A Non Linear Model to explain persons with Stroke

K Hari ohmProfessor in PT

MSAJ college of PTThe Indian Centre for Evidence Based Neuro-

Rehabilitation

Introduction

• Humans like many natural systems are complex

• How do we commonly study complex systems

Reductionism • Reductionism - understanding the

nature of complex things by reducing them to simpler or more fundamental things

• Philosophical position that a complex system is the sum of its parts, and that an account of it can be reduced to accounts of individual constituents

• Reductionism is the belief that human behavior can be explained by breaking it down into smaller component parts. Reductionism and Holism in Psychology by Saul McLeod

What is linearity

• Linearity• Linear systems satisfy the

properties of superposition and homogeneity.

• Add them up• Starting state- predictability of

complex system• Point to point relation

Applying reductionism in understanding and managing stroke

Why is not my patient walking?

Impairments

•Spasticity

•weakness

Disability

•Inability to walk

•unable to eat

handicap

•Unable to go to work

•Unable to go to marriage

WHAT IS THE DIFFERENCE BETWEEN A PATIENT WHO HAS LEARNED TO WALK AND WHO HAS NOT?

Paraphrasing Esther Thelen question

•IS BIOLOGICAL FACTORS ENOUGH ?•CAN HUMAN SYSTEM BE SUBJECTED TO REDUCTIONISM ?

Paradigm shift

x1 = x + rx

(1 —

x)

• Will be true if it is a Simple system or Static

1. Human systems are dynamic and complex2. Variable

Understanding variations

• In human biology – variation is normality

• Behavioural variability• Movement variability – Throw darts- for example, we are unable to hit the

‘bull’s eye’ on every attempt. – When we walk, our footprints never repeat

themselves exactly.– When we stand quietly, we continuously sway around

a central equilibrium point without ever remaining exactly still

Example of Increased Stride Time Variability in Elderly Fallers

Quantification of Stride-to-Stride Fluctuations

Time (min) Time (min)

Variability or noise• James Clerk Maxwell (1879), Henri Poincare

(1912), Edward Lorenz 1961

Non linearity

• This paradigm has no single name but has been described in terms of

1. Chaos2. Nonlinear dynamics (sometimes called

nonlinear dynamical systems theory), 3. Complexity theory 4. Self-organization. Scott Barton January 1994 • American Psychologist

Chaos, Self-Organization, and Psychology

What is Non linearity ?

• “Nonlinear dynamics,” can be defined as a system whose output is not proportional to its input.

• Nonlinear systems are more complex

Nonlinear

• Nonlinear equations are not additive; therefore, they are often difficult to solve.

• Sometimes a single solution can be obtained, but often the answer involves a pattern of solutions.

• Nonlinear systems tend to settle down over time.

x1 = x + rx (1

—x)

• Human beings are nonlinear because a small change in input can lead to a huge and unpredictable change in output.

• A minor change in initial conditions may lead to a significant, abrupt change of behavior

Some properties of non-linear dynamic systems are:

• They do not follow the principle of superposition (linearity and homogeneity)

• Timing and form of such changes are not fully predictable due to the complexity of the system

• They may have multiple isolated equilibrium points (linear systems can have only one)

• They may exhibit properties such as bifurcation, chaos, self organization emergence etc.

COMPLEX SYSTEM

Complex system

• Fundamentally a system is complex, if its behavior cannot be easily described.

• System consists of many components,

• Numerous relationships and interactions between these components.

• This is a nonlinear system because the input does not lead to a linear change in output.

Balance control in hemiparetic stroke patients: Main tools for evaluation Clarissa Barros de Oliveira et al J Rehabil Res Dev. 2008;45(8):1215-26.

Non linearity

• One of the fundamental principles of complex systems is non linearity

• Complex systems are dynamical systems they change over time

• Difficult to determine the boundaries of a complex system

• interdependence of variables in a nonlinear system, along with sensitivity to initial conditions, lead to the implication that studying each factor in isolation may not lead to useful knowledge about the behavior of the system as a whole

IMPLICATION FOR STROKE MANAGEMENT

Model of a person with stroke in non linear complex system

From Stroke rehabilitation : a functional activity based approach K Hari ohm R Vasanthan

Implication for stroke management

• Non linear systems are hard to solve– They cannot be broken into parts