The following deal with the *synchronisation* processes tied to the SOMA of the neuron and as such allow for
data flowing-in from the dendrites to be 'sliced and diced' due to synchronisation 'anomolies' etc. the focus in
transcendence is the EXAGGERATION of things - reflected in such processes as hormone release etc (which means an
exaggeration can also be in the form of an inhibiting as well as exciting). The recruitment emphasis is in maintaining
BALANCE in the transformation function and enabling an increase in bandwidth (e.g. gain control etc), and so transcendence,
a 'better' perspective, in the transcendence function.
As stated in the last list: Overall we are dealing with differentiations and integrations and differentiations
FROM integrations as well as integrations FROM differentiations - all concepts focused-upon in the IDM
model
================
Proc. Natl. Acad. Sci. USA, Vol. 99, Issue 12, 8378-8383, June 11, 2002
Neurobiology
Single-neuron correlates of subjective vision in the human medial temporal lobe
Gabriel Kreiman*,,, Itzhak Fried,§, and Christof Koch*
* Computation and Neural Systems Program, California Institute of Technology 139-74, Pasadena, CA 91125; Division
of Neurosurgery, University of California School of Medicine, Los Angeles, CA 90095; and § Department of Behavioral
Sciences and Psychiatry, Functional Neurosurgery Unit, Tel-Aviv Medical Center and Sackler School of Medicine,
Tel-Aviv University, Tel-Aviv 69978, Israel
Communicated by Francis Crick, The Salk Institute for Biological Studies, San Diego, CA, April 2, 2002 (received
for review March 15, 2002)
Visual information from the environment is transformed into perceptual sensations through several stages of neuronal
processing. Flash suppression constitutes a striking example in which the same retinal input can give rise to two
different conscious visual percepts. We directly recorded the responses of individual neurons during flash suppression
in the human amygdala, entorhinal cortex, hippocampus, and parahippocampal gyrus, allowing us to explore the neuronal
responses in untrained subjects at a high spatial and temporal resolution in the medial temporal lobe. Subjects
were patients with pharmacologically intractable epilepsy implanted with depth electrodes to localize the seizure
onset focus. We observed that the activity of two thirds of all visually selective neurons followed the perceptual
alternations rather than the retinal input. None of the selective neurons responded to a perceptually suppressed
stimulus. Therefore, the activity of most individual neurons in the medial temporal lobe of naive human subjects
directly correlates with the phenomenal visual experience.
================
Izv Akad Nauk Ser Biol 2000 Jan-Feb;(1):66-74 Related Articles, Links
[Circahoralian rhythms and integrative function of neurons]
[Article in Russian]
Zaguskin SL.
Research Institute of Physics, Rostov State University, Russia.
The neuron's integrative function is directly related to circumhoralian rhythms of energy and plastic processes
in the neuron's soma. The neuron's excitability and its integral reaction to a test stimulus are determined by
the energy-dependent accumulation of calcium ions and decreased aggregation of tigroid and mitochondria, as well
as by changes in the soma and axon hill geometry. Upon synchronization of functional load and energy of the cell,
an increased excitability of the neuron and formation of a temporal relationship are possible.
=================
Cell Mol Neurobiol 1998 Feb;18(1):29-43 Related Articles, Links
Synaptic modulation of oscillatory activity of hypothalamic neuronal networks in vitro.
Misgeld U, Zeilhofer HU, Swandulla D.
I. Physiologisches Institut, Universitat Heidelberg, Germany.
1. Rhythmic bursts of action potentials in neurosecretory cells are a key factor in hypothalamic neurosecretion.
Rhythmicity and synchronization may be accomplished by pacemaker cells synaptically driving follower cells or by
a network oscillator. 2. In this review we describe a hypothalamic cell culture which may serve as a model for
a hypothalamic network oscillator. An overview is given of neurochemical phenotypes, synaptic mechanisms and their
development, properties of receptors for fast synaptic transmission, and membrane properties of cells in dissociated
rat embryonic hypothalamic culture. 3. Rhythmic activity spreads in the cultured network through synapses that
release glutamate, activating a heteromultimeric AMPA-type receptor containing a GluR2 subunit which is associated
with a high-conductance channel for Na+ and K+. Rhythmic activity is controlled by synapses that release GABA to
activate GABAA receptors. The presumed function of the two receptor types is facilitated by their respective location,
GABAA receptors predominating near the soma and AMPA receptors being abundant in dendrites. 4. Network oscillators
may be more reliable for the presumed function than single-cell oscillators. They are controlled through synaptic
modulation, which may prove to represent a process important for the release of hormones.
