Damage to the primary visual cortex removes the major input from the eyes to the brain, causing significant visual loss as patients are unable to perceive the side of the world contralateral to the damage. Some patients, however, retain the ability to detect visual information within this blind region; this is known as blindsight. By studying the visual pathways that underlie this residual vision in patients, we can uncover additional aspects of the human visual system that likely contribute to normal visual function but cannot be revealed under physiological conditions. In this review, we discuss the residual abilities and neural activity that have been described in blindsight and the implications of these findings for understanding the intact system.
AdolphsRTranelDBuchananTW. 2005. Amygdala damage impairs emotional memory for gist but not details of complex stimuli. Nat Neurosci8(4):512–8.
2.
AjinaSKennardC. 2012. Rehabilitation of damage to the visual brain. Rev Neurol (Paris)168(10):754–61.
3.
AjinaSKennardCReesGBridgeH. 2015a. Motion area V5/MT+ response to global motion in the absence of V1 resembles early visual cortex. Brain38(1):164–78.
4.
AjinaSPestilliFRokemAKennardCBridgeH. 2015b. Human blindsight is mediated by an intact geniculo-extrastriate pathway. Elife4:e08935. doi:10.7554/eLife.08935.
5.
AjinaSReesGKennardCBridgeH. 2015c. Abnormal contrast responses in the extrastriate cortex of blindsight patients. J Neurosci35(21):8201–13.
6.
BarburJLWatsonJDFrackowiakRSZekiS. 1993. Conscious visual perception without V1. Brain116 (pt 6):1293–302.
7.
BaselerHAMorlandABWandellBA. 1999. Topographic organization of human visual areas in the absence of input from primary cortex. J Neurosci. 19(7):2619–27.
8.
BermanRAWurtzRH. 2010. Functional identification of a pulvinar path from superior colliculus to cortical area MT. J Neurosci30(18):6342–54.
9.
BermanRAWurtzRH. 2011. Signals conveyed in the pulvinar pathway from superior colliculus to cortical area MT. J Neurosci31(2):373–84.
10.
BlytheIMKennardCRuddockKH. 1987. Residual vision in patients with retrogeniculate lesions of the visual pathways. Brain110(pt 4):887–905.
11.
BolaMGallCSabelBA. 2013. The second face of blindness: processing speed deficits in the intact visual field after pre- and post-chiasmatic lesions. PLoS One8(5):e63700.
12.
BoyerJLHarrisonSRoT. 2005. Unconscious processing of orientation and color without primary visual cortex. Proc Natl Acad Sci U S A102(46):16875–9.
13.
BridgeHHarroldSHolmesEAStokesMKennardC. 2012. Vivid visual mental imagery in the absence of the primary visual cortex. J Neurol259(6):1062–70.
14.
BridgeHHicksSLXieJOkellTWMannanSAlexanderI, and others. 2010. Visual activation of extra-striate cortex in the absence of V1 activation. Neuropsychologia48(14):4148–54.
15.
BridgeHThomasOJbabdiSCoweyA. 2008. Changes in connectivity after visual cortical brain damage underlie altered visual function. Brain131(pt 6):1433–1444.
16.
CampionJLattoRSmithYM. 1983. Is blindsight an effect of scattered-light, spared cortex, and near-threshold vision. Behav Brain Sci6(3):423–47.
17.
CavézianCPerezCPeyrinCGaudryIObadiaMGoutO, and others. 2015. Hemisphere-dependent ipsilesional deficits in hemianopia: sightblindness in the ‘intact’ visual field. Cortex69:166–74.
18.
CeleghinAde GelderBTamiettoM. 2015. From affective blindsight to emotional consciousness. Conscious Cogn36:414–25.
19.
CoweyA. 2010. The blindsight saga. Exp Brain Res200(1):3–24.
20.
CoweyAStoerigPBannisterM. 1994. Retinal ganglion cells labelled from the pulvinar nucleus in macaque monkeys. Neuroscience61(3):691–705.
21.
