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P1098: Auditory evoked temporal “delta brushes” in human premature neonates
Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339
S237
Figure 1. Group-level session effects. Neuronal responses in the visual cortex to pattern flashes were significantly decreased in the post- compared to the pre-high frequency stimulation (HFS) session (p<0.01, uncorrected for multiple comparisons for display purposes).
after HFS were only partly overlapping. No association between location, extent and direction of the HFS-effect was observed. Discussion: The findings are unexpected in the light of existing HFSstudies, but mirror the high inter-subject variability, concerning even the directionality of the induced effects shown for other indices of LTP-like plasticity in the human brain. As this variability is not observed in LTP at the cellular level, a better understanding of LTP-like mechanisms on the macroscopic level is essential for establishing tools to quantify individual synaptic plasticity in-vivo.
P1098 Auditory evoked temporal “delta brushes” in human premature neonates
Figure 2. The delayed facilitation is present only in the NDH in both right-handed and left-handed subjects. Hempspheric differences emerge more in individuals exhibiting strong preference for the right hand. DH and NDH, however, don’t show a mirror-like behavior among right-handed and left-handed subjects.
excitability may be relevant to better understanding cortical plasticity processes and may provide new tools to study neurological disorders characterized by central fatigue and less capacity to recovery.
P682 Heterogeneity of stimulus-specific response modification – an fMRI study on neuroplasticity in the visual system J. Lahr 1 , J. Peter 1 , M. Bach 2 , I. Mader 3 , C. Nissen 4 , C. Normann 4 , C. Kaller 1 , S. Kloeppel 4 1 University Medical Center Freiburg, Neurology, Freiburg, Germany; 2 University Medical Center Freiburg, Ophtalmology, Freiburg, Germany; 3 University Medical Center Freiburg, Neuroradiology, Freiburg, Germany; 4 University Medical Center Freiburg, Psychiatry, Freiburg, Germany Question: Long-term potentiation (LTP) is a key element of synaptic plasticity. At the macroscopic level, similar effects can be induced in the human brain using repetitive stimulation with identical stimuli. High-frequency stimulation (HFS) can increase neuronal responses whereas low-frequency stimulation may produce the opposite effect. Optimal stimulation frequencies and characteristics for inducing stimulus-specific response modification differ substantially from those applied to brain tissue slices but have been explored in recent studies. In contrast, the individual manifestation of this effect regarding its spatial location and extent are unclear. Methods: Using functional MRI (fMRI) in 18 subjects, we attempted to induce LTP-like effects by HFS with checkerboard flashes at 9 Hz for 120 seconds. The fMRI signal in the visual cortex in response to low-frequency probe checkerboard stimuli shown before and after the HFS period was compared. Results: Flashes induced strong activation in primary and secondary visual cortices. Contrary to our expectations, we found clusters of decreased activations induced by pattern flashes after HFS at the border between primary and secondary visual cortices, significant in the right hemisphere. On the level of the individual subject, some showed significantly increased activations in the post-HFS session while the majority showed significant decreases. The locations of areas showing altered activations before and
A. Kaminska 1,2 , M. Colonnese 3,4 , M. Chipaux 5,2 , A. Mauguen 2 , M. Mokhtari 6 , M. Milh 3 , O. Dulac 2 , C. Chiron 2 , R. Khazipov 3,7 1 Necker Enfants Malades Hospital, Clinical Neurophysiology, Paris, France; 2 University Paris Descartes, Inserm U663, CEA Neurospin, Paris, France; 3 Aix-Marseille University, Inserm U901/Inmed, Marseille, France; 4 The George Washington University, Department of Pharmacology and Physiology and Institute of Neuroscience, Washington, DC, France; 5 Fondation Ophthalmologique A de Rothschild, Pediatric Neurosurgery, Paris, French Polynesia; 6 Kremlin Bicetre Hospital, Neonatal Intensive Care Department, Kremlin Bicetre, France; 7 Kazan Federal University, Laboratory of Neurobiology, Kazan, Russia, France The initial period of sensory cortical circuit formation during the third trimester of gestation in humans is characterized by a particular electroencephalographic activity pattern, “Delta-brushes” that consist in high amplitude slow wave superimposed with rapid oscillations. While deltabrushes are often thought to be spontaneously generated entirely within neo-cortex, recent work showed that they are reliably evoked in central cortical areas by sensory input resulting from spontaneous hand or foot twitches in a somatotopic manner and in occipital areas by light flashes. Here, we explored the role of auditory input in driving delta-brushes in temporal cortex in 46 premature neonates from 31 to 38 weeks of gestational age, using simultaneous electroencephalographic recordings and auditory stimuli mimicking ambient sounds, including low intensity technogenic “clicks” and human voices. Event detection, power frequency analysis and stimulus locked averaging showed that in the youngest premature (31-34 weeks of gestational age), both voices and low-volume “clicks” reliably evoke delta-brushes specifically in temporal cortical areas. Auditory-evoked delta-brushes consisted of temporal negative slow-waves and rapid oscillations similar to spontaneous delta-brushes. Around 35-36 weeks of gestational age auditory-evoked responses showed a dramatic change characterized by the disappearance of auditory-evoked delta-brushes and the emergence of low-amplitude auditory-evoked cortical potentials. “Click” and voice evoked auditory responses differentiated in their frequencypower topography starting from 34 weeks onwards. Along with findings in other sensory modalities (visual and somatosensory), these findings suggest that sensory driven delta-brushes represent a ubiquitous feature of the human sensory cortex during fetal stages thus probably contributing to the formation of cortical sensory maps by amplifying sensory input. Sensory evoked delta-brushes provide a test of functional cortical maturation during fetal development.
