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3. Visual Perception
• Visual perception is the ability to see and
interpret (analyze and give meaning to) the
visual information that surrounds us
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5. History
• The early 20th century by the German psychologists Max
Wertheimer, Kurt Koffka, and Wolfgang Köhler, who founded
the school of Gestalt psychology
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6. Gestalt Theory
• Gestalt means configuration or form.
• The central idea of the Gestalt psychologists???
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12. Visual Perception In Development
• At birth
• By 3 month
• By 5-6 months
• Between 6 and 9 months
• Between 9 months and 1 year
• By 2 years
• By 3 years
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19. Ocular dominance
• The integration of binocular input begins
in the primary visual cortex, the first level at
which individual neurons receive signals from
both eyes. The balance of input from the two
eyes, a property known as ocular dominance,
varies among cells in V1
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20. Visual Perception Is Mediated by the
Geniculostriate Pathway
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21. Eye Movement
• Vergence & divergence eye movement
• Conjugate eye movement:
Saccadic eye movement
Smooth pursuit eye movement
• Optokinetic reflex
• VOR
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26. Optokinetic
• The optokinetic response is a combination of
a slow-phase and fast-phase eye movements.
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27. Vestibulo- ocular reflex
• the vestibulo-ocular reflex (VOR) is a reflex,
where activation of the vestibular system
causes eye movement. This reflex functions to
stabilize image on the retina.
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28. Ocular Motor Nuclei
• Brainstem gaze center
*Horizontal(PPRF)
*Vertical(accessory oculomotor nuclei)
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40. • Because of the input it receives from the
retina and cortical eye fields and its output to
the brainstem gaze centers, this structure
undoubtedly plays a role as a visuomotor
integration center especially concerned with
reflex ocular movement
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41. Primary visual cortex
• The primary visual cortex constitutes the first
level of cortical processing of visual
information
• Ventral pathway
• Dorsal pathway
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43. Venrtal & dorsal pathway
• The pathways are interconnected so that
information is shared.
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44. Venrtal & dorsal pathway
• These feedback connections provide information
about cognitive functions:
• spatial attention
• stimulus expectation
• emotional content
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45. Dorsal pathway
• The dorsal pathway courses through the
parietal cortex, a region that uses visual
information to direct the movement of the
eyes and limbs, that is, for visuomotor
integration
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46. ventral pathway
• The inferior temporal cortex stores
information about the shapes and identities of
objects; one portion represents faces
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47. lateral intraparietal area
• representing points in space that are the
targets of eye movements or reaching
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48. MT(V5)
• contains neurons with a strong selectivity for
the direction of movement.
• middle temporal area:in the analysis of motion.
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49. The Parietal Cortex Provides Visual
Information to the Motor System
• Vision interacts with the supplementary and
pre motor systems to prepare the hands for
action
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51. Visual motor perception
four areas that analyze the visual world in ways
appropriate for individual motor systems and
project to areas of premotor cortex that control
individual movements
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52. Visual motor perception
• The neural operations behind visually guided
movements :
• identifying targets
• specifying their qualities
• generating a motor program
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55. Visual motor perception
• Visual perception connection of volunteer
attention and the programming and
reprogramming ability of the organs that are
responsible for motor activity.
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56. Visual motor perception
• the efficacy of programming speed occurs
while the tactile-perceptive information adjusts
to the visual information, due to the integrity
of cortical structures
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58. Visual Perception Impairment In CP
• is defined as a neurological disorder caused b
dysfunction of the retrochiasmatic visual
pathways.