=============
J Neurosci 1994 Nov;14(11 Pt 2):7087-98 Related Articles, Links
Role of neuronal synchronizing mechanisms in the propagation of spreading depression in the in vivo hippocampus.
Herreras O, Largo C, Ibarz JM, Somjen GG, Martin del Rio R.
Departamento Investigacion, Hospital Ramon y Cajal, Madrid, Spain.
To detect what initiates spreading depression (SD), the early prodromal events were investigated in hippocampal
CA1 of urethane-anesthetized rats. SD was provoked by microdialysis or focal microinjection of high-K+ solution.
Extracellular DC potentials and extracellular potassium concentration ([K+]o) were recorded, and spontaneous and
evoked potentials analyzed for current source-density (CSD). In the front of an approaching SD wave, several seconds
before the onset of the typical sustained negative potential shift (delta Vo) and the increased [K+]o, fast electrical
activity was detected. This consisted initially of small rhythmic (60-70 Hz) sawtooth wavelets, which then gave
way to a shower of population spikes (PSs) of identical frequency. Prodromal wavelets and PSs were synchronized
over considerable distances in the tissue. Sawtooth wavelets were identified as pacemakers of the prodromal PS
burst. Simultaneous recording at three depths revealed that the spontaneous prodromal PSs occurred exactly in phase
in dendrites and somata whereas synaptically transmitted PSs arose first in the proximal dendrites and were conducted
from there into the soma membrane. During a spike burst, stratum (st.) pyramidale served as current sink, while
in the proximal sublayer of st. radiatum spike-sinks gave way to spike sources that grew larger as the sinks in
st. pyramidale began to subside. Blocking synaptic transmission did not abolish the prodromal spike burst, yet
repetitive orthodromic activation inhibited it without altering the subsequent SD waveform. Complex changes in
cell excitability were detected even before fast spontaneous activities. We concluded that, in the initial evolution
of SD, changes in neuron function precede the regenerating depolarization by several seconds. We propose that the
opening of normally closed electric junctions among neurons can best explain the long-distance synchronization
and the flow current that occurs in the leading edge of a propagating wave of SD.
=============
J Neurophysiol 1991 Sep;66(3):1059-79 Related Articles, Links
Simulations of cortical pyramidal neurons synchronized by inhibitory interneurons.
Lytton WW, Sejnowski TJ.
Salk Institute, Computational Neurobiology Laboratory, La Jolla 92037.
===============
J Neurophysiol 1984 Jul;52(1):126-42 Related Articles, Links
Excitation of hippocampal pyramidal cells by an electrical field effect.
Taylor CP, Dudek FE.
The effects of electrical fields from antidromic stimulation of CA1 pyramidal cells were studied in slices of rat
hippocampus in which chemical synaptic transmission had been blocked by superfusion with physiological solution
containing Mn2+ and lowered concentration of Ca2+. Differential voltage recordings were made between two microelectrode
positions, on intracellular to a pyramidal cell and the other in the adjacent extracellular space. This technique
revealed brief transmembrane depolarizations that occurred synchronously with negative-going extracellular population
spikes in the adjacent cell body layer. Glial cells in this region did not exhibit these depolarizations. In some
pyramidal cells, alvear stimulation that was too weak to excite the axon of the impaled cell elicited action potentials,
which appeared to arise from transmembrane depolarizations at the soma. When subthreshold transmembrane depolarizations
were superimposed on subthreshold depolarizing current pulses, somatic action potentials were generated synchronously
with the antidromic population spikes. The depolarizations of pyramidal somata were finely graded with stimulus
intensity, were unaffected by polarization of the membrane, and were not occluded by preceding action potentials.
The laminar profile of extracellular field potentials perpendicular to the cell body layer was obtained with an
array of extracellular recording locations. Numerical techniques of current source-density analysis indicated that
at the peak of the somatic population spike, there was an extracellular current sink near pyramidal somata and
sources in distal dendritic regions. It is concluded that during population spikes an extracellular electrical
field causes currents to flow passively across inactive pyramidal cell membranes, thus depolarizing their somata.
The transmembrane depolarizations associated with population spikes would tend to excite and synchronize the population
of pyramidal cells.
====================
J Neurosci 2002 Aug 1;22(15):6426-36 Related Articles, Links
Recruitment of the kainate receptor subunit glutamate receptor 6 by cadherin/catenin complexes.
