h wi hin
eachable (sigh ed: 434 s. 459 ms; blind: 278 s. 315, p < 0.01, Bon e oni co ec ed) and non- eachable (sigh ed:
438 s. 457 ms; blind: 291 s. 318, p < 0.01) spaces. No addi ional Loca ion × Alignmen (F1,32 = 0.5; p = 0.49),
Loca ion × G oup (F1,32 = 0.3; p = 0.60), Alignmen × G oup (F1,32 = 1.1; p = 0.30), o Loca ion × Alignmen ×
G oup (F1,32 = 0.1; p = 0.91) in e ac ions we e signi ican .
In he con ol condi ion (Exp. 2C - ‘Con ol sound’ – Fig.2C), he LME showed o e lapping esul s wi h
he Exp. 2A (‘No agen ’), wi h a signi ican Alignmen e ec (F1,32 = 13.6; p = 0.001; pa ial η2 = 0.30) and a
Loca ion × Alignmen in e ac ion (F1,32 = 7.8; p = 0.009; pa ial η2 = 0.20). As in Exp. 2A, he Alignmen e ec
was es ic ed o he eachable space (sigh ed: 438 s. 461; blind: 267 s. 307; p < 0.001, Bon e oni co ec ed),
and no in he non- eachable spaces, in line wi h he Alignmen x Loca ion in e ac ion. A G oup e ec was addi-
ionally ound signi ican (F1,32 = 7.8; p = 0.009; pa ial η2 = 0.20). No signi ican Alignmen × G oup (F1,32 = 0.6;
p = 0.44), Loca ion × G oup (F1,32 = 0.1; p = 0.75), o Loca ion × Alignmen × G oup (F1,32 = 0.8; p = 0.40) in e -
ac ions we e ound, hus demons a ing no di e ences in he in e ac ion e ec s be ween sigh ed and congeni ally
blind indi iduals.
When assessing di e ences be ween g oups, he pos -hoc es s con i med small, hough signi ican , G oup
e ec s in bo h he ‘No agen ’ and ‘Con ol sound’ condi ions, as blind indi iduals showed o e all a sho e RT
han sigh ed indi iduals (sigh ed s. blind: 440 s. 328 ms; 413 s. 296 ms, espec i ely), bu no in he ‘P esen
Agen ’ (403 s. 311 ms).
In o de o measu e he speci ic e ec o he p esence o a po en ial agen on pa icipan s’ own pe ipe sonal
space, di e ences in he RTs be ween cong uen and incong uen ials in he non- eachable space o he h ee
di e en expe imen al condi ions we e en e ed in a LME epea ed-measu es model wi h ‘Expe imen al condi-
ion’ (No Agen , P esen Agen , Con ol Sound) and ‘G oup’ as wi hin-subjec s epea ed ixed ac o s, ‘Subjec s’
as andom ac o and ‘Age’ as co a ia e. Di e ences in RTs analysis e ealed a signi ican Expe imen al condi ion
e ec (F1,32 = 4.7; p = 0.017; pa ial η2 = 0.13), bu no signi ican G oup e ec (F1,31 = 0.8, p = 0.37) o a G oup
by Expe imen al condi ion (F1,32 = 0.5, p = 0.59). In de ails, di e ences in RTs we e signi ican ly g ea e o he
‘P esen Agen ’ as compa ed o he ‘No Agen ’ o ‘Con ol Sound’ condi ions in bo h g oups.
In o de o show he consis ency o he spa ial alignmen e ec s ac oss sigh ed and blind pa icipan s in he
wo se s o expe imen s, we epo ed single subjec da a in he Supplemen a y Figu es1 and 2.
Discussion
The o e all aim o he cu en s udy was o in es iga e whe he pe ipe sonal space ep esen a ion can de elop
independen ly om ( he lack o ) isual expe ience. Acco dingly, we ca ied ou wo se s o beha io al expe i-
men s aking ad an age o a spa ial alignmen pa adigm in o de o sc u inize how pe ipe sonal space ep esen a-
ion unc ions in bo h sigh ed and blind people. The e we e h ee main indings.
Fi s , sigh ed pa icipan s displayed a compa able spa ial alignmen e ec in bo h he isual and he audi o y
domains (Exp. 1A and 1B). The e ec occu ed only when he a o ding objec (a small ball) was bo h isually
and audi o ily p esen ed wi hin pa icipan s’ each. Second, in e es ingly a compa able spa ial alignmen e ec
occu ed in sigh ed and blind people when lis ened o he small ball bouncing close o hem (Exp. 1B). Thi d, and
e en mo e in e es ingly, a spa ial alignmen e ec was ound also when he a o ding objec was audi o ily p e-
sen ed a om sigh ed and congeni ally blind subjec s, p o ided ha he objec el wi hin he pe ipe sonal space
o ano he agen , whose p esence was audi o ily cued (Exp. 2B). Taken oge he , hese h ee indings sugges ha
sigh ed and congeni ally blind people did no di e in ep esen ing bo h hei own and ano he ’s pe ipe sonal
space.
