Are worms more complex than humans?

Rodrigo Quian Quiroga

Sloan-Swartz Center for Theoretical Neurobiology.

Caltech

Complexity measures

• Shannon information (entropy)

• Algorithmic complexity (length of the shortest code). Logical deep (time taken by the shortest code)

• Correlation dimension (topologic dimension of an attractor). Kolmogorov entropy.

• Neural Complexity (functional clustering)

Is it complex?

3 1 4 1 5 9 2 6 5 3 …

X1( 1 ) = 0.1

X2( 1 ) = 0.3

DO I = 1, N

X1(I+1) = 1.4 - X1(I)**2 + 0.3 * X2(I)

X2(I+1) = X1(I)

END DO

X1(I)

I

Claims:

1. There is no unique measure of complexity.

Amplitude distributions

Amplitude Amplitude

Which one is more complex?

Data points Data points

Frequency Frequency

Power spectraPhase space reconstruction

Which one is more complex?

Data points Data points

Amplitude distribution

Amplitudes AmplitudesFrequency Frequency

Power spectraPhase space reconstruction

Claims:

1. There is no unique measure of complexity.

2. Complexity depends on how we measure and represent the data.

Which one is more complex?

Complexity

Disorder

Adapted from P. Grassberger, ‘89

Claims:

1. There is no unique measure of complexity.

2. Complexity depends on how we measure and represent the data.

3. Complexity is low both for order and randomness.

Which one is more complex?

Complexity

Disorder

V1 V4

V3

T ~ < V >

V1

V2

Classical mechanics

Classical mechanics

Statistical mechanics

Tossing a coin

Claims:

1. There is no unique measure of complexity.

2. Complexity depends on how we measure and represent the data.

3. Complexity is low both for order and randomness.

But randomness is relative!(it depends on measurements, analysis

tools, computer power, etc.)

Complexity of the brain

Images from D. van Essen’s lab

Complexity of the brain

Oztia! The brain is simple, Just half a kilo of matter.

• Complexity Evolution

• Complexity Behavior

• Complexity Consciousness

Complexity of the brainGoogle: 374000 hits

Can we measure this from brain data?

Complexity and consciousness

Complexity

Disorder

Seizure EEG

Normal EEG

Complexity and consciousness

Quian Quiroga et al, 2001

Claims:

1. There is no unique measure of complexity.

2. Complexity depends on how we measure and represent the data.

3. Complexity is low both for order and randomness. (?!?!?!)

4. Is it useful?

30 sec EEG 30 sec EEG

Frequency (Hz) Frequency (Hz)

Complexity and Behavior

Awake Deep sleep

Thalamo-cortical networks

They generate sleep spindles and spike wave discharges

Adapted from M. Steriade’s work

Why worms can be more complex than humans?

• Ideally:– Background activity random (functional) conectivity

– Complex behavior activation of a complex network

• In practice:– A very complex network may look random, whereas a simpler

one may show high complexity.

– This depends on: measurement (# of neurons, noise, etc.), analysis tools, definition of complexity, etc.

Claims: (open for discussion)

1. There is no unique measure of complexity.

2. Complexity depends on how we measure and represent the data.

3. Complexity is low both for order and randomness. (?!?!?!)

4. Is it useful?

Which one is more complex?