Editing Memory-prediction framework (section)

== Neurophysiological implementation ==

The hierarchies described above are theorized to occur primarily in mammalian neocortex. In particular, neocortex is assumed to consist of a large number of [[cortical column|columns]] (as surmised also by [[Vernon Benjamin Mountcastle]] from anatomical and theoretical considerations). Each column is attuned to a particular feature at a given level in a hierarchy. It receives bottom-up inputs from lower levels, and top-down inputs from higher levels. (Other columns at the same level also feed into a given column, and serve mostly to inhibit the activation exclusive representations.) When an input is recognized – that is, acceptable agreement is obtained between the bottom-up and top-down sources – a column generates outputs which in turn propagate to both lower and higher levels.

=== Cortex ===
These processes map well to specific layers within mammalian cortex. (The cortical layers should not be confused with different levels of the processing hierarchy: all the layers in a single column participate as one element in a single hierarchical level). Bottom-up input arrives at layer 4 (L4), whence it propagates to L2 and L3 for recognition of the invariant content. Top-down activation arrives to L2 and L3 via L1 (the mostly axonal layer that distributes activation locally across columns). L2 and L3 compare bottom up and top-down information, and generate either the invariant 'names' when sufficient match is achieved, or the more variable signals that occur when this fails. These signals are propagated up the hierarchy (via L5) and also down the hierarchy (via L6 and L1).

=== Thalamus ===
To account for storage and recognition of ''sequences'' of patterns, a combination of two processes is suggested. The nonspecific [[thalamus]] acts as a 'delay line' – that is, L5 activates this brain area, which re-activates L1 after a slight delay. Thus, the output of one column generates L1 activity, which will coincide with the input to a column which is temporally subsequent within a sequence. This time ordering operates in conjunction with the higher-level identification of the sequence, which does not change in time; hence, activation of the sequence representation causes the lower-level components to be predicted one after the other. (Besides this role in sequencing, the thalamus is also active as sensory [[Layover|waystation]] – these roles apparently involve distinct regions of this anatomically non-uniform structure.)

=== Hippocampus ===
Another anatomically diverse brain structure which is hypothesized to play an important role in hierarchical cognition is the [[hippocampus]]. It is well known that damage to both hippocampi impairs the formation of long-term [[Explicit memory|declarative memory]]; individuals with such damage are unable to form new memories of episodic nature, although they can recall earlier memories without difficulties and can also learn new skills. In the current theory, the hippocampi are thought of as the top level of the cortical hierarchy; they are specialized to retain memories of events that propagate all the way to the top. As such events fit into predictable patterns, they become memorizable at lower levels in the hierarchy. (Such movement of memories down the hierarchy is, incidentally, a general prediction of the theory.) Thus, the hippocampi continually memorize 'unexpected' events (that is, those not predicted at lower levels); if they are damaged, the entire process of memorization through the hierarchy is compromised.
{{Further|place cell}}
{{Further|Papez circuit}}

In 2016 Hawkins hypothesized that [[cortical column]]s did not just capture a sensation, but also the relative location of that sensation, in three dimensions rather than two (''situated capture''), in relation to what was around it.<ref name="cadeMetz15October2018">{{cite news |url=https://www.nytimes.com/2018/10/14/technology/jeff-hawkins-brain-research.html |first=Cade |last=Metz |newspaper=[[The New York Times]] |date=October 15, 2018 |title=A new view of how we think |pages=B1, B4}} See: 'Clarity Over a Coffee Cup'</ref> "When the brain builds a model of the world, everything has a location relative to everything else" <ref name=cadeMetz15October2018 /> —Jeff Hawkins.

Some neuroscience research with animals supports the idea that the hippocampus integrates new information with existing memories to form predictive models. This process enables more efficient problem-solving and adaptation to new tasks.<ref>{{Cite journal |last1=Miller |first1=Adam M. P. |last2=Jacob |first2=Alex D. |last3=Ramsaran |first3=Adam I. |last4=De Snoo |first4=Mitchell L. |last5=Josselyn |first5=Sheena A. |last6=Frankland |first6=Paul W. |date=2023-06-21 |title=Emergence of a predictive model in the hippocampus |journal=Neuron |volume=111 |issue=12 |pages=1952–1965.e5 |doi=10.1016/j.neuron.2023.03.011 |pmid=37015224 |issn=0896-6273|pmc=10293047 }}</ref><ref>{{Cite journal |last1=Tse |first1=Dorothy |last2=Langston |first2=Rosamund F. |last3=Kakeyama |first3=Masaki |last4=Bethus |first4=Ingrid |last5=Spooner |first5=Patrick A. |last6=Wood |first6=Emma R. |last7=Witter |first7=Menno P. |last8=Morris |first8=Richard G. M. |date=2007-04-06 |title=Schemas and memory consolidation |url=https://pubmed.ncbi.nlm.nih.gov/17412951/ |journal=Science |volume=316 |issue=5821 |pages=76–82 |doi=10.1126/science.1135935 |issn=1095-9203 |pmid=17412951}}</ref>