Reliability of pattern separation by the cerebellar mossy fiber ? granule cell system

1974 ◽  
Vol 16 (2) ◽  
pp. 93-101 ◽  
Author(s):  
Jay E. Mittenthal
Keyword(s):  
Granule Cell ◽  
Mossy Fiber ◽  
Cell System ◽  
Pattern Separation

How Synaptic Release Probability Shapes Neuronal Transmission: Information-Theoretic Analysis in a Cerebellar Granule Cell

2010 ◽  
Vol 22 (8) ◽  
pp. 2031-2058 ◽  
Author(s):  
Angelo Arleo ◽  
Thierry Nieus ◽  
Michele Bezzi ◽  
Anna D'Errico ◽  
Egidio D'Angelo ◽  
...  
Keyword(s):  
Information Transmission ◽  
Numerical Simulations ◽  
Granule Cell ◽  
Mossy Fiber ◽  
Dendritic Tree ◽  
Long Term Potentiation ◽  
Cerebellar Granule Cell ◽  
Information Theoretic ◽  
Cerebellar Granule ◽  
Release Probability

A nerve cell receives multiple inputs from upstream neurons by way of its synapses. Neuron processing functions are thus influenced by changes in the biophysical properties of the synapse, such as long-term potentiation (LTP) or depression (LTD). This observation has opened new perspectives on the biophysical basis of learning and memory, but its quantitative impact on the information transmission of a neuron remains partially elucidated. One major obstacle is the high dimensionality of the neuronal input-output space, which makes it unfeasible to perform a thorough computational analysis of a neuron with multiple synaptic inputs. In this work, information theory was employed to characterize the information transmission of a cerebellar granule cell over a region of its excitatory input space following synaptic changes. Granule cells have a small dendritic tree (on average, they receive only four mossy fiber afferents), which greatly bounds the input combinatorial space, reducing the complexity of information-theoretic calculations. Numerical simulations and LTP experiments quantified how changes in neurotransmitter release probability (p) modulated information transmission of a cerebellar granule cell. Numerical simulations showed that p shaped the neurotransmission landscape in unexpected ways. As p increased, the optimality of the information transmission of most stimuli did not increase strictly monotonically; instead it reached a plateau at intermediate p levels. Furthermore, our results showed that the spatiotemporal characteristics of the inputs determine the effect of p on neurotransmission, thus permitting the selection of distinctive preferred stimuli for different p values. These selective mechanisms may have important consequences on the encoding of cerebellar mossy fiber inputs and the plasticity and computation at the next circuit stage, including the parallel fiber–Purkinje cell synapses.

scholarly journals Efficient generation of reciprocal signals by inhibition

2012 ◽  
Vol 107 (9) ◽  
pp. 2453-2462 ◽  
Author(s):  
Sung-min Park ◽  
Esra Tara ◽  
Kamran Khodakhah
Keyword(s):  
Purkinje Cells ◽  
Granule Cell ◽  
Granule Cells ◽  
Mossy Fiber ◽  
Cell Activity ◽  
Common Mechanism ◽  
Input Output ◽  
Firing Rates ◽  
Neuronal Computation ◽  
The Brain

Reciprocal activity between populations of neurons has been widely observed in the brain and is essential for neuronal computation. The different mechanisms by which reciprocal neuronal activity is generated remain to be established. A common motif in neuronal circuits is the presence of afferents that provide excitation to one set of principal neurons and, via interneurons, inhibition to a second set of principal neurons. This circuitry can be the substrate for generation of reciprocal signals. Here we demonstrate that this equivalent circuit in the cerebellar cortex enables the reciprocal firing rates of Purkinje cells to be efficiently generated from a common set of mossy fiber inputs. The activity of a mossy fiber is relayed to Purkinje cells positioned immediately above it by excitatory granule cells. The firing rates of these Purkinje cells increase as a linear function of mossy fiber, and thus granule cell, activity. In addition to exciting Purkinje cells positioned immediately above it, the activity of a mossy fiber is relayed to laterally positioned Purkinje cells by a disynaptic granule cell → molecular layer interneuron pathway. Here we show in acutely prepared cerebellar slices that the input-output relationship of these laterally positioned Purkinje cells is linear and reciprocal to the first set. A similar linear input-output relationship between decreases in Purkinje cell firing and strength of stimulation of laterally positioned granule cells was also observed in vivo. Use of interneurons to generate reciprocal firing rates may be a common mechanism by which the brain generates reciprocal signals.

