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Whole-scalp EEG mapping of somatosensory evoked potentials in macaque monkeys.

Gindrat AD, Quairiaux C, Britz J, Brunet D, Lanz F, Michel CM, Rouiller EM - Brain Struct Funct (2014)

Bottom Line: Most importantly, SSEP recordings were stable both intra- and interindividually.As a prerequisite, the present study demonstrated that a 300-mm(2) unilateral craniotomy over the sensorimotor cortex necessary to induce a cortical lesion, followed by bone flap repositioning, suture and gap plugging with calcium phosphate cement, did not induce major distortions of the SSEPs.In conclusion, SSEPs can be successfully and reproducibly recorded from high-density EEG caps in macaque monkeys before and after a craniotomy, opening new possibilities for the long-term follow-up of the cortical reorganisation of large-scale networks in macaque monkeys after a cortical lesion.

View Article: PubMed Central - PubMed

Affiliation: Domain of Physiology, Department of Medicine, Faculty of Sciences and Fribourg Center for Cognition, University of Fribourg, Chemin du Musée 5, 1700, Fribourg, Switzerland, anne-dominique.gindrat@unifr.ch.

ABSTRACT
High-density scalp EEG recordings are widely used to study whole-brain neuronal networks in humans non-invasively. Here, we validate EEG mapping of somatosensory evoked potentials (SSEPs) in macaque monkeys (Macaca fascicularis) for the long-term investigation of large-scale neuronal networks and their reorganisation after lesions requiring a craniotomy. SSEPs were acquired from 33 scalp electrodes in five adult anaesthetized animals after electrical median or tibial nerve stimulation. SSEP scalp potential maps were identified by cluster analysis and identified in individual recordings. A distributed, linear inverse solution was used to estimate the intracortical sources of the scalp potentials. SSEPs were characterised by a sequence of components with unique scalp topographies. Source analysis confirmed that median nerve SSEP component maps were in accordance with the somatotopic organisation of the sensorimotor cortex. Most importantly, SSEP recordings were stable both intra- and interindividually. We aim to apply this method to the study of recovery and reorganisation of large-scale neuronal networks following a focal cortical lesion requiring a craniotomy. As a prerequisite, the present study demonstrated that a 300-mm(2) unilateral craniotomy over the sensorimotor cortex necessary to induce a cortical lesion, followed by bone flap repositioning, suture and gap plugging with calcium phosphate cement, did not induce major distortions of the SSEPs. In conclusion, SSEPs can be successfully and reproducibly recorded from high-density EEG caps in macaque monkeys before and after a craniotomy, opening new possibilities for the long-term follow-up of the cortical reorganisation of large-scale networks in macaque monkeys after a cortical lesion.

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Interindividual reproducibility of left median nerve SSEPs. a Brainstem component and main cortical component SSEP waveforms after left median nerve stimulation in five monkeys: Mk-AT (blue), Mk-BB (green), Mk-DG (black), Mk-DI (red), and Mk-EN (yellow), during the first 50 ms following the stimulation. These data were obtained from 1 recording session in each animal. b Colour-scaled voltage maps obtained from 7 to 37 ms post-stimulus, at 3-ms interval. The colour scaling in microvolts is indicated for each animal and was adapted for each map. All the maps were obtained using the same cap model (Mk-EN). The locations of the electrodes where both components were recorded with the largest amplitude are represented on the maps with orange circles (brainstem component) and light green circles (main cortical component). Note that these locations can vary between animals. Same conventions as in Fig. 2
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Fig5: Interindividual reproducibility of left median nerve SSEPs. a Brainstem component and main cortical component SSEP waveforms after left median nerve stimulation in five monkeys: Mk-AT (blue), Mk-BB (green), Mk-DG (black), Mk-DI (red), and Mk-EN (yellow), during the first 50 ms following the stimulation. These data were obtained from 1 recording session in each animal. b Colour-scaled voltage maps obtained from 7 to 37 ms post-stimulus, at 3-ms interval. The colour scaling in microvolts is indicated for each animal and was adapted for each map. All the maps were obtained using the same cap model (Mk-EN). The locations of the electrodes where both components were recorded with the largest amplitude are represented on the maps with orange circles (brainstem component) and light green circles (main cortical component). Note that these locations can vary between animals. Same conventions as in Fig. 2

Mentions: The results presented in Figs. 2 and 4, acquired in a single animal (Mk-EN), showed high stability across recording sessions. Median nerve and tibial nerve SSEP recordings were also performed in four other monkeys (Mk-AT, Mk-BB, Mk-DG, Mk-DI). A qualitative analysis based on left median nerve SSEPs obtained from 1 recording session in the five animals showed that there were some differences in the relative amplitude and some shifts in latencies of the different SSEP components among the animals (Fig. 5a), i.e. the voltage maps at a given time point may differ slightly across animals. For example, maps from 13 ms in Mk-DI were delayed by 3–6 ms relative to the ones in the other monkeys. More importantly, however, voltage topographies at the scalp were conserved both in terms of spatial configuration and temporal sequence across the five individuals (Fig. 5b). This reproducibility of surface topographies across animals was also true for right median nerve SSEPs and left and right tibial nerve SSEPs (Online Resource Supplementary Figures 5–7).Fig. 5


Whole-scalp EEG mapping of somatosensory evoked potentials in macaque monkeys.

