A critical window for cooperation and competition among developing retinotectal synapses

Zhang, Li I.; Tao, Huizhong W.; Holt, Christine E.; Harris, William A.; Poo, Mu‐ming

doi:10.1038/25665

Cited by 790 publications

(747 citation statements)

References 47 publications

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“…2). This finding is robust and has been found in neurons from the hippocampus using acute, (23) organotypic slices, (31) or dissociated cell culture, (32) and in layers V (33,34) and II/III (35) of the cerebral cortex, as well as in vivo preparations using cat (36,37) and Xenopus (38) visual systems. The temporal window permissive for LTP induction is 10-20 ms (milliseconds) whereas the window in which the presynaptic spike can follow the postsynaptic spike in order to induce LTD ranges from 20 to 100 ms in different preparations.…”

Section: Introductionsupporting

confidence: 66%

“…Although Emptage and colleagues report that NMDAR-mediated release of Ca 2þ from stores underlies most of the Ca 2þ signal following single, subthreshold EPSPs, (83) this result has not been reproduced. (38,43,84) Moreover, our simulations, which quantitatively match Ca 2þ signaling profiles following an action potential, are able to account fully for the magnitude of the fluorescent Ca 2þ signal during an EPSP using conservative estimates of NMDAR numbers and single-channel Ca 2þ conductances, therefore suggesting that direct Ca 2þ influx through NMDARs is sufficient to account for the observed increase in intracellular Ca 2þ .…”

Section: Epsp-induced Ca 2þ Influxmentioning

confidence: 72%

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Complexity of calcium signaling in synaptic spines

Franks¹,

Sejnowski²

2002

BioEssays

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SummaryLong-term potentiation and long-term depression are thought to be cellular mechanisms contributing to learning and memory. Although the physiological phenomena have been well characterized, little consensus of their underlying molecular mechanisms has emerged. One reason for this may be the under-appreciated complexity of the signaling pathways that can arise if key signaling molecules are discretely localized within the synapse. Recent findings suggest an unanticipated degree of structural organization at the synapse, and improved methods in cellular imaging of living tissue have provided much-needed information about the intracellular dynamics of Ca 2þ , thought to be critical for both LTP and LTD. In this review, we briefly summarize some of these developments, and show that a more complete understanding of cellular signaling depends on the successful integration of traditional biochemistry and molecular biology with the spatial and temporal details of synaptic ultrastructure. Biophysically realistic computer simulations can have an important role in bridging these disciplines.

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Section: Introductionsupporting

confidence: 66%

Section: Epsp-induced Ca 2þ Influxmentioning

confidence: 72%

Complexity of calcium signaling in synaptic spines

Franks¹,

Sejnowski²

2002

BioEssays

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“…Recent experiments demonstrating that input timing on the order of milliseconds can be the difference between synaptic strengthening and weakening provides a potential mechanism that would allow sensory statistics to precisely control the connectivity and temporal dynamics of large networks of neurons (Bi and Poo, 1999;Feldman, 2000;Froemke and Dan, 2002;Schuett et al, 2001;Song and Abbott, 2001;Song et al, 2000;Yao and Dan, 2001;Zhang et al, 1998). Network models that incorporate this form of Hebbian learning, called spike-timing dependent synaptic plasticity (STDP), are highly sensitive to changes in input correlation (Song and Abbott, 2001).…”

Section: Potential Mechanismsmentioning

confidence: 99%

Asynchronous inputs alter excitability, spike timing, and topography in primary auditory cortex

