Hippocampus: GPS, Navigation, and Memory

Hippocampal GPS and the Brain

• The focus is on the brain, specifically the hippocampus, and how it encodes a map of the world..
• Neurons are dedicated to producing spatial representation.
• The hippocampus deals with space and creates a "map saurus".
• The hippocampus is involved in episodic memory, which stores memories of life events.
• Brain mapping and remembering events happen on a daily basis.

Navigation and the Hippocampus

• The first brain region damaged in Alzheimer's disease is the hippocampus.
• Damage to the hippocampus leads to deficits in navigation and memory recall.
• Navigation is defined broadly as the ability to move from one place to another.
• Spatial behaviors relate to both large distances like commuting and small-scale actions like navigating a kitchen.
• Spatial memory is needed for everyday tasks like making tea or coffee.

Episodic Memory and the Hippocampus

• Episodic memory stores memories for events in our lives
• Episodic memory is fundamental to human existence so we can tell each other stories of the past.
• Memory of events determines where we want to return to or otherwise.
• The hippocampus shrinks as one ages as part of healthy ageing.
• The hippocampus shrinks to a greater extent in those with diseases like Alzheimer's
• Navigation and episodic memory rely on the hippocampus.
• In Alzheimer's disease, hippocampal cells begin to die, which can be tracked via navigation and episodic memory tests.
• While there is no cure for diseases like Alzheimer's, lifestyle factors can slow it down:
• Exercise
• Diet
• Smoking
• Heavy Drinking
• Lifestyle factors contribute to the death of hippocampal cells.

Interventions and Research

• Lifestyle interventions can slow down disease progression
• Core cognitive research is trying to predict Alzheimer's disease via navigation and episodic memory
• Gold standard tests which determine episodic memory exists
• Navigational declines can be detected earlier in mild cognitive impairment stages.
• Hippocampal cells involved in navigation will be examined to see how they create episodic memories

Theoretical Understanding of Hippocampus and Disease

• The same brain region is involved in two separate types of memory.
• The biology of diseases will be looked at.
• Processes causing cell death in the hippocampus and theoretical applications for disease markers will be investigated.
• Theoretical concepts are being used to detect diseases

Hippocampal Encoding and Spatial Awareness

• The hippocampus encodes the spaces we walk through.
• Alice-centric and egocentric spatial encoding.
• Learning outcomes include mapping how people navigate based on theoretical concepts with associative learning versus the traditional idea of maps

Learning and Navigation Techniques

• Single-cell recording can uncover what we know about a place.
• Spatial memory and navigation are used daily from making a cup of tea to commuting from home.
• People avoid eating, sleeping, working, and socializing in the same place
• You have to go to another room to socialize.
• Navigation is a key part of day to day life.
• Locations within the world are learned.
• Navigation becomes efficient when you learn where locations are.
• There are two broad ways to get from the start to the destination.
• A familiar place is used as an example
• If the path is well rehearsed, sites are associated with turning in a particular direction.
• Landmark action associations involve chaining enough of those associations
• The undergraduate concept is chaining associative links where the brain learns to associate getting food by pressing a lever.

Spatial Understanding and Cognitive Maps

• Spatial learning happens with buildings instead of levers
• Spatial learning is fundamental to mammals
• Spatial relationships are linked to the concepts of learning, sex to learning
• You associate sites to turning directions
• If associations are chained, you end up at the destination
• Streets can be blocked, and consulting a map can assist in finding a detour
• Navigation around the world helps to understand spatial relationships
• Maps can help find landmarks and see if streets are blocked

Egocentric vs Allocentric

• Schematics can get you from A to B by visualizing landmarks, associative learning and stimulus
• Habitual turns are made up of stimulus and response
• Egocentric spatial terms are where positions in the world depend on where you are at the moment
• Egocentric examples include how the screens are behind someone currently depending on where they are located
• Egocentric is entirely based on where you are and what you're looking at.
• Allocentric representations are object-to-object encoding.
• World centered coding describes where something is based on what you can see in the world
• A screen is always north.
• Egocentric includes where you have to move depending on facing directions.

