David Soares

Universidade Federal do Oeste do Pará

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Dennis Q. Truong

Soterix Medical (United States)

John C. Rothwell

National Hospital for Neurology and Neurosurgery

Ingo Hahn

Munich University of Applied Sciences

André Zacharia

University of Geneva

Matteo Ciocca

Imperial College London

Carmen Rosa GARCÍA-DÁVILA

Instituto de Investigaciones de la Amazonía Peruana

Sven Bestmann

National Hospital for Neurology and Neurosurgery

Uwe Römer

Universität Trier

Fabrice Duponchelle

Centre National de la Recherche Scientifique

Jean‐François Renno

Institut de Recherche pour le Développement

Cooperative Institutions

University College London

National Hospital for Neurology and Neurosurgery

Sobell House

Instituto de Investigaciones de la Amazonía Peruana

Amazon (Germany)

Centre National de la Recherche Scientifique

Universidade Federal do Oeste do Pará

Institut de Recherche pour le Développement

Gabriel René Moreno Autonomous University

Institut de Recherche pour le Développement

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Expression of Kv3.1b potassium channel is widespread in macaque motor cortex pyramidal cells: A histological comparison between rat and macaque

The Journal of Comparative Neurology (2017)

David Soares Isabelle Goldrick Roger Lemon Alexander Kraskov Linda Greensmith

There are substantial differences across species in the organization and function of the motor pathways. These differences extend to basic electrophysiological properties. Thus, in rat motor cortex, pyramidal cells have long duration action potentials, while in the macaque, some pyramidal neurons exhibit short duration "thin" spikes. These differences may be related to the expression of the fast potassium channel Kv3.1b, which in rat interneurons is associated with generation of thin spikes. Rat pyramidal cells typically lack these channels, while there are reports that they are present in macaque pyramids. Here we made a systematic, quantitative comparison of the Kv3.1b expression in sections from macaque and rat motor cortex, using two different antibodies (NeuroMab, Millipore). As our standard reference, we examined, in the same sections, Kv3.1b staining in parvalbumin-positive interneurons, which show strong Kv3.1b immunoreactivity. In macaque motor cortex, a large sample of pyramidal neurons were nearly all found to express Kv3.1b in their soma membranes. These labeled neurons were identified as pyramidal based either by expression of SMI32 (a pyramidal marker), or by their shape and size, and lack of expression of parvalbumin (a marker for some classes of interneuron). Large (Betz cells), medium, and small pyramidal neurons all expressed Kv3.1b. In rat motor cortex, SMI32-postive pyramidal neurons expressing Kv3.1b were very rare and weakly stained. Thus, there is a marked species difference in the immunoreactivity of Kv3.1b in pyramidal neurons, and this may be one of the factors explaining the pronounced electrophysiological differences between rat and macaque pyramidal neurons.

Pyramidal tracts

Pyramidal cell

Interneuron

10.1002/cne.24192

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Citations (44)

tDCS changes in motor excitability are specific to orientation of current flow

bioRxiv (Cold Spring Harbor Laboratory) (2017)

Vishal Rawiji Matteo Ciocca André Zacharia David Soares Dennis Q. Truong

Abstract Measurements and models of current flow in the brain during transcranial Direct Current Stimulation (tDCS) indicate stimulation of regions in-between electrodes. Moreover, the cephalic cortex result in local fluctuations in current flow intensity and direction, and animal studies suggest current flow direction relative to cortical columns determines response to tDCS. Here we test this idea by measuring changes in cortico-spinal excitability by Transcranial Magnetic Stimulation Motor Evoked Potentials (TMS-MEP), following tDCS applied with electrodes aligned orthogonal (across) or parallel to M1 in the central sulcus. Current flow models predicted that the orthogonal electrode montage produces consistently oriented current across the hand region of M1 that flows along cortical columns, while the parallel electrode montage produces none-uniform current directions across the M1 cortical surface. We find that orthogonal, but not parallel, orientated tDCS modulates TMS-MEPs. We also show modulation is sensitive to the orientation of the TMS coil (PA or AP), which is through to select different afferent pathways to M1. Our results are consistent with tDCS producing directionally specific neuromodulation in brain regions in-between electrodes, but shows nuanced changes in excitability that are presumably current direction relative to column and axon pathway specific. We suggest that the direction of current flow through cortical target regions should be considered for targeting and dose-control of tDCS. Highlights Direction of current flow is important for tDCS after-effects. tDCS modulates excitability between two electrodes. tDCS differentially modulates PA and AP inputs into M1. Abbreviations PA postero-anterior AP antero-posterior ML medio-lateral tDCS transcranial direct current stimulation MEP motor evoked potential M1 primary motor cortex TMS transcranial magnetic stimulation; AP-TMS-MEPs motor evoked potentials elicited with anterior-posterior directed TMS; PA-TMS-MEPs motor evoked potentials elicited with posterior-anterior directed TMS Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Motor area

10.1101/149633

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Citations (5)

tDCS changes in motor excitability are specific to orientation of current flow

Brain stimulation (2017)