Gindrat AD, Quairiaux C, Britz J, Brunet D, Lanz F, Michel CM, Rouiller EM - Brain Struct Funct (2014)

Interindividual reproducibility of left median nerve SSEPs. a Brainstem component and main cortical component SSEP waveforms after left median nerve stimulation in five monkeys: Mk-AT (blue), Mk-BB (green), Mk-DG (black), Mk-DI (red), and Mk-EN (yellow), during the first 50 ms following the stimulation. These data were obtained from 1 recording session in each animal. b Colour-scaled voltage maps obtained from 7 to 37 ms post-stimulus, at 3-ms interval. The colour scaling in microvolts is indicated for each animal and was adapted for each map. All the maps were obtained using the same cap model (Mk-EN). The locations of the electrodes where both components were recorded with the largest amplitude are represented on the maps with orange circles (brainstem component) and light green circles (main cortical component). Note that these locations can vary between animals. Same conventions as in Fig. 2
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Related In: Results  -  Collection

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Fig5: Interindividual reproducibility of left median nerve SSEPs. a Brainstem component and main cortical component SSEP waveforms after left median nerve stimulation in five monkeys: Mk-AT (blue), Mk-BB (green), Mk-DG (black), Mk-DI (red), and Mk-EN (yellow), during the first 50 ms following the stimulation. These data were obtained from 1 recording session in each animal. b Colour-scaled voltage maps obtained from 7 to 37 ms post-stimulus, at 3-ms interval. The colour scaling in microvolts is indicated for each animal and was adapted for each map. All the maps were obtained using the same cap model (Mk-EN). The locations of the electrodes where both components were recorded with the largest amplitude are represented on the maps with orange circles (brainstem component) and light green circles (main cortical component). Note that these locations can vary between animals. Same conventions as in Fig. 2
Mentions: The results presented in Figs. 2 and 4, acquired in a single animal (Mk-EN), showed high stability across recording sessions. Median nerve and tibial nerve SSEP recordings were also performed in four other monkeys (Mk-AT, Mk-BB, Mk-DG, Mk-DI). A qualitative analysis based on left median nerve SSEPs obtained from 1 recording session in the five animals showed that there were some differences in the relative amplitude and some shifts in latencies of the different SSEP components among the animals (Fig. 5a), i.e. the voltage maps at a given time point may differ slightly across animals. For example, maps from 13 ms in Mk-DI were delayed by 3–6 ms relative to the ones in the other monkeys. More importantly, however, voltage topographies at the scalp were conserved both in terms of spatial configuration and temporal sequence across the five individuals (Fig. 5b). This reproducibility of surface topographies across animals was also true for right median nerve SSEPs and left and right tibial nerve SSEPs (Online Resource Supplementary Figures 5–7).Fig. 5

Bottom Line: Most importantly, SSEP recordings were stable both intra- and interindividually.As a prerequisite, the present study demonstrated that a 300-mm(2) unilateral craniotomy over the sensorimotor cortex necessary to induce a cortical lesion, followed by bone flap repositioning, suture and gap plugging with calcium phosphate cement, did not induce major distortions of the SSEPs.In conclusion, SSEPs can be successfully and reproducibly recorded from high-density EEG caps in macaque monkeys before and after a craniotomy, opening new possibilities for the long-term follow-up of the cortical reorganisation of large-scale networks in macaque monkeys after a cortical lesion.

View Article: PubMed Central - PubMed

Affiliation: Domain of Physiology, Department of Medicine, Faculty of Sciences and Fribourg Center for Cognition, University of Fribourg, Chemin du Musée 5, 1700, Fribourg, Switzerland, anne-dominique.gindrat@unifr.ch.

ABSTRACT
High-density scalp EEG recordings are widely used to study whole-brain neuronal networks in humans non-invasively. Here, we validate EEG mapping of somatosensory evoked potentials (SSEPs) in macaque monkeys (Macaca fascicularis) for the long-term investigation of large-scale neuronal networks and their reorganisation after lesions requiring a craniotomy. SSEPs were acquired from 33 scalp electrodes in five adult anaesthetized animals after electrical median or tibial nerve stimulation. SSEP scalp potential maps were identified by cluster analysis and identified in individual recordings. A distributed, linear inverse solution was used to estimate the intracortical sources of the scalp potentials. SSEPs were characterised by a sequence of components with unique scalp topographies. Source analysis confirmed that median nerve SSEP component maps were in accordance with the somatotopic organisation of the sensorimotor cortex. Most importantly, SSEP recordings were stable both intra- and interindividually. We aim to apply this method to the study of recovery and reorganisation of large-scale neuronal networks following a focal cortical lesion requiring a craniotomy. As a prerequisite, the present study demonstrated that a 300-mm(2) unilateral craniotomy over the sensorimotor cortex necessary to induce a cortical lesion, followed by bone flap repositioning, suture and gap plugging with calcium phosphate cement, did not induce major distortions of the SSEPs. In conclusion, SSEPs can be successfully and reproducibly recorded from high-density EEG caps in macaque monkeys before and after a craniotomy, opening new possibilities for the long-term follow-up of the cortical reorganisation of large-scale networks in macaque monkeys after a cortical lesion.

No MeSH data available.


Related in: MedlinePlus