151
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Bender VA, Bender KJ, Brasier DJ, Feldman DE. Two coincidence detectors for spike timing-dependent plasticity in somatosensory cortex. J Neurosci 2006; 26:4166-77. [PMID: 16624937 PMCID: PMC3071735 DOI: 10.1523/jneurosci.0176-06.2006] [Citation(s) in RCA: 305] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Many cortical synapses exhibit spike timing-dependent plasticity (STDP) in which the precise timing of presynaptic and postsynaptic spikes induces synaptic strengthening [long-term potentiation (LTP)] or weakening [long-term depression (LTD)]. Standard models posit a single, postsynaptic, NMDA receptor-based coincidence detector for LTP and LTD components of STDP. We show instead that STDP at layer 4 to layer 2/3 synapses in somatosensory (S1) cortex involves separate calcium sources and coincidence detection mechanisms for LTP and LTD. LTP showed classical NMDA receptor dependence. LTD was independent of postsynaptic NMDA receptors and instead required group I metabotropic glutamate receptors and calcium from voltage-sensitive channels and IP3 receptor-gated stores. Downstream of postsynaptic calcium, LTD required retrograde endocannabinoid signaling, leading to presynaptic LTD expression, and also required activation of apparently presynaptic NMDA receptors. These LTP and LTD mechanisms detected firing coincidence on approximately 25 and approximately 125 ms time scales, respectively, and combined to implement the overall STDP rule. These findings indicate that STDP is not a unitary process and suggest that endocannabinoid-dependent LTD may be relevant to cortical map plasticity.
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152
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Clem RL, Barth A. Pathway-specific trafficking of native AMPARs by in vivo experience. Neuron 2006; 49:663-70. [PMID: 16504942 DOI: 10.1016/j.neuron.2006.01.019] [Citation(s) in RCA: 187] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Revised: 01/10/2006] [Accepted: 01/23/2006] [Indexed: 11/23/2022]
Abstract
An accumulating body of evidence supports the notion that trafficking of AMPA receptors (AMPARs) underlies strengthening of glutamatergic synapses and, in turn, learning and memory in the behaving animal. However, without exception, these experiments have been performed using artificial stimulation protocols, cultured neurons, or viral-overexpression systems that can significantly alter the normal function of AMPARs. Using a single-whisker experience protocol that significantly enhances neuronal responses in vivo, we have targeted neurons in and around the spared whisker column of fosGFP transgenic mice for whole-cell recording. Here we show that in vivo experience induces the pathway-specific strengthening of neocortical excitatory synapses. By assaying AMPARs for rectification and sensitivity to joro spider toxin, we find that in vivo experience induces the delivery of native GluR2-lacking receptors at spared, but not deprived, inputs. These data demonstrate that pathway-specific trafficking of GluR2-lacking AMPARs is a normal feature of synaptic strengthening that underlies experience-dependent plasticity in the behaving animal.
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Affiliation(s)
- Roger L Clem
- Department of Biological Sciences and Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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153
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Choi SY, Chang J, Jiang B, Seol GH, Min SS, Han JS, Shin HS, Gallagher M, Kirkwood A. Multiple receptors coupled to phospholipase C gate long-term depression in visual cortex. J Neurosci 2006; 25:11433-43. [PMID: 16339037 PMCID: PMC6725895 DOI: 10.1523/jneurosci.4084-05.2005] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Long-term depression (LTD) in sensory cortices depends on the activation of NMDA receptors. Here, we report that in visual cortical slices, the induction of LTD (but not long-term potentiation) also requires the activation of receptors coupled to the phospholipase C (PLC) pathway. Using immunolesions in combination with agonists and antagonists, we selectively manipulated the activation of alpha1 adrenergic, M1 muscarinic, and mGluR5 glutamatergic receptors. Inactivation of these PLC-coupled receptors prevents the induction of LTD, but only when the three receptors were inactivated together. LTD is fully restored by activating any one of them or by supplying intracellular D-myo-inositol-1,4,5-triphosphate (IP3). LTD was also impaired by intracellular application of PLC or IP3 receptor blockers, and it was absent in mice lacking PLCbeta1, the predominant PLC isoform in the forebrain. We propose that visual cortical LTD requires a minimum of PLC activity that can be supplied independently by at least three neurotransmitter systems. This essential requirement places PLC-linked receptors in a unique position to control the induction of LTD and provides a mechanism for gating visual cortical plasticity via extra-retinal inputs in the intact organism.
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Affiliation(s)
- Se-Young Choi
- Mind/Brain Institute, Department of Neurosciences, Johns Hopkins University, Baltimore, Maryland 21218, USA
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154
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Andermann ML, Moore CI. A somatotopic map of vibrissa motion direction within a barrel column. Nat Neurosci 2006; 9:543-51. [PMID: 16547511 DOI: 10.1038/nn1671] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Accepted: 02/23/2006] [Indexed: 11/09/2022]
Abstract
Most mammals possess high-resolution visual perception, with primary visual cortices containing fine-scale, inter-related feature representations (for example, orientation and ocular dominance). Rats lack precise vision, but their vibrissa sensory system provides a precise tactile modality, including vibrissa-related 'barrel' columns in primary somatosensory cortex. Here, we examined the subcolumnar organization of direction preference and somatotopy using a new omni-directional, multi-vibrissa stimulator. We discovered a direction map that was systematically linked to somatotopy, such that neurons were tuned for motion toward their preferred surround vibrissa. This sub-barrel column direction map demonstrated an emergent refinement from layer IV to layer II/III. These data suggest that joint processing of multiple sensory features is a common property of high-resolution sensory systems.
