MOTORISKE SYSTEMER Kontroll av øyebevegelser ARVID LUNDERVOLD INSTITUTT FOR BIOMEDISIN 25 oktober 2017 oeyebevegelser_(a.lundervold)_20171025.pptx
Dobbelttime 1 2 3 4 5 Temablokk 3 - Motoriske systemer: Momentliste / Litteratur 16/10 Introduksjon (Referanser til Brodal: Sentralnervesystemet, 5.utg, 2013) 16/10 Muskelfysiologi Brodal: Kap. 13 s. 199-204; Kap. 21 s. 304;310-315,322-327 MEDOD1/Celle-1: Alberts, Bray & Hopkin (ABH). Essential Cell Biology, 4.utg, 2013, s. 591-601 (Sand et al. Menneskets fysiologi, 2.utg. 2014: Kap. 8 s.323-351) 18/10 Ryggmargen og spinale reflekser Brodal, Kap. 6, s. 101-107; Kap. 21, s. 307-310;315-322 18/10 Motorisk kontroll og sentrale motoriske baner Brodal: Kap. 22, s. 329-350 20/10 Basalgangliene Brodal: Kap. 23, s. 351-368 25/10a Cerebellum Brodal: Kap. 24, s. 369-386 25/10b Kontroll av øyebevegelser Brodal: Kap. 25, s. 387-395 25/10b Motoriske systemer oppsummering
Kontroll av øyebevegelser Momentliste - Ytre øyemuskler og deres innervasjon; øyemotilitet - Seks typer øyebevegelser (5 konjugerte + vergens) og nevronale kontrollsystemer - Sakkader og følgebevegelser - Miniatyrbevegelser av øynene: tremor, drift og mikrosakkader i visuell persepsjon; Troxle effekten - Den vestibulo-okulære refleks - Sentre i hjernestammen for vertikale og horisontale blikkbevegelser - Kortikal kontroll av øyebevegelser; frontale øyefelt (FEF), det supplementære øyefelt (SEF), dorsolateral prefrontal korteks (DLPFC), bakre parietal-korteks, area MT (V5) og middle superior temporal area (MST); fiksasjonssenter i frontallappen
Overflateanatomi Øyelokk (palpebrae) og øyeeple (bulbus oculi) (Gray s Anatomy, 2005; Fig 41.1)
Ytre øyemuskler m. levator palpebrae superioris m. rectus (superior, inferior, medialis, lateralis) m. obliquus (superior, inferior) NASALT TEMPORALT (Gray s Anatomy, 2005; Fig 41.6)
Ytre øyemuskler Optic nerve Six muscles, arranged in three pairs, control the movements of the eye as shown here in a cutaway view of the eye in its socket, or orbit. (Squire et al, 2003; Fig 33.1)
Øyemotilitet Axes of eye rotations. The eye muscles can rotate the eye along three axes; horizontal, vertical, and torsional. (Squire et al, 2003; Fig 33.2)
Øyets bevegelsesakser ( høyre øye sett fra oversiden ) Brodal (2016) Fig. 25.1 Note that all axes pass through the center of the eye bulb.
Virkningen til de ytre øyemuskler Obliquus inferior Rectus superior Obliquus inferior opp og ut Rectus lateralis Rectus medialis Rectus lateralis ned og ut Obliquus superior Rectus inferior Obliquus superior 3 = n. oculomotorius 4 = n. trochlearis 6 = n. abducens Brodal (2016) Fig 25.3
Virkningen til de ytre øyemuskler avhenger av øyets posisjon A: The right eye and eye muscles seen from above. With the eye in a neutral position the direction of force for the superior rectus forms 25 degrees with the visual axis of the eye. With 25-degree abduction of the eye, the lateral rectus becomes a pure elevator. With about 50-degree adduction, the superior oblique is a pure depressor. Brodal (2016) Fig 25.4 B: Scheme for testing the eye muscles. Based on testing in extreme positions in which the muscles produce relatively pure vertical or horizontal movements.
Temporalt Nasalt MR av høyre orbita før og etter voluntær bevegelse av øyeeplet. Axial magnetic resonance images (2 mm thickness, T1-weighted) of a right orbit taken at the level of the lens, fovea, and optic nerve, ON (top), and simultaneously in a more inferior image plane along the path of the inferior rectus muscle (bottom), in abduction (left) and adduction (right) From: Demer: Curr Opin Neurol, 2006;19(1):4-13.