CulhamJCCavina-PratesiCSinghalA. 2006. The role of parietal cortex in visuomotor control: what have we learned from neuroimaging?Neuropsychologia44(13):2668–84.
22.
DanckertJRossettiY. 2005. Blindsight in action: what can the different sub-types of blindsight tell us about the control of visually guided actions?Neurosci Biobehav Rev29(7):1035–46.
23.
de GelderBMorrisJSDolanRJ. 2005. Unconscious fear influences emotional awareness of faces and voices. Proc Natl Acad Sci U S A102(51):18682–7.
24.
de GelderBTamiettoMPegnaAJVan den StockJ. 2015. Visual imagery influences brain responses to visual stimulation in bilateral cortical blindness. Cortex72:15–26.
25.
de GelderBTamiettoMvan BoxtelGGoebelRSahraieAvan den StockJ, and others. 2008. Intact navigation skills after bilateral loss of striate cortex. Curr Biol18(24):R1128–9.
26.
de GelderBVroomenJPourtoisGWeiskrantzL. 1999. Non-conscious recognition of affect in the absence of striate cortex. Neuroreport10(18):3759–63.
27.
DineenJKeatingEG. 1981. The primate visual system after bilateral removal of striate cortex. Survival of complex pattern vision. Exp Brain Res41(3–4):338–45.
28.
EpsteinRAKanwisherN. 1998. A cortical representation of the local visual environment. Nature392(6676):598–601.
29.
FangFHeS. 2005. Cortical responses to invisible objects in the human dorsal and ventral pathways. Nat Neurosci8(10):1380–5.
30.
FangZLiHChenGYangJ. 2016. Unconscious processing of negative animals and objects: role of the amygdala revealed by fMRI. Front Hum Neurosci10:146.
31.
FarahM. 1990. Visual agnosias. Cambridge, MA: MIT Press.
32.
FrithCDFrithU. 2012. Mechanisms of social cognition. Annu Rev Psychol63:287–313.
33.
GlicksteinMWhitteridgeD. 1987. Tatsuji Inouye and the mapping of the visual fields on the human cerebral cortex. Trends Neurosci10(9):350–3.
34.
GobbiniMIGorsJDHalchenkoYOHughesHCCipolliC. 2013. Processing of invisible social cues. Conscious Cogn22(3):765–70.
35.
GoebelRMuckliLZanellaFESingerWStoerigP. 2001. Sustained extrastriate cortical activation without visual awareness revealed by fMRI studies of hemianopic patients. Vision Res41(10–11):1459–74.
36.
GoodaleMAMilnerAD. 1992. Separate visual pathways for perception and action. Trends Neurosci15(1):20–5.
37.
HallNColbyC. 2014. S-cone visual stimuli activate superior colliculus neurons in old world monkeys: implications for understanding blindsight. J Cogn Neurosci26(6):1234–56.
38.
HendricksonAEWilsonJROgrenMP. 1978. The neuroanatomical organization of pathways between the dorsal lateral geniculate nucleus and visual cortex in Old World and New World primates. J Comp Neurol182(1):123–36.
39.
Hernandez-GonzalezACavadaCReinoso-SuarezF. 1994. The lateral geniculate nucleus projects to the inferior temporal cortex in the macaque monkey. Neuroreport5(18):2693–6.
40.
HessRFPointerJS. 1989. Spatial and temporal contrast sensitivity in hemianopia. A comparative study of the sighted and blind hemifields. Brain112(pt 4):871–94.
41.
HolmesG. 1918. Disturbances of vision by cerebral lesions. Br J Ophthalmol2(7):353–84.
42.
HubelDHWieselTN. 1972. Laminar and columnar distribution of geniculo-cortical fibers in the macaque monkey. J Comp Neurol146(4):421–50.
43.
JayakumarJDreherBVidyasagarTR. 2013. Tracking blue cone signals in the primate brain. Clin Exp Optom96(3):259–66.
44.
JiangYHeS. 2006. Cortical responses to invisible faces: dissociating subsystems for facial-information processing. Curr Biol16(20):2023–9.
45.