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Affiliation(s)
- Mark L Andermann
- Harvard Program in Biophysics, Medical School Campus, Building C-2 Room 122, 240 Longwood Avenue, Boston, Massachusetts 02115, USA
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155
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Rosanova M, Ulrich D. Pattern-specific associative long-term potentiation induced by a sleep spindle-related spike train. J Neurosci 2006; 25:9398-405. [PMID: 16221848 PMCID: PMC6725710 DOI: 10.1523/jneurosci.2149-05.2005] [Citation(s) in RCA: 280] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Spindles are non-rapid eye movement (non-REM) sleep EEG rhythms (7-14 Hz) that occur independently or in association with slow oscillations (0.6-0.8 Hz). Despite their proposed function in learning and memory, their role in synaptic plasticity is essentially unknown. We studied the ability of a neuronal firing pattern underlying spindles in vivo to induce synaptic plasticity in neocortical pyramidal cells in vitro. A spindle stimulation pattern (SSP) was extracted from a slow oscillation upstate that was recorded in a cat anesthetized with ketamine-xylazine, which is known to induce a sleep-like state. To mimic the recurrence of spindles grouped by the slow oscillation, the SSP was repeated every 1.5 s (0.6 Hz). Whole-cell patch-clamp recordings were obtained from layer V pyramidal cells of rat somatosensory cortex with infrared videomicroscopy, and composite EPSPs were evoked within layers II-III. Trains of EPSPs and action potentials simultaneously triggered by the SSP induced an NMDA receptor-dependent short-term potentiation (STP) and an L-type Ca2+ channel-dependent long-term potentiation (LTP). The number of spindle sequences affected the amount of STP-LTP. In contrast, spindle trains of EPSPs alone led to long-term depression. LTP was not consistently induced by a regular firing pattern, a mirrored SSP, or a randomized SSP; however, a synthetic spindle pattern consisting of repetitive spike bursts at 10 Hz reliably induced STP-LTP. Our results show that spindle-associated spike discharges are efficient in modifying excitatory neocortical synapses according to a Hebbian rule. This is in support of a role for sleep spindles in memory consolidation.
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Affiliation(s)
- Mario Rosanova
- Department of Physiology, University of Bern, 3012 Bern, Switzerland
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156
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Shepherd GMG, Svoboda K. Laminar and columnar organization of ascending excitatory projections to layer 2/3 pyramidal neurons in rat barrel cortex. J Neurosci 2006; 25:5670-9. [PMID: 15958733 PMCID: PMC6724876 DOI: 10.1523/jneurosci.1173-05.2005] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Excitatory synaptic projections to layer 2/3 (L2/3) pyramidal neurons in brain slices from the rat barrel cortex were measured using quantitative laser-scanning photostimulation (LSPS) mapping. In the barrel cortex, cytoarchitectonic "barrels" and "septa" in L4 define a stereotypical array of landmarks, allowing alignment and averaging of LSPS maps from multiple cells in different slices. We distinguished inputs to L2 and L3 neurons above barrels and septa. Average input maps revealed that barrel-related ascending projections (L4-->2/3barrel) interdigitated with a novel septum-related projection (L5A-->2septum). We also explored the functional organization of these projections by comparing the input maps of multiple cells in individual slices. L2/3 cells sharing the same barrel-related column showed strong correlations in their input maps, independent of their precise locations within the column; otherwise, correlations fell rapidly as a function of intersomatic separation. Our data indicate that barrel-related and septum-related columns are associated with distinct functional circuits. These projections are likely to mediate parallel processing of somatosensory signals within the barrel cortex, with L4-->2/3barrel and L5A-->2septum representing the intracortical continuations of, respectively, the subcortical lemniscal and paralemniscal systems conveying somatosensory information to the barrel cortex.
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Affiliation(s)
- Gordon M G Shepherd
- Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
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157
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Abstract
Neural circuits are remarkably adaptable, providing animals with the ability to modify their behavior on the basis of experience. At the same time, they are extremely robust and maintain stability despite the changes associated with adaptation. This combination of adaptability and stability is difficult to achieve, and it provides a strong constraint on any models of plasticity in neural circuits. New evidence suggests that the effect of action potential timing on synaptic plasticity may be an important element in reconciling homeostasis with adaptability. In particular, spike-timing dependent plasticity can act as both an adaptive and a homeostatic mechanism, controlling overall firing rates and distributions of synaptic efficacies while making neurons selective for certain aspects of their inputs. It can also cause networks that initially represent the present state of a stimulus to predict its future state on the basis of experience, a theoretical result supported by experimental data in behaving rats.
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Affiliation(s)
- L F Abbott
- Volen Center, Department of Biology, Brandeis University, Waltham, MA 02454, USA.
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158
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Harwell C, Burbach B, Svoboda K, Nedivi E. Regulation of cpg15 expression during single whisker experience in the barrel cortex of adult mice. ACTA ACUST UNITED AC 2005; 65:85-96. [PMID: 16010668 PMCID: PMC3062911 DOI: 10.1002/neu.20176] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Regulation of gene transcription by neuronal activity is thought to be key to the translation of sensory experience into long-term changes in synaptic structure and function. Here we show that cpg15, a gene encoding an extracellular signaling molecule that promotes dendritic and axonal growth and synaptic maturation, is regulated in the somatosensory cortex by sensory experience capable of inducing cortical plasticity. Using in situ hybridization, we monitored cpg15 expression in 4-week-old mouse barrel cortex after trimming all whiskers except D1. We found that cpg15 expression is depressed in the deprived barrels and enhanced in the barrel column corresponding to the spared D1 whisker. Changes in cpg15 mRNA levels first appear in layer IV, peak 12 h after deprivation, and then decline rapidly. In layers II/III, changes in cpg15 expression appear later, peak at 24 h, and persist for days. Induction of cpg15 expression is significantly diminished in adolescent as well as adult CREB knockout mice. cpg15's spatio-temporal expression pattern and its regulation by CREB are consistent with a role in experience-dependent plasticity of cortical circuits. Our results suggest that local structural and/or synaptic changes may be a mechanism by which the adult cortex can adapt to peripheral manipulations.