Pandya¹,

Moucha²,

Engineer³

et al. 2005

Hearing Research

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Correlation-based synaptic plasticity provides a potential cellular mechanism for learning and memory. Studies in the visual and somatosensory systems have shown that behavioral and surgical manipulation of sensory inputs leads to changes in cortical organization that are consistent with the operation of these learning rules. In this study, we examine how the organization of primary auditory cortex (A1) is altered by tones designed to decrease the average input correlation across the frequency map. After one month of separately pairing nucleus basalis stimulation with 2 and 14 kHz tones, a greater proportion of A1 neurons responded to frequencies below 2 kHz and above 14 kHz. Despite the expanded representation of these tones, cortical excitability was specifically reduced in the high and low frequency regions of A1, as evidenced by increased neural thresholds and decreased response strength. In contrast, in the frequency region between the two paired tones, driven rates were unaffected and spontaneous firing rate was increased. Neural response latencies were increased across the frequency map when nucleus basalis stimulation was associated with asynchronous activation of the high and low frequency regions of A1. This set of changes did not occur when pulsed noise bursts were paired with nucleus basalis stimulation. These results are consistent with earlier observations that sensory input statistics can shape cortical map organization and spike timing.

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“…However, to learn the behavioral sequence rapidly via NMDA-dependent synaptic plasticity these neurons should be activated in the same temporal order within ,10 ms. We presented a computational mechanism that could accomplish this task, made several predictions using this mechanism, and verified these predictions experimentally using data from hippocampal place cells [1]. In an accompanying article, Melamed et al have raised several interesting open questions raised by our work [2]. Here, we point to potential solutions for three of these questions.…”

Section: Open Questionsmentioning

confidence: 95%

Coding and learning of behavioral sequences

Melamed

Gerstner

Maass

et al. 2004

Trends in Neurosciences

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A major challenge to understanding behavior is how the nervous system allows the learning of behavioral sequences that can occur over arbitrary timescales, ranging from milliseconds up to seconds, using a fixed millisecond learning rule. This article describes some potential solutions, and then focuses on a study by Mehta et al. that could contribute towards solving this puzzle. They have discovered that an experience-dependent asymmetric shape of hippocampal receptive fields combined with oscillatory inhibition can serve to map behavioral sequences on a fixed timescale.Behavioral sequences of events span several orders of magnitude of timescales. A piano player is able to play rapid scales or repetitions of a single tone at a rate of 12 or more keys per second, probably using an internal sequence of motor commands that is even faster. However, when playing a slow tune, commands are executed ten or twenty times slower. Such different temporal sequences should ideally all be learned using a synaptic learning rule that operates on a fixed neuronal timescale of milliseconds [1 -3]. How then, is learning of behavioral sequences across arbitrary timescales possible? Several studies have recently addressed this issue from different points of view, and have suggested potential solutions.Coding sequences at millisecond resolution One potential solution of the problem could be that all sequences, fast or slow, are in fact stored and retrieved at a millisecond resolution. Synfire chains (SFC) [4] -dominantly feedforward multi-layered architecture (chains) in which spiking activity can propagate in a synchronous wave of neuronal firing (a pulse packet) from one layer of the chain to the next -provide a conceptual framework for such an approach. The chain of neuronal activity evolves on a millisecond scale and, hence, on the natural timescale of spike-time-dependent plasticity. Because all information is represented by a sequence of firing neuronal times, the SFC would automatically solve the problem of sequence learning using a fixed-timescale learning rule. The fastest behavioral sequence would be one in which each time step of the neuronal chain corresponds to one behavioral event. A slow behavioral sequence would then simply be represented by several neuronal time steps per behavioral event. The problem with such an approach is that the representation of slow sequences of events (e.g. five events in one second) is rather expensive, because it requires hundreds of transitions that need to be precisely stored in neuronal connections [4][5][6].A recent study suggested that a mechanism closely related to neuronal SFCs is implemented in the premotor area of song-birds [7]. Neurons projecting from the nucleus hyperstriatum ventralis pars caudalis (HVC) to the forebrain robust nucleus of the archistriatum (RA) are active in a tight temporal sequence or 'clock'. In contrast to the SFC concept, however, each neuron emits not a single spike but a burst of three to four spikes within ,10 ms. Learning a song could then occur in the...

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A critical window for cooperation and competition among developing retinotectal synapses

Cited by 790 publications

References 47 publications

Complexity of calcium signaling in synaptic spines

Complexity of calcium signaling in synaptic spines

Asynchronous inputs alter excitability, spike timing, and topography in primary auditory cortex

Coding and learning of behavioral sequences

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