Overview Lecture V

Question 1

The Hippocampal Place Fields

Overview

Answer 1

• The hippocampal place field is bound to
  landmarks in the environment
• Once formed, place fields
  are stable in the dark

-No topography: place cells with
neighboring place fields are NOT
neighbors in hippocampus
(contrary to primary visual cortex)

- Same neurons will get new
place fields in a new environment
(or perhaps some won’t have any
place field in the new
environment)

• Place fields constitute a memory
  of familiar environments

Question 2

What place fields tell you about the
role of the hippocampus during
systems consolidation

Answer 2

Look @: Standard (classical) theory of
consolidation vs Multiple trace theory

-Place cells in the hippocampus encode the spatial context to which events are bound.

-Episodic memories =
events + spatial context. Hence,
the network representing episodic
memory will always involve the
hippocampus. --> MULTIPLE TRACE THEORY

Reveals the weakness of the STANDARD THEORY

Question 3

Hippocampus & Place Cells Summary

Answer 3

A collection of place cells forms unique
associations between landmarks/sensory stimuli
coded in cortex and spatial locations coded in the
hippocampus.

• Hippocampal/cortical replay helps to consolidate
the memory (repeated activation leading to late
LTP)

• Hippocampus is part of the long-term episodic
memory trace.

• Fragment of the experience can act as cue to
retrieve/reactivate complete engram

• Reactivation leads to reconsolidation, in which
the hippocampus again plays a crucial role.

– Reconsolidation can be a factor in ‘false memories’

Question 4

Responses of Hippocampal CA1 unit to a restraining tactile stimulus as Function of Rat’s Spatial Orientation Study

Answer 4

• Hippocampus provides Information about where to move in space and activates cells that determine those spatial orientations
• Hippo anticipates sensory stimuli consequent to particular movements
• If through damages in Hippocampus, Rats are deprived of this map:
• > Rats don’t notice environmental changes & can not move to particular spaces
• > Support of Multi Trace Theory, because Hippocampus crucial for spatial context