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Affiliation(s)
- Corey Harwell
- The Picower Center for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 50 Ames Street, E18-670, Cambridge, Massachusetts 02139, USA
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159
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Froemke RC, Tsay IA, Raad M, Long JD, Dan Y. Contribution of individual spikes in burst-induced long-term synaptic modification. J Neurophysiol 2005; 95:1620-9. [PMID: 16319206 DOI: 10.1152/jn.00910.2005] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Long-term synaptic modification depends on the relative timing of individual pre- and postsynaptic spikes, but the rules governing the effects of multispike bursts remain to be fully understood. In particular, some studies suggest that the spike timing dependence of synaptic modification breaks down with high-frequency bursts. In this study, we characterized the effects of pre- and postsynaptic bursts on long-term modification of layer 2/3 synapses in visual cortical slices from young rats. We found that, while pairing-induced synaptic modification depends on the burst frequency, this dependence can be explained in terms of the timing of individual pre- and postsynaptic spikes. Later spikes in each burst are less effective in synaptic modification, but spike efficacy is regulated differently in pre- and postsynaptic bursts. Presynaptically, spike efficacy is progressively weakened, in parallel with short-term synaptic depression. Postsynaptically, spike efficacy is suppressed to a lesser extent, and it depends on postsynaptic potassium channel activation. Such timing-dependent interaction among multiple spikes can account for synaptic modifications induced by a variety of spike trains, including the frequency-dependent transition from depression to potentiation induced by a postsynaptic burst preceding a presynaptic burst.
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Affiliation(s)
- Robert C Froemke
- Division of Neurobiology, Department of Molecular and Cell Biology, University of California, Berkeley, USA
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160
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Abstract
Neuronal circuits in the brain are shaped by experience during 'critical periods' in early postnatal life. In the primary visual cortex, this activity-dependent development is triggered by the functional maturation of local inhibitory connections and driven by a specific, late-developing subset of interneurons. Ultimately, the structural consolidation of competing sensory inputs is mediated by a proteolytic reorganization of the extracellular matrix that occurs only during the critical period. The reactivation of this process, and subsequent recovery of function in conditions such as amblyopia, can now be studied with realistic circuit models that might generalize across systems.
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Affiliation(s)
- Takao K Hensch
- RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan.
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161
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Braithwaite VA, Salvanes AGV. Environmental variability in the early rearing environment generates behaviourally flexible cod: implications for rehabilitating wild populations. Proc Biol Sci 2005; 272:1107-13. [PMID: 16024371 PMCID: PMC1559818 DOI: 10.1098/rspb.2005.3062] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The release of hatchery-reared fishes for restoring threatened and endangered populations is one of the most controversial issues in applied ecology. A central issue has been to determine whether releases cause extinction of local wild populations. This may arise either through domesticated or non-local fishes hybridizing with wild fishes, or through inappropriate behavioural interactions; for example, many hatchery fishes show exaggerated aggressive and competitive behaviour and out-compete wild counterparts. The impact of the impoverished hatchery environment in shaping behaviour is only now receiving attention. Attempts to counteract hatchery-related behavioural deficiencies have utilized intensive training programmes shortly before the fishes are released. However, we show here that simple exposure to variable spatial and foraging cues in the standard hatchery environment generates fishes with enhanced behavioural traits that are probably associated with improved survival in the wild. It appears that fishes need to experience a varying and changeable environment to learn and develop flexible behaviour. Using variable hatchery rearing environments to generate suitable phenotypes in combination with a knowledge of appropriate local genotypes, rehabilitation of wild fishes is likely to succeed, where to date it has largely failed.
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162
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Abstract
Sensory maps in neocortex are adaptively altered to reflect recent experience and learning. In somatosensory cortex, distinct patterns of sensory use or disuse elicit multiple, functionally distinct forms of map plasticity. Diverse approaches—genetics, synaptic and in vivo physiology, optical imaging, and ultrastructural analysis—suggest a distributed model in which plasticity occurs at multiple sites in the cortical circuit with multiple cellular/synaptic mechanisms and multiple likely learning rules for plasticity. This view contrasts with the classical model in which the map plasticity reflects a single Hebbian process acting at a small set of cortical synapses.
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Affiliation(s)
- Daniel E Feldman
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, Room 0357, La Jolla, CA 92093, USA.
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163
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Abstract
In the visual and somatosensory systems, maturation of neuronal circuits continues for days to weeks after sensory stimulation occurs. Deprivation of sensory input at various stages of development can induce physiological, and often structural, changes that modify the circuitry of these sensory systems. Recent studies also reveal a surprising degree of plasticity in the mature visual and somatosensory pathways. Here, we compare and contrast the effects of sensory experience on the connectivity and function of these pathways and discuss what is known to date concerning the structural, physiological, and molecular mechanisms underlying their plasticity.
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Affiliation(s)
- Kevin Fox
- Cardiff School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3US, United Kingdom.
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164
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Foeller E, Celikel T, Feldman DE. Inhibitory sharpening of receptive fields contributes to whisker map plasticity in rat somatosensory cortex. J Neurophysiol 2005; 94:4387-400. [PMID: 16162832 PMCID: PMC3070316 DOI: 10.1152/jn.00553.2005] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The role of inhibition in sensory cortical map plasticity is not well understood. Here we tested whether inhibition contributes to expression of receptive field plasticity in developing rat somatosensory (S1) cortex. In normal rats, microiontophoresis of gabazine (SR 95531), a competitive gamma-aminobutyric acid (GABA)-A receptor antagonist, preferentially disinhibited surround whisker responses relative to principal whisker responses, indicating that GABA(A) inhibition normally acts to sharpen whisker tuning. Plasticity was induced by transiently depriving adolescent rats of all but one whisker; this causes layer 2/3 (L2/3) receptive fields to shift away from the deprived principal whisker and toward the spared surround whisker. In units with shifted receptive fields, gabazine preferentially disinhibited responses to the deprived principal whisker, unlike in controls, suggesting that GABA(A) inhibition was acting to preferentially suppress these responses relative to spared whisker responses. This effect was not observed for L2/3 units that did not express receptive field plasticity or in layer 4, where receptive field plasticity did not occur. Thus GABA(A) inhibition promoted expression of sensory map plasticity by helping to sharpen receptive fields around the spared input.
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Affiliation(s)
- Elisabeth Foeller
- Division of Biological Sciences, University of California San Diego, La Jolla, USA.