The i s inding ex ends and s eng hens p e ious s udies ca ied ou by ou g oup showing a bo h beha io al
and neu onal le el ha he spa ial alignmen e ec occu s when a o ding objec s a e isually p esen ed wi hin
he agen ’s each only23,25. The cu en s udy demons a es ha his holds in he audi o y domain oo, sugges ing
ha sigh ed indi iduals do no di e in ep esen ing pe ipe sonal space when capi alizing on ei he isual o non
isual esou ces.
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The second inding o he cu en s udy conce ns he occu ence o a compa able space alignmen e ec in
sigh ed and congeni ally blind pa icipan s, which speaks o a simila pe ipe sonal space ep esen a ion in bo h
g oups. P e ious s udies showed ha audi o y s imuli can be mapped on o one’s own space no di e en ly om
he isual ones. Fo ins ance, i has been epo ed ha bo h app oaching isual and audi o y s imuli enhance
he co icospinal exci abili y10,11,32. Simila esul s ha e also been ob ained compa ing he ac ile and audi o y
domains9. This indica es ha pe ipe sonal space migh be ep esen ed in senso y domains o he han ision. The
Figu e 2. Expe imen al p ocedu es and esul s o Expe imen s 2. Exempla go s imuli and exempla ial o
Exp. 2 (uppe panel); (A) Es ima ed ma ginal mean RTs o Exp. 2A, (B) Exp. 2B and (C) Exp. 2C ac oss sigh ed
and congeni ally blind pa icipan s. In he g aphs, e o ba s indica e s anda d e o s; es ima ed ma ginal mean
RTs o cong uen (blue) and incong uen ( ed) ials a e epo ed; a ull ci cle and an emp y ci cle indica e
es ima ed ma ginal mean RTs o he sigh ed and congeni ally blind samples, espec i ely; as e isks highligh
signi ican Loca ion × Cong uency in e ac ions and pos -hoc T- es compa isons.
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SCien i iC REPOR S | 7: 17673 | DOI:10.1038/s41598-017-17896-9
cu en s udy mo es a s ep o wa d by sugges ing ha ( he lack o ) isual expe ience does no signi ican ly a ec
he de elopmen o pe ipe sonal space ep esen a ion.
This inding seems o be, appa en ly a leas , in con as wi h he isual dominance in space ep esen a ion,
as p oposed in Röde e al.17. Speci ically, hese au ho s ook ad an age o an audi o y e sion o he Simon ask
by asking sigh ed, la e and congeni ally blind pa icipan s o p ess a le o igh esponse key depending on he
bandwid h o pink noise bu s s p esen ed om ei he a le o igh loudspeake , al e na ing be ween pe o ming
he ask wi h unc ossed o c ossed hands. The esul s showed ha he Simon e ec occu ed in bo h condi ions
o he sigh ed and la e blind pa icipan s; while i was e e sed when congeni ally blind pa icipan s c ossed hei
hands. This e e sion was e en s onge when he ask equi ed an explici ma ching o he sound loca ion wi h
he posi ion o he esponding hand. This would sugges ha isual expe ience a ec s space ep esen a ion by
inducing he de aul use o an ex e nal coo dina e ame o mul isenso y ac ion con ol.
A candida e explana ion o he di e ence be ween ou and Röde e al.’s indings poin s i s o he di e ence
be ween asks. This explana ion seems o be suppo ed by a ecen s udies demons a ing a clea dissocia ion
be ween he Simon and he spa ial alignmen e ec s33. And his also may accoun o why we did no ind any spa-
ial alignmen e ec wi h an ac ion-un ela ed sound (e.g., a neu al en i onmen al sound - Exp. 1C), e en when
i was p esen ed wi h a le - igh spa ial compa ibili y wi h pa icipan s’ hand.
The di e ence in ask also e lec s a di e ence in space ep esen a ion. Röde e al.17 explici ly used he Simon
e ec , con as ing he unc ossed and c ossed hand condi ions, wi h he aim o in es iga ing he ame o e e ence
which is supposed o be used by de aul in ac ion con ol and how isual expe ience migh induce a shi om
an in e nal o an ex e nal one. Ou aim was di e en : we explo ed how he pe ipe sonal space is ep esen ed, by
manipula ing he eachabili y o ac ion- ela ed isually and audi o ily cued objec s. No doub ha he ex e nal
ame e e ence can be use ul in mapping space loca ions o ac ion con ol pu poses. Howe e , he e is subs an-
ial e idence ha when handling wi h eady- o-hand objec s, he space su ounding one’s own body is p ima ily
ep esen ed as an ac ion space34. In addi ion, se e al s udies showed ha he bounda ies o he su ounding space
ep esen a ion a ies wi h he a ying o he ange o one’s own ac ion6. Fo ins ance, a seminal single cell s udy27
showed ha he ex en o hand- ela ed space ep esen a ion changed when he monkeys used a ake o e ie e
o he wise un eachable pieces o ood, sh inking back o i s no mal ex ension when he monkeys s opped using
he ake and jus hold i 35. Simila esul s ha e been ob ained in heal hy25,36 and b ain-damaged humans37–41.
