**Brain Dynamics and Plastic Deformation of Self Circuitries in the Dementia Patient Circuitries in the Dementia Patient**

**Brain Dynamics and Plastic Deformation of Self** 

DOI: 10.5772/intechopen.71054

Denis Larrivee Denis Larrivee Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.71054

#### **Abstract**

Despite improved medical care that has resulted in greatly extended life expectancies, significant increases in numbers of individuals suffering age related cognitive defects is expected, making the improved understanding of normal and pathological aging an important priority. Current studies indicating that brain activity requires a dynamical architecture to preserve functional order in the face of persistent and extraneous activity suggests that cognitive impairments are likely to be closely linked to dysfunctional dynamical activity of brain systems. Cognitive impairments such as those introduced by Alzheimer's dementia (AD), that affect fundamental operational constructs like the self, are thus likely to implicate global dynamics that oversee whole brain operation. This paper explores plastic events associated with dynamical elements used in the normal construction of the self percept and the etiology of their deconstruction in the course of AD. It is proposed that the evolution of the disease involves the increasing impairment of a global dynamical operation that is normally engaged in forming a stable and coherent self image needed to flexibly engage task related, motor plans and effectors.

**Keywords:** brain dynamics, Alzheimer's dementia, dynamic neural fields, attractors, self circuits, oscillations

### **1. Introduction: the dynamical self and Alzheimer's dementia**

United Nations' estimates project that by 2050 20% of the world's population will be nearly 60 or more years of age, with considerably higher percentages in developed nations [1]. Despite improved medical care resulting in greatly extended life expectancies, significant increases in numbers of those suffering age related cognitive defects, including various dementias, is expected. This reality makes the improved understanding of normal and pathological aging an important priority. Among the most promising avenues to such

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

understanding today are studies related to brain dynamical systems and globally operant phenomena, including self awareness and consciousness. Significantly, and unlike the activity of peripheral sensory and motoric neural processes, brain activity is ongoing and not intermittent, dynamically sustaining a wide variety of metastable and plastic states, including such perceptual phenomena as the self that are progressively impaired in dementias. Changes in brain dynamics, therefore, are clearly evoked during the evolution of these pathologies.

This self percept is usually taken in its subjective sense, yet the elements that contribute to the percept are objective features closely related to the neural architecture that underlies its

Brain Dynamics and Plastic Deformation of Self Circuitries in the Dementia Patient

http://dx.doi.org/10.5772/intechopen.71054

107

The present chapter will adopt a perspective of the self that is dynamical and interactivist, that is, an operational perspective of how the individual autonomously engages the exterior world [5, 6]. It will consider the self's role in initiating and structuring the actions that the individual carries out as it negociates a variable environment, that is, its interactive dimension, that will be termed here the performative self. There are several reasons for adopting this conception, that, while not covering the rich depth of understanding that is associated with the concept of the self [4, 6], are yet likely to be both valid and useful in the context of its contribution to understanding the etiology and evolution of dementias. First, it offers a tractable construct that possesses conceptual clarity vis-à-vis its behavioral and neural expression. The self is here understood to be that individual representation that acts to secure the vital dimensions needed for viability. Second, the neural and biological foundation of this conception of the self is increasingly well understood and likely to shed light on events that are abnormal, such as cognitive diseases like Alzheimer's dementia (AD). Current evidence, for example, indicates that the self is associated with the whole of the individual, that is, it is a totality whose origin and association is linked to the entire corpus, and not restricted to an isolated domain of representation lying within the brain [7], one that is the product of the progressive integration of regionally distributed, somatotopic afferent input. Significantly, this perceptual image appears to be invested with protagonist features and to assist in the construction of an intentional image used for counterfactual affordances [8]; in other words, this 3-D body image of the self enables the individual to

'situate and to conceive of himself' in different goal-directed planning trajectories.

neural processes, and is needed for unitary, goal-directed activity.

**2.1. Neuroplastic mechanisms in dynamical systems representations**

There is good evidence to suggest, moreover, that the body image is the neural product of dynamical systems mechanisms that serve as its operational basis. Among other findings, for example, limb positions for navigation are topologically mapped [9] as are the external trajectories navigated, where they are linked to environmental cues later recalled to guide movement in association with exploration. The neurophysiological basis of such memories appears to involve dynamical systems processes that encapsulate the memories in energetically stable activity zones, such as Hopfield attractors [10]. Taken together, the performative self appears to be a construct that represents the whole individual bodily, engages dynamical

This performative model thus affords a physically defined and physiologically relevant neural terrain encompassing global brain and body operation that can be explored in terms of an ongoing etiological progression. In the next sections, I will consider underlying mechanisms of normal plastic changes involving dynamical system operation related to the self and then subsequently consider how these are likely to be affected by the progression of the disease.

The operational perspective of the self adopted here is situated by the need to sustain a continuous stream of neural activity. Constituted as a goal directed and autonomous entity

subjective expression.

Although promising, brain dynamical studies have yet to find a role in studies of self representation and its loss with pathological progression. This is especially pertinent since there is the increasing realization that self circuitries underlie global phenomena that are key to individual performance. Accordingly, this chapter will consider three themes that are intended to illustrate how the loss of self representation is related to plastic changes in brain system dynamics. The first theme will build upon the traditional linkage that has been forged between brain activity and its modulation by neuroplastic events underlying its physiological expression, Donald Hebb's oft-quoted rule, what fires together wires together [2]. Expanding on this foundation it will explore how connectivity changes modulate the stability of energetically favored resonances, for example, attractors, that are naturally exploited as operational motifs of larger scale networks [3] and how these are used to build a three-dimensional self image. The second will evidence how the regulation of motif stability assists the generation of self representations, particularly during development as sensorial, somatotopic input progressively shapes the brain, creating the self percept for mature interactivity with the world. The third will contextualize pathological distortions as loss of function etiologies that can be modeled by a change of system dynamics, evidenced in the loss of function of global dynamical systems underlying construction of the self image.

The outcome of this exploration will be the creation of a portrait of brain dynamics that both reciprocally and iteratively relates brain dynamics to the evolution of self representation in dementias. It will assist in clarifying the relationships between neuroplastic mechanisms of connectivity, their modulation of brain dynamical elements that create spatial representations of the embodied self, and distortions in regulating this representation as dementias increasingly impact global operation.
