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This research delves into the anatomy and physiology of the human visuomotor system, exploring topics such as retinotopic mapping, the What/Where and Action/Perception theories, and vision/motor connections. By focusing on the dorsal stream pathway, relevant insights for robotics are uncovered, emphasizing the importance of flexible motor organization and visuomotor transformations in emulating human-like behaviors.
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Deciphering the Human Visuomotor System Cheryl Card March 13, 2001
Anatomy of the Brain • General terms: superior, inferior, ventral, dorsal • Lobes: frontal, parietal, temporal, occipital
Physiology of Visual System • Optic nerve projects to superior colliculus and to LGN • SC mediates predator/prey reflexes • LGN projects to primary visual cortex • From primary visual cortex, the dorsal and ventral visual pathways diverge
Retinotopic mapping • Head-centred vs. retina-centred map of world? • Henriques et al (1998) proved retinotopic mapping is used by brain • Could this technique be used with robots?
The What/Where Theory • Mishkin and Ungerleider (1982) • Ventral stream for “what” vision • Dorsal stream for “where” vision • Early anatomical evidence supported this theory • More recently, theory has been challenged
DANGER! DANGER! The Action/Perception Theory • Milner and Goodale (1996) • Ventral = perception • Dorsal = action • Evidence from frog experiments…
Evidence for Action/Perception • Dorsal lesion = optic ataxia • Patient can recognise objects but can’t pick them up • Ventral lesion = visual form agnosia • Patient can’t recognise objects, but can navigate using visual information
Vision/Motor Connections • Dorsal stream linked to premotor areas used for oculomotor control, reaching and grasping • Ventral stream connected to areas for learning, memory, and social behaviour • So for robotics, concentrate on dorsal stream research!
Organization of Motor Cortices • The homunculus • Overlapping, dynamic organization
Transformations • Cell specificity • Synapses • Neurotransmitters • Other methods?
Synapses and Neurotransmitters • Chemical synapses work by releasing neurotransmitters • Electrical synapses have low resistance intercellular channels • Neuromodulation involves multiple molecules, receptors, and channels • Many reaction chains are 4th or 5th order
Conclusions for Robotics • Use a dynamic, retinotopic map to (possibly) save processing time • Concentrate on dorsal pathway research (action pathway) • Motor organization must be flexible to emulate human brain • Visuomotor transformations: • Massively interconnected neural network • Multi-step chemical reactions in synapses