These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. !Announcements*!!!"Readings:!Ch.20!Outline*of*Today’s*Lecture**I. Eye!Movements*Today’s*Lecture*Eye*Movements*Slide*1*!• When!you!foveate!(point!your!eyes!in!the!middle)!that!is!where!the!visual!acuity!is!the!greatest!• The!letters!in!the!middle!have!same!level!of!acuity!as!the!outside!letters!if!staring!exactly!in!the!middle!• We!move!our!eyes!to!see!better!Slide*2*!L11EyeMovements, intro Acuity falls off with eccentricity in visual space Eye Movements are Not Random !BISC*421*Hirsch,*Judith*2012*Fall*Week*6*Lecture*18*October*10*! !• We!tend!to!fixate!on!certain!parts!of!the!image"!most!atten t io n !sp e nt!on!eye s !a n d !n ose !and!mouth"!very!import a n t!t o !sc a n !the!faces!of!peop le !n e a r!u s!• “eye!movements!aren’t!random”"!ya rb is !Slide*3*!• gave!people!different!goals!when!they!looked!at!the!picture!• for!2)!not!focusin g!on !face s!bu t!sca nn ing !ob jects !in!the!ro om!• for!3)!fixate!on!face s!of!individuals!• Tell!us!how!important!it!is!to!fixate!on!something!of!interest"!looking!at!th in g s!t h a t!a re !most!importa n t!t o !u s!****Seven records of eye movements by the same subject viewing a painting called the “Unexpected visitor” for 3 minutes. 1) Free examination. After that, the subject was asked to: 2) estimate the economic status of the family; 3) give the ages of the people; 4) guess what the family had been doing before the arrival of the "unexpected visitor;" 5) remember the clothes worn by the people; 6) remember the position of the people and objects in the room; 7) estimate how long the "unexpected visitor" had been away from the family. Yarbus 1967 Yarbus, 1967! !Slide*4*!• Now!we!use!an!infrared!eye!tracking!system!Slide*5*!Eye Tracker Usual subject Subject with calcified amydala Eye movements help relay socially important facial expressions! !• Patient!with!syndrome!where!amygdala!calcified!and!cant!recognize!fear!• Told!her!to!assess!how!these!actors!felt"!she!ju st !lo o k e d !a t!n o s e s!which!is!n o t !th e !most!expressive!part!of!their!faces"!she!c o u ld n 't!r e p o rt !e m otions!• When!they!told!her!to!look!at!the!whole!face!she!did!better"!she!needed !t o !b e !cued!!Slide*6*!• How!do!we!make!these!movements!• Memorize!all!of!the!eye!muscles!Slide*7*Eye Muscles! !!• Each!muscle!has!a!job!and!a!direction!to!tug!the!eye!**********Muscles Responsible for Horizontal Movement Lateral Rectus --abduction away from the nose Medial Rectus --adduction towards the nose Muscles Responsible for Vertical Movement Superior Rectus --elevation Inferior Rectus --depression Muscles Responsible for Torsional Movements (movement of top of the eye towards or away from the nose) Superior Oblique --intorsion (top of the eye towards the nose) Inferior Oblique --extorsion (top of the eye away from the nose) L11EyeMovements, muscles Different Muscles Move the Eyes in Different Directions! !Slide*8*!• How!are!these!muscles!innervated!• Need!to!memorize!this!slide"!will!come!up!a ga in !• The!cranial!nerve!from!the!oculomotor!mucleus!3!takes!care!of!4!of!the!muscles!(medial!rectus,!superior!rectus,!inferior!oblique,!inferior!rectus)"!ipsilateral!!(s a me!side!o f!t h e !b o d y )!• Lateral!rectus!muscle!innervated!by!cranial!nerve!6!(ipsilateral)!• Trochlear!nerve!innervates!the!contralateral!superior!oblique!******All muscles except the superior oblique are innervated ipsilaterally. Innervation of the Extraocular Muscles! !Slide*9*!• Once!you!start!a!saccade!you!cant!stop!it"!very!jerk y"!oldest!fo r m!of!eye!movement!• Smooth!pursuit!is!used!to!track!objects!• Conjugate!eye!movements!are!what!you!usually!do"!both!look in g !rig h t!o r !le ft"!both!go ing!the!same!way!• Vergeance!movemen t"!crossey e d !d is co n jugate!!• Movements!that!allow!you!to!keep!your!eyes!on!one!target!when!you!move!your!head!(C)!******Types of eye movements: A) Those that direct gaze to targets of interest or track those targets as they move. e.g. saccades, smooth pursuit, optokinetic nystagmus (nystagmus just means an involuntary movement of the eye). (chameleons movie) B) Those that help align the fovea of each eye on the target of interest when the distances between each eye and the target are different. These are disconjugate vs .conjugate movements – the eyes move in different directions. e.g. vergence movements (L11EyeMovements, vergence) C) Movements that compensate for head movements to keep the target of interest centered on the fovea. vestibulo-ocular movements (later lecture).! !*Slide*10*!• Staring!at!the!target!and!then!the!target!moves"!take !a b o u t !2 00 ms!to!m o v e !th e !e y e !to !t h e !n e w!target!position"!once!th e !e ye !s tarts!to!move!the!eye!cant!be!stopped!(saccade)!• Smooth!pursuit"!much !slo wer.!Nee d e d!a!catch !u p !sa c c ade!to!find !t h e !moving!ta r ge t !a n d !th e n!you!follow!it.!We!need!a!target!to!keep!our!eyes!doing!this!********Metrics of Saccades Metrics Smooth Pursuit! !Slide*11*!• How!the!eye!muscles!move"!mov e !b e ca u s e !th e y !a re !inn e rv at ed!• Recording!from!a!single!motor!neuron!in!the!abducens!neuron"!when!we !s ta rt !th e !e y e !is!pointing!medially"!there!is!no !te nsion!on !t h e !la te ra l!r e ct u s!muscle!so!no!firing !b u t !n o w!if!we!want!to!move!eye!the!neuron!fires!and!moves!a!little!bit"!then!want!to!maintain!the!eye!in!the!lateral!po sit io n!must!kee p !firin g !********Neural Firing During Movement and at Rest! !*Slide*12*!• When!eyes!are!moved!to!the!right"!there !a re !d if fe re nt!levels!o f!c o n tr o l!fo r !e y e!movements!• Right!now!in!the!brainstem!in!the!PPRF"!called!the !h o r izo ntal!gaze !ce n t e r!• Neuron!in!the!PPRF!will!synapse!onto!cells!that!will!control!eye!movements!on!both!sides!of!the!head!• To!move!right!eye!right!contract!lateral!rectus!muscle!and!medial!rectus!muscle!• To!get!to!the!other!side!of!the!head!must!move!through!the!medial!longitundinal!fascucluus!which!will!innervate!the!left!ocular!nucleus!*****Horizontal gaze center Paramedian pontine reticular formation Horizontal Movement of the Eyes to the Right abducens or 6th nerve oculomotor or 3rd nerve (axons of internuclear neurons) - + + + +! !Slide*13*!•