Brain Rhythms: key questions
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Coordination of processing across space

Coherence in perception, e.g. synchrony & binding,
cognitive moment, causation/objects.
 Large-scale systems, e.g. asynchronous pulsed VLSI
 Dynamic connection of sub-processors, e.g. synchrony
between brain regions (perception, memory retrieval)?

Coordination of processing across time
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Clocking/chunking time for perception & memory
Organising/storing order of segments
Using phase within clock cycles, e.g. phase coding in
olfactory bulb and hippocampus.
Brain Rhythms: key questions

Combining temporal and rate codes
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Rhythms part of ‘Rosetta stone’ of neural code?
Temporal augments rate, e.g. coordination in space & time
Temporal and rate parallel & independent (immense
power, harder to coordinate?), e.g. hpc phase code for
location, rate code for speed, trajectory, objects.
Learning/adaption

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Find equivalent to rate-learning by synaptic modification,
e.g. experience-dependent modification of frequencies or
dynamics (olfactory cortex?).
Interaction with synaptic modification – rate and temporal
pattern dependence: parallel or interacting use of same
synapses?
Hard / software analogues/ implementation.
Brain Rhythms: key questions

Are rhythms themselves important?
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Important indicator/side-effect of basic mechanisms
BUT not causal themselves.
Computational models important & we do have direct
effects of synch./oscillations to neural firing, transmission,
synaptic modification. These can be causal.
V. important to investigate the BEHAVIOURAL/cognitive
problems and the NEURAL mechanisms involved.
Technological advance in large-scale single-unit recording
at least as important as advances in monitoring
oscillations.
Brain Rhythms: key questions

Useful analogies for artificial systems?

We can use time-stamps and global clocks already –
perhaps this motivates synchrony of rhythms in diverse
areas: phase coding in brain provides efficient time-stamp
if common rhythm is present.

Availability of massive memory and processing
capability/ coordination of large-scale connected
systems (inc WWW), excitable media might
require creative brain-inspired solutions.
Brain Rhythms: prospects

Recent progress/new questions in both
neuroscience re. use of rhythms and temporal
processing, possibly needed in future hard/software .

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Links between synapses, single units, EEG & BOLD with
behavior; availability of massive memory and processing
capability/ coordination of large-scale connected systems
(inc WWW).
Novelty of field and wide potential implications =>
examples from biology might be useful to CS, while CS
examples and analysis useful for functional interpretation
of neuroscience.
But don’t forget the neural mechanisms.
Dual rate and
phase coding
by place cells.
Phase relative
to EEG theta
codes for
position within
field (O’Keefe &
Recce, 1993)
Independence of phase
and rate
Huxter, Burgess, O’Keefe,
Nature in press
Phase precession occurs
on low and high rate runs
and in low and high rate
cells, across low and high
rate sections of place field
Firing rate codes for
running speed (+trajectory,
odors, reinforced stimuli)
Hirase et al, Wood et al, Frank
et al, Blair et al
A weak correlation of phase with rate arises from strong
correln of phase with position & rate dependence on position
phase
rate
x
phase
x
rate
Rate of phase precession adjusts to
length of field
Amount and rate of phase precession does not correlate
with field skew (r=0.13, p=0.23; r=0.09, p=0.44, n=94).