Hippocampus and spatial
memory
A case study of Jon.
King, J. A., Trinkler, I., Hartley, T., Vargha-Khadem, F., & Burgess, N. (2004). The
Hippocampal Role in Spatial Memory and the Familiarity-Recollection Distinction: A
Case Study. Neuropsychology. 18(3), 405-417. [Muriel Delsoin]
Who is Jon?
What does he suffer from?
• He is an man who has developmental
amnesia, and suffers from perinatal
anoxia.
-perinatal anoxia is lack of oxygen to the
brain. http://www.meritcare.com/specialties/rehab/brain/abi/Anoxia/definition.aspx
• His hippocampus is reduced in volume by
50%. He is impaired in episodic, temporal
and spatial memory.
Jon’s ability to navigate visually was tested using a video game.
Duke Nukem (from 3D Realms Entertainment, Dallas, TX)
The video game involves moving through a virtual scene, like a town, and shooting
enemy forces (aliens).
He was a good video game player in general, but his navigation was inaccurate.
He was also expected to draw maps in the Speirs, Burgess et al. study and his maps
were also inaccurate.
- This shows his recollection impairment.
- He also could not recognize scenes from the virtual town when such scenes
were compared with foils, unlike control subjects who could.
- spatial memory impairment.
Jon’s memory deficits : retrieval of episodic events
—comparing memory events’ content with memory context of events
retrieval of spatial information
—comparing memory for object locations from the same view as at
presentation with memory from a shifted viewpoint.
Episodic memory test within the VR town:
participants follow a path and meeting with virtual characters in
different places and receiving a different object each time, for a
total of 16 objects. Context-dependent memory for each event (the
receipt of an object) was tested by presenting 2 of the received
objects next to a location and a character and asking which object
had been received in that location or from that character, or which
had been received first (see Figure 1). Recognition of the familiarity
of an object was tested by presenting a received object and
a similar looking foil and asking which had previously been
received.
Results:
Confirming his impaired episodic memory, Jon performed
at chance on the context-dependent memory questions but
was unimpaired on the object-recognition question (Spiers, Burgess,
et al., 2001).
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Jon’s spatial memory was investigated:
Used virtual reality paradigm (King et al., 2002).
Jon views an array of placeholders, located in a small town
square, while virtually looking down from the surrounding
rooftops. A series of objects appears on random placeholders,
and then Jon is tested by presenting each object randomly in its original
location, along with a number of copies of each in foil locations.
-The task is to identify the one in the correct original location. Between
presentation and testing, Jon either remains in the original position or is
moved instantly to a new location. The difficulty of a condition can be
varied with the number of objects and foils.
-Jon using two foil objects at random locations.
Results:
showed good performance in the same-view condition for short list
lengths, with performance reducing from near ceiling to 50% for
List Length 10 (chance performance would be 33%). In the shiftedview condition, he performed at chance for all list lengths
greater than 1.
•Jon’s relative impairment compared to control participants in the shifted-view
versus same view conditions was not clear, so researchers tried to reduce control
participants’ performance overall, by testing them with five randomly placed foil
objects. Now, Jon’s differential deficit at shorter list lengths (4 and 7) became clear:
- He performed significantly worse than controls in the shifted-view
condition and performed better than them in the same-view condition. Jon’s
impaired performance from a shifted view indicates impaired
allocentric memory. By contrast, his relatively preserved same view
performance on short lists could be due to familiarity-based
recognition using preserved egocentric representations. The size of
the differential deficit on short lists makes the test a potentially
powerful indicator of hippocampal damage, given Jon’s generally
spared recognition memory.
It was concluded that: Jon’s deficits in spatial memory (from new viewpoints) show
an inability to store object locations in an allocentric framework. A close
relationship functioning of episodic and spatial memory exists, in which the
hippocampus seems to be involved.
We learn that the hippocampus really is associated with and influences spatial
memory.
Question:
• “Do the processes required by the
allocentric system relate to the
hippocampal contribution to contextdependent recognition and episodic
recollection?”