These indings clea ly indica e ha he pe ipe sonal space p ima ily unc ions as a space o ac ion. Ou s udy
demons a es ha such ac ion space ep esen a ion migh be de eloped independen ly om ( he lack o ) isual
expe ience. This could explain why congeni ally blind people may e icien ly handle wi h a su ounding wo ld
hey ha e ne e seen18,19,42. Indeed, compa able pe o mances o sigh ed indi iduals ha e been e en desc ibed o
objec iden i ica ion and manipula ion in he su ounding space43. In addi ion, simila ly o sigh ed indi iduals,
ool use has been shown o ex end pe ipe sonal space ep esen a ion in blind people, whe e his ex ension u ned
ou o be dynamically and unc ionally depending on con ex ual mo o demands44. Finally, no di e en ly om
sigh ed indi iduals, a le wa d bias in he ep esen a ion o spa ial ex en s has been ound in congeni ally blind
people when bisec ing ho izon al ods45.
Ou and hese indings do no imply ha isual expe ience has no e ec on space ep esen a ion, o cou se. As
al eady men ioned, blind and sigh ed indi iduals may ep esen he ex e nal wo ld elying on di e en e e ence
ames17 and se e al s udies indica ed ha blind indi iduals a e mo e inclined o p ima ily ely on body-cen e ed
coo dina e sys em, whe eas sigh ed indi iduals by de aul shi o an ex e nal ame o e e ence18–20,46. Indeed, i
has been shown ha isual expe ience acili a es allocen ic spa ial ep esen a ion when people a e equi ed o
memo ize a gi en a ay o objec s21. Mo e ecen ly, isual expe ience has been demons a ed o c i ically impac
e en he localiza ion o s a ic and mo ing sounds. Sigh ed indi iduals esul ed mo e accu a e han he blind
g oup in doing his, and his di e ence could be accoun ed o o a di e ence in he ame o e e ence used (i.e.,
allocen ic ins ead egocen ic)47. Finally, he e is also e idence ha blind and sigh ed indi iduals may capi alize
on di e si ied cogni i e s a egies19,20,48,49. Howe e , all hese di e ences a e no in con as wi h ou main inding
o a simila ac ion space ep esen a ion in congeni ally blind and sigh ed people. When equi ed o ac upon
su ounding objec s, congeni ally blind and sigh ed people do no di e in ep esen ing hei own pe ipe sonal
space. S ikingly, ha hey do no also di e in ep esen ing ano he ’s pe ipe sonal space, as ou hi d inding
shows.
The hi d inding was ha he spa ial alignmen e ec occu ed in bo h sigh ed and congeni ally blind pa -
icipan s when he bouncing ball was audi o y p esen ed a om hem bu close o ano he agen whose p es-
ence was also audi o ily igge ed. As o he sigh ed pa icipan s, his inding expands o he audi o y domain
wha has been p e iously ound in he isual domain only30,31. Indeed, he ep esen a ion o pe ipe sonal space
is modula ed by he isual p esence o ano he po en ial agen . By using a e y simila spa ial alignmen pa a-
digm30, pa icipan s we e as e in pan omiming a each- o-g asp mo emen owa d a cong uen ly han owa d a
no-cong uen ly o ien ed a o ding objec (e.g., a handled mug), e en when he objec was isually p esen ed a
om hem, p o ided ha i u ned ou o be isually close o a i ual agen such as an a a a . A neu onal coun-
e pa o his beha io al inding has been ob ained by a TMS s udy ca ied ou by ou g oup31. We magne ically
s imula ed he le p ima y mo o co ex and eco ded mo o -e oked po en ials (MEPs) while pa icipan s we e
p esen ed wi h a handled mug close ei he o hem o o an a a a . Highes MEPs we e ound bo h when he mug
was nea enough o be ac ually eachable o he pa icipan s and also when i was ou o each o hem, p o-
ided ha i was eady o he a a a ’s hand. In e es ingly, simila esul s ha e been also epo ed in non-human
p ima es. A single cell s udy showed ha p emo o neu ons ypically in ol ed in encoding a o ding objec ea-
u es (e.g., canonical neu ons) usually esponded o objec s p esen ed wi hin monkey’s each. A po ion o hese
neu ons has been eco ded also o espond o objec s p esen ed ou side he monkey’s each, p o ided ha hese
objec s we e close o ano he agen ’s hand29.
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Blind pa icipan s showed signi ican ly as e eac ion imes as compa ed o sigh ed indi iduals in he second
se o expe imen s. Fas e esponses o he blind sample we e p esen , e en i no signi ican , also in Exp. 1B.
