Elsevier

Neurocomputing

Volumes 52–54, June 2003, Pages 19-24
Neurocomputing

Detection of spike patterns using pattern filtering, with applications to sleep replay in birdsong

https://doi.org/10.1016/S0925-2312(02)00746-4Get rights and content

Abstract

Consolidation of memories during sleep may involve neuronal replay of daytime activity patterns. A precise replay phenomenon was observed in the song system nucleus RA. We developed statistical pattern filtering to investigate replay in HVc, where spiking activity is more variable. Long spike sequences during sleep were convolved with filters constructed from exemplar auditory spike sequences. Examining peaks in the filter responses, we found many examples of HVc spike trains with temporal patterns similar to the exemplars, confirming a replay phenomenon for HVc. Statistical pattern filtering has general utility for finding spike patterns when a referent pattern is known.

Introduction

In the zebra finch forebrain nucleus robustus archistriatalis (RA), neurons generate sequences of spike bursts during spontaneous sleep activity that exhibit similar temporal patterns as the pre-motor activity during singing and the auditory responses to song playback in the sleeping animal [2], [3]. This sleep replay phenomenon is hypothesized to play an important role in learning and memory consolidation of the birdsong system [2], [7], which gives rise to the question of whether and how other parts of the song system participate in replay during sleep. The forebrain nucleus HVc is a sensorimotor center of the birdsong system. It projects to RA, and is thought to play an important role in vocal learning, auditory input integration, and higher level motor command. State-dependent auditory responses have also been observed for the HVc [9], [10]. We thus investigated whether the replay phenomenon also occurs in spontaneous sleep activity of HVc.

Instead of searching for individual replayed spike bursts [2], our goal was to find burst sequences that have similar temporal patterns as pre-motor activity or auditory responses [6], [8]. This is challenging for two reasons. First, unlike pre-motor or auditory data, for sleep spontaneous neuronal data, there are no reliable observables to mark the occurrence of neuronal events of interest. Second, the neuronal activity in HVc has far more variability than RA activity.

Section snippets

Pattern filtering

We developed a statistical methodology using linear filtering to address the above difficulty. In general, let S be an exemplar train of spikes registered at s1<s2<⋯<sp, sk∈[0,σ]. Given a small number ε>0, fix two functions K(x) and B(x), with K(x)≠0 only for x∈(−ε,ε) and B(x)⩽0 for all x. The functions will be referred to as the “time window function” for a spike and the “background function”, respectively, and ε the “window size”. Define F on [0,σ] byF(x)=max1⩽k⩽pK(x−sk)ifx∈JS,B(x)otherwise,

The underlying statistical model

Pattern filtering is a likelihood ratio test, as opposed to likelihood test in the unitary event analysis [4], [5]. To illustrate, consider the simplest filter constructed from the time window function K(x)≡α>0, x∈(−ε,ε), and the background function B(x)≡−β⩽0. Then (3) leads to R(x)=#{ti∈T∩[x,x+σ]:ti−x∈JS}×α−#{ti∈T∩[x,x+σ]:ti−x∉JS}×β. Because JS⊂[0,σ], the formula is simplified intoR(x)=#{ti∈T:ti−x∈JS}×α−#{ti∈T:ti−x∉JS}×β.

Detection using this filter is derived from three statistical

Results

We implemented pattern filtering for HVc single unit data recorded during sleep. For each unit, the spike sequences in response to the bird's own song (‘BOS’) broadcast to the sleeping bird in multiple trials were selected as templates. Then, in the subsequent spontaneous activity of the unit when no acoustical stimulus was presented, segments with similar temporal patterns as the templates were searched. For the neuronal activity in HVc, several types of variability have to be taken into

Zhiyi Chi entered Peking University, Beijing, China in 1989. He entered Brown University, Providence, Rhode Island in 1993. He received an Sc.M.from the Department of Mathematics the next year. In 1998, he graduated from the Division of Applied Mathematics with a Ph.D. for work on ‘Probability Models for Complex Systems’ under the supervision of Stuart Geman. Since then he has been Assistant Professor in the Department of Statistics at the University of Chicago. He is currently also a member of

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    The sleep-associated, “auditory-like” song responses in RA are similar to those normally seen in wakefulness in auditory-responsive neurons which project to RA from the HVC (high vocal center) nucleus (Dave & Margoliash, 2000; Dave et al., 1998). During sleep, HVC neurons burst in a temporal pattern which mimics the pattern associated with the sound of the bird’s own song (Chi, Rauske, & Margoliash, 2003). The gating of HVC auditory input to RA during wakefulness is mediated by noradrenergic and cholinergic signaling within HVC; local agonist application within HVC, or basal forebrain stimulation leads to suppression of auditory responses in RA, but not HVC (Dave et al., 1998; Rauske, Shea, & Margoliash, 2003).

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Zhiyi Chi entered Peking University, Beijing, China in 1989. He entered Brown University, Providence, Rhode Island in 1993. He received an Sc.M.from the Department of Mathematics the next year. In 1998, he graduated from the Division of Applied Mathematics with a Ph.D. for work on ‘Probability Models for Complex Systems’ under the supervision of Stuart Geman. Since then he has been Assistant Professor in the Department of Statistics at the University of Chicago. He is currently also a member of the Committee on Computational Neuroscience at the University of Chicago.

Peter Rauske studied physics at the University of Chicago, graduating in 1994. He is currently studying the neurobiology of birdsong production and learning using chronic recording techniques with Daniel Margoliash's group at the University of Chicago, where he is pursuing a Ph.D. in the Department of Organismal Biology and Anatomy.

Daniel Margoliash studied biology at the California Institute of Technology. After graduating in 1975 he entered the Bioinformation Systems program in Engineering Science at Caltech. Eventually joining the laboratory of Masakazu Konishi, he studied auditory responses in the birdsong system. He received an M.Sc. in 1981, and in 1983 he received his Ph.D. for work on ‘Songbirds, Grandmothers, and Templates: A Neuroethological Approach’. After a brief postdoctoral fellowship with Nobuo Suga at Washington University, St. Louis, he joined the faculty of the then Department of Anatomy at the University of Chicago in 1986. He is currently Professor in the Departments of Organismal Biology and Anatomy & Psychology, and the Committees on Neurobiology & Computational Neuroscience at the University of Chicago.

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