understanding the brain: a work in progress
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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 - PowerPoint PPT PresentationTRANSCRIPT
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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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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B
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DABC
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
NL=0.002L= 0.0035
NL=0.0001L= 0.00055
Theta ↑Gamma ↓
Gamma ↑Theta ↓
Decreased synchronization as theta/gamma ratio increases
Downstream neuron
Model IT
Excitatoryneurons
Synch(1) De-synch
(2)
Downstreamneuron
Output
(1) (2)
How desynchronization alone can produce potentiation
Excitatoryneurons
Synch(1) De-synch
(2)
Downstreamneuron
Output
(1) (2)
How desynchronization alone can produce potentiation
Excitatoryneurons
Synch(1) De-synch
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Downstreamneuron
Output
(1) (2)
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