103_14_full

103_14_full - PSYC 103 Winter 2011 Lecture 14 Landmarks...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: PSYC 103 Winter 2011 Lecture 14 Landmarks Tinbergen (1951) Fixed location objects that can guide an animal’s navigation in relation to a target or goal; typically used when features of a goal are imperceptible at a distance 1.  Wasps preferentially use landmark objects that are large, nearby and threedimensional 2.  Learn geometric relation of multiple landmarks: With multiple landmarks, changing absolute size has little effect; only the orientation matters. Landmark encoding Snapshots and geometry Snapshot memory: compare the current view with a stored memory, or “snapshot”, of the landmarks Cartwright et al. (1983): bees trained to look 50m south of black cylinder; when cylinder is small, bees look closer. •  Size of landmark image on retina controls distance. •  However, this does not occur in gerbils. •  •  Cheng (1986) showed that rats trying to find food in previously baited spots made many errors in diagonally opposite corner - termed “rotational errors.” Suggests that rats use the environmental geometry -- i.e. relation between long and short wall. Requires impoverished environment, otherwise spatial landmarks take precedence & decrease errors Landmarks migration Emlen 1970 Early learning experience calibrates the celestial compass in indigo buntings Groups of birds were were raised in planetarium under either: 1.  2.  3.  a normal night sky (north star polar rotation) a night sky rotated around Beutlegeuse starless night sky. When migration began, the birds oriented normally, in the opposite direction, or randomly, depending on prior experience. Ink pad Cognitive Maps Local images and route maps are relatively inflexible Cognitive map: Mental representation of space If animals represent the world this way, then they should be able to take new routes when previously effective routes have been blocked or impeded. Tolman (1946): Latent learning: free exploration of a maze a satiated rat leads to subsequent ability to locate food very rapidly Shortcut: when an old route in maze is blocked, rats will take the next shortest route, even if they have very little experience with that route. Cognitive Maps Plans of the mazes used in the two stages of the experiment by Tolman et al. (1946). Throughout the experiment a light bulb was located at H. Cognitive Maps •  Gould (1986) trained honeybees to get food from feeders placed at one of two locations (F1 or F2), but not both. Neither food site was visible from the other. •  Bees were captured as they left the hive, and tested by being released at the other (untrained) food site. Their compass direction was measured when they flew off. Results: bees go predominately to old (trained) food source. Honeybees Cognitive Maps bees Caveats…. •  Problems with Gould (1986): –  Experience of foragers was not controlled (could have actually remembered route). –  Flying up from food source gives bees a better view of the landscape (e.g. landmarks). •  Dyer (1991, 1994) –  Source A is in a quarry, while source B is on normal elevation. –  Bees trained at B could not get back to B when released from source A. The Morris Water Maze: a spatial learning task Strategy 1: Learn the position of the submerged platform relative to landmark cues. Inference --> encode the spatial relationships between the platform and landmarks. Strategy 2: Cued (beacon) learning: Associate the visible platform position (or some other cue) with escape from the water. The platform can be moved and the rat locates it easily. Human Hippocampus Effects of hippocampal lesions on spatial learning: 1. In humans, lesions to the hippocampus affect only certain types of memories; specifically declarative or episodic memories, but not procedural memories. •  •  Episodic memories: memories for facts and events Procedural memories: riding a bicycle, playing tennis etc. 2. Lesions to the hippocampus also cause marked deficits in spatial learning tasks in rats. Effects of hippocampal lesions on spatial learning: 1. In humans, lesions to the hippocampus affect only certain types of memories; specifically declarative or episodic memories, but not procedural memories. •  •  Episodic memories: memories for facts and events Procedural memories: riding a bicycle, playing tennis etc. 2. Lesions to the hippocampus also cause marked deficits in spatial learning tasks in rats. Effects of hippocampal lesions on spatial learning: 1.  Lesions to several parts of the hippocampus and adjacent structures cause errors in spatial learning; perseveration visiting the same arm many times. 2. Same lesions do not affect cued learning! Hippocampal lesions Hippocampal lesions affect spatial learning in the Morris Water maze. Lesions to the cortex, or sham lesions have no effect. Lesions do not affect cued learning. Only tasks requiring spatial learning are affected. Lesioned rats can learn new cued learning tasks, but not new spatial task. Principles of Hippocampal Function The hippocampus is necessary for acquisition and storage of short(er) term, but not very long term memories. •  As the time between the training and lesion increases, the effect of the lesion decreases Hippocampus processes spatial information imbedded in working memory and/or reference memory tasks •  If lesions precede training, acquisition of both working and reference memory are impaired. •  Cued learning is never impaired. Hippocampal place cells Hippocampal place cells: (discovered by John O’Keefe) •  •  Firing pattern of the cell increases when animal moves to specific locations within an area. Firing field of the cell: spatial area within which the place cell is active. Firing pattern of a place cell as the animal navigates in the environment. Four different place cells within the same arena Preferred region Place cells fire regularly, and repeatedly, as a rat moves through space 18 What cues drive ‘place cell’ spatial preference? The wandering rat experiments… 1.  Different cells encode different regions of space. 2.  The size and shape of a place field can differ. 3.  A place field develops over time in novel environments, but remains relatively constant as long as the environment does not change. 4.  Visual cues are important for place cell selectivity. If visual cues are rotated, place field will rotate as well. 5.  If all external cues are removed, the place field remains intact, but drifts. (ideothetic cues) ...
View Full Document

This note was uploaded on 03/24/2012 for the course PSYC 103 taught by Professor Pearlberg during the Spring '07 term at UCSD.

Ask a homework question - tutors are online