Ytre øyemuskler og deres innervasjon A B Lateral rectus Midbrain A. The contributions of the six extraocular muscles to vertical and horizontal eye movements. Horizontal movements are mediated by the medial and lateral rectus muscles, while vertical movements are mediated by the superior and inferior rectus and the superior and inferior oblique muscle groups. Nu. oculomotorius Caudal midbrain Cranial nerve IV Nu. trochlearis Cranial nerve III B. Organization of the cranial nerve nuclei that govern eye movements, showing their innervation of the extraocular muscles. The abducens nucleus innervates the lateral rectus muscle; the trochlear nucleus innervates the superior oblique muscle; and the oculomotor nucleus innervates all the rest of the extraocular muscles (the medial rectus, inferior rectus, superior rectus, and inferior oblique). Pons Nu. abducens (Purves et al, 2004; Fig 19.2&3) Cranial nerve VI
Obliquus inferior (Brodal, 2007; Fig 15.3) Pasient med utfall i ve. obliquus superior ned og ut Når pasienten ser rett frem, vil venstre øye være noe rotert oppad relativt til høyre side (A). Obliquus superior Rectus superior Rectus lateralis Rectus inferior Enkel metode for å teste øyemusklene enkeltvis For å unngå diplopi: (Duus, 1998, Fig 3.20) (Kendal et al, 2000, Fig. 39-8)
Seks typer øyebevegelser / nevronale kontrollsystemer Konjugerte øyebevegelser (samme bevegelsesutslag i samme retning) Sakkader : raske, sprangvise rotasjoner av øyeeplet (voluntære eller reflektoriske) Følgebevegelser: langsomme, kontinuerlige rotasjoner (voluntære eller reflektoriske) Opto-kinetisk refleks: sakkader el. følgebevegelser når hele synsfeltet beveger seg i forholdet til hodeposisjon; drevet av visuelle stimuli Vestibulo-oculare reflekser (VOR): holder bildet i ro på netthinnen under kortvarige hodebevegelser; drevet av signaler fra det vestibulære system Fiksasjon: holder øyet i ro under voluntær fiksasjon, gjennom aktiv suppresjon av øyebevegelser Diskonjugerte øyebevegelser (øynene beveger seg i ulike retninger) Vergens : samsyn når vi fokuserer på objekter i varierende avstand
Fem typer øyebevegelser: Optokinetisk refleks (i tillegg kommer fiksasjon) Sakkader Vestibulo-ocular refleks Følgebevegelser Vergens
Sakkadiske øyebevegelser brukes for å undersøke de visuelle omgivelser Alfred Yarbus (1967) discovered that the pattern of an observer s eye movements can describe the objects of attention in the environment. In Yarbus experiment an observer looks at the picture of a woman for 1 min. The resulting eye positions are shown superimposed on the picture of the woman as dark lines. Note that the eye movements concentrate on certain features of the face. The eye lingers over the woman s eyes and mouth (fixations) and spends less time over intermediate positions. The rapid movements between fixation points are saccades. Kendal et al, 2000, Fig. 39-1
Sakkade Følgebevegelse Kendal et al, 2000, Fig. 39-3 Kendal et al, 2000, Fig. 39-2 Eye position, target position, and eye velocity are plotted against time. At the beginning of the plot the eye is on target the traces representing eye and target positions are superimposed. Suddenly the target jumps to the right (dotted line). Almost immediately, 200 ms later, the eye moved to bring the target back to the fovea. Note the smooth symmetric velocity profile. Because eye movements are rotations of the eye in the orbit they are described in terms of the angle of rotation. Similarly, objects in the visual world are described by the angle of arc they subtend at the eye. A thumb, viewed at arm s length subtends an angle of about 1 O. A saccade from one side of the thumb to the other traverses 1 O of arc. Eye position plotted over time with the target position superimposed (dotted line). Eye and target velocity are plotted beneath. In this example the subject was asked to make a saccade to a target that jumps away from the center of gaze and then moves back. Note that the very first movement seen in the position and velocity traces is a smooth pursuit movement with the same velocity as the target. As can be seen from the eye position trace, the eye briefly moves away from the target. The saccade enables the eye to adjust its position to catch the target, and from then on the smooth pursuit keeps the eye on the target. The saccade velocity trace is clipped so that the movement can be shown on the scale of the pursuit movement, an order of magnitude slower than the saccade.