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165
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Shoykhet M, Land PW, Simons DJ. Whisker trimming begun at birth or on postnatal day 12 affects excitatory and inhibitory receptive fields of layer IV barrel neurons. J Neurophysiol 2005; 94:3987-95. [PMID: 16093330 DOI: 10.1152/jn.00569.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In rats, whisker trimming during development leads to persistent alterations in the function of cortical barrel circuits and to behavioral deficits later in life. Here we examined how whisker trimming begun either at birth (P0) or on postnatal day 12 (P12), around the onset of whisking behavior, affects receptive fields of layer IV barrel neurons. All whiskers on the left face were trimmed for 40-45 days and then allowed to regrow fully. Extracellular single-unit recordings and controlled deflections of principal and adjacent whiskers (PW and AW, respectively), individually or in paired combinations, were used to assess excitatory and suppressive effects of neighboring whiskers on barrel neurons. Results indicate that whisker trimming both from P0 and P12 leads to enlarged excitatory and weakened inhibitory receptive fields in layer IV neurons. PW- and AW-evoked responses are larger in magnitude in trimmed than in control animals; AW-evoked responses are disproportionately affected, decreasing the spatial focus of barrel neurons. Deprivation after P12 accounts for approximately 50% of the total effect observed in P0 trimmed animals. Suppressive interactions, evoked by two whiskers deflected in succession, are weaker in trimmed than in control animals. Suppressive caudal/rostral and ventral/dorsal gradients, however, seem unaffected by sensory deprivation. Thus the developmental period during which experience persistently modifies maturing barrel circuitry extends up to and likely beyond the onset of whisking behavior. Sensory deprivation during this time affects development of both excitatory and inhibitory receptive fields of barrel neurons and likely impairs cortical integration of sensory information from multiple whiskers.
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Affiliation(s)
- Michael Shoykhet
- Department of Neurobiology, University of Pittsburgh School of Medicine, PA 15261, USA
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166
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Fusi S, Drew PJ, Abbott LF. Cascade models of synaptically stored memories. Neuron 2005; 45:599-611. [PMID: 15721245 DOI: 10.1016/j.neuron.2005.02.001] [Citation(s) in RCA: 303] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2004] [Revised: 11/12/2004] [Accepted: 02/01/2005] [Indexed: 10/25/2022]
Abstract
Storing memories of ongoing, everyday experiences requires a high degree of plasticity, but retaining these memories demands protection against changes induced by further activity and experience. Models in which memories are stored through switch-like transitions in synaptic efficacy are good at storing but bad at retaining memories if these transitions are likely, and they are poor at storage but good at retention if they are unlikely. We construct and study a model in which each synapse has a cascade of states with different levels of plasticity, connected by metaplastic transitions. This cascade model combines high levels of memory storage with long retention times and significantly outperforms alternative models. As a result, we suggest that memory storage requires synapses with multiple states exhibiting dynamics over a wide range of timescales, and we suggest experimental tests of this hypothesis.
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Affiliation(s)
- Stefano Fusi
- Institute of Physiology, University of Bern, Bühlplatz 5, CH-3012, Bern, Switzerland
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167
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Wolters A, Schmidt A, Schramm A, Zeller D, Naumann M, Kunesch E, Benecke R, Reiners K, Classen J. Timing-dependent plasticity in human primary somatosensory cortex. J Physiol 2005; 565:1039-52. [PMID: 15845584 PMCID: PMC1464551 DOI: 10.1113/jphysiol.2005.084954] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Animal experiments suggest that cortical sensory representations may be remodelled as a consequence of changing synaptic efficacy by timing-dependent associative neuronal activity. Here we describe a timing-based associative form of plasticity in human somatosensory cortex. Paired associative stimulation (PAS) was performed by combining repetitive median nerve stimulation with transcranial magnetic stimulation (TMS) over the contralateral postcentral region. PAS increased exclusively the amplitude of the P25 component of the median nerve-evoked somatosensory-evoked potential (MN-SSEP), which is probably generated in the superficial cortical layers of area 3b. SSEP components reflecting neuronal activity in deeper cortical layers (N20 component) or subcortical regions (P14 component) remained constant. PAS-induced enhancement of P25 amplitude displayed topographical specificity both for the recording (MN-SSEP versus tibial nerve-SSEP) and the stimulation (magnetic stimulation targeting somatosensory versus motor cortex) arrangements. Modulation of P25 amplitude was confined to a narrow range of interstimulus intervals (ISIs) between the MN pulse and the TMS pulse, and the sign of the modulation changed with ISIs differing by only 15 ms. The function describing the ISI dependence of PAS effects on somatosensory cortex resembled one previously observed in motor cortex, shifted by approximately 7 ms. The findings suggest a simple model of modulation of excitability in human primary somatosensory cortex, possibly by mechanisms related to the spike-timing-dependent plasticity of neuronal synapses located in upper cortical layers.
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Affiliation(s)
- Alexander Wolters
- Human Cortical Physiology Laboratory, Department of Neurology, University of Rostock, Germany
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168
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Hickmott PW. Changes in intrinsic properties of pyramidal neurons in adult rat S1 during cortical reorganization. J Neurophysiol 2005; 94:501-11. [PMID: 15758053 DOI: 10.1152/jn.00924.2004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Peripheral denervation causes significant changes in the organization of developing or adult primary somatosensory cortex (S1). However, the basic mechanisms that underlie reorganization are not well understood. Most attention has been focused on possible synaptic mechanisms associated with reorganization. However, another important determinant of cortical circuit function is the intrinsic membrane properties of neurons in the circuit. Here we document changes in the intrinsic properties of pyramidal neurons in cortical layer 2/3 in adult rat primary somatosensory cortex (S1) after varying durations of forepaw denervation. Denervation of the forepaw induced a rapid and sustained shift in the location of the border between the forepaw and lower jaw representations of adult S1 (reorganization). Coronal slices from the reorganized region were maintained in vitro and the intrinsic properties of layer 2/3 pyramidal neurons of S1 were determined using whole cell recordings. In general, passive membrane properties were not affected by denervation; however, a variety of active properties were. The most robust changes were increases in the amplitudes of the fast and medium afterhyperpolarization (AHP) and an increase in the interval between action potentials (APs). Additional changes at some durations of denervation were observed for the AP threshold. These observations indicate that changes in intrinsic properties, mostly reflecting a decrease in overall excitation, may play a role in changes in cortical circuit properties during reorganization in adult S1, and suggest a possible role for AHPs in some of those changes.
