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دانشگاه صنعتی امیرکبیر دانشکده مهدسی پزشکی سمینار درس کنترل سیستمهای عصبی-عضلانی. ناوبری در سیستمهای زیستی و مهندسی. استاد درس: آقای دکتر توحیدخواه توسط: محمد علی احمدی پژوه پاییز 87. Topics. What is Navigation What parts of the brain contribute in navigation Hippocampus Models
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دانشگاه صنعتی امیرکبیردانشکده مهدسی پزشکیسمینار درس کنترل سیستمهای عصبی-عضلانی ناوبری در سیستمهای زیستی و مهندسی استاد درس: آقای دکتر توحیدخواه توسط: محمد علی احمدی پژوه پاییز 87
Topics • What is Navigation • What parts of the brain contribute in navigation • Hippocampus • Models • Research methods • Disorders
Tasks Motor Com Ref Planning Controller Musculoskeletal System Sensor Data Processing Navigation Sensors
Two basic methods for dealing with space • Sensory-motor interaction with the environment: look – find target – move towards target – look • requires sensory access to environment • requires sensory-motor coupling Knowledge in the world • Representing space in memory, representing the problem, reasoning on basis of representation • requires spatial memory and a representation of the environment • requires spatial inference Knowledge in the head
Stars and other constellations helped sailors to figure out their position. The red arrow is pointing to the North Star, which is also known as Polaris.
This is a quadrant. A sailor would see the North Star along one edge, and where the string fell would tell approximately the ship’s latitude. A sailor could also use this astrolabe. You lined it up so the sun shone through one hole onto another, and the pointer would show your latitude.
Sailors didn’t even have good tools to tell where they were going! Look at these old charts. They were not very accurate. No wonder ships often sailed off course! These were made over hundreds of years by sailors observing the land from the ship.
In cognitive map of Toronto created by somebody from Toronto Personal Communication, Created by: Meaghan Ferguson, November 02, 2004 Mapquest.com, search engine: Google.ca Accessed Novemeber 03, 2004
Insects • Bees • Ants
Visual Landmarks • Map of local landmarks • coasts, rivers, valleys, mountain ranges: flyways? • Finding nests, caches, fruiting trees: controlled by hippocampus of the brain, which controls spatial memory and cognitive memory: also well developed in cowbirds • But, when cover homing pigeons with frosted lenses, they still find their way back to their loft
Solar Compass • Kramer’s funnel ink experiments with starlings: can orient as long as they see the sun • Matthews’ homing pigeons have a chronometer and understand the changing position of the sun relative to the direction of the destination • to fly east at 6AM, you fly toward the sun, but because your internal clock tells you it is noon, you know that the sun is in the south and that to fly east, you must fly 90 degrees to the left of the sun • Light bulb experiments • train birds to feed out of a northwest food cup. When exposed to the sun, they continued to feed at this cup. When sun replaced by an immobile light bulb, shifted more and more to the left, thus compensating for the assumed change in position of the sun
Solar compass, cont. • Clock-shifting experiments • if you reset internal clocks using artificial photoperiods to a noon-to-midnight period. When release bird at noon, it will think that it is 6AM
Stellar compass • Birds can also navigate on cloudy days and nights • Radiotelemetry: thrushes fly 650 km on a firm compass bearing at night, meaning that they can compensate for the wind • Planetarium experiments
Sunset cues • Birds use polarized light from the setting sun
Geomagnetism, 1 • Provides both a compass and a map • Earth is a huge magnet: the magnetic and true poles are offset, which means that measuring the angular difference between true and magnetic north gives you your position on the earth’s surface.