This obse a ion is consis en wi h se e al s udies p e iously assessing a signi ican ly educed audi o y eac-
ion ime in congeni ally blind pa icipan s as compa ed o sigh ed pa icipan s ac oss di e en asks (e.g.50–52).
None heless, due o he limi ed size o he blind samples and o he sha ed pa icipa ion o six blind subjec s
ac oss bo h expe imen al sessions, any u he conside a ion on supe io i y o pe o mance o compensa o y
mechanisms in blind indi iduals could jus be pa ial.
As o he congeni ally blind pa icipan s, he inding ha hey do no di e om sigh ed indi iduals in map-
ping objec s eady o bo h hei own and ano he ’s hands s eng hens he hypo hesis ha pe ipe sonal space
ep esen a ion migh be de eloped la gely independen om isual expe ience. This hypo hesis seems o be also
consis en wi h se e al s udies demons a ing, a he neu al le el, ha space and ac ion migh be ep esen ed
independen ly om isual expe ience. Speci ically, dis inc unc ional ne wo ks p ocessing ask-speci ic in o -
ma ion independen ly om isual expe ience ha e been also desc ibed in bo h sigh ed and congeni ally blind
indi iduals o spa ial p ocessing and ep esen a ion in pa ie o-occipi al a eas18,19,48. Fu he mo e a la ge ac i a-
ion o e lap in a eas o he do sal pa hway has been ound o congeni ally blind and sigh ed pa icipan s du -
ing pe o mance and wo king memo y main enance o kines he ically guided hand mo emen s53. Congeni ally
blind and sigh ed indi iduals ha e also been shown o ep esen eaching and g asping ac ions by ec ui ing
a e y simila do so-pa ie al ne wo k54. This would sugges a isual expe ience independen de elopmen o
ac ion ep esen a ion and con ol. In e es ingly a pa ie o-p emo o ne wo k p ocessing ac ion speci ic in o ma-
ion independen ly om isual expe ience has been also desc ibed in bo h sigh ed and congeni ally blind indi-
iduals du ing audi o y ecogni ion o mo o ac ions55,56. Al oge he , hese indings suppo he iew ha b ain
mo phological and unc ional a chi ec u es a e mos ly selec ed o de elop and wo k independen ly om isual
expe ience and ha dis inc co ical a eas a e able o build senso y independen ep esen a ions o ac ion14–16.
Fu he mo e, hey indica e ha hese senso y-independen ep esen a ions a e c i ical no only o dealing wi h
su ounding hings bu also o in e ac ing wi h o he people.
The hi d inding o he cu en s udy mo es a s ep u he in his di ec ion, sugges ing ha pe ipe sonal
space ep esen a ion does no conce n he su ounding space o ou body only, bu also migh be in ol ed in
mapping he space a ound o he bodies, hus con ibu ing o b idge he gap, pa ially a leas , be ween us and
o he s57. To his ega d, a seminal single cell s udy eco ding om he in e io pa ie al lobule (a ea VIP) om he
macaque b ain demons a ed ha he e we e bimodal neu ons which esponded, no only o ac ile and isual
s imuli deli e ed wi hin he su ounding space o he monkey, bu also o isual s imuli p esen ed wi hin he
su ounding space o he expe imen e acing he monkey. C i ically, when isual s imuli we e p esen ed a he
same dis ance om he monkey bu in he absence o he expe imen e , he esponses disappea ed. Acco ding o
he au ho s, hese neu ons migh con ibu e o an in e pe sonal bodily space mapping which could be ele an o
sel and o he in e ac ions58. The cu en s udy suppo s he hypo hesis ha his in e pe sonal mapping should
be ex ended o he ac ion domain, highligh ing how people migh sha e hei own ac ion space ep esen a ion o
map o he s’ ac ion space24,30,31. And e en mo e in e es ingly, i demons a es, o he i s ime, ha he de elop-
men o in e pe sonal mapping in he ac ion domain is la gely independen om ( he lack o ) isual expe ience.
Me hods
Expe imen 1. Pa icipan s. A g oup o congeni ally blind and h ee g oups o sigh ed heal hy adul s ook
pa in Expe imen s 1: 14 sigh ed (6 M/8 F, mean age 27 ± 6 yea s) in Exp. 1A; 25 sigh ed (10 M/15 F, 34 ± 15) in
Exp. 1B; 25 sigh ed (12 M/13 F, 36 ± 15) in Exp. 1C; 10 blind (5 M/5 F, 43 ± 11; age g oup compa isons: p = 0.11
o Exp. 1B; p = 0.17 o Exp. 1C) in Exp. 1B and 1C. All subjec s we e igh -handed (wi h he excep ion o wo
sigh ed o Exp. 1B and one blind le -handed pa icipan s), had no mal audi o y acui y (and no mal o co ec -
ed- o-no mal isual acui y o SC). All subjec s we e d ug- ee and ecei ed an in e iew o exclude any medical
o neu opsychia ic diso de . All isually-dep i ed pa icipan s we e blind om bi h and had no ecollec ion
o any isual memo y (only pe iphe al causes o congeni al blindness we e admi ed - Table SI). Sigh ed and
blind pa icipan s ga e hei in o med consen a e he p ocedu es had been explained and e ained he igh
o wi hd aw om he s udy a any momen . The s udy was conduc ed unde a p o ocol app o ed by he E hical
Commi ee o he Uni e si y o Pisa (1616/2003). All expe imen s we e pe o med in acco dance wi h ele an
in e na ional guidelines and egula ions.