Sakkade-systemet Saccades are quick, simultaneous movements of both eyes in the same direction. Initiated by the frontal lobe of the brain (Brodmann area 8), saccades serve as a mechanism for fixation, refixation, rapid eye movements and the fast phase of optokinetic nystagmus 200 ms By moving the eye so that small parts of a scene can be sensed with greater resolution, body resources can be used more efficiently. If an entire scene were viewed in high resolution, the diameter of the optic nerve would need to be larger than the diameter of the eyeball itself. Subsequent processing of such a high-resolution image would require a brain many times larger than its current size. The dynamics of saccadic eye motion give insight into the complexity of the mechanism that controls the motion of the eye. The saccade is the fastest movement of an external part of the human body. The peak angular speed of the eye during a saccade reaches up to 1000 degrees per second. Saccades last from about 20 to 200 milliseconds. http://en.wikipedia.org/wiki/saccadic_eye_movement
Motoneuron-aktivitet i relasjon til sakkadiske øyebevegelser Eksperimentelt oppsett In this example, an abducens lower motor neuron fires a burst of activity (upper trace) that precedes and extends throughout the movement (solid line). An increase in the tonic level of firing is associated with more lateral displacement of the eye. Note also the decline in firing rate during a saccade in the opposite direction. (Purves et al, 2004; Fig 19.6)
Vergens The convergence angle depends on target distance Trajectory of a saccade, viewed from above, that shifts the point of gaze laterally and in depth. Vergence mechanisms begin to converge the eyes prior to the saccade. The saccade then begins and the rate of vergence accelerates. After the saccade, vergence mechanisms continue to alter the convergence angle unit until both foveas are aligned with the target.
Vergens Focus på et fjell When the eyes focus on a distant mountain, the nearer tree occupies relatively different retinal positions in the two eyes and is seen as a double image. When the viewer wishes to look at the tree, the vergence system must rotate each eye inward. Fjell Tre Focus på et tre Now the tree image occupies the same position on both retinas and is seen as one object, but the mountain occupies different locations on the retinas and appears double. Kendal et al, 2000, Fig. 39-4
Hovedelementene i den vestibulookulære refleksbuen Cerebellum Flocculus VOR Parallell-fiber Purkinjecelle Kun eksitatoriske forbindelser er vist Refleksbuen består av tre nevroner fra buegangene til de ytre øyemusklene. Korncelle Klatrefiber Oliva inferior Pretektal kjerne Mosfiber 1 2 3 Labyrinten (bueganger) Vestibularis kjerne Øyemuskelkjerne
Kontroll av horisontale konjugerte øyebevegelser Figuren illustrerer hvordan skade av fasciculus longitudinalis medialis fører til blikklammelse i medial retning på samme side som skaden sitter (internukleær oftlamoplegi). Blikklammelse gjelder konjugerete øyebevegelser, men ikke konvergensbevegelser. Dvs. m. rectus medialis motonevroner aktiveres av forskjellige baner ved konvergensbevegelser og ved horisontale konjugerte øyebevegelser. PPRF = paramedian pontine reticular formation Brodal (2016) Fig. 25.6
Sentre for vertikale og horisontale blikkbevegelser Senter for vertikale og rotatoriske øyebevegelser (rimlf) Senter for horisontale øyebevegelser (PPRF) rimlf = the rostral interstitial nucleus of the medial longitudinal fasciculus PPRF = paramedian pontine reticular formation Brodal (2016) Fig. 25.6
Retningsorientering av fovea mot et objekt når hodet beveger seg krever koordinerte hodeog øyebevegelser A Small gaze shift Eye Head Gaze Target B Large gaze shift Kendal et al, 2000, Fig. 39-13 Time (s)
Nature Reviews Neuroscience 5, 229-240 (2004); Susana Martinez-Conde, Stephen L. Macknik & David H. Hubel THE ROLE OF FIXATIONAL EYE MOVEMENTS IN VISUAL PERCEPTION Our eyes continually move even while we fix our gaze on an object. Although these fixational eye movements (tremor, drift, and microsaccades) have a magnitude that should make them visible to us, we are unaware of them. If fixational eye movements are counteracted, our visual perception fades completely as a result of neural adaptation. So, our visual system has a builtin paradox we must fix our gaze to inspect the minute details of our world, but if we were to fixate perfectly, the entire world would fade from view. Moreover, because we are not aware of these eye movements, they have been studied to understand the underpinnings of visual awareness. Recent studies of fixational eye movements have focused on determining how visible perception is encoded by neurons in various visual areas of the brain.
