understanding the brain: a work in progress. the brain performs an incredible range of functions...

Understanding the brain: a work in progress

The brain performs an incredible range of functions

• Controls body functions and motivates us to obtain appropriate resources to maintain life

• Movement• Detect and interpret sensory information and

social cues• Attend to specific things rather than others• Learn and remember information and integrate it

with past knowledge• Guide behaviour through emotional responses • Generate conscious awareness of the external

environment, self and others

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High speed supercomputers 2000-2010• 2000 IBM ASCI White 7.226 TFLOPS

DoE-Lawrence Livermore National Laboratory USA • 2002 NEC Earth Simulator 35.86 TFLOPS

Earth Simulator Center, Japan • 2004 IBM Blue Gene/L 70.72 TFLOPS DoE/IBM • 2005 136.8 TFLOPS DoE/U.S. National Nuclear

Security, Lawrence Livermore National Laboratory 280.6 TFLOPS

• 2007/8 478.2 TFLOPS IBM Roadrunner 1.026 PFLOPS DoE-Los Alamos National Laboratory 1.105 PFLOPS

• 2009 Cray Jaguar 1.759 PFLOPS DoE-Oak Ridge National Laboratory, USA

IBM Sequoia Supercomputer

20 PFLOPS speed1.6 PFLOPS memory318m296 racks7megawatts

Neurons

Neuroglial cellsAstrocytes - anchor neurons to blood vessels and transport of nutrients/ waste. Have receptors, produce growth factors and modulate synaptic transmission. Signal to one another via gap junctions using calcium. Microglia - defence against pathogens and monitor the condition of neurons. Ependymal cells - line the fluid-filled cavities in brain and spinal cord. Produce, transport, and circulate the cerebrospinal fluid. Oligodendrocytes- produce the myelin sheath in the CNS which insulates and protects axons.

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2009ProteinLounge.com 2009ProteinLounge.com

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The molecular brain!

Major subdivisions of the brain

Reticular activating system

Neural plasticityNeural plasticity

Learning – turning the gain up and the noise down

Imitating the actions of others (mirror neurons)

Control Autistic

How is information represented in the brain?

Advantages/disadvantages of spatial encoding

pre-stimulus during stimulus

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Correlation and pattern changes

Advantages and disadvantages of temporal encoding

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Combined spatial and temporal encoding

•Most robust solution, allowing brains to be a reasonable size

•Makes it easier to both separate, integrate and decode information

The Sensory Brain

Sensory maps - vision

Sensory maps - hearing

Somatosensory and motor maps

The somatosensory homunculus

Integration of sensory information

• Multisensory brain areas• One sense can influence interpretation of

another one (see a mouth shape the word “bait” and hear the word “gate”, you think you hear “date”) – McGurk Illusion

• Facial expressions, even if not consciously perceived, modify the perception of emotion in the voice of the speaker

The brain as an interpreter

Illusions

Synaesthesia

Synaesthesia

Synaesthesia

Synaesthesia

We may all start offexperiencing the world through synaesthesia

Neural encoding of faces

"Who are you?", "how do you feel?"

"do i like you"?” Answers in <300

milliseconds!

Face processing in the brain

Face processing in the brain

Single cell vs population encoding

Quian-Quiroga et al (2005) Nature

Andrews et alJ Neurosci (2010)

The brain as an interpreter

Encoding face identity and face emotion cues simultaneously

Operant discrimination between different faces

Face discrimination learning

Brain rhythms and face recognition learning

30-120Hz

4-8Hz

Coupling between fast and slow oscillations (theta and gamma)

Phase locking between IT neuronal activity and theta

>75% of IT electrodes show coupling between theta phase and gamma amplitude

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Correlations between discriminationperformance and altered theta/gamma activity

Neural network models

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Decreased synchronization as theta/gamma ratio increases

Downstream neuron

Model IT

Excitatoryneurons

Synch(1) De-synch

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Output

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How desynchronization alone can produce potentiation

Excitatoryneurons

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Output

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How desynchronization alone can produce potentiation

Excitatoryneurons

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How desynchronization alone can produce potentiationDecorrelation reduces noise

Decorrelation improves discriminability of patterns

The problems of consciousness

• There is no single seat of consciousness in the brain

• Many things are processed without conscious awareness

• Often similar patterns of brain activation are seen when information is processed with or without conscious awareness

• There are different levels of consciousness• Individuals may be aware even when they show

no obvious signs of consciousness

Spatial imagery Motor imagery

Assessing conscious awareness in “vegetative state” brain damaged patients

Study found 10% of vegetative state patients could perform motor/spatial imagery tasks

Monti et al (2010)New Eng J Med

Using brain imaging to enable vegetative state patients to communicate

Monti et al(2010)New Eng J Med

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Alkire et al (2008) Science

Effects of anaesthesia and sleep on cortical integration

Reduced unidirectional information flow and long distance connections, and increased short-loop feedback

Effects of deep anaesthesia on cortical processing

How does consciousness emerge?

• Perhaps widespread and integrated flow of activity in the neocortex generates a metarepresentation.

• When information is processed unconsciously a metarepresentation does not form due to lack of integrated flow between cortical processing nodes.

Establishing functional connections in the brain using Granger causality

Future progress

• Stronger links between mathematicians, computer scientists and neuroscientists

• A greater emphasis on revealing key functional connectivity changes in the brain

• Provide a better understanding of temporal/patterning aspects of neural encoding

• Further advances in technologies for measuring the activity of the working brain