P ocedu e. In Exp. 1A, wo se s o isual s imuli we e employed. The i s se o s imuli included b/w pic u es
depic ing ei he a igh o a le hand pan omiming o a g asping mo emen . The second se o s imuli included
3D ooms (simila o hose used in23), wi h a able and a ball on i , c ea ed wi h 3D S udiomax .13. In hal o he
ials, he ball was placed ei he on he igh o on he le side o he able, and wi hin he pa icipan s’ each o
in hei non- eachable space (Fig.1, uppe panel). In Exp. 1B, wo se s o isual s imuli we e employed. The i s
se o s imuli included a neu al beep (800 Hz, du a ion 150 ms; 32 bi quan iza ion). The second se o s imuli
was he sound o a bouncing solid ball (0–24 KHz, 800 ms; 32 bi , s e eo), eco ded in an anechoic oom a wo
dis ances om he mic ophone o ep oduce expe imen al condi ions ( eachable and non- eachable). Sound
s imuli we e no malized using Audaci y®2.0.5 (h p://audaci y.sou ce o ge.ne /). The neu al beep was used as
he ins uc ion s imulus and was lis ened ei he o he igh o o he le ea . The sounds o a bouncing ball we e
used as he go s imulus. These las s imuli comp ised ou di e en sounds o he ball ha was placed ei he on he
igh o on he le side o he able, and when, in hal o he ials he ball was bouncing wi hin he pa icipan s’
eachable space, while in he o he hal in he non- eachable space (Fig.1, uppe panel). Pa icipan s e alua ed
s imuli be o e s a ing he main expe imen s: he ‘ eachable’ go s imulus was labeled as nea and eachable by
all pa icipan s wi h an es ima ed dis ance o 21 ± 9 cm, while he ‘no eachable’ go s imulus was labeled as a
and no eachable wi h an es ima ed dis ance o 150 ± 30 cm. Two se s o s imuli we e used in Exp. 1C. The i s
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se o s imuli included a neu al beep (as in 1B) as ins uc ion s imulus. The second se o s imuli was a neu al,
ac ion-un ela ed en i onmen al sound (blowing wind: equency ange 0–24 KHz, 1,800 ms; 32 bi , s e eo, www.
soungle.com). F equency and ampli ude we e no malized wi h he ‘go s imulus’ o Exp. 1B (Audaci y®2.0.5),
while i s olume was modi ied o simula e he eachable and non- eachable condi ions and be used as he go s im-
ulus. The en i onmen al sound was lis ened ei he o he igh o o he le ea , and, in hal o he ials, wi hin
he pa icipan s’ eachable space, while in he o he hal in he non- eachable space. Visual s imuli we e p esen ed
by means o a p ojec ing display (Toshiba TLP-780 p ojec o ; Na i e Resolu ion: 1024 × 768; Aspec Ra io: 4:3 –
XGA; FOV ~60° × 40°). Pa icipan s sea abou 50 cm a om he display. Audi o y s imuli we e p esen ed by a
headphone sys em (Philips, SHP1900) and pa icipan s we e blind olded.
Each ial consis ed on he p esen a ion o he ins uc ion s imulus (i.e., image o he g asping hand o he
isual condi ion, beep sound o he audi o y condi ions) o 150 ms ollowed, a e a a iable delay (ISI anging
om 150 o 450 ms), by he go-s imulus (i.e., isual 3D scenes wi h a ball placed on a side o a able o a monola -
e al sound o a bouncing ball). ITI was 6,000 ms. Pa icipan s we e eques ed o pan omime a g asp- o- each
mo emen p omp ed by he i s ins uc ion s imuli (image o g asping hand o monola e al beep sound) as soon
as he go-s imulus was iewed o lis ened o (Fig.1). Thus, cong uen ials e e o he condi ion in which a pa -
icipan had o pan omime a each- o-g asp ac wi h ei he he igh o he le hand ipsila e ally, ei he o he side
o he able whe e a ball was isually o audi o ily placed, while incong uen ials e e o he condi ion in which
he esponding hand and he isual o audi o y a ge we e in opposi e hemispaces. A he beginning o each ial,
pa icipan s es ed hei index inge s on wo esponse bu ons a anged ho izon ally on a no epad keyboa d.
