Lecture 6

Lecture Updates

• Spatial memory will be covered today
• Decision making will be covered next week
• Object physics will be covered next week, excluding pages 259-268

Recap of Lecture 5

• Time and number are fundamental aspects of cognition
• Time and numbers are linked theoretically and anatomically
• Spatial memory is the third of the "big three"
• Spatial memory is essential for navigating our environment

Finding The Way

• Many organisms spend much of their time moving from one place to another
• Spatial movement in familiar or unfamiliar environments is required for foraging, hunting, searching for mates, caring for young, and finding the way home

"Getting There" vs. "Knowing Where"

• "Getting there" is an elementary system that directs animals to different, often unknown locations
• Organisms do this when orienting towards places where they may find food, mates, etc
• The "getting there" system operates by initiating motor patterns in response to internal(hormones) or external signals (sensory cues)
• Bacteria move from areas of low to high nutrient content as an example
• "Knowing where" allows animals to reach a particular destination
• This includes; food caching, migration, and navigating unknown environments
• It relies primarily on previous experience (food caching)
• It allows animals to travel back and forth between seasonal habitats (migration)

Adaptive Value - Food Caching

• Birds learned to recover mealworms after a 4-hour retention interval
• Birds learned to recover peanuts after a 124-hour retention interval
• A replenish group was used as a control, where fresh worms were always provided after the 124-hour retention interval
• These birds always searched for worms as a result

Spatial Learning Abilities

• Spatial learning abilities differ among members of the crow (corvid) family
• Male pinyon jays make fewer errors than females when retrieving seeds from caches
• Females stay in the nest and incubate eggs, while males relocate seeds cached months earlier and bring them to the nest

Adaptive Value - Sex Differences in Spatial Memory

• Evolutionary pressures to find the way may be different for makes versus females
• Male animals often spend more time travelling and searching for mates, reflected in spatial memory tasks where males seem to have an advantage
• Female subjects, on the other hand, tend to outperform males in object recognition tasks
• Males seem to rely more heavily on global directional information
• Females are more sensitive to information about the position of uniquely identified cues (Healy, 2006)
• The ultimate explanation of sex differences in spatial memory is based on hunter gatherer division of labor, (Silverman et al, 2007)
• Males inherit cognitive precesses related to hunting, females gather/identify/remember location of plants

Brood Parasites

• Brood parasite species (ex: some species of cuckoo, cowbirds) deposit their eggs in the nest of other host birds
• The brood parasite exploits these birds to raise their young: different strategies are used by different species, like Mafia-hypothesis versus cryptic eggs
• Female brown-headed cowbirds have a larger hippocampus and better spatial memory than males of their species

Adaptive Value - Migration

• Migration involves the seasonal movement between spatially distinct habitats
• Enormous time and energy costs must be offset by advantages of new habitat
• Evolution likely resulted in features that facilitate long-distance travel (ex: larger wing span, increased capacity to store fat)
• Spatial memory is also affected, since migratory garden warblers remember feeding sites for 12 months
• Closely related but non-migratory Sardinian warblers remember the same information for only 2 weeks (Meeke-Hoffman & Gwinner, 2003)

Types of movement

• Orientation involves kinesis and taxis
• Small-scale navigation involves landmarks, beacons, geometry, path integration, and cognitive maps
• Large-scale navigation involves homing versus migration, sun compass or star compass, magnetic fields or olfactory cues and experience

Orientation & Navigation

• Spatial behaviours are typically organized in two categories: orientation and navigation
• Orientation is mechanisms that point animals in the right direction, typically described in terms of kinesis and taxis
• Navigation is divided into small-scale and large-scale travel

Kinesis vs. Taxis

• Kinesis and taxes are often described in terms of invertebrates
• They involve basic movement in response to stimuli that is non-directional (kinesis) or directional (taxis)
• Kinesis is possibly the most simple form of orientation, where non-directional movement responds to a stimulus
• A stimulus intensity determines the movement, and guides animal to a preferred location
• For example; a Woodlouse moves about a drier surface in search for a more humid space
• Taxis is directional movement in response to a stimulus that may be towards (+) or away from (-) stimulus
• Taxis often takes the form of phototaxis and chemotaxis
• For example; tracking the scent of a potential mate in animals or movements of sperm towards an egg cell