Coussen F, Normand E, Marchal C, Costet P, Choquet D, Lambert M, Mege RM, Mulle C.
Centre National de la Recherche Scientifique Unite Mixte de Recherche 5091, Institut Francois Magendie, Paris 75005,
France.
Kainate receptors modulate synaptic transmission by acting either at presynaptic or at postsynaptic sites. The
precise localization of kainate receptors as well as the mechanisms of targeting and stabilization of these receptors
in neurons are largely unknown. We have generated transgenic mice expressing the kainate receptor subunit glutamate
receptor 6 (GluR6) bearing an extracellular myc epitope (myc-GluR6), in forebrain neurons, in which it assembles
with endogenous kainate receptor subunits. In transgenic mice crossed with GluR6-deficient mice, myc-GluR6 efficiently
rescues the missing subunit. Immunoprecipitation of transgenic brain extracts with anti-myc antibodies demonstrates
an interaction with cadherins, beta-catenin, and p120 catenin, as well as with the associated proteins calcium
calmodulin-dependent serine kinase and Velis, but not with alpha-catenin. In glutathione S-transferase-pulldown
experiments, beta-catenin interacts, although indirectly, with the last 14 aa of GluR6. Transfected myc-GluR6 colocalizes
with beta-catenin at cell-cell junctions in non-neuronal cells. Finally, activation of N-cadherins by ligand-covered
latex beads recruits GluR6 to cadherin/catenin complexes. These results suggest an important role for cadherin/catenin
complexes in the stabilization of kainate receptors at the synaptic membrane during synapse formation and remodeling.
=====================
Nat Neurosci 2002 Aug;5(8):751-9 Related Articles, Links
Rapid recruitment of NMDA receptor transport packets to nascent synapses.
Washbourne P, Bennett JE, McAllister AK.
Center for Neuroscience, University of California Davis, 1544 Newton Ct., Davis, California 95616, USA.
Although many of the molecules involved in synaptogenesis have been identified, the sequence and kinetics of synapse
assembly in the central nervous system (CNS) remain largely unknown. We used simultaneous time-lapse imaging of
fluorescent glutamate receptor subunits and presynaptic proteins in rat cortical neurons in vitro to determine
the dynamics and time course of N-methyl-D-aspartate receptor (NMDAR) recruitment to nascent synapses. We found
that both NMDA and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) subunits are present
in mobile transport packets in neurons before and during synaptogenesis. NMDAR transport packets are more mobile
than AMPAR subunits, moving along microtubules at about 4 microm/min, and are recruited to sites of axodendritic
contact within minutes. Whereas NMDAR recruitment to new synapses can be either concurrent with or independent
of the protein PSD-95, AMPARs are recruited with a slower time course. Thus, glutamatergic synapses can form rapidly
by the sequential delivery of modular transport packets containing glutamate receptors.
====================
Neuron 2002 Jun 13;34(6):945-60 Related Articles, Links
Comment in:
Neuron. 2002 Jun 13;34(6):856-8.
Coordinated interaction of neurogenesis and angiogenesis in the adult songbird brain.
Louissaint A Jr, Rao S, Leventhal C, Goldman SA.
Department of Neurology and Neuroscience, Cornell University Medical Center, 1300 York Avenue, New York, NY 10021,
USA.
Neurogenesis proceeds throughout life in the higher vocal center (HVC) of the adult songbird neostriatum. Testosterone
induces neuronal addition and endothelial division in HVC. We asked if testosterone-induced angiogenesis might
contribute importantly to HVC neuronal recruitment. Testosterone upregulated both VEGF and its endothelial receptor,
VEGF-R2/Quek1/KDR, in HVC. This yielded a burst in local HVC angiogenesis. FACS-isolated HVC endothelial cells
produced BDNF in a testosterone-dependent manner. In vivo, HVC BDNF rose by the third week after testosterone,
lagging by over a week the rise in VEGF and VEGF-R2. In situ hybridization revealed that much of this induced BDNF
mRNA was endothelial. In vivo, both angiogenesis and neuronal addition to HVC were substantially diminished by
inhibition of VEGF-R2 tyrosine kinase. These findings suggest a causal interaction between testosterone-induced
angiogenesis and neurogenesis in the adult forebrain.
================
Neural Comput 2002 Jul;14(7):1669-89 Related Articles, Links
Attentional recruitment of inter-areal recurrent networks for selective gain control.
Hahnloser RH, Douglas RJ, Hepp K.