Responses we e gi en by li ing he index inge o he esponse hand and hen making he g asping mo emen as
ins uc ed. This allowed us o measu e li o ime (RT - i.e. he ime be ween onse o he go-s imulus and ini ial
hand mo emen ). Each session consis ed o 16 ials ha we e epea ed eigh imes o Exp. 1A and 1B, and ou
imes o Exp. 1C. The e o e, each pa icipan p o ided wi h 32 ials (16 o Exp. 1C) pe condi ion (i.e. eacha-
ble/cong uen ; eachable/incong uen ; non- eachable/cong uen ; non- eachable/incong uen ). The p esen a ion
o he s imuli and he eco ding o he pa icipan s’ esponses (in e ms o mo emen onse ) we e con olled by
P esen a ion so wa e (Neu obeha io al Sys ems, Inc., Be keley, CA). Indi iduals we e adminis e ed Exp. 1B and
1C pa adigms in a andomly al e na ed manne , o limi any no el y, lea ning o a igue bias due o he o de o
adminis a ion.
Da a analysis. T ials in which subjec s ailed o espond (e.g. an icipa ion o mo emen ) we e disca ded and
e o a es we e compa ed ac oss condi ions wi h pai ed T compa isons be ween condi ions (i.e. cong uen
s. incong uen and eachable s. non- eachable). E o a es did no di e ac oss condi ions in Exp. 1 in bo h
sigh ed and blind pa icipan s (p > 0.05, Bon e oni co ec ed). The mean RT o he co ec esponses was calcu-
la ed o each condi ion wi hin session, hus o ob ain 8 indi idual mean RTs o each condi ion. The RT alues
o he co ec ed esponses we e co ec ed o possible ou lie s h ough imming. Speci ically, esponses ei he
sho e han he 5 h pe cen ile o longe han he 95 h pe cen ile o all 128 o 64 indi idual RTs we e ea ed as
ou lie s and no conside ed (i.e. abou 10% o he co ec ed esponses)59. Due o unequal sample size and unequal
sample a iance (Le ene es , p < 0.05) be ween expe imen al g oups, RTs we e en e ed in a linea mixed e ec
(LME) epea ed-measu es model wi h he Loca ion o he objec ( eachable space s. non- eachable space) and
Alignmen (cong uen s. incong uen ) as wi hin-subjec s epea ed ixed ac o s; Subjec s as andom ac o , and
Age as Co a ia e ( ixed ac o ). Fo Exp. 1B and 1C, da a we e en e ed in a LME model, simila o Exp. 1A, bu
wi h an addi ional G oup (sigh ed s. blind) a iable, as be ween-subjec s ixed ac o . Pos -hoc T- es compa -
isons we e pe o med on he es ima ed ma ginal means when signi ican e ec s o in e ac ion we e ound in
he LME analyses (p < 0.05, Bon e oni co ec ed). S a is ical analyses we e pe o med by using IBM® SPSS®
S a is ics 21.
Expe imen 2. Pa icipan s. Twen y- i e sigh ed (12 M/13 F, 34 ± 15 yea s) and 9 blind (5 M/4 F, 42 ± 12
yea s; g oup compa ison, p = 0.28 - Table SI) heal hy pa icipan s ook pa o Exp. 2. All subjec s we e
igh -handed (wi h he excep ion one blind). All pa icipan s ga e hei w i en in o med consen .
P ocedu e. In o de o ep oduce an audi o y-based expe imen al condi ion simila o ou p e ious expe i-
men s30, wo se s o s imuli we e used. The i s se o s imuli included a neu al beep (as Exp. 1) used as ins uc-
ion s imulus. The second se o s imuli included h ee di e en sounds (Fig.2, uppe panel): a bouncing solid
ball, same as Exp. 1B – ‘No agen ’ condi ion; a bouncing solid ball and a simul aneous human oice sound (sim-
ula ing he p esence o a human agen close o he ball p onouncing he exclama ion ‘hey’; 0–24 KHz, 800 ms;
32 bi , s e eo) – ‘P esen agen ’; a bouncing solid ball and a simul aneous neu al a i icial (i.e., mechanical) sound
simula ing he p esence o a non-human objec close o he ball (0–24 KHz, 800 ms; 32 bi , s e eo) – ‘Con ol
sound’. Each s imuli we e modi ied in i s ampli ude (Audaci y®2.0.5) o simula e he eachable and non- eachable
condi ions, and was adminis e ed ei he o he igh o o he le ea o simula e cong uen o incong uen condi-
ions. P esen a ion o he ball sound wi h he human oice o he neu al a i icial sound and simple p esen a ion
we e equally di ided ac oss all ials. Each ime he bouncing ball sound was p esen ed in associa ion o ei he
he human oice o he neu al a i icial sound, he wo s imuli we e p esen ed a he same dis ance and o he
same side. Expe imen al p ocedu es we e iden ical o Exp. 1. Each session consis ed o 96 ials and was epea ed
ou imes.