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Affiliation(s)
- Peter W Hickmott
- Department of Psychology and Interdepartmental Neuroscience Program, University of California, OLMH 1344, Riverside, California 92521, USA.
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169
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Abstract
LTP and LTD, the long-term potentiation and depression of excitatory synaptic transmission, are widespread phenomena expressed at possibly every excitatory synapse in the mammalian brain. It is now clear that "LTP" and "LTD" are not unitary phenomena. Their mechanisms vary depending on the synapses and circuits in which they operate. Here we review those forms of LTP and LTD for which mechanisms have been most firmly established. Examples are provided that show how these mechanisms can contribute to experience-dependent modifications of brain function.
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Affiliation(s)
- Robert C Malenka
- Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Palo Alto, CA 94304, USA.
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170
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Abstract
Recent findings of spike timing-dependent plasticity (STDP) have stimulated much interest among experimentalists and theorists. Beyond the traditional correlation-based Hebbian plasticity, STDP opens up new avenues for understanding information coding and circuit plasticity that depend on the precise timing of neuronal spikes. Here we summarize experimental characterization of STDP at various synapses, the underlying cellular mechanisms, and the associated changes in neuronal excitability and dendritic integration. We also describe STDP in the context of complex spike patterns and its dependence on the dendritic location of the synapse. Finally, we discuss timing-dependent modification of neuronal receptive fields and human visual perception and the computational significance of STDP as a synaptic learning rule.
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Affiliation(s)
- Yang Dan
- Division of Neurobiology, Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720 USA.
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171
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Mierau SB, Meredith RM, Upton AL, Paulsen O. Dissociation of experience-dependent and -independent changes in excitatory synaptic transmission during development of barrel cortex. Proc Natl Acad Sci U S A 2004; 101:15518-23. [PMID: 15492224 PMCID: PMC524435 DOI: 10.1073/pnas.0402916101] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A fundamental problem in the study of cortical development is the extent to which the formation and refinement of synaptic circuitry depends upon sensory experience. The barrel cortex is a useful model system to study experience-dependent cortical development because there is a simple mapping of individual whiskers to the corresponding barrel columns in the cortex. We investigated experience-dependent and -independent changes in glutamatergic synaptic transmission in the barrel cortex during the second postnatal week by comparing synaptic responses from whisker-intact mice at postnatal day (P) 7 and P14 with those from whisker-deprived mice at P14. alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA)-receptor-mediated excitatory synaptic responses were recorded from layer 2/3 pyramidal cells in vitro during voltage-clamp in response to stimulation in layer 4. We observed that the ratio of synaptic AMPA- to NMDA-receptor-mediated current (A/N ratio) increased with developmental age. The development of the A/N ratio was unchanged by deprivation of the whisker input throughout the second postnatal week. In contrast, the NMDA-receptor current decay and sensitivity to the NMDA receptor 2B subunit-selective antagonist ifenprodil was affected strongly by such deprivation. These results demonstrate a concurrent dissociation between sensory experience-dependent and -independent changes of glutamatergic transmission in the barrel cortex during the second postnatal week. Furthermore, they suggest that the development of subunit composition of synaptic receptors is dependent on sensory experience, whereas maturation of the synaptic A/N ratio is independent of such experience. Thus, different components of synaptic development may be governed by different developmental rules.
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Affiliation(s)
- Susanna B Mierau
- University Laboratory of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, United Kingdom
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172
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Abstract
Neuronal circuits are shaped by experience during critical periods of early postnatal life. The ability to control the timing, duration, and closure of these heightened levels of brain plasticity has recently become experimentally accessible, especially in the developing visual system. This review summarizes our current understanding of known critical periods across several systems and species. It delineates a number of emerging principles: functional competition between inputs, role for electrical activity, structural consolidation, regulation by experience (not simply age), special role for inhibition in the CNS, potent influence of attention and motivation, unique timing and duration, as well as use of distinct molecular mechanisms across brain regions and the potential for reactivation in adulthood. A deeper understanding of critical periods will open new avenues to "nurture the brain"-from international efforts to link brain science and education to improving recovery from injury and devising new strategies for therapy and lifelong learning.
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Affiliation(s)
- Takao K Hensch
- Laboratory for Neuronal Circuit Development, Critical Period Mechanisms Research Group, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
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173
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Grassi S, Dieni C, Frondaroli A, Pettorossi VE. Influence of visual experience on developmental shift from long-term depression to long-term potentiation in the rat medial vestibular nuclei. J Physiol 2004; 560:767-77. [PMID: 15331680 PMCID: PMC1665278 DOI: 10.1113/jphysiol.2004.069658] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The influence of visual experience deprivation on changes in synaptic plasticity during postnatal development was studied in the ventral part of the rat medial vestibular nuclei (vMVN). We analysed the differences in the occurrence, expressed as a percentage, of long-term depression (LTD) and long-term potentiation (LTP) induced by high frequency stimulation (HFS) of the primary vestibular afferents in rats reared in the light (LR) and those in the dark (DR). In LR rats, HFS only induced LTD in the early stages of development, but the occurrence of LTD progressively decreased to zero before their eyes opened, while that of LTP enhanced from zero to about 50%. Once the rats' eyes had opened, LTD was no longer inducible while LTP occurrence gradually reached the normal adult value (70%). In DR rats, a similar shift from LTD to LTP was observed before their eyes opened, showing only a slightly slower LTD decay and LTP growth, and the LTD annulment was delayed by 1 day. By contrast, the time courses of LTD and LTP development in DR and LR rats showed remarkable differences following eye opening. In fact, LTD occurrence increased to about 50% in a short period of time and remained high until the adult stage. In addition, the occurrence of LTP slowly decreased to less than 20%. The effect of light-deprivation was reversible, since the exposure of DR rats to light, 5 days after eye opening, caused a sudden disappearance of LTD and a partial recover of LTP occurrence. In addition, we observed that a week of light deprivation in LR adult rats did not affect the normal adult LTP occurrence. These results provide evidence that in a critical period of development visual input plays a crucial role in shaping synaptic plasticity of the vMVN, and suggest that the visual guided shift from LTD to LTP during development may be necessary to refine and consolidate vestibular circuitry.