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60. • visual discrimination of formand spatial
relationships
• figure ground discrimination
• processing motion for efficient way
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61. • Children with visual perception deficiency
show difficulties with wearing shoes, using
clips, completing jig-saw puzzles, playing with
toys and building blocks, color identification,
and learning letters, all of which influence
their daily living and general activities such as
social participation
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isual timing deficits in the dorsal stream, thereby improving processing speed, reading fluency, and the executive control functions of attention and working ...
binocular vision is a type of vision in which an animal having two eyes is able to perceive a single three-dimensional image of its surroundingsThis can be
disrupted by amblyopia (poor vision in one eye) or
strabismus (misalignment of the eyes
Stereopsis is detection of depth from disparity, meaning that the inputs to the two eyes vary even when they are directed to the same point in visual space.
made possible by specialized cells in primary visual cortex grouped into ‘ocular dominance’ columns that receive inputs from the two eyes and register the amount of disparity between them
An important cue for the perception ofdepth is the difference between the two eyes’ views of the world, which must be computed and reconciled by the brain
is the tendency to prefer visual input from one eye to the other. It is somewhat analogous to the laterality of right- or left-handedness
. It is seen when an individual follows a moving object with their eyes, which then moves out of the field of vision at which point their eye moves back to the position it was in when it first saw the object. The reflex develops at about 6 months of age
in gaze stabilization responses during head rotation and translation.
during head movement by producing eye movements in the direction opposite to head movement, thus preserving the image on the center of the visual field(s).
medulla
The pretectal area, or pretectum, is a midbrain structure composed of seven nuclei and comprises part of the subcortical visual system. Through reciprocal bilateral projections from the retina, it is involved primarily in mediating behavioral responses to acute changes in ambient light such as the pupillary light reflex, the optokinetic reflex, and temporary changes to the circadian rhythm.[1][2][3][4][5] In addition to the pretectum's role in the visual system, the anterior pretectal nucleus has been found to mediate somatosensory and nociceptive informatio
The latter are responsible for reflex turning of the head and eyes in response to startling pain or auditory stimuli
Reciprocity is an important feature of the connectivity between cortical areas. All connections between cortical areas are reciprocal.
The pulvinar in the thalamus serves as a relay between cortical areas
Orienting visual attention
riority map to help guide the allocation of covert attention and eye movements (overt attention)
axonal projections to the frontal eye field, When an attention-grabbing, but irrelevant, distracter stimulus appears while the animal is preparing a saccade directed elsewhere, the activity of LIP neurons closely tracks the short-lived shift of attention to the distracter and its subsequent return to the intended location of the saccade.
, lesions of this area produce deficits in the ability to track moving objects.
ells are tuned to the speed and direction of moving visual
Lesion studies have also supported the role of MT in motion perception and eye movements.[46] Neuropsychological studies of a patient unable to see motion, seeing the world in a series of static 'frames' instead, suggested that V5 in the primate is homologous to MT in the human.
and that what we see is this summed representation of the visual world
The diagram shows the route taken by information travelling from the posterior parietal cortex to the pre-motor and supplmentary motor areas the control complex movements. The posterior parietal association cortex integrates visual and tactile space, i.e. the position of the limb as signalled by proprioceptors and by the visual system.
Four functionally discrete areas inthe intraparietal sulcus project to areas in thepremotor cortex. The medial intraparietal cortex(MIP) represents targets of arm movements andprojects to the arm-control area of F2 in the dorsalpremotor area (PMd). The lateral intraparietal cortex(LIP) represents targets of eye movements andprojects to the frontal eye !eld (FEF). The anteriorintraparietal cortex (AIP) represents targets forgrasping and projects to the hand-control area ofF5 in the ventral premotor area (PMv). The ventralintraparietal cortex (VIP) represents the face andprojects to the face-control area of F4 in the ventralpremotor area.
Neurons in the anterior intraparietal cortexrespond selectively to speci !c shapes. The neuron shownhere is selective for a rectangle, whether viewing the object orreaching for it. The neuron is not responsive to the cylinder ineither case. (Reproduced, with p
areasand give rise to various disorders ranging from reduced visual acuity and visual field, oculomotor incoordination,and complex associative disorder, reffered as as visual
perceptual impairment (VPI)