Da a analysis. Same as Exp. 1B. E o a es did no di e ac oss condi ions (p > 0.05). In addi ion, o speci ically
demons a e he e ec o he po en ial agen on one’s own pe ipe sonal space, ac oss asks, he di e ences in he
RTs be ween cong uen and incong uen condi ions in he non- eachable space o he h ee di e en expe i-
men al condi ions we e en e ed in a LME epea ed-measu es model wi h ‘Expe imen al condi ion’ (No Agen ,
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P esen Agen , Con ol Sound) and ‘G oup’ as wi hin-subjec s epea ed ixed ac o s, ‘Subjec s’ as andom ac o
and ‘Age’ as co a ia e.
Da a a ailabili y. The da a ha suppo he indings o his s udy a e a ailable om he co esponding
au ho upon easonable eques .
Re e ences
1. Jeanne od, M., A bib, M. A., Rizzola i, G. & Saka a, H. G asping objec s: he co ical mechanisms o isuomo o ans o ma ion.
T ends Neu osci. 18, 314–320 (1995).
2. Mu a a, A. e al. Objec ep esen a ion in he en al p emo o co ex (a ea F5) o he monkey. J. Neu ophysiol. 78, 2226–2230
(1997).
3. Raos, V., Umil a, M. A., Mu a a, A., Fogassi, L. & Gallese, V. Func ional p ope ies o g asping- ela ed neu ons in he en al
p emo o a ea F5 o he macaque monkey. J. Neu ophysiol. 95, 709–729 (2006).
4. Buccino, G., Sa o, M., Ca aneo, L., Roda, F. & Riggio, L. B oken a o dances, b oken objec s: a TMS s udy. Neu opsychologia 47,
3074–3078 (2009).
5. Rizzola i, G., Fadiga, L., Gallese, V. & Fogassi, L. P emo o co ex and he ecogni ion o mo o ac ions. B ain Res. Cogn. B ain Res.
3, 131–141 (1996).
6. di Pelleg ino, G. & Lada as, E. Pe ipe sonal space in he b ain. Neu opsychologia 66, 126–133 (2015).
7. G aziano, M. S., Reiss, L. A. & G oss, C. G. A neu onal ep esen a ion o he loca ion o nea by sounds. Na u e 397, 428–430 (1999).
8. Cohen, Y. E. & Ande sen, R. A. A common e e ence ame o mo emen plans in he pos e io pa ie al co ex. Na . Re . Neu osci.
3, 553–562 (2002).
9. A enan i, A., Annela, L. & Se ino, A. Supp ession o p emo o co ex dis up s mo o coding o pe ipe sonal space. Neu oimage 63,
281–288 (2012).
10. Finisgue a, A., Canzone i, E., Se ino, A., Pozzo, T. & Bassolino, M. Mo ing sounds wi hin he pe ipe sonal space modula e he
mo o sys em. Neu opsychologia 70, 421–428 (2015).
11. Se ino, A., Annella, L. & A enan i, A. Mo o p ope ies o pe ipe sonal space in humans. PLoS One 4, e6582 (2009).
12. Fe ona o, P. A., Domello , E. & Ronnq is , L. Ea ly in luence o audi o y s imuli on uppe -limb mo emen s in young human
in an s: an o e iew. F on . Psychol. 5, 1043 (2014).
13. Riccia di, E. & Pie ini, P. New ligh om he da k: wha blindness can each us abou b ain unc ion. Cu . Opin. Neu ol. 24,
357–363 (2011).
14. Riccia di, E., Bonino, D., Pelleg ini, S. & Pie ini, P. Mind he blind b ain o unde s and he sigh ed one! Is he e a sup amodal
co ical unc ional a chi ec u e? Neu osci. Biobeha . Re . 41, 64–77 (2014).
15. Cecche i, L., Kupe s, R., P i o, M., Pie ini, P. & Riccia di, E. A e Sup amodali y and C oss-Modal Plas ici y he Yin and Yang o
B ain De elopmen ? F om Blindness o Rehabili a ion. F on . Sys . Neu osci. 10, 89 (2016).
16. Riccia di, E., Handja as, G. & Pie ini, P. The blind b ain: How (lack o ) ision shapes he mo phological and unc ional a chi ec u e
o he human b ain. Exp. Biol. Med. (Maywood) 239, 1414–1420 (2014).
17. Rode , B., Kusmie ek, A., Spence, C. & Schicke, T. De elopmen al ision de e mines he e e ence ame o he mul isenso y
con ol o ac ion. P oc. Na l. Acad. Sci. USA 104, 4753–4758 (2007).
18. C ollen, V. & Collignon, O. Embodied space in ea ly blind indi iduals. F on . Psychol. 3, 272 (2012).
19. Ca aneo, Z. e al. Image y and spa ial p ocesses in blindness and isual impai men . Neu osci. Biobeha . Re . 32, 1346–1360 (2008).
