@article{pmid12569169,

title = {Gain control of firing rate by shunting inhibition: roles of synaptic noise and dendritic saturation},

author = {Steven A Prescott and Yves De Koninck},

doi = {10.1073/pnas.0337591100},

issn = {0027-8424},

year  = {2003},

date = {2003-02-01},

journal = {Proc Natl Acad Sci U S A},

volume = {100},

number = {4},

pages = {2076--2081},

abstract = {Adjusting input-output gain is crucial for information processing by the brain. Gain control of subthreshold depolarization is commonly ascribed to increased membrane conductance caused by shunting inhibition. But contrary to its divisive effect on depolarization, shunting inhibition on its own fails to divisively modulate firing rate, apparently upsetting a critical tenet of neural models that use shunting inhibition to achieve gain control. Using a biophysically realistic neuron model, we show that divisive modulation of firing rate by shunting inhibition requires synaptic noise to smooth the relation between firing rate and somatic depolarization; although necessary, noise alone endows shunting inhibition with only a modest divisive effect on firing rate. In addition to introducing noise, synaptic input is associated with a nonlinear relation between somatic depolarization and excitation because of dendritic saturation; this nonlinearity dramatically enhances divisive modulation of firing rate by shunting inhibition under noisy conditions. Thus, shunting inhibition can act as a mechanism for firing rate gain control, but its modulatory effects (which include both divisive and subtractive components) are fully explained only when both synaptic noise and dendritic saturation are taken into account.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid11839606,

title = {Aging causes a preferential loss of cholinergic innervation of characterized neocortical pyramidal neurons},

author = {Maria Antonietta Casu and T P Wong and Yves De Koninck and Alfredo Ribeiro-da-Silva and A Claudio Cuello},

doi = {10.1093/cercor/12.3.329},

issn = {1047-3211},

year  = {2002},

date = {2002-03-01},

journal = {Cereb Cortex},

volume = {12},

number = {3},

pages = {329--337},

abstract = {Aging is known to markedly affect the number and structural characteristics of both pre- and post-synaptic sites in the cerebral cortex. There is evidence that lamina V pyramidal neurons, and their basilar dendrites in particular, are affected by age-related decline. Furthermore, layer V is the area where the greatest overall age- related losses in the total population of synaptic boutons and of cholinergic boutons are observed. Since both pyramidal neurons and cortical cholinergic input are characteristically compromised in aging, we investigated whether aging altered the pattern of cholinergic boutons in apposition to the soma, proximal and distal basal dendrites of intracellularly labeled lamina V large pyramidal neurons in the parietal cortex of young and aged rats. We observed a significant age-related decrease in the population of both total and cholinergic boutons apposed to proximal and distal dendrites of layer V large pyramidal neurons. However, the age-related decreases of cholinergic presynaptic boutons were higher than those in the total bouton population apposed to the pyramidal neurons. The average decrease in cholinergic boutons in aged rats was 3.7-fold more pronounced than the diminution in the overall number of presynaptic boutons. Our results add important new evidence in support of the concept that the age-related learning and memory deficits are attributable, at least partially, to a decline in the functional integrity of the forebrain cholinergic systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid11897852,

title = {Four cell types with distinctive membrane properties and morphologies in lamina I of the spinal dorsal horn of the adult rat},

author = {Steven A Prescott and Yves De Koninck},

doi = {10.1113/jphysiol.2001.013437},

issn = {0022-3751},

year  = {2002},

date = {2002-03-01},

journal = {J Physiol},

volume = {539},

number = {Pt 3},

pages = {817--836},

abstract = {Lamina I of the spinal dorsal horn plays an important role in the processing and relay of nociceptive information. Signal processing depends, in part, on neuronal membrane properties. Intrinsic membrane properties of lamina I neurons were therefore investigated using whole cell patch clamp recordings in a slice preparation of adult rat spinal cord. Based on responses to somatic current injection, four cell types were identified: tonic, which fire comparatively slowly but continuously throughout stimulation; phasic, which fire a high frequency burst of variable duration; delayed onset, which fire irregularly and with a marked delay to the first spike; and single spike, which typically fire only one action potential even when strongly depolarised. Classification by spiking pattern was further refined by identification of characteristic stimulus-response curves and quantification of several response parameters. Objectivity of the classification was confirmed by cluster analysis. Responses to stimulus trains and synaptic input as well as the kinetics of spontaneous synaptic events revealed differences in the signal processing characteristics of the cell types: tonic and delayed onset cells appeared to act predominantly as integrators whereas phasic and single spike cells acted as coincidence detectors. Intracellular labelling revealed a significant correlation between morphological and physiological cell types: tonic cells were typically fusiform, phasic cells were pyramidal, and delayed onset and single spike cells were multipolar. Thus, there are multiple physiological cells types in lamina I with specific morphological correlates and distinctive signal processing characteristics that confer significant differences in the transduction of input into spike trains.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}