Lecture 3: The Hippocampus and spatial
cognition
The hippocampus as a neural map of space
Hippocampus Anatomy; evidence for a role in spatial cognition
Gross anatomy
• Hippocampus anatomy well conserved structure across the mammalian group
o The gross hippocampal anatomy changes between species (e.g. proportionally larger
Hpp in rat brains.) At level of internal hippocampal anatomy, it is very similar across
species:
§ Sub àCA1 à CA2 à CA3 à DG
Preserved anatomical features (entorhinal cortex, hippocampus (hippocampus proper, dentate
gyrus, subiculum)), but:
• CA1 in monkey and humans have many more cells than in rats
• Hippocampal commissural connections very strong in rat and very sparse in monkey and
humans
Hippocampus lies in the bed of the ventricle
Ancient organisational features
Located in archiocortex (3 layered)
1. Neuropil (dendrites + axons)
2. Cell layer (bodies)
3. Neuropil
Other areas include isocortex (neocortex, 6 layers) and proisocortex (found at archiocortex-
neocortex transition zone, 6 layers)
• Para hippocampal cortex = proisocortex
o Functionally part of hippocampus
Intra-hippocampal connectivity
Hippocampus has a distinctive pattern of internal connectivity, differing from neocortex (i.e.
reciprocal connectivity)
Hippocampus has an overwhelmingly unidirectional flow of information
ER-(pp)-DG-(mf)-CA3-(schaffer collaterals)-CA1-Sub
• Subiculum is key output station of hippocampus, can also project back to entorhinal cortex
(main hippocampal gateway)
• Unidirectional re-entrant loop of information processing
,Cortical and sub-cortical connections
• Majority of cortical inputs reach Hpp via ERCx
o EC is gateway to hippocampus: controls information flow from cortical sensory
inputs and motor outputs from hippocampus
• Subiculum and CA1 also have strong outputs to cortical areas, like EC, but all the cortical
sensory information enters via EC
• Subcortical (neuromodulation) inputs reach the Hpp directly
o VTA—(DA)—Hpp
o Don’t require the EC gate system, but there are direct dopaminergic projections
from the VTA to entire hippocampus, some parts more than other
o Hpp is subjected to direct subcortical neuromodulatory control e.g. dopamine,
serotonin, cholinergic projections from other subcortical areas (nuclei)
Hippocampus in spatial cognition, navigation and memory
• Hippocampus has important role, in vertebrates, in large-scale spatial cognition (e.g. nest to
borrow, foraging areas, forming a cognitive map)
o Key basis of spatial navigation and memory in humans
• (O’Keefe & Nadel, 1978) - Hpp is the seat of ‘cognitive maps’
• Hpp also has an additional role in episodic memory in humans
o ‘What-when-where’ memories
There are different forms of spatial reference/ types of spatial map to be made.
Hippocampus subserves maps of large-scale space that the organism moves around in; this type of
reference frame is ‘allocentric’
Spatial coding systems:
• Allocentric - independent of own position, relative to room/city axis or geocentric e.g.
North. Large-scale space.
o Hippocampus
• Egocentric - map of space relative to your body e.g. Left/Right. Position of objects can
change with movement of observer, even if object doesn’t move itself.
o We don’t believe that the hippocampus has a role in egocentric processing, but Commented [IM51]: Some could argue that the ventral
hiippocmapus shows evidence of egocentric processing with regards
instead the Parietal Cortex to reward prediction (value of state) (Royer et al. 2010)
Essay point
How do we know that animals have mental map?
• Edward Tolman (1940s) Commented [IM52]: At a time where behaviourist theories of
learning where strong (Stimulus-response), as opposed to Incentive
o Pretraining Apparatus; Choice Apparatus (Sunburst Maze) Motivation Theory
o Stimulus-Response learning —> would expect association of running down central
corridor = reward; enacts exact series of motor patterns
o Proof of mental map: Instead, Rat has representation of reward in brain and spatial
map, allowing for short-cuts to be chosen in Choice Apparatus
§ Not just a series of stimulus-response association
§ Tolman’s spatial/mental map in the brain inspired O’Keefe and Nadel (1978)
, The Morris water maze
• Rats with Hpp lesion couldn’t learn maze tasks
o BUT: How do you know its space being affected by lesion? Could be complex
association of stimulus-response/ different odours and places in maze.
