Pierre Pouget | Sorbonne University (original) (raw)

Papers by Pierre Pouget

Journal of neurophysiology, Jan 10, 2016

The presence of a respiratory-related cortical activity during tidal breathing is abnormal and a ... more The presence of a respiratory-related cortical activity during tidal breathing is abnormal and a hallmark of respiratory difficulties, but its detection requires superior discrimination and temporal resolution. The aim of this study was to validate a computational method using EEG covariance (or connectivity) matrices to detect a change in brain activity related to breathing. In 17 healthy subjects, EEG was recorded during resting unloaded breathing (RB), voluntary sniffs and breathing against an inspiratory threshold load (ITL). EEG were analyzed by the specially developed covariance-based classifier, event-related potentials and time-frequency (T-F) distributions. Nine subjects repeated the protocol. The classifier could accurately detect ITL and sniffs compared to the reference period of RB. For ITL, EEG-based detection was superior to airflow-based detection (p<0.05). A coincident improvement in EEG-airflow correlation in ITL compared to RB (p<0.05) confirmed that EEG-dete...

Biophysical journal, Jan 5, 2016

Determining the electrical properties of the extracellular space around neurons is important for ... more Determining the electrical properties of the extracellular space around neurons is important for understanding the genesis of extracellular potentials, as well as for localizing neuronal activity from extracellular recordings. However, the exact nature of these extracellular properties is still uncertain. Here, we introduce a method to measure the impedance of the tissue, one that preserves the intact cell-medium interface using whole-cell patch-clamp recordings in vivo and in vitro. We find that neural tissue has marked non-ohmic and frequency-filtering properties, which are not consistent with a resistive (ohmic) medium, as often assumed. The amplitude and phase profiles of the measured impedance are consistent with the contribution of ionic diffusion. We also show that the impact of such frequency-filtering properties is possibly important on the genesis of local field potentials, as well as on the cable properties of neurons. These results show non-ohmic properties of the extrac...

Numerous studies have described different functional cell types in the frontal eye field (FEF), b... more Numerous studies have described different functional cell types in the frontal eye field (FEF), but the reliability of the distinction between these types has been uncertain.

G. 1995; Van der Loos 1976) with a special class of cortical Sirota. Sharp, local synchrony among... more G. 1995; Van der Loos 1976) with a special class of cortical Sirota. Sharp, local synchrony among putative feed-forward inhibineuron in the topographically aligned barrel column 1 of pritory interneurons of rabbit somatosensory cortex. J. Neurophysiol. mary somatosensory cortex (S1). These cortical neurons are 79: 567-582, 1998. Many suspected inhibitory interneurons believed to be inhibitory interneurons (suspected inhibitory (SINs) of primary somatosensory cortex (S1) receive a potent interneurons, SINs). They are identified by a high-frequency monosynaptic thalamic input (thalamocortical SINs, SINstc). It (ú600 Hz) burst of three or more spikes to electrical stimuhas been proposed that nearly all such SINstc of a S1 barrel column lation of afferent pathways, and they have action potentials (BC) receive excitatory synaptic input from each member of a of short duration (Swadlow 1989. It was found subpopulation of neurons within the topographically aligned venthat most of the SINs within and near layer 4, and some of trobasal (VB) thalamic barreloid. Such a divergent and convergent network leads to several testable predictions: sharply synchronous those found in layer 5, received a potent monosynaptic input activity should occur between SINstc of a BC, sharp synchrony from VB thalamus (thalamocortical SINs, SINstc). Experishould not occur between SINstc of neighboring BCs, and sharp ments examining functional synaptic connectivity between synchrony should not occur between SINs or other neurons of the individual VB barreloid neurons and topographically aligned same BC that do not receive potent monosynaptic thalamic input. SINstc lead to the proposal that a subclass of barreloid neu-These predictions were tested by cross-correlating the activity of rons have axons that diverge to provide synaptic input to SINstc of the same and neighboring BCs. Correlations among denearly all of the SINstc of the aligned S1 barrel column scending corticofugal neurons of layer 5 (CF-5 neurons, identified A recent proposal (Swadlow 1995) maintains that a richly 1 We have adopted the term ''barrel column'' from Van der Loos and divergent and convergent axonal network links ventrobasal colleagues (e.g., ) to refer to a layer 4 barrel (Woolsey and Van der Loos 1970) plus the cortical tissue above and below it.