The eye movements of a subject viewing a picture of Queen Nefertiti. Eye movements during visual fixation. An observer The bust at the left is what the subject views a picture (left) while eye positions are monitored saw; the diagram on the right shows (right). The eyes jump, seem to fixate or rest momentarily, the subject s eye movements over a 2 producing a small dot on the trace, then jump to a new minute viewing period. region of interest. However, even during these fixation, or Purves et al., 2004, Fig. 19.1 'rest' times, the eyes are never still, but continuously produce fixational eye movements drifts, tremor and microsaccades.
Høyre-hemisfære pasient med neglekt Eye-movement scan path of a right-hemisphere patient with neglect searching for letter Ts embedded among distractor letter Ls (From: Malhotra: Curr Opin Neurol, Volume 19(1).February 2006.14 20)
Fiksasjonsbevegelser Fikser på det sentrale sorte punktet i 1 min. Deretter på det hvite punktet i den sorte ruten ovenfor Hva opplever du? Pattern for showing fixational eye movements. To experience it, look at the central black dot for about a minute, then look at the white dot in the adjacent dark square. The dark after-image of the white line pattern should be seen in constant motion owing to fixational eye movements.
Drift Tremor Mikrosakkade Fixational eye movements carry the image across the retinal photoreceptors. High-frequency tremor is superimposed on slow drifts (curved lines). Microsaccades are fast jerk-like movements, which generally bring the image back towards the centre of vision (straight lines). The diameter of the patch of the fovea shown here is 0.05 mm.
Fixational eye movements increase retinal activity. a Continuous recording from 54 retinal ganglion cells in the turtle during darkness, after switching on a stationary grating, and during wobbling of this grating. The grating was wobbled to simulate periodic (tremor-like) eye movement. b Responses of a single ganglion cell to a drifting contrast border of velocity comparable to ocular drifts. c When the drift is superimposed on wobbling, the responses of the cell shown in b markedly increase.
Visual fading outside the laboratory: Troxler's effect Although perfect retinal stabilization is most easily achieved under laboratory conditions, fading of objects in our visual periphery occurs often in normal vision. Peripheral fading of stationary objects was first noticed by Troxler in 1804. Troxler reported that, under voluntary fixation, stationary objects in the periphery of vision tend to fade and disappear. In the late 1950s, Clarke made a connection between Troxler's fading and the fading of stabilized images in the laboratory and attributed both phenomena to neural adaptation. The simplest explanation for Troxler's peripheral fading is that receptive fields in the periphery of our vision can be considerably larger than fixational eye movements (especially as accurate fixation tends to eliminate microsaccades). Drifts and tremor, being smaller than the peripheral receptive fields, do not provide effective visual stimulation to prevent peripheral visual fading, especially in the case of low-contrast stimuli. The figure is a demonstration of Troxler's effect. To experience it, fixate precisely on the red spot, while paying attention to the bluish annulus. After a few seconds of careful fixation, the annulus will disappear, and the red spot will appear to be surrounded by a completely white field. Movements of the eyes will immediately bring the blue annulus back to perception.