20. Thinus-Blanc, C. & Gaune , F. Rep esen a ion o space in blind pe sons: ision as a spa ial sense? Psychol. Bull. 121, 20–42 (1997).
21. Pasqualo o, A., Spille , M. J., Jansa i, A. S. & P oulx, M. J. Visual expe ience acili a es allocen ic spa ial ep esen a ion. Beha . B ain
Res. 236, 175–179 (2013).
22. Bub, D. N. & Masson, M. E. G asping bee mugs: on he dynamics o alignmen e ec s induced by handled objec s. J. Exp. Psychol.
Hum. Pe cep . Pe o m. 36, 341–358 (2010).
23. Cos an ini, M., Amb osini, E., Tie i, G., Sinigaglia, C. & Commi e i, G. Whe e does an objec igge an ac ion? An in es iga ion
abou a o dances in space. Exp. B ain Res. 207, 95–103 (2010).
24. Ca dellicchio, P., Sinigaglia, C. & Cos an ini, M. The space o a o dances: a TMS s udy. Neu opsychologia 49, 1369–1372 (2011).
25. Cos an ini, M., Amb osini, E., Sinigaglia, C. & Gallese, V. Tool-use obse a ion makes a objec s eady- o-hand. Neu opsychologia
49, 2658–2663 (2011).
26. Ma a i a, A. & I iki, A. Tools o he body (schema). T ends Cogn. Sci. 8, 79–86 (2004).
27. I iki, A., Tanaka, M. & Iwamu a, Y. Coding o modi ied body schema du ing ool use by macaque pos cen al neu ones. Neu o epo
7, 2325–2330 (1996).
28. Fa ne, A. & Lada as, E. Dynamic size-change o hand pe ipe sonal space ollowing ool use. Neu o epo 11, 1645–1649 (2000).
29. Bonini, L., Ma anesi, M., Li i, A., Fogassi, L. & Rizzola i, G. Ven al p emo o neu ons encoding ep esen a ions o ac ion du ing
sel and o he s’ inac ion. Cu . Biol. 24, 1611–1614 (2014).
30. Cos an ini, M., Commi e i, G. & Sinigaglia, C. Ready bo h o you and o my hands: mapping he ac ion space o o he s. PLoS
ONE6, e17923 (2011).
31. Ca dellicchio, P., Sinigaglia, C. & Cos an ini, M. G asping a o dances wi h he o he ’s hand: a TMS s udy. Soc. Cogn. A ec Neu osci.
8, 455–459 (2013).
32. Makin, T. R., Holmes, N. P., B ozzoli, C., Rosse i, Y. & Fa ne, A. Coding o isual space du ing mo o p epa a ion: App oaching
objec s apidly modula e co icospinal exci abili y in hand-cen e ed coo dina es. J. Neu osci. 29, 11841–11851 (2009).
33. Saccone, E. J., Chu ches, O. & Nicholls, M. E. Explici spa ial compa ibili y is no c i ical o he objec handle e ec . J. Exp. Psychol.
Hum. Pe cep . Pe o m. 42, 1643–1653 (2016).
34. Rizzola i, G., Fadiga, L., Fogassi, L. & Gallese, V. The space a ound us. Science 277, 190–191 (1997).
35. Ishibashi, H., Hiha a, S. & I iki, A. Acquisi ion and de elopmen o monkey ool-use: beha io al and kinema ic analyses. Can. J.
Physiol. Pha macol. 78, 958–966 (2000).
36. Ma a i a, A., Spence, C., Kenne , S. & D i e , J. Tool-use changes mul imodal spa ial in e ac ions be ween ision and ouch in
no mal humans. Cogni ion 83, B25–34 (2002).
37. Be i, A. & F assine i, F. When a becomes nea : emapping o space by ool use. J. Cogn. Neu osci. 12, 415–420 (2000).
38. Pegna, A. J. e al. So nea ye so a : neglec in a o nea space depends on ool use. Ann. Neu ol. 50, 820–822 (2001).
39. Ack oyd, K., Riddoch, M. J., Humph eys, G. W., Nigh ingale, S. & Townsend, S. Widening he sphe e o in luence: using a ool o
ex end ex ape sonal isual space in a pa ien wi h se e e neglec . Neu ocase 8, 1–12 (2002).
40. Neppi-Modona, M. e al. Bisec ing lines wi h di e en ools in igh b ain damaged pa ien s: he ole o ac ion p og amming and
senso y eedback in modula ing spa ial emapping. Co ex 43, 397–410 (2007).
41. C os an ini, M. e al. When a lase pen becomes a s ick: emapping o space by ool-use obse a ion in hemispa ial neglec . Exp. B ain
Res. 232, 3233–3241 (2014).
42. Collignon, O., Voss, P., Lassonde, M. & Lepo e, F. C oss-modal plas ici y o he spa ial p ocessing o sounds in isually dep i ed
subjec s. Exp. B ain Res. 192, 343–358 (2009).