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Affiliation(s)
- Silvarosa Grassi
- Department of Internal Medicine, Section of Human Physiology, University of Perugia, Via del Giochetto, I-06100 Perugia, Italy.
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174
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Sjöström PJ, Turrigiano GG, Nelson SB. Endocannabinoid-dependent neocortical layer-5 LTD in the absence of postsynaptic spiking. J Neurophysiol 2004; 92:3338-43. [PMID: 15240760 DOI: 10.1152/jn.00376.2004] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Long-term depression (LTD) was induced in neocortical layer 5 pyramidal connections by pairing presynaptic firing with subthreshold postsynaptic depolarization (dLTD) or via a spike-timing protocol (tLTD). Like tLTD, dLTD reduced short-term depression and increased the coefficient of variation consistent with a presynaptic site of expression. Also like tLTD, dLTD was blocked by CB1 cannibinoid receptor blockade and required activation of presumably presynaptic NR2B-containing N-methyl-D-aspartate receptors. The two forms of LTD had identical magnitudes and time courses and occluded one another, and neither depended on frequency. Finally, dLTD shares with tLTD the asymmetric temporal window of induction. In conclusion, the types of LTD induced by these two protocols are indistinguishable, suggesting that the mechanism that underlies tLTD paradoxically does not require postsynaptic spiking: The subthreshold postsynaptic depolarizations of dLTD appear to fully substitute for postsynaptic spiking.
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Affiliation(s)
- Per Jesper Sjöström
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454-9110, USA
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175
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Siebner HR, Lang N, Rizzo V, Nitsche MA, Paulus W, Lemon RN, Rothwell JC. Preconditioning of low-frequency repetitive transcranial magnetic stimulation with transcranial direct current stimulation: evidence for homeostatic plasticity in the human motor cortex. J Neurosci 2004; 24:3379-85. [PMID: 15056717 PMCID: PMC6730024 DOI: 10.1523/jneurosci.5316-03.2004] [Citation(s) in RCA: 519] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Recent experimental work in animals has emphasized the importance of homeostatic plasticity as a means of stabilizing the properties of neuronal circuits. Here, we report a phenomenon that indicates a homeostatic pattern of cortical plasticity in healthy human subjects. The experiments combined two techniques that can produce long-term effects on the excitability of corticospinal output neurons: transcranial direct current stimulation (TDCS) and repetitive transcranial magnetic stimulation (rTMS) of the left primary motor cortex. "Facilitatory preconditioning" with anodal TDCS caused a subsequent period of 1 Hz rTMS to reduce corticospinal excitability to below baseline levels for >20 min. Conversely, "inhibitory preconditioning" with cathodal TDCS resulted in 1 Hz rTMS increasing corticospinal excitability for at least 20 min. No changes in excitability occurred when 1 Hz rTMS was preceded by sham TDCS. Thus, changing the initial state of the motor cortex by a period of DC polarization reversed the conditioning effects of 1 Hz rTMS. These preconditioning effects of TDCS suggest the existence of a homeostatic mechanism in the human motor cortex that stabilizes corticospinal excitability within a physiologically useful range.
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Affiliation(s)
- Hartwig R Siebner
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College of London, London WC1N 3BG, United Kingdom
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176
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Murakami H, Kamatani D, Hishida R, Takao T, Kudoh M, Kawaguchi T, Tanaka R, Shibuki K. Short-term plasticity visualized with flavoprotein autofluorescence in the somatosensory cortex of anaesthetized rats. Eur J Neurosci 2004; 19:1352-60. [PMID: 15016093 DOI: 10.1111/j.1460-9568.2004.03237.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In the present study, short-term plasticity of somatosensory neural responses was investigated using flavoprotein autofluorescence imaging in rats anaesthetized with urethane (1.5 g/kg, i.p.) Somatosensory neural activity was elicited by vibratory skin stimulation (50 Hz for 1 s) applied on the surface of the left plantar hindpaw. Changes in green autofluorescence (lambda = 500-550 nm) in blue light (lambda = 450-490 nm) were elicited in the right somatosensory cortex. The normalised maximal fluorescence responses (deltaF/F) was 2.0 +/- 0.1% (n = 40). After tetanic cortical stimulation (TS), applied at a depth of 1.5-2.0 mm from the cortical surface, the responses elicited by peripheral stimulation were significantly potentiated in both peak amplitude and size of the responsive area (both P < 0.02; Wilcoxon signed rank test). This potentiation was clearly observed in the recording session started 5 min after the cessation of TS, and returned to the control level within 30 min. However, depression of the responses was observed after TS applied at a depth of 0.5 mm. TS-induced changes in supragranular field potentials in cortical slices showed a similar dependence on the depth of the stimulated sites. When TS was applied on the ipsilateral somatosensory cortex, marked potentiation of the ipsilateral responses and slight potentiation of the contralateral responses to peripheral stimulation were observed after TS, suggesting the involvement of commissural fibers in the changes in the somatosensory brain maps. The present study clearly demonstrates that functional brain imaging using flavoprotein autofluorescence is a useful technique for investigating neural plasticity in vivo.
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Affiliation(s)
- Hiroatsu Murakami
- Department of Neurophysiology, Brain Research Institute, Niigata University, Asahi-machi, Niigata 951-8585, Japan
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177
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Celikel T, Szostak VA, Feldman DE. Modulation of spike timing by sensory deprivation during induction of cortical map plasticity. Nat Neurosci 2004; 7:534-41. [PMID: 15064767 PMCID: PMC3082358 DOI: 10.1038/nn1222] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2003] [Accepted: 03/12/2004] [Indexed: 11/08/2022]
Abstract
Deprivation-induced plasticity of sensory cortical maps involves long-term potentiation (LTP) and depression (LTD) of cortical synapses, but how sensory deprivation triggers LTP and LTD in vivo is unknown. Here we tested whether spike timing-dependent forms of LTP and LTD are involved in this process. We measured spike trains from neurons in layer 4 (L4) and layers 2 and 3 (L2/3) of rat somatosensory cortex before and after acute whisker deprivation, a manipulation that induces whisker map plasticity involving LTD at L4-to-L2/3 (L4-L2/3) synapses. Whisker deprivation caused an immediate reversal of firing order for most L4 and L2/3 neurons and a substantial decorrelation of spike trains, changes known to drive timing-dependent LTD at L4-L2/3 synapses in vitro. In contrast, spike rate changed only modestly. Thus, whisker deprivation is likely to drive map plasticity by spike timing-dependent mechanisms.
