Color imaging of parietal and frontal somatosensory potential fields evoked by stimulation of median or posterior tibial nerve in man

Somatosensory evoked potentials (SEPs) to median or fingers or posterior tibial nerve stimulation were recorded with earlobe reference in normal young adults. A system of 16 electrodes on the scalp served to create bit-mapped images of the potential fields at 1 msec intervals. The P14 (median SEP) or P30 (tibial SEP) far fields thought to reflect the afferent volley in the medial lemniscus produced widespread positivity over the scalp. Subsequent components had a characteristic focal distribution suggesting that they reflected one or more generators in cortical areas. For the median SEP, the parietal N20 and the prerolandic P22 showed differences in onset and offset times as well as distribution that precluded their being related to the same generator. While N20 was contralateral, P22 extended ipsilaterally. P22 may be generated in the motor area 4 and the supplementary motor area. P22 was also distinct from the P27 field restricted to the contralateral parietal region. The frontal N30 had a bilateral distribution and the P45 presented variable features. For the tibial SEP, no phase reversal was confirmed between the parietal P38 (midline-ipsilateral focus) and N33 (contralateral focus). N37 over the contralateral prerolandic region might reflect a generator in the motor region. P58 was more symmetrically distributed than P38, possibly because it reflected generators more posteriorly on the parietal convexity. N75 had a widespread field with focus on the ipsilateral side of midline. © 1985.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Brain stem auditory evoked potentials in normal aging in man

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Exteroceptive suppression of masseter mononeurones in man

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The cognitive P40, N60 and P100 components of somatosensory evoked potentials and the earliest electrical signs of sensory processing in man

Selective attention tasks involving random sequences of electrical stimulation of fingers were designed to compare cerebral potentials to identical stimuli (for example to the left thumb) when they are 'infrequent target' signals or 'frequent-neglected' signals in the series. The experiments were carried out in normal adult subjects. The early SEP components were analyzed for the earliest cortical electrical sign of information processing stages. Two new components, P40 (with onset at 26 msec) and N60, precede the processing positivity P100 which may be more significant in somatosensory processing than the negativities recorded in auditory or visual tasks. © 1983.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Bit-mapped color imaging of human evoked potentials with reference to the N20, P22, P27 and N30 somatosensory responses

Bit-mapped color imaging of scalp potential fields evoked by sensory stimulation in humans disclosed significant features not indentified by mere inspection of multichannel traces. Methodological problems are considered in detail for early cortical SEPs which include several components with sharp rise times occurring at spatially distinct scalp locations. A manageable yet efficient imaging system requires recording electrodes in adequate number and scalp locations, bandpass fidelity to resolve slow and fast components, consistency of bioelectric input data, optimal interpolation and mapping algorithms, and consistent color scaling. Critical steps in these procedures were investigated in conjunction with new evidence on the scalp topography and neural generators of the N20, P20, P22, P27 and N30 SEP components. It is concluded that N20-P20 reflect a tangential equivalent dipole in parietal area 3b while P22 reflects a radial equivalent dipole in motor area 4. © 1987.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Réponses synchronisées du muscle masséter à la vibration

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REPONSES SYNCHRONISEES DU MUSCLE MASSETER A LA VIBRATION

SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe

The p40 and p100 processing positivities that precede p300 closure in serial somatosensory decision tasks

SCOPUS: NotDefined.jFLWNAinfo:eu-repo/semantics/publishedBrain and Information: Event-Related Potential

Impact of invasive little fire ants Wasmannia auropunctata on rainforest soil fauna: implications for conservation of the endangered flightless kagu of New Caledonia

International audienceThe little fire ant, Wasmannia auropunctata , is an invasive species known to negatively affect many native species in its introduced range. Here, we studied the effect of little fire ant presence on the biomass of soil fauna in rainforest of New Caledonia to assess if little fire ants have an impact on an endangered endemic flightless bird, the kagu, Rhynochetos jubatus. The average biomass of soil fauna (except for millipedes) was lower in 53 sample plots with little fire ants than in 597 sample plots without little fire ants and the biomass decreased with increasing density of little fire ant nests. Millipedes on the contrary seemed to be positively impacted as their average biomass was higher in areas with fire ants than in areas without, but even millipede biomass decreased with increasing nest density of fire ants. Kagu density decreased with increasing area of rainforest invaded by little fire ants, suggesting, given their observed negative impact on soil fauna biomass, that they may limit food resources for kagu. Little fire ants might therefore transform rainforest into a less suitable habitat for the kagu by reducing the biomass of their prey and thus have a negative impact for kagu conservation

Invasive rats strengthen predation pressure on bird eggs in a South Pacific island rainforest

International audienceInvasive rats (Rattus spp.) are known to have pervasive impacts on island birds, particularly on their nesting success. To conserve or restore bird populations, numerous invasive rat control or eradication projects are undertaken on islands worldwide. However, such projects represent a huge investment and the decision-making process requires proper assessment of rat impacts. Here, we assessed the influence of two sympatric invasive rats (Rattus rattus and R. exulans) on native bird eggs in a New Caledonian rainforest, using artificial bird-nest monitoring. A total of 178 artificial nests containing two eggs of three different sizes were placed either on the ground or 1.5 m high and monitored at the start of the birds' breeding season. Overall, 12.4% of the nests were depredated during the first 7 days. At site 1, where nests were monitored during 16 days, 41.8% of the nests were depredated. The main predator was the native crow Corvus moneduloides, responsible for 62.9% of the overall predation events. Rats were responsible for only 22.9% of the events, and ate only small and medium eggs at both heights. Our experiment suggests that in New Caledonia, predation pressure by rats strengthens overall bird-nest predation, adding to that by native predators. Experimental rat control operations may allow reduced predation pressure on nests as well as the recording of biodiversity responses after rat population reduction