PSYCH261 Lecture Notes - Thalamus, Abducens Nerve, Strabismus

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Vision
Chapter 6
The Stimulus
*Sensory Receptors
*Neurons that detect a particular category of physical events.
*Sensory Transduction
*Process by which sensory stimuli are transduced into slow, graded receptor
potentials.
*Receptor Potential
*Slow, graded electrical potential produced by receptors in response to physical
stimuli.
*Actual electronic potential that happens in Sensory transduction
The Stimulus
*Perceptual dimensions of colour
*Hue – the dominant wavelength; the color of the light that’s coming into the eye
*Shorter wavelengths – bluish – violet colors
*Longer ones – reddish color
*Perceptual dimensions of colour
*Brightness – intensity; increase in brightness, increase in intensity
*Saturation – purity; increase in saturation, increase in wavelengths
The Eyes
*Eye movements
*Vergence – cooperative eye movements, ensures the image falls on identical
portions of each retina.
*Convergence (looking towards the same point) vs. Divergence (looking
into different directions)
*Saccades – rapid, ballistic eye movements (video, moving back and forth eye)
*Overt attention – bring power of fovea to bear on objects
*Smooth Pursuit – eye movements tracking a moving object.
The Eyes
*Oculomotor muscles
*Three of twelve cranial nerves dedicated to controlling eye movements (oculomotor,
trochlear, abducens)
Vestibular-ocular Reflex
Eye movements that compensate for head movements
Nystagmus – alternating smooth pursuit in one direction followed by saccades in the
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opposite direction
*Anatomy of the Eye
*Lens
*Ciliary Muscles – control the shape of the lens.
**They didn’t work for older peoplehyperopia
*Accommodation – changes in thickness of the lens, accomplished by the
ciliary muscles, focuses images of near or distant objects on the retina.
The Eye
*Retina
*Photoreceptors – transduces photic energy into electrical potentials.
*Rods – sensitive to light of low intensity; sensitive to light, changes in contrast,
movement and motion; used for night visions
*Cones – maximally sensitive distinct wavelengths; encodes color.
*receptors sensitive to color; very sensitive to different wavelengths or light;
where your details come from
*Fovea – region of the retina that processes central 4 to 6° of vision.;
*Cones the only photoreceptor found in the fovea
*Bipolar Cells – middle layer of retina, conveying information from
photoreceptors to ganglion cells.
*Blue one – horizontal cell – connects adjacent rods and cones; connects
them and aggravates and make them function as one giant receptor
*Ganglion Cells – conveys information from bipolar cells to brain via the optic
nerve.
*Not important: Horizontal Cells – interconnects adjacent photoreceptors and
the outer processes of bipolar cells; connects the rods and cones and
connects them all and makes one big receptor
*Amacrine Cells – interconnects adjacent ganglion cells and the inner
processes of bipolar cells.
The Eye
*Optic disc and the blind spot – where your optic nerve
*The brain fills in the missing info in the blind spot
*We’re not aware of our blind spots
*Photoreceptors
*Lamellae – layers containing photopigments.
*Photopigment – protein dye bonded to retinal (a lipid) responsible for transduction
of visual information.
*Opsin – class of protein that act as a photopigment.
*Retinal – chemical synthesized from vitamin A that acts as a photopigment
The Eye
Change Blindness
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Document Summary

*neurons that detect a particular category of physical events. *process by which sensory stimuli are transduced into slow, graded receptor. *slow, graded electrical potential produced by receptors in response to physical stimuli. *actual electronic potential that happens in sensory transduction. *hue the dominant wavelength; the color of the light that"s coming into the eye. *brightness intensity; increase in brightness, increase in intensity. *saturation purity; increase in saturation, increase in wavelengths. *vergence cooperative eye movements, ensures the image falls on identical portions of each retina. *convergence (looking towards the same point) vs. divergence (looking into different directions) *saccades rapid, ballistic eye movements (video, moving back and forth eye) *overt attention bring power of fovea to bear on objects. *smooth pursuit eye movements tracking a moving object. *three of twelve cranial nerves dedicated to controlling eye movements (oculomotor, trochlear, abducens) Nystagmus alternating smooth pursuit in one direction followed by saccades in the opposite direction. *ciliary muscles control the shape of the lens.

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