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Affiliation(s)
- Tansu Celikel
- Division of Biological Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
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178
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Petersen CCH, Brecht M, Hahn TTG, Sakmann B. RETRACTED: Synaptic changes in layer 2/3 underlying map plasticity of developing barrel cortex. Science 2004; 304:739-42. [PMID: 15118164 DOI: 10.1126/science.1096750] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The functional and anatomical rearrangements of cortical sensory maps accompanying changes in experience are not well understood. We examined in vivo and in vitro how the sensory map and underlying synaptic connectivity of the developing rat barrel cortex are altered when the sensory input to the cortex is partially deprived. In the nondeprived cortex, both the sensory responses and synaptic connectivity between columns were strengthened through an increase in the synaptic connection probability between L2/3 pyramids in adjacent columns. This was accompanied by a selective growth of L2/3pyramid axonal arbors between spared columns. In contrast, deprived and nondeprived cortical columns became weakly connected in their L2/3 pyramid connections.
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Affiliation(s)
- Carl C H Petersen
- Department of Cell Physiology, Max-Planck-Institute for Medical Research, Jahnstrasse 29, Heidelberg D-69120, Germany.
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179
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Erzurumlu RS. Somatosensory cortical plasticity: recruiting silenced barrels by active whiskers. Exp Neurol 2004; 184:565-9. [PMID: 14769350 PMCID: PMC3671918 DOI: 10.1016/s0014-4886(03)00396-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Accepted: 07/28/2003] [Indexed: 11/18/2022]
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180
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Mezey S, Doyère V, De Souza I, Harrison E, Cambon K, Kendal CE, Davies H, Laroche S, Stewart MG. Long-term synaptic morphometry changes after induction of long-term potentiation and long-term depression in the dentate gyrus of awake rats are not simply mirror phenomena. Eur J Neurosci 2004; 19:2310-8. [PMID: 15090057 DOI: 10.1111/j.0953-816x.2004.03334.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mechanisms of expression of long-term synaptic plasticity are believed to involve morphological changes of the activated synapses and remodelling of connectivity. Here, we investigated changes in synaptic and neuronal parameters in the dentate gyrus 24 h after induction of long-term potentiation (LTP) and long-term depression (LTD) in awake rats. In dentate granule cells, tetanization of the medial or lateral perforant paths induces LTP in specific synaptic bands along the dendrites in the middle and outer molecular layers, respectively, and tetanization of the lateral path induces robust LTD heterosynaptically in the middle molecular layer. This functional segregation allowed us to assess morphological changes associated with LTP and LTD in each pathway in the same population of neurons. Electron microscopy and unbiased counting methods were used to estimate neuronal density, axospinous, axodendritic and perforated synapse density, multiple synapse bouton density and postsynaptic density (PSD) area. Whereas there was no change in neuronal density, PSD area and multiple synapse boutons 24 h after either LTP or LTD, there was a noninput-specific increase in unperforated axospinous synapses after both LTP and LTD. However, we found that LTP of the medial, but not lateral, perforant path is associated with a specific increase in perforated axospinous synapses in the potentiated area. We also show that heterosynaptic LTD is associated with an input-specific increase in axodendritic synapse density. These results suggest that each perforant pathway may differ with respect to the nature of LTP-induced long-term changes and show that morphologically LTD is not simply the converse of LTP.
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Affiliation(s)
- Szilvia Mezey
- Department of Biological Sciences, The Open University, Milton Keynes MK7 6AA, UK
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181
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Maravall M, Stern EA, Svoboda K. Development of intrinsic properties and excitability of layer 2/3 pyramidal neurons during a critical period for sensory maps in rat barrel cortex. J Neurophysiol 2004; 92:144-56. [PMID: 14973314 DOI: 10.1152/jn.00598.2003] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The development of layer 2/3 sensory maps in rat barrel cortex (BC) is experience dependent with a critical period around postnatal days (PND) 10-14. The role of intrinsic response properties of neurons in this plasticity has not been investigated. Here we characterize the development of BC layer 2/3 intrinsic responses to identify possible sites of plasticity. Whole cell recordings were performed on pyramidal cells in acute BC slices from control and deprived rats, over ages spanning the critical period (PND 12, 14, and 17). Vibrissa trimming began at PND 9. Spiking behavior changed from phasic (more spike frequency adaptation) to regular (less adaptation) with age, such that the number of action potentials per stimulus increased. Changes in spiking properties were related to the strength of a slow Ca(2+)-dependent afterhyperpolarization. Maturation of the spiking properties of layer 2/3 pyramidal neurons coincided with the close of the critical period and was delayed by deprivation. Other measures of excitability, including I-f curves and passive membrane properties, were affected by development but unaffected by whisker deprivation.
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Affiliation(s)
- Miguel Maravall
- Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
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182
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Abstract
Sensory experience drives plasticity of the body map in developing and adult somatosensory cortex, but the synaptic mechanisms underlying such plasticity are not well understood. Recently, several mechanisms that are likely to contribute to map plasticity have been directly observed in response to altered experience in vivo. These mechanisms include long-term potentiation and long-term depression at specific excitatory synapses, competition between lemniscal (barrel) and non-lemniscal (septal) processing streams, and regulation of the number of inhibitory synapses.
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Affiliation(s)
- Elisabeth Foeller
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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183
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Kandler K. Activity-dependent organization of inhibitory circuits: lessons from the auditory system. Curr Opin Neurobiol 2004; 14:96-104. [PMID: 15018944 DOI: 10.1016/j.conb.2004.01.017] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In contrast to our detailed knowledge about the development and plasticity of excitatory neuronal circuits, little is known about the development of inhibitory circuits. Recent studies from the developing mammalian auditory system have revealed the presence of substantial activity-dependent synaptic reorganization in several inhibitory pathways. These studies importantly shed some new light on the general rules and cellular mechanisms that manage the organization of precise inhibitory circuits in the developing brain.