Proceedings of the National Academy of Sciences, 2008

Tactile discrimination depends on integration of information from the discrete receptive fields (... more Tactile discrimination depends on integration of information from the discrete receptive fields (RFs) of peripheral sensory afferents. Because this information is processed over a hierarchy of subcortical nuclei and cortical areas, the integration likely occurs at multiple levels. The current study presents results indicating that neurons across most of the extent of the hand representation in monkey primary somatosensory cortex (area 3b) interact, even when these neurons have separate RFs. We obtained simultaneous recordings by using a 100-electrode array implanted in the hand representation of primary somatosensory cortex of two anesthetized owl monkeys. During a series of 0.5-s skin indentations with single or dual probes, the distance between electrodes from which neurons with synchronized spike times were recorded exceeded 2 mm. The results provide evidence that stimuli on different parts of the hand influence the degree of synchronous firing among a large population of neurons. Because spike synchrony potentiates the activation of commonly targeted neurons, synchronous neural activity in primary somatosensory cortex can contribute to discrimination of complex tactile stimuli.

Vision Research, 2013

Detailed measurements of saccadic latency -the time taken to make an eye movement to a suddenlypr... more Detailed measurements of saccadic latency -the time taken to make an eye movement to a suddenlypresented visual target -have proved a valuable source of detailed and quantitative information in a wide range of neurological conditions, as well as shedding light on the mechanisms of decision, currently of intense interest to cognitive neuroscie ntists. However, there is no doubt that more complex oculomotor tasks, and in particular the antisaccade task in which a participant must make a saccade in the opposite direction to the target, are potentially more sensitive indicators of neurolo gical dysfunction, particularly in neurodegenerative conditions. But two obstacles currently hinder their widespread adoption for this purpose. First, that much of the potential information from antisaccade experiments, notably about latency distribution and amplitude, is typically thrown away. Second, that there is no standardised protocol for carrying out antisaccade experiments, so that results from one laboratory cannot easily be compared with those from another. This paper, the outcome of a recen t international meeting of oculomotor scientists and clinicians with an unusually wide experience of such measure ments, sets out a proposed protocol for clinical antisaccade trials: its adoption will greatly enhance the clinical and scientific benefits of making these kinds of measure ments.

Journal of Neurophysiology, 2005

The latency and variability of latency of single-unit responses to identical visual stimulation w... more The latency and variability of latency of single-unit responses to identical visual stimulation were measured in the frontal eye field (FEF), supplementary eye field (SEF), and anterior cingulate cortex (ACC) of macaque monkeys performing visually guided saccades. The mean visual response latency was significantly shorter in FEF (64 ms) than in SEF (81 ms) or ACC (100 ms), and latency values determined by four methods agreed. The latency variability of the visual response was respectively less in FEF (21 ms) than in SEF (37 ms) or ACC (41 ms). Latency, variability of latency, and magnitude of the visual responses were correlated within FEF and SEF but not ACC. These characteristics of the visual response are consistent with the degree of convergence of visual afferents to these areas and constrain hypotheses about visual processing in the frontal lobe.

PLoS ONE, 2014

The passage of time can be estimated either explicitly, e.g. before leaving home in the morning, ... more The passage of time can be estimated either explicitly, e.g. before leaving home in the morning, or implicitly, e.g. when catching a flying ball. In the present study, the latency of saccadic eye movements was used to evaluate differences between implicit and explicit timing. Humans were required to make a saccade between a central and a peripheral position on a computer screen. The delay between the extinction of a central target and the appearance of an eccentric target was the independent variable that could take one out of four different values (400, 900, 1400 or 1900 ms). In target trials, the delay period lasted for one of the four durations randomly. At the end of the delay, a saccade was initiated by the appearance of an eccentric target. Cue&target trials were similar to target trials but the duration of the delay was visually cued. In probe trials, the duration of the upcoming delay was cued, but there was no eccentric target and subjects had to internally generate a saccade at the estimated end of the delay. In target and cue&target trials, the mean and variance of latency distributions decreased as delay duration increased. In cue&target trials latencies were shorter. In probe trials, the variance increased with increasing delay duration and scalar variability was observed. The major differences in saccadic latency distributions were observed between visually-guided (target and cue&target trials) and internally-generated saccades (probe trials). In target and cue&target trials the timing of the response was implicit. In probe trials, the timing of the response was internally-generated and explicitly based on the duration of the visual cue. Scalar timing was observed only during probe trials. This study supports the hypothesis that there is no ubiquitous timing system in the brain but independent timing processes active depending on task demands.