Cognitive Maps and Spatial Learning

• Encoding and navigation are based on whether you encode things based on where you are, where you can see, following a compass.
• Navigation behaviours are driven by both concepts
• Following well known routes you can get stuck if it's blocked.
• Most mammals create cognitive maps to determine the best path to go down when you see an obstacle.
• Cognitive maps determine flexible navigational processes.
• Cognitive maps create an idea of spatial layout.
• Detours or short cuts can be made with cognitive maps
• You don't need google maps, and you can just automatically do it with a cognitive map

Hippocampal Cell

• Hippocampal cells are hardwired to create maps as we move through learning spaces.
• Places will start to feel familiar in the brain creating familiar maps
• Nobel Prize was awarded for discovering hippocampal cells.
• Realisation that hippocampal cells represent the abstract concept of place, rather than a concrete object or visual stimulus, had important implications.
• Space's representation is of profound interest to many academics
• Finding the system in the brain that represents space is very important.
• The hippocampal GPS system found in the early 70's.
• Hippocampal GPS system was found accidentally

Hippocampus and patient HM

• Knowledge of the hippocampus in terms of cognitive abilities based on patient H.M.
• Patient H.M had severe epilepsy and had medial temporal lobes removed in a surgical procedure as a cure.
• Side effects included memory loss such as anterograde and retrograde amnesia
• Day to day experience were forgotten, where he also had trouble recalling past events.
• Brain regions dealing with episodic memory were removed with event memory.
• Sue Cooke studies multiple case studies on patients similar to H.M.
• H.M could not recall memories of personal events.
• HM didn't remember specific details of what he was doing.
• Recollection of episodes was possible, and early scientific thought was that this was due to psychology.
• The hippocampus involves memory events.

Neural Recording

• Miss Whittingham was related to memory and wanted to record single neurons in a hippocampus
• A specific technique was wanted to record a single neuron as a moving animal.
• In the early 60s others can record single neurons too in cats.
• Single neurons right in the occipital lobe.
• Researchers interested in what the cat can see and what they're coding for in terms of what the cat could see
• Cat would initialising by pinning the cats eye lid for them to see stimulus.
• Electrode inserted into the cats brain.
• Animals must be fixed in position anethetised.
• Process involved recording from a single neuron as an animal moves around its environment
• Recording would allow you to do what we say spiked or fires

Neural Activity

• This gives better idea on what neurons were doing freely
• Animals are behaving more normal
• Micro electrode looks like a syringe.
• Inserting an electrode on an animal's skull,
• Electrical activity that occurs allows an action potential to occur
• Neuroses generate activity during an action potential.
• Recording is possible while animals are moving
• Geiger counter noises indicates a neurone firing where we're recording from seven different cells
• Movement determines whether neuron firing.
• Neurone firing can be fine tuned. FMRI can allow people to walk around
• Study the hippocampus as as whole with fMRI.
• Recording from single neurons can reduce to a neural level
• Neurones can be active in the hippocampus.
• Accidental discovery by Keith came from work in the thalamus.
• Inserting inadvertently into hippocampus instead of the thalamus laterally.
• Sacrificing the brain shows where electrode was inserted.
• The researcher was in the thalamus when he was really recording from the hippocampus
• The cell recording has properties of movement

The HippoCampus as a Spatial Map

• Recording may link events in life and memory
• Responds to animal movements in space
• The structure of a rat and human hippocampus is similar
• Theyre evolutionary ancient parts of the rain
• Mice, rats, monkeys and humans all have similar hippocampus
• The neurone hippocampus responds to the animals movement'
• The function is to identify what the hippocampus can do by memory.
• Studies consist of MSC Project research
• Animals move via a seed experiment
• Researcher scatters seed that animals would "hoover up".
• Animal movement includes chamber chambers
• Animals can be shown to press levers with lights coming on.
• Enclosures track where animal moves

Coding and Place Cells

• Electrodes record data while an animal moves from the middle to outlines meeting the animals.
• An enclosure assists married square chamber animal
• Heatmaps interpret cell activity
• If a cell is not firing, it will have a dark blue match
• Cell activity relates to the animal’s location within an enclosure.
• Neurone turns red when visiting the area.
• Cells are often silent.
• They care about where the animal is only when coming to a region of space.
• Neurones coded that corner of the box.
• Cells can code when an animal comes up to the opposite side
• Cells can start to map places.
• "Place" is an appropriate name
• Encodes a specific place.
• These cells are place cells.
• There are thousands in the HPC
• You can track what's happening in a location via the cells the respond
• Animal has to be in a corner if the cell is firing.
• Location relates to firing.
• These place cells can start to code a location where animals are within an environment