JiangYShannonRWVizuetaNBernatEMPatrickCJHeS. 2009. Dynamics of processing invisible faces in the brain: automatic neural encoding of facial expression information. Neuroimage44(3):1171–7.
46.
KaasJHLyonDC. 2007. Pulvinar contributions to the dorsal and ventral streams of visual processing in primates. Brain Res Rev55(2):285–96.
47.
KangMSBlakeRWoodmanGF. 2011. Semantic analysis does not occur in the absence of awareness induced by interocular suppression. J Neurosci31(38):13535–45.
48.
KanwisherNMcDermottJChunMM. 1997. The fusiform face area: a module in human extrastriate cortex specialized for face perception. J Neurosci17(11):4302–11.
49.
KeshavanMSDiwadkarVADeBellisMDickEKotwalRRosenbergDR, and others. 2002. Development of the corpus callosum in childhood, adolescence and early adulthood. Life Sci70(16):1909–22.
50.
LehSEJohansen-BergHPtitoA. 2006. Unconscious vision: new insights into the neuronal correlate of blindsight using diffusion tractography. Brain129(pt 7):1822–32.
51.
LiddellBJBrownKJKempAHBartonMJDasPPedutoAet al. 2005. A direct brainstem-amygdala-cortical ‘alarm’ system for subliminal signals of fear. Neuroimage24(1):235–43.
52.
LinZHeS. 2009. Seeing the invisible: the scope and limits of unconscious processing in binocular rivalry. Prog Neurobiol87(4):195–211.
53.
ListerWTHolmesG. 1916. Disturbances of vision from cerebral lesions, with special reference to the cortical representation of the macula. Proc R Soc Med 9(Sect Ophthalmol):57–96.
54.
LyonDCNassiJJCallawayEM. 2010. A disynaptic relay from superior colliculus to dorsal stream visual cortex in macaque monkey. Neuron65(2):270–9.
55.
LysakowskiAStandageGPBeneventoLA. 1988. An investigation of collateral projections of the dorsal lateral geniculate nucleus and other subcortical structures to cortical areas V1 and V4 in the macaque monkey: a double label retrograde tracer study. Exp Brain Res69(3):651–61.
56.
MarcelAJ. 1998. Blindsight and shape perception: deficit of visual consciousness or of visual function?Brain121(pt 8):1565–88.
57.
MarksDF. 1973. Visual imagery differences in the recall of pictures. Br J Psychol64(1):17–24.
58.
MaslandRH. 2001. The fundamental plan of the retina. Nat Neurosci4(9):877–86.
59.
Mendez-BertoloCMorattiSToledanoRLopez-SosaFMartinez-AlvarezRMahYH, and others. 2016. A fast pathway for fear in human amygdala. Nat Neurosci19(8):1041–9.
60.
MorlandABJonesSRFinlayALDeyzacDLêSKempS. 1999. Visual perception of motion, luminance and colour in a human hemianope. Brain122(pt 6):1183–98.
61.
MorlandABLeSCarrollEHoffmannMBPambakianA. 2004. The role of spared calcarine cortex and lateral occipital cortex in the responses of human hemianopes to visual motion. J Cogn Neurosci16(2):204–18.
62.
MorrisJSDeGelderBWeiskrantzLDolanRJ. 2001. Differential extrageniculostriate and amygdala responses to presentation of emotional faces in a cortically blind field. Brain124(pt 6):1241–52.
63.
MorrisJSFrithCDPerrettDIRowlandDYoungAWCalderAJ, and others. 1996. A differential neural response in the human amygdala to fearful and happy facial expressions. Nature383(6603):812–5.
64.
NellesGPschererAde GreiffAForstingMGerhardHEsserJet al. 2009. Eye-movement training-induced plasticity in patients with post-stroke hemianopia. J Neurol256(5):726–33.
65.
NellesGWidmanGde GreiffAMeistrowitzADimitrovaAWeberJet al. 2002. Brain representation of hemifield stimulation in poststroke visual field defects. Stroke33(5):1286–93.
66.
