Psych/Cogst 231

Lecture 6: narrative selves

— the narrative Self: the great unifier

— personal/episodic memory: the developmental angle

— the brain basis of personal memory (Merker, 2004)

— from personal memory to the narrative Self

— some implications

two "models" of the narrative self (Gallagher, 2000)

(a) Center of narrative gravity. In this model (Dennett, 1991), the self is defined as an abstract "center of narrative gravity," where the various stories told about the person, by himself and others, meet.

(b) An extended and more distributed model of the narrative self, less unified than the one proposed by Ricoeur, but importantly distinct from Dennett's model in that the self is not an abstract "center," but rather, an extended self which is decentered and distributed.

personal/episodic memory

The emergence of autobiographical memory in childhood.

Language specificity of autobiographical memory.

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phenomenal and narrative selves

The interaction [between "the (sensory) world" and "the (motivated) person"] yields the contents of awareness in the form of observer-centered personal experience with its motivational, hedonic and goal-related biases as its short-term ("on-line") result, and personal history in the form of the record of the fate of an individual's motivated acts in the world over time as its long term residue.

Merker (2004)

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Merker's case for seeing the cortex as a personal history device

Only mammals have the neo- or isocortex.

In mammals, body and brain size correlates with longevity.

The neocortex makes a disproportionately large contribution to brain size variance, without losing the relation to longevity.

The neocortex acts to decrease rate of external mortality over the lifespan.

A promising candidate for a mediating variable is lifelong, continuous, and cumulative storage of information in memory.

Information storage is "space occupying": neural tissue is consumed ("used up") in the process of storing information.
An information-storage perspective on cortical function might account for the observed correlations on fundamental grounds.

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the power of permanent memory

Lifelong cumulative memory can reduce the odds of external mortality in two principal ways:

1. Only permanent memory allows its possessor to retain information concerning things like who did what to whom months, years or decades ago. It is the only means for capitalizing on experience of statistically rare but exceptional or anomalous events and contingencies, situations which may not recur for years but memory for which may be highly advantageous.

2. Many global ("higher order", "deeper") statistical invariants of environmental contingencies, such as long-term patterns of fruiting succession across diverse species and locations of trees, can be extracted from experience only over the long run of many seasons/cycles/years. That is, the very acquisition of knowledge of such statistical features of the environment requires permanent and cumulative memory storage over the same time horizons.

Global statistical knowledge of the kind featured in (2) provides the interpretive framework for (1); the two forms of memory contents are two functional poles of a single form of cortical inductive knowledge which combines item specificity with classificatory generality.

To do so, memory must achieve global coherence: each content element should be related to every other via its place and significance in the stored experiential history. This is most readily accomplished by organizing memory contents contextually.

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cortical architecture for contextual embedding of memories

Cortical area connections are characterized by a "small world" property. By virtue of this elementary cortico-cortical connectivity alone, cortex exhibits a staggered global connectivity with obligatory contextual organization.

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making sense of the cortical anatomy

Connective relations of the cortical map system of the macaque, from Young (1995).

Cortical areas are represented as labelled points. The degree of anatomical connectedness between areas is represented by their proximity in the plane of the figure. Sensory domains occupy the lower part of the figure, while the frontolimbic domain is at the top. The visual system is on the left, the somatosensory-motor on the lower right, the auditory on the upper right. In the visual domain, connections of "dorsal stream" areas with auditory and somatosensory areas split the visual system into two subdomains. Note that in connective terms the frontal eye fields are grouped with the visual areas of posterior cortex despite their frontal anatomical placement. Reciprocal connections depicted in red.

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the globalizing consequences of inter-area connections

Individual cortical areas are two-dimensional topographic sheets and inter-areal projections tend to connect corresponding points in these topographies.

Through juxtaposition of corresponding points in their areal topographies, the areas will superpose in topographic register.

The net effect is a superposition of areas in a "map stack" whose axis runs orthogonal to the plane of superposition. Systematically extended to all connected areas this concept generates a single "neural solid" crowned by frontolimbic cortex and branching downwards into sensory domains (or modality "substreams").