Vishal Rawji Matteo Ciocca André Zacharia David Soares Dennis Q. Truong

BackgroundMeasurements and models of current flow in the brain during transcranial Direct Current Stimulation (tDCS) indicate stimulation of regions in-between electrodes. Moreover, the folded cortex results in local fluctuations in current flow intensity and direction, and animal studies suggest current flow direction relative to cortical columns determines response to tDCS.MethodsHere we test this idea by using Transcranial Magnetic Stimulation Motor Evoked Potentials (TMS-MEP) to measure changes in corticospinal excitability following tDCS applied with electrodes aligned orthogonal (across) or parallel to M1 in the central sulcus.ResultsCurrent flow models predicted that the orthogonal electrode montage produces consistently oriented current across the hand region of M1 that flows along cortical columns, while the parallel electrode montage produces non-uniform current directions across the M1 cortical surface. We find that orthogonal, but not parallel, orientated tDCS modulates TMS-MEPs. We also show modulation is sensitive to the orientation of the TMS coil (PA or AP), which is thought to select different afferent pathways to M1.ConclusionsOur results are consistent with tDCS producing directionally specific neuromodulation in brain regions in-between electrodes, but shows nuanced changes in excitability that are presumably current direction relative to column and axon pathway specific. We suggest that the direction of current flow through cortical target regions should be considered for targeting and dose-control of tDCS.

Motor area

10.1016/j.brs.2017.11.001

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Citations (133)

Description of Apistogramma allpahuayo sp. n., a new dwarf cichlid species (Teleostei: Perciformes: Geophaginae) from in and around the Reserva Nacional Allpahuayo Mishana, Loreto, Peru

Vertebrate Zoology (2012)

Uwe Römer Joscha Beninde Fabrice Duponchelle Antonia Díaz Hernán Ortega

A new species of Apistogramma is described from Peru, based on a total of 51 specimens collected in small forest brooks in and around the Reserva Nacional Allpahuayo Mishana in the drainage of the Nanay river basin about 30 kilometres southwest of Iquitos, Departamento Loreto (approximately 73° 25’ W/03° 59’ S). Apistogramma allpahuayo sp. n. is distinguished from all other Apistogramma species by the combination of black w-shape marking on lower jaw, (in adult males) lyrate caudal fin, massive jaws and hypertrophied orange lips, distinct roundish caudal-peduncle spot clearly separated from lateral band ending at vertical bar 7, serrated dorsal fin with conspicuous extensions of first membranes, and proportions of dorsal-fin spines differing from those otherwise typical within genus. Apistogramma allpahuayo sp. n. is thought to be a representative of the Apistogramma cacatuoides complex within the Apistogramma cacatuoides lineage.

Perciformes

Teleostei

Dorsal fin

Peduncle (anatomy)

Cichlid

Fish fin

10.3897/vz.62.e31386

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Re-description of Apistogramma payaminonis KULLANDER, 1986, with descriptions of two new cichlid species of the genus Apistogramma (Teleostei, Perciformes, Geophaginae) from northern Peru

Vertebrate Zoology (2015)

Uwe Römer David Soares Carmen Rosa GARCÍA-DÁVILA Fabrice Duponchelle Jean‐François Renno

Apistogramma payaminonis Kullander, 1986 is redescribed based on the only two type specimens available, and two new, closely-related Apistogramma species are described from Peru. Data from the original description of A. payaminonis are supplemented with information on phenotypic appearance, which is important for differentiating the taxon from several other species discovered in the last few years. Apistogramma feconat sp. n. is described from four specimens from the catchment of the Río Tigre, Loreto; information on its ecology, biology, and current conservation status is summarised. Apistogramma wolli sp. n. is described from six specimens from the catchment of the Napo river, Loreto, close to the Peru-Ecuador border; information on its ecology and biology is sparse. Both newly described species are representatives of the Apistogramma nijsseni complex that live in small forest streams influenced by blackwater. Information on differentiating females of some members of this group of related species is presented. At present no clear information based on voucher specimens is available regarding the possible distribution of the two species in Ecuador. Man-made environmental hazards potentially endangering the aquatic fauna in the western catchment of the Río Marañón and the Rio Amazonas, between their tributaries the Rio Pastaza and the Rio Napo, are discussed.

Cichlid

Perciformes

Teleostei

10.3897/vz.65.e31523

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First Record of the Green Thorny‐Tail Iguana Uracentron azureum guentheri (Squamata: Tropiduridae) in the Tapajós/Xingú Interfluve Brazilian Amazonia

Austral Ecology (2025)

David Soares Ilson Carlos MARTINS Raidel Reis dos Santos Síria Ribeiro Alfredo P. Santos‐Jr

ABSTRACT The lizard genus Uracentron , family Tropiduridae, is composed of the species Uracentron flaviceps (Guichenot, 1855) and Uracentron azureum (Linnaeus, 1758). Both species have arboreal habits and are endemic to the Amazon. Here we report a new geographical record of Uracentron azureum guentheri from western Pará State, Brazil, and the first record for the species in the Tapajós/Xingú interfluve. Two specimens were recorded in a fragment of secondary forest on the right bank of the Curuá‐Una River, downstream of the Curuá‐Una Hydroelectric Power Plant dam, in Santarém, Pará, Brazil. The specimen has colour and morphological features that fit guentheri subspecies. With this new record, Uracentron azureum guentheri is now known in 15 locations in Peru (Loreto department) and Brazil (Amazonas, Mato Grosso, Pará, and Rondônia States), expanding its distribution approximately 209 km southeast of the nearest previously known location (Oriximiná Municipality). Recording and reporting such new geographical records is essential since it allows distribution gaps to be filled and is important for understanding biodiversity patterns, speciation processes and phenotypic variations, as well as contributing to conservation planning. The identification of priority areas for protection can be improved with such data, helping to reduce environmental impacts and preserve local biodiversity.

Iguana

10.1111/aec.70029

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