O’BrienBJAbelPLOlavarriaJF. 2001. The retinal input to calbindin-D28k-defined subdivisions in macaque inferior pulvinar. Neurosci Lett312(3):145–8.
67.
PasikPPasikTSchilderP. 1969. Extrageniculostriate vision in the monkey: discrimination of luminous flux-equated figures. Exp Neurol24(3):421–37.
68.
PasleyBNMayesLCSchultzRT. 2004. Subcortical discrimination of unperceived objects during binocular rivalry. Neuron42(1):163–72.
PegnaAJKhatebALazeyrasFSeghierML. 2005. Discriminating emotional faces without primary visual cortices involves the right amygdala. Nat Neurosci8:24–5.
71.
PerryVHCoweyA. 1984. Retinal ganglion cells that project to the superior colliculus and pretectum in the macaque monkey. Neuroscience12(4):1125–37.
72.
PessoaLAdolphsR. 2010. Emotion processing and the amygdala: from a ‘low road’ to ‘many roads’ of evaluating biological significance. Nat Rev Neurosci11(11):773–83.
73.
PoppelEHeldRFrostD. 1973. Residual visual function after brain wounds involving the central visual pathways in man. Nature243(5405):295–6.
74.
PoppelreuterW. 1917. Die psychischen Schadigungen durch Kopfschuss im Kriege 1914-16; die Storungen der niederen und hoheren Sehleistungen durch Verletzungen des Okzipitalhirns. Leipzig, Germany: Voss.
75.
RiddochG. 1917. On the relative perceptions of movement and a stationary object in certain visual disturbances due to occipital injuries. Proc R Soc Med10(Neurol Sect):13–34.
76.
RizzoMRobinDA. 1996. Bilateral effects of unilateral visual cortex lesions in human. Brain119(pt 3):951–63.
77.
RudermanLLamyD. 2012. Emotional context influences access of visual stimuli to anxious individuals’ awareness. Conscious Cogn21(2):900–14.
78.
SchadowJDettlerNParameiGVLenzDFründISabelBA, and others. 2009. Impairments of Gestalt perception in the intact hemifield of hemianopic patients are reflected in gamma-band EEG activity. Neuropsychologia47(2):556–68.
79.
SchmidMCPanagiotaropoulosTAugathMALogothetisNKSmirnakisSM. 2009. Visually driven activation in macaque areas V2 and V3 without input from the primary visual cortex. PLoS One4(5):e5527.
80.
SchoenfeldMANoesseltTPoggelDTempelmannCHopfJMWoldorffMG, and others. 2002. Analysis of pathways mediating preserved vision after striate cortex lesions. Ann Neurol52(6):814–24.
81.
SerenoMAllmanJ. 1991. Cortical visual areas in mammals. In: LeventhalA, editor. The Neural Basis of Visual Function. London: Macmillan. p. 160–72.
82.
SheinbergDLogothetisNK. 1997. The role of temporal cortical areas in perceptual organization. Proc Natl Acad Sci U S A94:3408–13.
83.
SilvantoJCaweyALavieNWalshV. 2007. Making the blindsighted see. Neuropsychologia45(14):3346–50.
84.
SincichLCParkKFWohlgemuthMJHortonJC. 2004. Bypassing V1: a direct geniculate input to area MT. Nat Neurosci7(10):1123–8.
85.
SinghalAMonacoSKaufmanLDCulhamJC. 2013. Human fMRI reveals that delayed action re-recruits visual perception. PLoS One8(9):e73629.
86.
SolcaMGuggisbergAGSchniderALeemannB. 2015. Facial blindsight. Front Hum Neurosci9:522.
87.
SteinTSterzerP. 2011. High-level face shape adaptation depends on visual awareness: evidence from continuous flash suppression. J Vis11(8):5.
88.
SterzerPHaynesJDReesG. 2008. Fine-scale activity patterns in high-level visual areas encode the category of invisible objects. J Vis8(15):1–12.
89.
SterzerPJalkanenLReesG. 2009. Electromagnetic responses to invisible face stimuli during binocular suppression. Neuroimage49(3):803–8.