Mossy Fiber–Granule Cell Synapses in the Normal and Epileptic Rat Dentate Gyrus Studied With Minimal Laser Photostimulation

1999 ◽  
Vol 82 (4) ◽  
pp. 1883-1894 ◽  
Author(s):  
Péter Molnár ◽  
J. Victor Nadler
Keyword(s):  
Status Epilepticus ◽  
Dentate Gyrus ◽  
Granule Cell ◽  
Granule Cells ◽  
Mossy Fiber ◽  
Hippocampal Formation ◽  
Control Groups ◽  
Small Component ◽  
Fiber Growth ◽  
And Control

Dentate granule cells become synaptically interconnected in the hippocampus of persons with temporal lobe epilepsy, forming a recurrent mossy fiber pathway. This pathway may contribute to the development and propagation of seizures. The physiology of mossy fiber–granule cell synapses is difficult to characterize unambiguously, because electrical stimulation may activate other pathways and because there is a low probability of granule cell interconnection. These problems were addressed by the use of scanning laser photostimulation in slices of the caudal hippocampal formation. Glutamate was released from a caged precursor with highly focused ultraviolet light to evoke action potentials in a small population of granule cells. Excitatory synaptic currents were recorded in the presence of bicuculline. Minimal laser photostimulation evoked an apparently unitary excitatory postsynaptic current (EPSC) in 61% of granule cells from rats that had experienced pilocarpine-induced status epilepticus followed by recurrent mossy fiber growth. An EPSC was also evoked in 13–16% of granule cells from the control groups. EPSCs from status epilepticus and control groups had similar peak amplitudes (∼30 pA), 20–80% rise times (∼1.2 ms), decay time constants (∼10 ms), and half-widths (∼8 ms). The mean failure rate was high (∼70%) in both groups, and in both groups activation of N-methyl-d-aspartate receptors contributed a small component to the EPSC. The strong similarity between responses from the status epilepticus and control groups suggests that they resulted from activation of a similar synaptic population. No EPSC was recorded when the laser beam was focused in the dentate hilus, suggesting that indirect activation of hilar mossy cells contributed little, if at all, to these results. Recurrent mossy fiber growth increases the density of mossy fiber–granule cell synapses in the caudal dentate gyrus by perhaps sixfold, but the new synapses appear to operate very similarly to preexisting mossy fiber–granule cell synapses.

Distal infrapyramidal granule cell axons possess typical mossy fiber morphology

1981 ◽  
Vol 6 (2) ◽  
pp. 119-124 ◽  
Author(s):  
James R. West ◽  
Cheryl A. Hodges ◽  
Asa C. Black
Keyword(s):  
Granule Cell ◽  
Mossy Fiber ◽  
Fiber Morphology

Optical Recording Study of Granule Cell Activities in the Hippocampal Dentate Gyrus of Kainate-Treated Rats

2000 ◽  
Vol 83 (4) ◽  
pp. 2421-2430 ◽  
Author(s):  
Yo Otsu ◽  
Eiichi Maru ◽  
Hisayuki Ohata ◽  
Ichiro Takashima ◽  
Riichi Kajiwara ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Granule Cell ◽  
Granule Cells ◽  
Mossy Fiber ◽  
Molecular Layer ◽  
Mossy Fibers ◽  
Optical Recording ◽  
Granule Cell Layer ◽  
Gabaergic Inhibition ◽  
Mossy Fiber Sprouting

In the epileptic hippocampus, newly sprouted mossy fibers are considered to form recurrent excitatory connections to granule cells in the dentate gyrus and thereby increase seizure susceptibility. To study the effects of mossy fiber sprouting on neural activity in individual lamellae of the dentate gyrus, we used high-speed optical recording to record signals from voltage-sensitive dye in hippocampal slices prepared from kainate-treated epileptic rats (KA rats). In 14 of 24 slices from KA rats, hilar stimulation evoked a large depolarization in almost the entire molecular layer in which granule cell apical dendrites are located. The signals were identified as postsynaptic responses because of their dependence on extracellular Ca2+. The depolarization amplitude was largest in the inner molecular layer (the target area of sprouted mossy fibers) and declined with increasing distance from the granule cell layer. In the inner molecular layer, a good correlation was obtained between depolarization size and the density of mossy fiber terminals detected by Timm staining methods. Blockade of GABAergic inhibition by bicuculline enlarged the depolarization in granule cell dendrites. Our data indicate that mossy fiber sprouting results in a large and prolonged synaptic depolarization in an extensive dendritic area and that the enhanced GABAergic inhibition partly masks the synaptic depolarization. However, despite the large dendritic excitation induced by the sprouted mossy fibers, seizurelike activity of granule cells was never observed, even when GABAergic inhibition was blocked. Therefore, mossy fiber sprouting may not play a critical role in epileptogenesis.

Multiple Erythroid Ankyrin Isoforms in the Mouse Cerebellum: Differential Localization in Purkinje Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1725-1725
Author(s):  
Connie B. Birkenmeier ◽  
Timothy H. Young ◽  
Jane E. Barker ◽  
Luanne L. Peters
Keyword(s):  
Axonal Transport ◽  
Purkinje Cells ◽  
Granule Cell ◽  
Mossy Fiber ◽  
Mossy Fibers ◽  
Granule Cell Layer ◽  
Specific Marker ◽  
Functional Link ◽  
Mouse Cerebellum ◽  
And Function