The dynamics of visual selection and saccade preparation by the frontal eye field was investigate... more The dynamics of visual selection and saccade preparation by the frontal eye field was investigated in macaque monkeys performing a search-step task combining the classic double-step saccade task with visual search. Reward was earned for producing a saccade to a color singleton. On random trials the target and one distractor swapped locations before the saccade and monkeys were rewarded for shifting gaze to the new singleton location. A race model accounts for the probabilities and latencies of saccades to the initial and final singleton locations and provides a measure of the duration of a covert compensation process—target-step reaction time. When the target stepped out of a movement field, noncompensated saccades to the original location were produced when movement-related activity grew rapidly to a threshold. Compensated saccades to the final location were produced when the growth of the original movement-related activity was interrupted within target-step reaction time and was replaced by activation of other neurons producing the compensated saccade. When the target stepped into a receptive field, visual neurons selected the new target location regardless of the monkeys' response. When the target stepped out of a receptive field most visual neurons maintained the representation of the original target location, but a minority of visual neurons showed reduced activity. Chronometric analyses of the neural responses to the target step revealed that the modulation of visually responsive neurons and movement-related neurons occurred early enough to shift attention and saccade preparation from the old to the new target location. These findings indicate that visual activity in the frontal eye field signals the location of targets for orienting, whereas movement-related activity instantiates saccade preparation.

Neuropsychologia, Jan 27, 2015

Patients with right hemisphere damage and visual neglect have severe problems to orient attention... more Patients with right hemisphere damage and visual neglect have severe problems to orient attention towards left-sided objects, often associated with the tendency to produce inappropriate rightward saccades. In its most severe form, this tendency can assume the compulsive character of a rightward deviation of gaze as soon as the visual scene deploys (so-called "magnetic attraction of gaze"). However, little is known about the exact nature of inappropriate rightward saccades, their relation with impaired conscious perception of left-sided stimuli, and their lesional correlates. To explore these issues, we studied three groups of patients with right brain damage: patients with signs of left visual neglect associated to left homonymous hemianopia, neglect patients without hemianopia, and patients without neglect or hemianopia. Participants searched for a gap missing within a target, presented among distractors. Manual responses for target detection were required, while particip...

Contemporary Trends in ADHD Research, 2012

... Castellanos FX, Tannock R. Neuroscience of attention-deficit/hyperactivity disorder: the sear... more ... Castellanos FX, Tannock R. Neuroscience of attention-deficit/hyperactivity disorder: the search for endophenotypes. ... 1996, 15;40(10): 964-80 Stuss DT, Meiran N, Guzman A, Lafleche G, Wilmer J. Do long tests yield a more accurate diagnosis of dementia than short tests ? ...

Journal of neurophysiology, Jan 15, 2014

It is known that sensory deprivation, including postnatal whisker trimming, can lead to severe de... more It is known that sensory deprivation, including postnatal whisker trimming, can lead to severe deficits in the firing rate properties of cortical neurons. Recent results indicate that development of synchronous discharge among cortical neurons is also activity influenced, and that correlated discharge is significantly impaired following loss of bilateral sensory input in rats. Here we investigate whether unilateral whisker trimming (unilateral deprivation or UD) after birth interferes in the same way with the development of synchronous discharge in cortex. We measured the coincidence of spikes among pairs of neurons recorded under urethane anesthesia in one whisker barrel field deprived by trimming all contralateral whiskers for 60 days after birth (UD), and in untrimmed controls (CON). In the septal columns around barrels, UD significantly increased the coincident discharge among cortical neurons compared with CON, most notably in layers II/III. In contrast, synchronous discharge w...