Memory Mechanisms One

Spatial Memory The ability to remember the position or location of objects and places. – important in foraging for food in the wild – Memory for the location of food – Food Caching and Recovery Covered in Chapter 12 – Where you left your keys – Getting back home after a night out foraging Spatial short-term “working memory “ information relevant to current navigation task Spatial Long-term “reference” information about locations from previous experience often referred to as a cognitive map

Spatial Memory in Mazes Mazes were one of the earlies experimental apparatus for studying learning Willard Small (1901) in the laboratory of Edmund Sanford at Clark University in the late 1890s – to study "home-finding.“ in rats using a replica of the Hampton Court Maze in England – Around the same time Thorndike had been experimenting with baby chicks in maze constructed by placing books on end in various configurations, Research using mazes reached their heyday in the 1930s and 1940s, when Tolman could claim that rat behavior at a choice point was the key to psychological knowledge Tolman (1886 – 1959) – best known for his studies of learning in rats using mazes, – Purposive Behavior in Animals and Men, 1932 – Tolman introduced the concept of a cognitive map,cognitive map

The Radial Arm Maze Olton 1976 based on Tolman’s maze – Radial maze with eight arms Figure 11.4 Food located on each arm Rat started in the middle and allowed to go to any of the arms Requires several days of experience to become efficient Typical behavior on a radial maze – Rats do not randomly select among arms – remember visited arms and avoid returning to those arms Do not need to get food reinforcement to avoid visited arms preexisting tendency to avoid already-visited places – Mean number of correct choices is just above 7 – Figure 11.5 – Video of radial arm maze Video of radial arm maze

FIGURE 11.4 Rat foraging on an elevated radial maze. The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved. Based on Olton 1976 radial maze

The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

The Radial Arm Maze Navigational cues for Radial Maze – Rats appear NOT to use urine odor cues or enter the arms in a fixed order – Reference memory of the location of the platform Landmarks in the room around the maze such as tables, chairs, doors windows shape of the room – Working memory of where they currently are on the maze Current location based on cues in the room Using larger mazes: Spatial memory storage capacity – 17 arms Crystal and Babb (2008) – Interruption procedure Take them off the maze after four arms and returned to their home cage For either one hour or 25 hours “retention interval” – Interruption of 25 hours had more effect Figure 11.6 Working Spatial memory duration can be long The working memory did not reset

FIGURE 11.6 Proportion of correct maze choices in an eight-arm radial maze following a 1-hour or a 25-hour retention interval after the first four arm entries. Independent groups of rats were trained with either a 24-hour or a 48-hour intertrial interval (ITI). Chance performance is indicated by the dashed line. The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

Morris Water Maze A circular tank filled with water – photograph of Morris water maze photograph rats swim to a platform to get out of the water – Escape response during training – Platform is above the surface – rats swim around until they find the platform – Establishes long-term reference memory for location of the platform During testing they can not directly see the platform – surface of the platform is just below the water line – the water is made opaque with dye Morris water maze video

Morris Water Maze Escape latency – Time it takes to find the platform – Decreases with expeience – Figure 11.3 – Useful for studies on memory mechanisms Drug effects Neurology effects Navigational cues for Morris water maze – Reference memory of the location of the platform Landmarks in the room around the tank such as tables, chairs, doors windows shape of the room – Working memory of where they currently are in the pool no visual cues inside the tank locate the platform based on cues in the room

The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

Memory Mechanisms Three phases of memory processes: – Acquisition: the process of acquiring or gaining information through some experience – Retention: holding on to information after the experience has ended either in short-term or long-term memory – Retrieval: recalling information from long-term memory

Acquisition and the Problem of Stimulus Coding Acquisition: the process of acquiring or gaining information through some experience, i.e. learning. – Information is encoded in the nervous system In a working memory task where multiple items – need to be encoded in a brief period of time – selection of an efficient coding strategy is crucial Stimulus coding: experiences are encoded in the nervous system as memory – Use of Cognitive Maps – Other Navigational codes – Serial list learning

Tolman’s studies of learning using mazes Cognitive Maps in Rats and Men Tolman and Hull disagreed on the mechanisms for learning a maze – Hull: behavior of rats is a matter of mere simple stimulus-response connections. – Tolman: ““field theorists” a field map of the environment gets established in the rat's brain. “ p. 193 cognitive-like map of the environment "Latent Learning" Experiments. Fig. 5. – Group II were not fed in the maze for the first six days On the seventh day (indicated by the small cross) the rats found food at the end of the maze for the first time "Spatial Orientation" Experiments. – Trained to cross a round platform and then up a path to food Fig. 15. – Tested on a “sun-burst” maze with many arms radiating from the platform fig. 16. – Rats preferred path six which went directly to the food fig. 17.

Cognitive Maps and Other Navigational Codes A cognitive map is a mental model of objects’ spatial configuration that permits navigation along optimal path between arbitrary pairs of points.cognitive map What are the components of a cognitive map? – Other Navigational codes Beacon following: – object near the goal, also called dead reckoning – When food is hidden at the base of an object such as a pyramid – This is similar to sign tracking Landmarks: – any distinctive object in the environment not near the food – Palm trees or the pyramid – Landmark relationships: distance and geometry of landmarks Geometric cues: – shape of the area – for example rectangular shape four corners with different wall lengths – Figure 11.8

FIGURE 11.8 Diagram of a spatial task in which food is hidden in corner 2 of a rectangular arena. Notice the beacon near the goal object and a landmark some distance away from the goal object. The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.