Troxler's fading In this example, the lilac spots in the lilac chaser fade away after about 20 seconds, leaving a grey background and black cross. Some viewers may notice that the moving space has faded into a moving blue-green spot, possibly with a short trail following it. Furthermore, moving ones eyes away from the image after a period of time may result in a brief, strong afterimage of a circle of green spots. http://en.wikipedia.org/wiki/troxler's_fading
Basal Ganglia Loops and Non-Motor Brain Functions ( Purves et al. Neuroscience, 3rd ed., 2004 )
Kortikale områder av særlig betydning for kontroll av øyebevegelser (FEF) FEF = frontal eye field MT = middle temporal area MST = middle superior temporal area Ikke alle områder er vist, blant annet finnes det flere mindre områder på medialsiden av hemisfæren. Brodal (2016) Fig. 25.8
Corticale områder for sakkadiske øyebevegelser hos menneske FEF SEF This lateral scan of a human brain shows areas of cortex activated during saccades. (Reproduced from Curtis and Connelly 2010.) Kendal et al, 2013, Fig. 39-10
Sakkader (FEF, SC) Horisontale blikk-bevegelser Følgebevegelser (PEF) Vertikale blikk-bevegelser Commisura posterior PPRF = paramedian pontine reticular formation rimlf= rostral interstitial nucleus of the medial longitudinal fasciculus (Gray s Anatomy, 2005; Fig 24.3) Summary of eye movement control. The central drawing shows the supranuclear connections from the frontal eye field (FEF) and the posterior eye field (PEF) to the superior colliculus (SC), rostral interstitial nucleus of the medial longitudinal fasciculus (rimlf), and the paramedian pontine reticular formation (PPRF). The FEF and SC are involved in the production of saccades, while the PEF is thought to be important in the production of pursuit. The drawing on the left shows the brain stem pathways for horizontal gaze. Axons from the PPRF travel to the ipsilateral abducens nucleus innervating lateral rectus (LR). Abducens internuclear axons cross the midline and travel in the medial longitudinal fasciculus (MLF) to the portion of the oculomotor nucleus (III) innervating medial rectus (MR) of the contralateral eye. The drawing on the right shows the brain stem pathways for vertical gaze. Important structures include the rimlf, PPRF, the interstitial nucleus of Cajal (INC), and the posterior commissure (PC). Other abbreviations: DLPFC, dorsolateral prefrontal cortex; IV, trochlear nucleus; SEF, supplementary eye field; VN, vestibular nucleus.
Kontroll av øyebevegelser - oppsummering Seks kontroll-systemer holder fovea på målet - Et aktivt fiksasjonssystem holder øynene (fovea) på et stasjonært mål - Kontrollsystem for sakkader orienterer foevea mot objekter som fanger interesse - Kontrollsystem for jevne følgebevegelser holder bevegelige objekter fast på fovea - Kontrollsystem for vergens-bevegelser gir samsyn ved fokusering på objekter i ulik avstand Øyet beveges av seks muskler - Øyebevegelser er å betrakte som rotasjonsbevegelser av øyet i orbita - Seks ekstraokulære muskler danner tre komplementære par - Ekstraokulære muskler blir styrt av tre ulike hjernenerver (III, IV, VI) - Ekstraokulære motonevroner signaliserer øyeposisjon og rotasjonshastighet
Kontroll av øyebevegelser - oppsummering Nevronale kretser for sakkade-bevegelser ligger i hjernestammen - Horisontale sakkader blir generert i retikulærsubstansen i pons (PPRF) - Vertikale sakkader blir generert i retikulærsubstansen i mesencephalon (rimlf) - Pasienter med hjernestammelesjoner har karakteristiske utfall i øyemotilitet Sakkader blir styrt av cerebral cortex - Colliculus superior integrerer visuell og motorisk informasjon til okulomotoriske signaler i hjernestammen - Rostrale deler i colliculus superior fasiliterer visuell fiksasjon - Basalgangliene inhiberer colliculus superior - Parietal cortex styrer visuell oppmerksomhet - Frontale øyefelt sender spesifikke motoriske signaler til colliculus superior - Styring av sakkader kan modifiseres gjennom erfaring (økt gain ved muskelsvekkelse)
Kontroll av øyebevegelser - oppsummering Følgebevegelser, vergens og opto-kinetiske bevegelser blir styrt av ulike systemer - Styring av jevne følgebevegelser involverer cerebral cortex, cerebellum og pons - Vergens blir organisert i mesencephalon - Styring av blikket (opto-kinetisk kontroll) kombinerer både hodebevegelser og øyebevegelser
Computer vision: Face recognition, salient features & tracking using a MBP Object detector uses the Viola-Jones detection algorithm and a trained classification model [1]. To track the face over time, this example uses the Kanade-Lucas-Tomasi (KLT) algorithm [3,4]. Identify feature points that can be reliably tracked (Shi & Tomasi [2]) [1] Viola, Paul A. and Jones, Michael J. "Rapid Object Detection using a Boosted Cascade of Simple Features", IEEE CVPR, 2001. [2] Jianbo Shi and Carlo Tomasi. Good Features to Track, IEEE Conference on Computer Vision and Pattern Recognition, 1994. [3] Bruce D. Lucas and Takeo Kanade. An Iterative Image Registration Technique with an Application to Stereo Vision, International Joint Conference on Artificial Intelligence, 1981. [4] Carlo Tomasi and Takeo Kanade. Detection and Tracking of Point Features, Carnegie Mellon University Technical Report CMU-CS-91-132, 1991. MATLAB Computer Vision Toolbox: my_visionfacetrackingklt.m