Taxis & Kinesis

• Neither kinesis nor taxis can fully explain how animals move through their environment
• Specific sensory stimuli sets a specific motor pattern in action, which is a building block for more complex orienttion

Navigation

• The process identifies a specific location regardless of current position, for instance animals retrieving hidden food, revisiting feeding sites, or returning home
• It's determined by a destination or goal, in contrast to mere orientation
• Discussed in terms of small-scale (roughly a few km) and large-scale, though this distinction is not absolute

Navigational Cues

• Landmarks
• Beacons
• Geographic Cues

Landmarks

• Landmark usage in digger wasps was investigated by Tinbergen (1951)
• Pine cones were placed around periphery of wasp nests, these pinecones acted as a landmark
• Wasps subsequently searched the center of the pine cones for their nest even when the pine cones were moved

Landmarks vs. Beacons

• Investigations were done using the Morris water maze in 1981
• Water was made opaque with non-toxic paint
• Animal used spatial cues to find landmark when the platform was submerged
• When the platform was visible, the animal used the platform as the beacon

Cue Competition

• Animals can use both landmarks and beacons, but may have preference for a certain type of cue
• In one paradigm, animals trained to locate a target(food reward) which has a fixed relationship to environmental cues (landmarks) and fixed cues at goal location (beacons)
• During testing, beacons (but not landmarks) are moved
• Landmark use shown when animal goes to original beacon location
• Beacon use shown when the animal goes to the new beacon location
• Food caching animals rely more heavily on landmarks when they are further away
• They switch to beacons as they get closer to target, beacons maybe more difficult to detect at a distance (Gould et al., 2010)

Ecological Validity

• Ecological validity refers to the extent to which the findings of a research study are able to be generalized to real-life settings

Comparative Data - 8-arm Depletion Task

• Experiments are conducted on dogs, rats and pigeons

Path Integration

• Allows animals to return to a starting location (usually home) by tracking the distance and direction travelled on a single trip (also know as dead reckoning)
• Ants were found using path integration
• Requires continuous montiroing of location in relation to starting points, organisms receive ongoing feed back on it's movement of time
• Mammals appear to use the vestibular system for path integration
• Small calculation errors can have profound effects on navigation and lead to being far from home
• Animals use path integration initally then switch to landmarks and beacons as they get closer to their gaol
• Ants use a pedometer, honeybees use visual flow information

Cognitive Maps

• Behaviourists suggested animals navigated things like mazes by leaning a series of correct responses (when to turn, avoid dead ends)
• Tolman (1948) argued animals form a cognitive map as they travel through the maze
• Cognitive maps allow animals to utilize information about landmarks, beacons, and geometric cues combined with their position to these cues
• Animals can form a novel route to a location

Evidence of Cognitive Maps

• Chimps hide food different locations in their enclosure, will retrieve food in different route order (Menzel, 1973)
• Vervet monkeys do the same thing, but do not remember as many locations (gallisel & Kramer, 1996)
• Rats learn direct hidden platform with water maze from new start locations
• Use extramaze cues
• Meerkats directly escape into nearest hole when alarm call (Manser & Bell, 2004)
• Marsh tits do not follow the same path when retrivieng food caches (shelltleworth & Krebs, 1982)

Interactive Systems

• Most species can use different cues during small-scale navigation, though one strategy is preferentially used
• Ecology determines which system is used
• Food caching birds likely use a cognitivie map rather than geometric cuts, because they approach there caches from different locations
• Animals also use spatial cues to adapt to the envionrment (Gould et al, 2010)
• Animals use both landmarks and beacons but do not combine information, this is not due to cognitive load
• Landmarks, beacons and geometry are independent to one another, makes sense in terms of place and grid cells
• Path integration and cognitive maps are in parrallel to lanmark or geometric cues. These operate simultaneously combined with representations of landmarks, Path Integration may back up navigation when animals get off track
• Computations for path integration is ongoing, but only come into play if cues fail