o That critisism could also be applied to sunburst maze
• Need to remove uncontrolled odour/place cues, to actually navigate in large-scale space —>
thus the invention of the Morris water maze
• Classic test of spatial memory and hippocampal function
• Aim is to navigate and find hidden platform (before/after learning)
o Test is extremely sensitive to hippocampal damage
• In early 80s this was considered one of the key pieces of information that O’Keefe and Nadel
where correct in their Theory that hippocampus has a role in supporting a spatial map of
large-scale space
Since then, many have looked for the role of spatial navigation in hippocampal-like regions in
reptiles and fish (species outside mammals) (Reviewed in Salas et al. 2003)
• Reptiles and fish do not have classic interlocking C/archiocortex shapes Commented [IM53]: Difficult comparative anatomy outside of
annimals
• Found hippocampal analogous brain structures do play a role in spatial navigation also
Belief that hippocampus has a role in spatial navigation conserved, not only across mammals, but
the entire vertebrate group
cognition
The hippocampus as a neural map of space
Hippocampus Anatomy; evidence for a role in spatial cognition
Gross anatomy
• Hippocampus anatomy well conserved structure across the mammalian group
o The gross hippocampal anatomy changes between species (e.g. proportionally larger
Hpp in rat brains.) At level of internal hippocampal anatomy, it is very similar across
species:
§ Sub àCA1 à CA2 à CA3 à DG
Preserved anatomical features (entorhinal cortex, hippocampus (hippocampus proper, dentate
gyrus, subiculum)), but:
• CA1 in monkey and humans have many more cells than in rats
• Hippocampal commissural connections very strong in rat and very sparse in monkey and
humans
Hippocampus lies in the bed of the ventricle
Ancient organisational features
Located in archiocortex (3 layered)
1. Neuropil (dendrites + axons)
2. Cell layer (bodies)
3. Neuropil
Other areas include isocortex (neocortex, 6 layers) and proisocortex (found at archiocortex-
neocortex transition zone, 6 layers)
• Para hippocampal cortex = proisocortex
o Functionally part of hippocampus
Intra-hippocampal connectivity
Hippocampus has a distinctive pattern of internal connectivity, differing from neocortex (i.e.
reciprocal connectivity)
Hippocampus has an overwhelmingly unidirectional flow of information
ER-(pp)-DG-(mf)-CA3-(schaffer collaterals)-CA1-Sub
• Subiculum is key output station of hippocampus, can also project back to entorhinal cortex
(main hippocampal gateway)
• Unidirectional re-entrant loop of information processing
,Cortical and sub-cortical connections
• Majority of cortical inputs reach Hpp via ERCx
o EC is gateway to hippocampus: controls information flow from cortical sensory
inputs and motor outputs from hippocampus
• Subiculum and CA1 also have strong outputs to cortical areas, like EC, but all the cortical
sensory information enters via EC
• Subcortical (neuromodulation) inputs reach the Hpp directly
o VTA—(DA)—Hpp
o Don’t require the EC gate system, but there are direct dopaminergic projections
from the VTA to entire hippocampus, some parts more than other
o Hpp is subjected to direct subcortical neuromodulatory control e.g. dopamine,
serotonin, cholinergic projections from other subcortical areas (nuclei)
Hippocampus in spatial cognition, navigation and memory
• Hippocampus has important role, in vertebrates, in large-scale spatial cognition (e.g. nest to
borrow, foraging areas, forming a cognitive map)
o Key basis of spatial navigation and memory in humans
• (O’Keefe & Nadel, 1978) - Hpp is the seat of ‘cognitive maps’
• Hpp also has an additional role in episodic memory in humans
o ‘What-when-where’ memories
There are different forms of spatial reference/ types of spatial map to be made.
Hippocampus subserves maps of large-scale space that the organism moves around in; this type of
reference frame is ‘allocentric’
Spatial coding systems:
• Allocentric - independent of own position, relative to room/city axis or geocentric e.g.
North. Large-scale space.
o Hippocampus
• Egocentric - map of space relative to your body e.g. Left/Right. Position of objects can
change with movement of observer, even if object doesn’t move itself.
o We don’t believe that the hippocampus has a role in egocentric processing, but Commented [IM51]: Some could argue that the ventral
hiippocmapus shows evidence of egocentric processing with regards
instead the Parietal Cortex to reward prediction (value of state) (Royer et al. 2010)
Essay point
How do we know that animals have mental map?
• Edward Tolman (1940s) Commented [IM52]: At a time where behaviourist theories of
learning where strong (Stimulus-response), as opposed to Incentive
o Pretraining Apparatus; Choice Apparatus (Sunburst Maze) Motivation Theory
o Stimulus-Response learning —> would expect association of running down central
corridor = reward; enacts exact series of motor patterns
o Proof of mental map: Instead, Rat has representation of reward in brain and spatial
map, allowing for short-cuts to be chosen in Choice Apparatus
§ Not just a series of stimulus-response association
§ Tolman’s spatial/mental map in the brain inspired O’Keefe and Nadel (1978)
, The Morris water maze
• Rats with Hpp lesion couldn’t learn maze tasks
o BUT: How do you know its space being affected by lesion? Could be complex
association of stimulus-response/ different odours and places in maze.
o That critisism could also be applied to sunburst maze
• Need to remove uncontrolled odour/place cues, to actually navigate in large-scale space —>
thus the invention of the Morris water maze
• Classic test of spatial memory and hippocampal function
• Aim is to navigate and find hidden platform (before/after learning)
o Test is extremely sensitive to hippocampal damage
• In early 80s this was considered one of the key pieces of information that O’Keefe and Nadel
where correct in their Theory that hippocampus has a role in supporting a spatial map of
large-scale space
Since then, many have looked for the role of spatial navigation in hippocampal-like regions in
reptiles and fish (species outside mammals) (Reviewed in Salas et al. 2003)
• Reptiles and fish do not have classic interlocking C/archiocortex shapes Commented [IM53]: Difficult comparative anatomy outside of
annimals
• Found hippocampal analogous brain structures do play a role in spatial navigation also
Belief that hippocampus has a role in spatial navigation conserved, not only across mammals, but
the entire vertebrate group