Geomagnetism,2 • Also provides compass because of the inclination of the magnetic field lines (poleward and equatorward) • Walcott and Helmholtz coils
Reference Systems • Need an external reference to figure out where to go. • Critical for young birds: vagrancy • use both geomagnetism and stellar patterns • planetarium experiments with altered points of rotation • need some sort of celestial orientation • stellar cues are important at the start of migration, but then geomagnetism takes over
Integration of a Complex System • Star compass with rotation most important during ontogeny • Magnetic field most important during migration • Sunset cues also important • Landscape features
Factors influencing learning and use of information • Age • Individual differences • Personality • Social and cultural background • Education • Gender differences • Visual impairment • Familiarity and experience • Effort effects (e.g. travel time)
Sensors: • External: • Visual • Hearing • Vestibular • Tactile • Olfactory • Internal: • Muscle Spindle • Golgi Organs • Skin • Joint Sensor
Wayfinding in Normals • Route-based representations • Linear: Describes information that encodes a sequential record of steps from a starting point, through landmarks, and finally to a destination • The coupling of landmarks and instructions • Grounded in an egocentric coordinate frame • Inflexible
Wayfinding in Normals • Map-like Representations • O’Keefe & Nadel, The Hippocampus as a Cognitive Map (1978): “Whereas a route specifies a starting point, a goal, and a particular direction of movement from the former to the latter, a map specifies none of these, either in its construction or usage. It can be used with equal facility to get from any particular place to any other. Additional flexibility derives from the freedom from specific objects and behaviors. If one path is blocked another can easily be found and followed.” (p. 87)
Wayfinding in Normals • Use of Different Navigational Strategies at Different Times • Different conditions can lead humans to use different navigational strategies and environmental representations • What are these different conditions? • The first is the kind of text description or view given: • Given aerial or survey descriptions, subjects tend to form map-like representations • Given more route-based descriptions, subjects tend to form route-based representations • The second is environmental characteristics: • Feature-poor environments lead to map-like representations • Feature-rich environments lead to route-based representations
Spatial distortion How accurately are spatial relations represented in the mind? • Distortion of distance (Berendt) • Distortion of orientation • Distortion of shape / configuration (Stevens / Coupe, Barkowsky) 11.3
a) Distortion of distance Cognitive distance ≠ spatial distance B. Berendt 1998 11.3.1
Cognitive Distance and Route Selection JanWiener 11.3.1.3
Experiment 1 Subjects view approaching a place, to the left is the landmark associated with that place. 11.3.1.4
Experiment 1 Schematic map of the environment, numbered circles represent places, different shades of gray represent the different regions (all places from one region carried landmarks belonging to the same category -> there was a car-, an animal- and an art-region) 11.3.1.5
Experiment 1 – example for a test route One of the critical navigation tasks in the test phase (after exploration- and test-phase) : the black rectangle represents the starting place, the black circles represent the target places. Subjects were instructed to visit all target places using the shortest possible route. 11.3.1.6
Results from 25 Subjects Subjects preferred routes that crossed fewer rather than more region boundaries Jan M. Wiener 11.3.1.7
Experiment 2 Birds-eye view of the virtual environment 11.3.1.8
Experiment 2 Subjects view approaching a place, each place (junction) carried a unique landmark that was invisible until subjects entered the corresponding place (we call those pop-up landmarks), landmarks from one island were of the category animals, landmarks from the other island were of the category cars. 11.3.1.9
Experiment 2 Schematic map of the environment, numbered circle represent places, all places from one island carried landmarks belonging to the same category -> there was a car-, and an animal-island 11.3.1.10
Experiment 2- Examples for test routes Examples for the critical navigation tasks in the test phase (after exploration- and test-phase): the black rectangle represents the starting position, the black circle represents the target place. Subjects were instructed to find the shortest possible route. Note that there are at least two alternative optimal solutions 11.3.1.11
Experiment 2 - Results Results: subjects preferred routes that allowed for fastest access to the region containing the target. 11.3.1.12
Conclusion [Distance] Environmental regions influence human route planning behavior this suggests that regions are represented in human spatial memory (along the lines of hierarchical theories of spatial representation) Route planning takes into account region-connectivity and is not based on place-connectivity alone 11.3.1.13
Orientation • Cognitive orientation: Categorization of spatial orientation • In orientation memory, we ‘idealize’ perceived angles to get closer to multiples of 90° 11.3.2
Nevada Reno California San Diego N Distortion of shape / configuration • Capacity restrictions do not allow us to represent all details • Rather than leaving holes in our cognitive map, we represent coarse knowledge • Shapes and configurations are simplified • Representation requires fewer relations 11.3.3
TL Function: Processes visual and auditory information, and integrates them for emotion, spatial navigation and spatial and object recognition. Includes all the tissue that lies below the Sylvian sulcus and anterior to the OL. Includes subcortical structures: limbic cortex, amygdala, and hippocampus.