Howard Hughes Medical Institute, Department of Brain and Cognitive Sciences, MIT, Cambridge, MA 02139 USA. rhahnloser@mit.edu
There is strong anatomical and physiological evidence that neurons with large receptive fields located in higher
visual areas are recurrently connected to neurons with smaller receptive fields in lower areas. We have previously
described a minimal neuronal network architecture in which top-down attentional signals to large receptive field
neurons can bias and selectively read out the bottom-up sensory information to small receptive field neurons (Hahnloser,
Douglas, Mahowald, & Hepp, 1999). Here we study an enhanced model, where the role of attention is to recruit
specific inter-areal feedback loops (e.g., drive neurons above firing threshold). We first illustrate the operation
of recruitment on a simple example of visual stimulus selection. In the subsequent analysis, we find that attentional
recruitment operates by dynamical modulation of signal amplification and response multistability. In particular,
we find that attentional stimulus selection necessitates increased recruitment when the stimulus to be selected
is of small contrast and of small distance away from distractor stimuli. The selectability of a low-contrast stimulus
is dependent on the gain of attentional effects; for example, low-contrast stimuli can be selected only when attention
enhances neural responses. However, the dependence of attentional selection on stimulus-distractor distance is
not contingent on whether attention enhances or suppresses responses. The computational implications of attentional
recruitment are that cortical circuits can behave as winner-take-all mechanisms of variable strength and can achieve
close to optimal signal discrimination in the presence of external noise
================
Behav Brain Res 2002 Jun 15;133(1):31-43 Related Articles, Links
Social change affects the survival of new neurons in the forebrain of adult songbirds.
Lipkind D, Nottebohm F, Rado R, Barnea A.
Department of Zoology, Tel-Aviv University, Ramat-Aviv, Israel.
Many new neurons are added to the adult avian brain. Most of them die 3-5 weeks after they are born (Nature (Lond.)
335 (1988) 353; J. Comp. Neurol 411 (1999) 487). Those that survive replace, numerically, older ones that have
died (Neuron 25 (2000) 481). It has been suggested that the new neurons enhance the brain's ability to acquire
new long-term memories (review in Sci. Am. 260 (1989) 74). If so, perhaps an increase in social complexity affects
the survival of new neurons in a social species. To test this hypothesis, we treated adult zebra finches (Taeniopygia
guttata) with [3H]-thymidine immediately before introducing them into one of three different social environments
that differed in complexity and killed them 40 days later. There was a significant difference between experimental
groups in the number of [3H]-labeled neurons in neostriatum caudale (NC), high vocal center (HVC) and Area X, three
forebrain regions that are involved in vocal communication. In these regions, birds placed in a large heterosexual
group had more new neurons than birds kept singly or as male-female pairs. Regulation of new neuron survival by
extent of circuit use may be a general mechanism for ensuring that neuronal replacement is closely attuned to environmental
change.
=================
J Neurosci 2002 Jun 1;22(11):4428-36 Related Articles, Links
Activity-dependent recruitment of extrasynaptic NMDA receptor activation at an AMPA receptor-only synapse.
Clark BA, Cull-Candy SG.
Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom. b.clark@ucl.ac.uk.
We have identified an excitatory synapse in cerebellar molecular layer interneurons at which the level of presynaptic
activity determines the receptor type involved in the postsynaptic response. When small numbers of parallel fibers
are activated, EPSCs are mediated solely by AMPA receptors (AMPARs), despite our finding that NMDA receptors (NMDARs)
are present in the dendrites of these cells. The EPSC kinetics are fast (tau decay = 0.82 +/- 0.05 msec at room
temperature), consistent with the role these interneurons are thought to play in precisely timed inhibitory control
of Purkinje cells. NMDARs are activated only when glutamate release is increased either by facilitation with brief
high-frequency trains or by recruiting more presynaptic fibers with higher stimulus intensities. Under these conditions,
EPSCs consist of a fast-rising AMPAR-mediated current followed by a slow component mediated by both NMDARs and
AMPARs. Inhibitors of glutamate transport increase the amplitude and prolong the time course of the compound EPSCs.
In contrast, the properties of fast AMPAR EPSCs resulting from the activation of few inputs remain unchanged when
glutamate uptake is blocked. Our results suggest that, at these synapses, the postsynaptic density contains AMPARs
alone. It is only when transmitter release is high enough for glutamate to diffuse to the extrasynaptic space and
to reach concentrations sufficient to activate extrasynaptic receptors that NMDARs are involved in the postsynaptic
response. We suggest that such a spatial separation of receptor types may provide a mechanism for rapid changes
in EPSC properties, depending on the amount of synaptic activity.
