Schacter Ch 3,2
Dec 3
Development
Development sets up the brain to receive and interprete relevant information.
It does this through trophic and activity dependent processes.
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During the earliest points in development trophic factors dictate the basic
architecture of the system.
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e.g. The axons from the eye generally find their way to the lateral geniculate
nucleus of the thalamus and not the neocortex or red nucleus.
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Once the basic architecture is set up then activity dependent processes
are involved in organizing the specific connectivity patterns and intrinsic
connections. These patterns will be influenced by the input that
the system receives.
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e.g. Ocular dominance columns seen in the neocortex.
Implications of this developmental scenario for learning and memory theories
are :
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Perceptual aspects will be stored first. For instance learning that
the points on a line are generally representivie of a single object.
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Storage and retrieval systems are in flux throughout the first few years
of life.
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Memories from childhood are stored in a very different fashion, if at all,
and therefore are not retrievable by adult retrieval systems.
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Source misattribution can be explained by this theory as can omission,
false beliefs etc. In ch 7 poor source memory per se is e attributed to
a slowly developing frontal lobe system. This would fit in with what
the developmental scenario proposed above because the frontal lobe system
is the last to develop.
PDP
Given that the system is set up properly and the basic perceptual
aspects of the world are encoded how is new information stored? One
possiblility is that it is stored as a database with all the characteristics
of a given experience stored and linked together and each new experience
is separately cataloged. Under the database scenario information
should either be retrievable or not. While omission may be support
this view most observations of memory distortion (blending, etc) point
to another mode of storage. This other mode is referred to as a parallel
distributed network and is the result of a activity dependent changes in
connections between many cells in different systems.
Under this hypothesis characteristics of a given experience are stored
relative to prior knowledge and linked together with the prior experiences.
Hence if the prior knowledge is not very extensive new information will
be stored ina very minimalistic manner. Memories are then reconstructed
when they are retrieved. This mechanism for encoding and storing
information can be simulated on a computer. Output from networks
such as these demonstrate many of the phenomenon discussed in the Memory
Distortion book such as omission, blending, false beliefs, cryptomania.
These models employ biologically plausible networks and synaptic modification
rules that mimic those seen in studies of activity dependent synaptic plasticity.