Conclusions: Small Scale Navigation

• Animals do not travel randomly, they locate goals using landmarks, environment geometry, path intergration and cognitive maps
• All animals frequently switch between strategies depending based on learnt behaviour

Next Up: Large Scale Navigation

• Long distance travel, difference depends on species being studied
• Homing Versus Migration

Homing

• The ability to return to a nest or burrow from a distant site, such as carrier pigeons in 19th and early 20th century
• Natal homing is when they return to their birthplace, Green sea turtle hatches on one beach, immediately heads into water, and spends life feeding elsewhere, then returns to reproduce.

Migration

• Large-scale, seasonal movement between habitats
• Humpback whale feeds in cooler northern waters and during winter travels up to 25,000km to warmer waters for reproduction
• Monarch butterflies make transgenerational migration from Canada to Mexico

Homing vs. Migration

• Similarities, however, are independent of one another
• Homing and migration may have evolved from a common process with differential evolutionary pressures leading to homing in some species and migration in others

Mechanisms of Large-Scale Navigation

• Cognitive mechanisms mediating large-scale navigation must provide animals with information on when to leave, which direction to go, where to go, and where to stop
• Different species using the following, sun compass, star compass, magnetic cues, and olfacotry cues

Large-Scale Navigation Mechanisms

• An Emlen funnel has a glass top and ink pad on the bottom, where foot traces are left on the sides as the bird tries to escape
• Useful in the study of migratory restlessness (zugunruhe) with photoperiod sensitivity
• Increase in night-time activity (even when raised in captivity) shows there is a genetic mechanism keeping track of yearly cycles
• The directionality of migration inherited, also a genetic trait
• With the European blackcaps crossing over with offspring migrating in-between those two locations
• How do the animals point in the right direction?

Sun Compass

• Manipulated with phase shift to shift the animal's circadian rhythm. Animals also make errors based on where the sun is at the given time
• For example, in the experiment midday peak occurs at midnight, and the sun is in the East
• The Monarch butterfly integrates sunlight by using antennae and internal clocks

Star Compass

• Animals use the constellations and organization of stars as directional cues
• Emlen (1970) indigo buntings raised with normal light dark cycle, but different exposure to stars- those who never show constellations showed more restlessness at migration time, with no preferred direction of travel

Magnetic Cues

• Earth's magnetic fields are also directional cue that discovered when Walcott & Green (1974) used pigeons with small coils that had difficulty homing
• Migratory direction shifted magnetic field outside of a bird's cage
• Very also be importnat for marine animals (Benhamou et al., 2011; Horton et al., 2011)

Olfactory Cues

• Most controversial mechanism
• Pigeons detect proportion of atmospheric gases to find home(Papi et al, 1972)
• Disrupted homing behaviour when disrupting the Olfaction
• Pacific Coho Salmon use to find spawning grounds

Role of Experience

• Migratory patterns are inherited
• European starlings have relocation and displaced from the Netherlands to Switz prior to migration
• First time migrants end up in the wrong locations
• 2nd time migrants learned to do the correction

Conclusions - Synthesis of Mechanisms

• Most species combine various different approaches, rather than relying on one over another
• Birds with no light orient to magnetic field. If exposed to light, a sun compass becomes the dominant mechanism

Role Of Hippocampus In Navigation

• neuroscience researchers, focus on small-scale navigation
• Cognitive maps of the hippocampus was suggested by Tolman(1948)
• O'Keefe and Nadel(1978) confirmed relation between hippocampus & cognitive mapping

Place Cells and Grid Cells Study

• The strongest relating is from hippocampus, discovery of place cells (O'Keefe & Distrovsky, 1971 & grid cells Fyhn et al., 2004)
• Also, place cells & grid cells are pyramidal neurons in hippocampus that fire animal in a certain spot

Conclusions

• Large-scale navigation is controlled by more than process
• Discovering place cells & grid cells show use of neurobiological, used on cognitive maps
• Studies like the London taxi cab drivers indicates hippocamus plasticity