Transcript Biological Cybernetics

Biological Cybernetics
By: Jay Barra
Sean Cain
Biological Cybernetics
• An interdisciplinary medium for
experimental, theoretical and applicationoriented aspects of information processing
in organisms.
• Sensory, motor, cognitive, and ecological
phenomena
• Experimental studies of biological systems
Biological Cybernetics
• Topics Covered:
• Experimental studies of biological systems
• Quantitative modeling
• Computational, technical, or theoretical studies
• Understanding biological information processing
• Artificial implementation of biological information
processing and self-organizing principles
Biological Cybernetics
• Performance and Function of systems:
• Communication between life sciences and
technical or theoretical disciplines
• Neural Interactions a specific interest
Coupled Van der Pol Oscillators - A model of
excitatory and inhibitory neural interactions
• Relate basic neural activities on the cellular level to:
• The various observed electroencephalograms (EEG)
• Potential differences in the cortex
• Interactions between and within excitatory and inhibitory
neurons
• Modeled by Wilson and Cowan
• EEG phenomena studied in relation to such models
• Simple models explaining the rhythmicity of the EEG
• Based on Wilson and Cowan model
• A feedback loop through a third set of neurons – Lopes da Silva et al.
• Positive and negative feedback loops with two excitatory and one inhibitory
subsets of neurons – Zetterberg et al.
Coupled Van der Pol Oscillators
• Van der Pol Oscillators:
• Mutually coupled relaxation oscillators
• Done as a mathematical model for the electrical activity of the human
and animal gastro-intestinal tract
• Reasonable to model EEG phenomena by a number of coupled
oscillators
• Distribution of entrained oscillator frequencies can show the peakdip shape of the EEG
• Phenomenological mathematical models:
• Explain EEG data
• Offer a guide for experiments on the EEG
Biological Systems
• Biological clocks consist of:
• A group of interacting oscillators.
• Circadian rhythms, biochemical oscillators,
pacemaker neurons, etc.
• May be related to biological oscillators
• Interesting subject in biological systems:
• The entrainment of oscillators under periodic forces
• The entrainment of a number of interacting oscillators
Biological Systems
• Apart from biological systems
• Nonlinear circuit theory
• Can be combined with biological systems for a better
understanding of EEG phenomena
• Relation of physiological parameters to the coefficients in the
circuits
Study Conclusions
• Hope to further the understanding of very
generalized cortex-like tissue in
conjunction with the EEG phenomena
System-Theoretical Analysis of the
Clare Bishop Area (CBA) in the Cat
• Clare Bishop Area:
• Retinotypically organized cortical area of the
cat brain
• Connected to a great variety of visual areas in
a very complex way
Experimental Analysis
• Difficult because:
• The greater the distance from the retina, the more
specific the signal combinations necessary to analyze
the system become
• Feedback loops cannot be opened, unequivocal
identification of CBA cell properties is impossible
• Nonlinear character has a great influence on signal
processing
Experimental Analysis
• Circumvent Difficulties:
• Specific signal combinations have been developed,
being restricted to:
• Deterministic and stochastic signals
• Determination of a number of cell properties
• Hypotheses on the function of the CBA are
tested
Conclusions
• Only moving stimuli produce responses
• Reaction of Cells:
• Direction specific
• Prefer the extrafoveal direction
• Systems existent in the CBA:
• Have different behavior for:
• Space
• Time
• Amplitude
Study Conclusions
• CBA primary task:
• Orientation
• Exact localization of objects independent of
velocity
• Treatment of objects in relation to background
stimuli
Cybernetics of Limb Movement
• Determine stresses on joints during motion
• Neural planing involved in mapping spatial
planning to move joint to new position
• Example, hand reaches for an apple
• Hand is the extension, upper arm and fore arm
movements are automtically mapped
Computations in controlling
movement
• Joint Torque
• Masses of individual segments
• Effects of gravity and momentum
Conclusions
• Normal straight line motion of joints
involves
– Compensation for dynamic interaction at each
joint segment
Information Content of Texture
Gradients
• Information gradients determine
responses in stimuli sensory systems
– Hairs on the back of the hand
• Touching one hair may not be felt, touching three
will
Visual gradients
• Non-linear
distribution gives
interpretation of
horizons in a 2D
image
– This is why
perspective works
in drawings
Visual Gradients
Clear Horizon
Horizon diminishes
Thresholds for activation
•
•
•
•
Affected by regularity of the information
gradient
Global Uniformity
Shape containing the pattern
Foreshortening (perspective)
Pattern types
•
Locally regular and globally uniform
–
•
Locally regular but globally varying
–
•
Waves on a lake
Locally irregular but globally uniform
–
•
Field of flowers, cars in parking lot
Field of rocks, boulders and pebbles
Locally irregular and globally varying
Works Cited
•
System-Theoretical Analysis of the Clare Bishop Area in the Cat. Jensen
H.J. Springer-Verlag Biological Cybernetics 39 53-66 (1980).
•
Coupled Van der Pol Oscillators – A model of Excitatory and Inhibitory
Neural Interactions. Kawahara, Takuji. Springer-Verlag. Biological
Cybernetics 39, 37-43 (1980).
•
Dynamic Interactions between Limb Segments During Planar Arm
Movement, S. Kemmerling, D. Varju, Biological Cybernetics 44 67-77
(1982)
•
The Information Content of Texture Gradients, Steven, Kent, Biological
Cybernetics 42 95-105(1981)