90.
StoerigP. 2006. Blindsight, conscious vision, and the role of primary visual cortex. Prog Brain Res155:217–34.
TamiettoMPullensPde GelderBWeiskrantzLGoebelR. 2012. Subcortical connections to human amygdala and changes following destruction of the visual cortex. Curr Biol22(15):1449–55.
93.
TeuberH-LBattersbyWSBenderMB. 1960. Visual field defects after penetrating missile wounds of the brain. Cambridge, MA: Harvard University Press.
94.
TongFNakayamKVaughanJTKanwisherN. 1998. Binocular rivalry and visual awareness in human extrastriate cortex. Neuron21(4):753–9.
95.
TootellRBHamiltonSLSwitkesE. 1988. Functional anatomy of macaque striate cortex. IV. Contrast and magno-parvo streams. J Neurosci8(5):1594–609.
96.
TrevethanCTSahraieAWeiskrantzL. 2007. Form discrimination in a case of blindsight. Neuropsychologia45(9):2092–103.
97.
TroianiVSchultzRT. 2013. Amygdala, pulvinar, and inferior parietal cortex contribute to early processing of faces without awareness. Front Hum Neurosci7:241.
98.
TsuchiyaNMoradiFFelsenCYamazakiMAdolphsR. 2009. Intact rapid detection of fearful faces in the absence of the amygdala. Nat Neurosci12:1224–5.
99.
Van den StockJTamiettoMSorgerBPichonSGrézesJde GelderB. 2011. Cortico-subcortical visual, somatosensory, and motor activations for perceiving dynamic whole-body emotional expressions with and without striate cortex (V1). Proc Natl Acad Sci U S A108(39):16188–93.
100.
Van EssenDCNewsomeWTBixbyJL. 1982. The pattern of interhemispheric connections and its relationship to extrastriate visual areas in the macaque monkey. J Neurosci. 2(3):265–83.
101.
WarnerCEGoldshmitYBourneJA. 2010. Retinal afferents synapse with relay cells targeting the middle temporal area in the pulvinar and lateral geniculate nuclei. Front Neuroanat4:8.
102.
WarnerCEKwanWCBourneJA. 2012. The early maturation of visual cortical area MT is dependent on input from the retinorecipient medial portion of the inferior pulvinar. J Neurosci32(48):17073–85.
103.
WeberJTHuertaMFKaasJHHartingJK. 1983. The projections of the lateral geniculate nucleus of the squirrel monkey: studies of the interlaminar zones and the S layers. J Comp Neurol213(2):135–45.
104.
WeiskrantzL. 1987. Residual vision in a scotoma. A follow-up study of ‘form’ discrimination. Brain110(1):77–92.
105.
WeiskrantzLWarringtonEKSandersMDMarshallJ. 1974. Visual capacity in the hemianopic field following a restricted occipital ablation. Brain97(4):709–28.
106.
WhitwellRLStriemerCLNicolleDAGoodaleMA. 2011. Grasping the non-conscious: preserved grip scaling to unseen objects for immediate but not delayed grasping following a unilateral lesion to primary visual cortex. Vision Res51(8):908–24.
107.
WilliamsMAMorrisAPMcGloneFAbbottDFMattingleyJB. 2004. Amygdala responses to fearful and happy facial expressions under conditions of binocular suppression. J Neurosci24(12):2898–904.
108.
Wong-RileyMT. 1976. Projections from the dorsal lateral geniculate nucleus to prestriate cortex in the squirrel monkey as demonstrated by retrograde transport of horseradish peroxidase. Brain Res109(3):595–600.
109.
ZekiSFfytcheDH. 1998. The Riddoch syndrome: insights into the neurobiology of conscious vision. Brain121 (pt 1):25–45.
110.
ZemanADewarMDella SalaS. 2015. Lives without imagery—congenital aphantasia. Cortex73:378–80.
111.
ZhangXKedarSLynnMJNewmanNJBiousseV. 2006. Natural history of homonymous hemianopia. Neurology66:901–5.
