Active Processes in Perception, in Vision and in Electric Fish. Curtis Bell Neurological Sciences Institute Oregon Health and Science University
Three ways in which Perception is an Active Process • The organism exerts behavioral control over a sensory surfaces (eye movements, ear movements, hand movements, sniffing etc.). • The organism provides the energy that activates sensory receptors (echolocation, electrolocation, active touch). • The organism creates the world it experiences. Perception as an active response to environmental stimuli.
Perception is unconscious inference. - Helmholtz
Satellite Picture? X-ray Image?
Or Cow’s Face?
Most Connections Are Probably Plastic
Examined Object and Eye Movements Exploring It Yarbus
Contrast and Luminance Vary Between Fixation Points as Does Time Between Saccades. These Differences Will Affect Neural Responses. Mante et al., 2006
Integration of the scene requires information about eye position at different fixation points. This information may be provided by eye movement corollary discharge signals. Mante et al., 2006
Intended Eye Movements Remap Visual Space Duhamel et al., 1992
Remapping occurs before saccade and so requires corollary discharge mechanism. Duhamel et al., 1992
Corollary Discharge Signals Keep the World Stable During Smooth Pursuit Eye Movements Thier, Lindner & Haarmeier
Eye Movements Constrain (Disambiguate) Visual Perception Hafez and Krauzlis, 2006
Hafez and Krauzlis, 2006
Non-Conducting Conducting Object Object Lissman, 1963
Nate Sawtell and Alan Williams
Forms of Active Sensation in Mormyrid Fish • Generation of the energy that activates receptors (EODs). • Variation in the frequency of EODs. • Variation in the position of the energy source (electric organ). • Variation in the position and orientation of the sensory surface (fish’s body).
Electroreceptors on the Trunk of the Fish 1 mm
Afferent Fiber from Mormyromast Electroreceptor Szabo and Fessard, 1965
Effects of Objects on Afferent Responses Gomez et al., 2003
Sawtell, Williams, von der Emde, & Bell
Dependence of Latency on EOD Interval Constant amplitude stimuli presented at a naturally occurring sequence of intervals. Nate Sawtell and Alan Williams
Contrast and Luminance Vary Between Fixation Points as Does Time Between Saccades. These Differences Will Affect Neural Responses. Mante et al., 2006
Electric Organ Corollary Discharge Effects in Active Electrolocation System
Use of Corollary Discharge to Measure Afferent Latency
Variation in corollary discharge could be used to minimize effects of interval and amplitude changes.
Electric Organ Corollary Discharge Effects in Active Electrolocation System
Schema of Cerebellum-like Structures
Anti-Hebbian Spike Timing Dependent Synaptic Plasticity
Electric Organ Corollary Discharge Plasticity
Response to central corollary discharge signal is essentially the same as response to sensory stimulus.
Corollary Discharge Signals Keep the World Stable During Smooth Pursuit Eye Movements Thier, Lindner & Haarmeier
Collaborators • Angel Caputi (Uruguay) - In vivo studies. • Kirsty Grant (France) - In vivo and in vitro studies. • Victor Han (NSI) - In vitro studies. • Hans Meek (Netherlands) - Morphology • Patrick Roberts (NSI) - Mathematical modeling. • Nathaniel Sawtell (NSI) - In vivo studies • Alan Williams (NSI) - In vivo studies and mathematics • Gerhard von der Emde (Germany) - In vivo and behavioral studies.
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