Abstract The erythroid ankyrin gene (Ank1) produces a large and varied number of isoforms due to alternative splicing of the mRNA. In addition to expression in erythroid tissues, some of these Ank1 proteins are highly expressed in the Purkinje cells (PKC) of the mouse cerebellum. Mice deficient in Ank1 as a result of a mutation in the Ank1 gene (normoblastosis, nb) show a progressive loss of PKCs with an attendant ataxia. We have generated a panel of Ank1 antibodies to aid in sorting out the expression pattern and function of Ank1 proteins in the cerebellum. Two of these antibodies are specific to the alternatively spliced A and B COOH-terminal segments of Ank1. Immunohistochemical (IHC) experiments using these antibodies show strikingly different patterns of localization. Anti-C-termA (α-A) stains the PKC cell body and dendrites while anti-C-termB (α-B) is restricted to the PKC membrane. Both antibodies stain structures in the granule cell layer (GCL) including the granule cell membrane (α-B) and structures known as glomeruli where granule cell dendrites synapse with mossy fiber axons (α-A and α-B). Mossy fibers are a major afferent system that inputs to the cerebellum. α-A, α-B, antibodies to the α-1 subunit of Na+/K+ATPase (NaK-α1) and anti-Synapsin 1, a specific marker for synaptic vesicles, all co-localize in the glomeruli, suggesting a possible functional link. PKC membrane staining with α-B is absent in nb/nb cerebellum whereas PKC staining with α-A is unaffected. GCL staining with both antibodies is reduced in the mutant and this deficit may be important to PKC survival since granule cell axons are a major input system to PKC dendrites. Immunoblots stained with α-A and α-B are consistent with the IHC findings. In addition to the typical large isoforms (∼210kD) that are deficient in the nb mutant, immunoblots of cerebellar lysates reveal a number of small Ank1 related proteins ranging in size from 17 to 50 kD. The α-A and α-B banding patterns are unaffected by the nb mutation suggesting that they may be produced by splicing out the exon containing the nb mutation (E36) or by using an alternative promoter in the 3′ end of the gene as was found for the small Ank1 isoforms in skeletal muscle. Additional IHC findings using GFP-tagged PKC show a PKC axonopathy in nb/nb cerebellum. PKC axons exhibit multiple swellings that accumulate with age raising the possibility that axonal transport is abnormal in the nb PKCs. In summary 1) immunoblots reveal multiple previously undescribed small Ank1 isoforms in cerebellum, 2) two of the alternate Ank1 COOH-termini show very different localization in PKC suggesting distinct functions for the Ank1 proteins carrying them, 3) in the GCL, antibodies to the two COOH-termini co-localize with antibodies to the Na+/K+ATPase α-1 subunit in synaptic densities, 4) deficiencies of Ank1 in the GCL of nb/nb mice may influence PKC survival and 5) axonal transport may be affected in nb/nb PKC. These findings indicate that Ank1 proteins play a more varied role in the cerebellum than previously suspected and suggest new directions for the study of Ank1 function.

scholarly journals Recruitment of an inhibitory hippocampal network after bursting in a single granule cell

2007 ◽  
Vol 104 (18) ◽  
pp. 7640-7645 ◽  
Author(s):  
Masahiro Mori ◽  
Beat H. Gähwiler ◽  
Urs Gerber
Keyword(s):  
Pyramidal Cell ◽  
Granule Cell ◽  
Mossy Fiber ◽  
Mossy Fibers ◽  
Pyramidal Cells ◽  
Network Activity ◽  
Inhibitory Input ◽  
Inhibitory Interneurons ◽  
Failure Rates ◽  
Ca3 Pyramidal Cells

The hippocampal CA3 area, an associational network implicated in memory function, receives monosynaptic excitatory as well as disynaptic inhibitory input through the mossy-fiber axons of the dentate granule cells. Synapses made by mossy fibers exhibit low release probability, resulting in high failure rates at resting discharge frequencies of 0.1 Hz. In recordings from functionally connected pairs of neurons, burst firing of a granule cell increased the probability of glutamate release onto both CA3 pyramidal cells and inhibitory interneurons, such that subsequent low-frequency stimulation evoked biphasic excitatory/inhibitory responses in a CA3 pyramidal cell, an effect lasting for minutes. Analysis of the unitary connections in the circuit revealed that granule cell bursting caused powerful activation of an inhibitory network, thereby transiently suppressing excitatory input to CA3 pyramidal cells. This phenomenon reflects the high incidence of spike-to-spike transmission at granule cell to interneuron synapses, the numerically much greater targeting by mossy fibers of inhibitory interneurons versus principal cells, and the extensively divergent output of interneurons targeting CA3 pyramidal cells. Thus, mossy-fiber input to CA3 pyramidal cells appears to function in three distinct modes: a resting mode, in which synaptic transmission is ineffectual because of high failure rates; a bursting mode, in which excitation predominates; and a postbursting mode, in which inhibitory input to the CA3 pyramidal cells is greatly enhanced. A mechanism allowing the transient recruitment of inhibitory input may be important for controlling network activity in the highly interconnected CA3 pyramidal cell region.

Sign in / Sign up

Export Citation Format

Share Document