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Lecture 06 - detail

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Matthias Niemeier

PSYB51 Lecture 06 Space Perception & Binocular Vision - Why talk about eye movements in a course on perception? o Spatial Constancy eye movements themselves are not perception but they are very significant for vision as we move our fovea it influence our vision &inhibits vision for some time causing problem for vision such as spatial constancy Eye Movements - How to describe a location of an object in space given that space has three dimension take profs body as the object in space so the orientation of the body could be explained in 3 possible axis (3 possible axis in which the body can rotate) o So can explain the orientation of object in space w 3 NUMBERS along the rotation axis the object can be described in space using 6 DIMENSIONS (3 for location & 3 for orientation) - 098,88:209K0K0,L889,-O0 eyes could also rotate around 3 axis (3 DIMENSION) so how many muscles are needed to rotate around 1 AXIS given that muscles can only contract or relax need 2 MUSCLES to rotate o THUS, NEED 6 MUSCLES IN TOTAL FOR EYE MOVEMENT - Six muscles are attached each eye & are arranged in three pairs this the minimum number of muscles needed to control eye movements o Inferior Superior Rectus & Lateral Medical Rectus - around the side, top, below on the eyes so for horizontal & vertical axis (horizontal & vertical eye movements) o Inferior Superior Oblique torsional eye movement (movement around the line of sight) difficult to notice & not voluntary if made voluntarily there must be something wrong w your brainstem Can fixate on an point in space & rotate your head vestibular system will tell the eyes to COUNTER-ROTATE to the head only for about 5 DEGREES N after this the eye will make quick saccadic eye movement (jerk-like movement) in the torsional space (snap into new position) at this point you are perceiving the object that you were fixating on as NOT STABLE Can make voluntarily torsional movement w your head o Superior Oblique Muscles (weird structure) originate from beside the nose & it runs through a bone that is like a hook so when muscle pulls backward it pulls the eye around torsional axis o Inferior Oblique Muscle --. Does something similar to Superior Oblique Muscles - Muscles are Controlled (control on the low level) by 3 Cranial Nerves (indirectly by the brain) sitting on the brain stem they innovates the muscles o cranial nerve III : Oculomotor nucleus controls the Medial, Superior, Inferior Rectus Muscles, as well as Inferior Oblique Muscles o cranial nerve IV : Trochlear nucleus controls the Superior Oblique Muscles o cranial nerve VI : Abducens nucleus controls the Lateral Rectus Muscles Out of these nuclei have the soma of the neurons axons radiate out & form the CRANIAL NERVES III, IV, VI these nerves are name after the nuclei from which the axons grow N E.g. Oculomotor nucleus Oculomotor Nerve ( Cranial Nerve III) - Levels of Control where one control system connected to another system Complicated o Eye movements is controlled by extensive network of structures in the brain e.g. Frontal eye field some structures in the Cerebral Cortex will innovate Superior Collciulus (a set of nucleus) - Superior Collciulus a structure in the Midbrain ( brainstem) that plays an important role in initiating & guiding eye movements similar to the LGN - it has more than one map & is organized in a Topographic way o There is layers involved in motor control, there is also other layer that is involved in visual perception lumbar (not just visual is multisensory BUT MAINLY VISUAL) - When you have eye movements in response to some stimulus in quick manner a reaction time about 8 milliseconds or less it is most likely an eye movement controlled by the Superior Collciulus rather than Cerebral Cortex o Basically eye movements can be controlled by short cuts have visual input that goes not only through the Primary Pathway but directly to the Superior Collciulus as well from Superior Collciulus directly into Motor control regions win the Superior Collciulus & down to muscles Research w Cats shows this When stimulated w electrical signals, eye movements can be observed Different Type of Eye Movements
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