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COECOE 出張報告 2006年12月出張報告 2006年12月14日14日
Tutorials – December 4, 2006Conference Sessions – December 4-7, 2006Hyatt Regency, Vancouver, B.C., Canada
Workshops – December 8-9, 2006Westin and Hilton, Whistler, B.C., Canada
Neural Information Processing Systems 2006
物理学第一教室 非線形動力学研究室 島崎 秀昭
参加者数参加者数 約1000人約1000人発表件数発表件数 204件204件
論文投稿 833件
Peer Review (Double blind)2~4 人の レビューアーによる採点 10点満点4人による採点
合否 204件が受理 ポスター発表
63件が口頭発表(講演 20 分 / スポットライト2分)
NIPS*0NIPS*066
HistogramHistogram
The duration for eruptions of the Old Faithful geyser in Yellowstone National Park (in minutes)
Bin widthBin width
2ˆMISE t t dt Histogram
Underlying Rate
2
2( )n
k vC
Optimizing a time-Optimizing a time-histogramhistogram
Unknown
MethodsMethods
1
1,
N
ii
k kN
2
1
1( )
N
ii
v k kN
2
2( )
( )n
k vC
n
Calculate the mean and variance of the number of spikes.
Compute the cost function
Repeat i through iii while changing the bin size Δ. Find Δ* that minimize the cost function.
Divide spike sequences with length T [s] into N bins of width Δ.
Method: Selection of the Bin SizeMethod: Selection of the Bin Size(i)
(ii)
(iii)
(iv)
Data : Britten et al. (2004) neural signal archive
Rate modulation of an MT Rate modulation of an MT neuronneuron
2
1 1( )m n
kC n C
m n n
Extrapolation
Too few to make
a Histogram !
Estimation: At least 12 trials are
required.
Optimized Histogram
How many trials are required to make a How many trials are required to make a Histogram?Histogram?
Required # of sequences (Estimation)
Extrapolated:
Finite optimal bin size
Original: Optimal bin size diverges
Optimal bin size v.s. m
# of sequences used
2
1 1( )m n
kC n C
m n n
( )nC
Required # of trials
2
1 2 1 22 0 0
1
nC n
t t dt dtn
2 31 1( ) 0 0 0 ( )
3 12nC On
(i) Expansion of the cost function by :
1 3
6~
0 n
2
2
1 1~ | |
1 1 1 1
n
c
C t dt t t dtn
un n
1cn t dt
(ii) Expansion of the cost function by 1/
Critical number of trials:
The second order phase transition.
Scaling of the optimal bin size:
Theoretical cost function:Theoretical cost function:
The mean and correlation function of the underlying rate is known.
See also Koyama, S. and Shinomoto, S. J. Phys. A, 37(29):7255–7265. 2004
ReferenceReference
A Method for Selecting the Bin Size of a Time Histogram
Hideaki Shimazaki and Shigeru ShinomotoNeural Computation in Press
島崎秀昭 学位論文 @ 4階図書室
•http://www.ton.scphys.kyoto-u.ac.jp/~hideaki/
Time-Varying Rate
Spike Sequences
Time Histogram
The spike count in the bin obeys the Poisson distribution*:
A histogram bar-height is an estimator of :
The mean underlying rate in an interval [0, ]:
0
1t dt
( )
k
nnp k n e
k
ˆ k
n
*When the spikes are obtained by repeating an independent trial, the accumulated data obeys the Poisson point process due to a general limit theorem.
TheoryTheory
22
0
1ˆMISE ( ) .tE dt
2 2
0 0
1 1ˆ ˆMISE ( ) ( )T
t t n tE dt dtE
T
Expectation by the Poisson statistics, given the rate.
2 22
0 0
1 1t tdt dt
Variance of the rate Variance of
an ideal histogram
Decomposition of the Systematic Error
Systematic ErrorSampling Error
Average over segmented bins.
Independent of
Method I. Selection of the Bin SizeMethod I. Selection of the Bin Size
2
0
22
1( ) MISE
ˆ( )
T
n t
n
C dtT
E
22ˆ ˆ ˆ2n n n nC E E E
22 ˆ ˆ ˆn n n nC E E E
n
Variance of a Histogram
2 22ˆ ˆ ˆ( ) .n n nE E E
2 1ˆ ˆ( )n nE En
Introduction of the cost function:
The variance decomposition:
Mean of a Histogram
The Poisson statistics obeys:
Unknown: Variance of ideal histogramSampling error
Variance of a histogram Sampling error