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Affiliation(s)
- Karl Kandler
- Department of Neurobiology, University of Pittsburgh School of Medicine, 3500 Terrace Street, Pittsburgh, PA 15261, USA.
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184
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Development of columnar topography in the excitatory layer 4 to layer 2/3 projection in rat barrel cortex. J Neurosci 2003. [PMID: 14507976 DOI: 10.1523/jneurosci.23-25-08759.2003] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The excitatory feedforward projection from layer (L) 4 to L2/3 in rat primary somatosensory (S1) cortex exhibits precise, columnar topography that is critical for columnar processing of whisker inputs. Here, we characterize the development of axonal topography in this projection using single-cell reconstructions in S1 slices. In the mature projection [postnatal day (P) 14-26], axons of L4 cells extending into L2/3 were confined almost entirely to the home barrel column, consistent with previous results. At younger ages (P8-11), however, axonal topography was significantly less columnar, with a large proportion of branches innervating neighboring barrel columns representing adjacent whisker rows. Mature topography developed from this initial state by targeted axonal growth within the home column and by growth of barrel columns themselves. Raising rats with all or a subset of whiskers plucked from P8-9, manipulations that induce reorganization of functional whisker maps and synaptic depression at L4 to L2/3 synapses, did not alter normal anatomical development of L4 to L2/3 axons. Thus, development of this projection does not require normal sensory experience after P8, and deprivation-induced reorganization of whisker maps at this age is unlikely to involve physical remodeling of L4 to L2/3 axons.
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185
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Petersen CCH. The barrel cortex--integrating molecular, cellular and systems physiology. Pflugers Arch 2003; 447:126-34. [PMID: 14504929 DOI: 10.1007/s00424-003-1167-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2003] [Accepted: 08/05/2003] [Indexed: 10/26/2022]
Abstract
A challenge for neurobiology is to integrate information across many levels of research, ranging from behaviour and neuronal networks to cells and molecules. The rodent whisker signalling pathway to the primary somatosensory neocortex with its remarkable somatotopic barrel map is emerging as a key system for such integrative studies.
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Affiliation(s)
- Carl C H Petersen
- Laboratory of Sensory Processing, Brain and Mind Institute, SV-INS-LSENS, AAB105, EPFL, 1015 Lausanne, Switzerland.
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186
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Lu HC, She WC, Plas DT, Neumann PE, Janz R, Crair MC. Adenylyl cyclase I regulates AMPA receptor trafficking during mouse cortical 'barrel' map development. Nat Neurosci 2003; 6:939-47. [PMID: 12897788 DOI: 10.1038/nn1106] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2003] [Accepted: 06/02/2003] [Indexed: 11/08/2022]
Abstract
Cortical map formation requires the accurate targeting, synaptogenesis, elaboration and refinement of thalamocortical afferents. Here we demonstrate the role of Ca2+/calmodulin-activated type-I adenylyl cyclase (AC1) in regulating the strength of thalamocortical synapses through modulation of AMPA receptor (AMPAR) trafficking using barrelless mice, a mutant without AC1 activity or cortical 'barrel' maps. Barrelless synapses are stuck in an immature state that contains few functional AMPARs that are rarely silent (NMDAR-only). Long-term potentiation (LTP) and long-term depression (LTD) at thalamocortical synapses require postsynaptic protein kinase A (PKA) activity and are difficult to induce in barrelless mice, probably due to an inability to properly regulate synaptic AMPAR trafficking. Consistent with this, both the extent of PKA phosphorylation on AMPAR subunit GluR1 and the expression of surface GluR1 are reduced in barrelless neurons. These results suggest that activity-dependent mechanisms operate through an AC1/PKA signaling pathway to target some synapses for consolidation and others for elimination during barrel map formation.
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Affiliation(s)
- Hui-Chen Lu
- Division of Neuroscience and Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza S-603, Houston, Texas 77030, USA.
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187
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Abstract
In this issue of Neuron, Sjöström et al. provide evidence for a novel presynaptic mechanism for coincidence detection in induction of timing-dependent LTD. In their scheme, simultaneous activation of presynaptic NMDA receptors and CB1 endocannabinoid receptors induces a long-lasting reduction in presynaptic transmitter release.
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Affiliation(s)
- Robert C Froemke
- Division of Neurobiology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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188
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Heynen AJ, Yoon BJ, Liu CH, Chung HJ, Huganir RL, Bear MF. Molecular mechanism for loss of visual cortical responsiveness following brief monocular deprivation. Nat Neurosci 2003; 6:854-62. [PMID: 12886226 DOI: 10.1038/nn1100] [Citation(s) in RCA: 230] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2003] [Accepted: 06/17/2003] [Indexed: 11/09/2022]
Abstract
A dramatic form of experience-dependent synaptic plasticity is revealed in visual cortex when one eye is temporarily deprived of vision during early postnatal life. Monocular deprivation (MD) alters synaptic transmission such that cortical neurons cease to respond to stimulation of the deprived eye, but how this occurs is poorly understood. Here we show in rat visual cortex that brief MD sets in motion the same molecular and functional changes as the experimental model of homosynaptic long-term depression (LTD), and that prior synaptic depression by MD occludes subsequent induction of LTD. The mechanisms of LTD, about which there is now a detailed understanding, therefore contribute to visual cortical plasticity.
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Affiliation(s)
- Arnold J Heynen
- Howard Hughes Medical Institute, The Picower Center for Learning and Memory, and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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189
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190
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Abstract
Ocular dominance plasticity, classically thought to be restricted to an early critical period, is now described by Sawtell et al. in fully adult mice. Adult plasticity, like critical period plasticity, requires cortical NMDA receptors but involves different functional changes in cortical circuits.
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Affiliation(s)
- Dan Feldman
- Neurobiology Section 0357, Division of Biology, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA
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