Perception Lecture 1.6 Motion (PDF)

Foundations of Perception and Cognition Motion detection Dr Deanne Green  We acknowledge and pay our respects to the Kaurna people, the traditional custodians whose ancestral lands we gather on. We acknowledge the deep feelings of attachment and relationship of the Kaurna people to country...

Foundations of Perception and Cognition Motion detection Dr Deanne Green  We acknowledge and pay our respects to the Kaurna people, the traditional custodians whose ancestral lands we gather on. We acknowledge the deep feelings of attachment and relationship of the Kaurna people to country and we respect and value their past, present and ongoing connection to the land and cultural beliefs.  Warning Warning Geometric shapes and patterns used in this lecture may be problematic for people with photosensitive epilepsy. Perception Lectures What will you learn 1. Intro to sensation and perception 2. Methods 3. Spatial vision 4. Body senses 5. Depth perception 6. Motion perception Motion detection Part 1 What is motion Types of motion Motion illusions Motion detection What is motion Physical world (reality) Ø continuous change in an object's location as a function of time Retina (sensory) Ø change physiological reaction of photorecptors which at the same rate as the object’s transition Brain (perceptual) Ø the ability to discern the distance and speed of a moving object in response to sensory input What is motion Real motion Ø the physical movement of a stimulus against its background Ø causes a change in luminance across the retina Ø can track objects with our eyes (no change across retina) A note about saccades Quick movement of the eyes Happen when you track objects Brain fills in the gaps to give impression of smooth tracking What is motion Real motion Apparent motion Ø motion illusions What is motion Real motion Apparent motion Ø motion illusions Ø beta motion What is motion Real motion Apparent motion Ø motion illusions Ø beta motion Ø phi motion What is motion Real motion Apparent motion Ø motion illusions Ø beta motion Ø phi motion Ø induced motion What is motion Real motion Apparent motion Ø motion illusions Ø beta motion Ø phi motion Ø induced motion Ø motion aftereffect Physiology of motion detection Part 2 The retina A crash course in terminology Physiology of motion Lateral Geniculate Nucleus (LGN) detection Directional cells (V1) Extra-Striate Cortex Motion pathways The retina The retina Cones have better temporal resolution than rods Rods have a longer refractory period than cones Cones Rods Dorsal Dorsal Ventral Ventral Dorsal Ventral  Dorsal Ventral Ventral Dorsal The Lateral Geniculate Nucleus (LGN) Relay system between the retina and the primary visual cortex Functional Imaging of the Human Lateral Geniculate Nucleus, Fehd, H., 2012 Directional cells (V1) Extra-Striate Cortex encompasses areas of the visual cortex: V3, V4, V5/MT, which are sensitive to motion Extra-Striate Cortex Motion pathways Retinotectal Ø Reactive Ø Primitive Geniculo-cortical pathway Ø Complex Ø Cortical (thinking) Geniculo-cortical pathway Retina Retinotectal pathway Lateral Superior Geniculate Colliculus Nucleus Primary Visual Cortex (V1) Pulvinar Parietal Prefrontal V2 Cortex Cortex Ventral Dorsal Frontal Eye Stream Stream Fields Saccadic Eye V4 V3 Movement Inferior Medial Temporal Temporal Lobe Area Medial Superior Temporal Area Geniculo-cortical pathway Retina Retinotectal pathway Lateral Superior Geniculate Colliculus Nucleus Primary Visual Cortex (V1) Pulvinar Parietal Prefrontal V2 Cortex Cortex Ventral Dorsal Frontal Eye Stream Stream Fields Saccadic Eye V4 V3 Movement Inferior Medial Temporal Temporal Lobe Area Medial Superior Temporal Area Geniculo-cortical pathway Via the lateral geniculate nucleus Ventral stream Ø “what” pathway Ø object recognition and form representation Dorsal stream Ø “where” pathway Ø guidance of actions and recognising where objects are in space Both essential for movement detection Functionality of motion detection Part 3 Evolutionary advantages Functionality of Figure and ground segregation motion detection Deficiencies in motion detection Evolutionary advantages of motion detection Motion detection is need for both hunters and prey Can anyone name the world’s most accurate hunter? Cat? Human? Wolf? Dragonfly Figure and ground segregation Ambiguous figures Cannot tell foreground from background Figure Ground Segregation The University of Adelaide Slide 53 Deficiencies in motion detection Patient LM (in Mather, 2016, pg. 354) Lost ability to detect movement after TBI (Akinetopsia) Damage to lateral temporo-occipital cortex Deficiencies in motion detection Patient LM Ø Couldn’t pour liquid into a cup because the fluid appeared to be frozen Ø Face-to-face conversations difficult Ø Crowded rooms or streets made her feel unwell, because “people were suddenly here or there but I have not seen them moving” Adaptation Ø learned to avoid conditions with multiple visual motion stimuli Ø developed very efficient coping strategies: e.g., estimated the distance of moving vehicles by means of sound detection Exam advice for Perception Use the lecture slides to guide your studies The summative quiz (available now) will give you a good idea of what the exam questions are like Material from the SDL, tutorials, and lectures are assessable Readings and chapter references support the material from the lectures Summary Motion: continuous change in an object's location over Summary time, perceived differently in the physical world, retina, and brain. ”Real” motion: physical movement of a stimulus against its background, while apparent motion includes motion illusions like beta and phi motion. Physiology of motion detection involves understanding the retina, lateral geniculate nucleus (LGN), and parts of the visual cortex Perception summary Explored how our senses and brain work together to Perception Summary understand the world around us Learned about two-point perception how we detect if something touches us in one spot or two Learned about our vestibular sense Explored how we see depth, distance, and movement Investigated how we see things move and why Explored different ways scientists figure out how our senses and perception work References Snowden, R., Thompson, P & Troscianko, T (2006): Basic Vision Oxford University Press, Oxford. Chapter 6 Mather, G (2016): Foundations of sensation and perception Psychology Press Ltd., Hove Chapter 12