==================
Brain Behav Evol 2001;58(5):276-95 Related Articles, Links
Neurogenesis and neuronal regeneration in the adult reptilian brain.
Font E, Desfilis E, Perez-Canellas MM, Garcia-Verdugo JM.
Instituto Cavanilles de Biodiversidad y Biologia Evolutiva, Universidad de Valencia, Spain. enrique.font@uv.es
Evidence accumulated over the last few decades demonstrates that all reptiles examined thus far continue to add
neurons at a high rate and in many regions of the adult brain. This so-called adult neurogenesis has been described
in the olfactory bulbs, rostral forebrain, all cortical areas, anterior dorsal ventricular ridge, septum, striatum,
nucleus sphericus, and cerebellum. The rate of neuronal production varies greatly among these brain areas. Moreover,
striking differences in the rate and distribution of adult neurogenesis have been noted among species. In addition
to producing new neurons in the adult brain, lizards, and possibly other reptiles as well, are capable of regenerating
large portions of their telencephalon damaged as a result of experimentally-induced injuries, thus exhibiting an
enormous potential for neuronal regeneration. Adult neurogenesis and neuronal regeneration take advantage of the
same mechanisms that are present during embryonic neurogenesis. New neurons are born in the ependyma lining the
ventricles and migrate radially through the brain parenchyma along processes of radial glial cells. Several lines
of evidence suggest that radial glial cells also act as stem cells for adult neurogenesis. Once they reach their
final destination, the young neurons extend axons that reach appropriate target areas. Tangential migration of
neurons alongside the ventricular ependyma has also been reported. Most of these tangentially migrating neurons
seem to be destined for the olfactory bulbs and are, thus, part of a system similar to the mammalian rostral migratory
stream. The proliferation and recruitment of new neurons appear to result in continuous growth of most areas showing
adult neurogenesis. The functional consequences of this continuous generation and integration of new neurons into
existing circuits is largely conjectural, but involvement of these phenomena in learning and memory is one likely
possibility. Copyright 2002 S. Karger AG, Basel
==============
: J Neurophysiol 2002 Apr;87(4):1859-66 Related Articles, Links
Intrinsic activation of human motoneurons: reduction of motor unit recruitment thresholds by repeated contractions.
Gorassini M, Yang JF, Siu M, Bennett DJ.
Division of Neuroscience, Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta T6G 2S2,
Canada. monica.gorassini@ualberta.ca
The main purpose of this study was to examine whether facilitation of human motor unit recruitment by repeated
voluntary contractions is mediated, in part, by time and activity-dependent increases in the intrinsic excitability
of the parent motoneuron. To do this, pairs of tibialis anterior or soleus motor units were recorded during slowly
increasing and then decreasing voluntary contractions. The firing rate of the lower-threshold motor unit of the
pair (control unit) was used as a measure of effective synaptic excitation (i.e., drive) to the motoneurons. This
rate was used to estimate the recruitment threshold of the higher-threshold unit of the pair (test unit). The test
unit was repeatedly recruited and de-recruited in a series of contractions, and the interval between the de-recruitment
and re-recruitment of the test unit (interactivation interval) was systematically varied between 0.6 and 60 s.
An increase in intrinsic excitability of a unit was considered to have occurred if the level of estimated synaptic
input (as measured by the firing rate of the control motor unit) needed to recruit a unit was reduced. At short
interactivation intervals (1-2 s), the control unit firing frequency was significantly lower when the test unit
was recruited on the second contraction, compared with the first (by 3.9 Hz or a 64% reduction). This suggested
that the intrinsic excitability of the test motor unit had increased during the second contraction because it could
be recruited at a much lower level of estimated synaptic drive. Longer interaction intervals (2-6 s) produced less
recruitment facilitation. At even longer interactivation intervals (>6 s) there was no significant facilitation
(time constant of effect was 4.8 s). In some motor units, the effect of this short-term facilitation appeared to
be so pronounced that it resulted in reversing the order of de-recruitment with the other initially lower-threshold
motor units. Such reversals were occasionally observed for orderly re-recruitment. The time course and behavior
of the observed short-term facilitation of motor unit discharge was qualitatively similar to the warm-up phenomenon
of plateau potentials seen in motoneurons of reduced preparations (e.g., 4-6 s). The possibility of warm-up contributing
to the time and activity-dependent facilitation of human motor unit recruitment is discussed.
===============