Local convergence-divergence of connectivity ensures that points on maps higher in the sequence tend to subsume and to have broader functional scope than their congeners earlier in the sequence.

The "place systems" of the two-dimensional parameter spaces of individual cortical areas are connectively integrated into a global representational space. No two points have the same functional content and all points are coherently related by nested contextual subsumption.

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connective consolidation

The cortical map system as a pyramid-like "neural solid."

a: Simple "cortical hierarchy"; areas are represented by boxes, connections by lines.

b: Connections between three sample areas, indicating their topography.

c: Topographic superposition of areas in b through minimization of connection length. Convergence-divergence principle of functional connectivity indicated by cone.

d: The operation shown in b and c generalized to the entire cortical map system generates a "neural solid" with global pyramid architecture.

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counter-current computation

The basic assumption of the present proposal is that the accretion of personal history is directly dependent upon interaction between feedforward and feedback pathways, in two functionally linked ways.

First, interaction between the two currents establishes the neural conditions for conscious awareness (Lamme et al., 2000) as the sole functional "gate" through which information enters personal history.

Secondly, this same interaction between the two currents is needed to sustain levels of neural activity at a given cortical locus with sufficient intensity and over sufficient lengths of time to effect lasting excitability changes in cortical synapses required for the long-term storage of information in personal history. Only cortical loci activated by a sufficiently broad set of bi-directional afferents make a lasting addition to personal history. Convergence from this set of sources — the "connective context set" — ensures the contextual coherence of the storage process.

Ultimately these are only different aspects of one single function, viewed in terms of its antecendents and its consequences, respectively.

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functional partitioning of the representation space

The functional partitioning the "epistemic space" of the cortical solid into "compartments" by activity in the two streams of the countercurrent and their overlap.

In the "continuity condition" there are four such compartments, while the discontinuity condition adds a fifth in the form of information temporarily held in an "overflow buffer."

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the "overflow buffer"

A suitable "overflow buffer" is available in exactly the right place — the complex of structures included in the hippocampal formation at the high end of the neural solid.

Anatomically, it forms a "hinge" of the countercurrent system, as schematically illustrated on the next slide. Neocortical feedforward connections are converted to neocortical feedback connections through a connective loop traversing the parahippocampal and perirhinal cortices, the entorhinal cortex, dentate gyrus, CA fields, and subiculum back to the entorhinal cortex and the neocortex.

These connections put "old cortex" at the high end of a vastly larger neocortical pyramid structure. There its old memory function allows events in neocortex arriving on feedforward pathways to influence later neocortical events through return feedback pathways, provided they fall within the temporal limits of hippocampal formation memory.

The unique memory role of this graded storage buffer presumably derives from its position at the high end of the cortical pyramid, that is, at the most global level of contextual subsumption.

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the role of the hippocampus

The place of the hippocampal formation in relation to the laminar basis of the cortical countercurrent system.

CA: cornu ammonis, with fields CA3 and CA1 indicated by numerals.

DG: dentate gyrus;

Sub.: subiculum.

FF and FB: feedforward and feedback connections, respectively.

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Merker's summary

The meaning of a situation has no definition apart from the nature and purposes of the organism finding itself in that situation. Once the characteristics of the agent are given, scene interpretation translates into action plans. The world whose significance the brain is assessing is the arena on which the consequences of its interpretations and choices will be experienced. The countercurrent organization of cortex provides the means for "inserting" the personal subject-centered "viewpoint" into the structure of the world.

The origin of the feedforward current in sensory areas mapping current states of the world in high-resolution detail supplies the objective or veridical pole of this process ["the (sensory) world"], while frontolombic feedback with its motivational, state- and goal-related functions supplies the subjective or personal pole ["the (motivated) person"].

Their interaction brings the needs, motives, goals and purposes of the individual to bear on circumstances such as they exist in the world, and drives the reconciliation of these two domains in instances where they turn out to be discrepant or in conflict.

The interaction yields the contents of awareness in the form of observer-centered personal experience with its motivational, hedonic and goal-related biasses as its short-term result, and personal history in the form of the record of the fate of an individual's motivated acts in the world over time as its long term residue.

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