S237
Figure 1. Group-level session effects. Neuronal responses in the visual cortex to pattern flashes were significantly decreased in the post- compared to the pre-high frequency stimulation (HFS) session (p<0.01, uncorrected for multiple comparisons for display purposes).
after HFS were only partly overlapping. No association between location, extent and direction of the HFS-effect was observed. Discussion: The findings are unexpected in the light of existing HFSstudies, but mirror the high inter-subject variability, concerning even the directionality of the induced effects shown for other indices of LTP-like plasticity in the human brain. As this variability is not observed in LTP at the cellular level, a better understanding of LTP-like mechanisms on the macroscopic level is essential for establishing tools to quantify individual synaptic plasticity in-vivo.
P1098 Auditory evoked temporal “delta brushes” in human premature neonates
Figure 2. The delayed facilitation is present only in the NDH in both right-handed and left-handed subjects. Hempspheric differences emerge more in individuals exhibiting strong preference for the right hand. DH and NDH, however, don’t show a mirror-like behavior among right-handed and left-handed subjects.
excitability may be relevant to better understanding cortical plasticity processes and may provide new tools to study neurological disorders characterized by central fatigue and less capacity to recovery.
P682 Heterogeneity of stimulus-specific response modification – an fMRI study on neuroplasticity in the visual system J. Lahr 1 , J. Peter 1 , M. Bach 2 , I. Mader 3 , C. Nissen 4 , C. Normann 4 , C. Kaller 1 , S. Kloeppel 4 1 University Medical Center Freiburg, Neurology, Freiburg, Germany; 2 University Medical Center Freiburg, Ophtalmology, Freiburg, Germany; 3 University Medical Center Freiburg, Neuroradiology, Freiburg, Germany; 4 University Medical Center Freiburg, Psychiatry, Freiburg, Germany Question: Long-term potentiation (LTP) is a key element of synaptic plasticity. At the macroscopic level, similar effects can be induced in the human brain using repetitive stimulation with identical stimuli. High-frequency stimulation (HFS) can increase neuronal responses whereas low-frequency stimulation may produce the opposite effect. Optimal stimulation frequencies and characteristics for inducing stimulus-specific response modification differ substantially from those applied to brain tissue slices but have been explored in recent studies. In contrast, the individual manifestation of this effect regarding its spatial location and extent are unclear. Methods: Using functional MRI (fMRI) in 18 subjects, we attempted to induce LTP-like effects by HFS with checkerboard flashes at 9 Hz for 120 seconds. The fMRI signal in the visual cortex in response to low-frequency probe checkerboard stimuli shown before and after the HFS period was compared. Results: Flashes induced strong activation in primary and secondary visual cortices. Contrary to our expectations, we found clusters of decreased activations induced by pattern flashes after HFS at the border between primary and secondary visual cortices, significant in the right hemisphere. On the level of the individual subject, some showed significantly increased activations in the post-HFS session while the majority showed significant decreases. The locations of areas showing altered activations before and
A. Kaminska 1,2 , M. Colonnese 3,4 , M. Chipaux 5,2 , A. Mauguen 2 , M. Mokhtari 6 , M. Milh 3 , O. Dulac 2 , C. Chiron 2 , R. Khazipov 3,7 1 Necker Enfants Malades Hospital, Clinical Neurophysiology, Paris, France; 2 University Paris Descartes, Inserm U663, CEA Neurospin, Paris, France; 3 Aix-Marseille University, Inserm U901/Inmed, Marseille, France; 4 The George Washington University, Department of Pharmacology and Physiology and Institute of Neuroscience, Washington, DC, France; 5 Fondation Ophthalmologique A de Rothschild, Pediatric Neurosurgery, Paris, French Polynesia; 6 Kremlin Bicetre Hospital, Neonatal Intensive Care Department, Kremlin Bicetre, France; 7 Kazan Federal University, Laboratory of Neurobiology, Kazan, Russia, France The initial period of sensory cortical circuit formation during the third trimester of gestation in humans is characterized by a particular electroencephalographic activity pattern, “Delta-brushes” that consist in high amplitude slow wave superimposed with rapid oscillations. While deltabrushes are often thought to be spontaneously generated entirely within neo-cortex, recent work showed that they are reliably evoked in central cortical areas by sensory input resulting from spontaneous hand or foot twitches in a somatotopic manner and in occipital areas by light flashes. Here, we explored the role of auditory input in driving delta-brushes in temporal cortex in 46 premature neonates from 31 to 38 weeks of gestational age, using simultaneous electroencephalographic recordings and auditory stimuli mimicking ambient sounds, including low intensity technogenic “clicks” and human voices. Event detection, power frequency analysis and stimulus locked averaging showed that in the youngest premature (31-34 weeks of gestational age), both voices and low-volume “clicks” reliably evoke delta-brushes specifically in temporal cortical areas. Auditory-evoked delta-brushes consisted of temporal negative slow-waves and rapid oscillations similar to spontaneous delta-brushes. Around 35-36 weeks of gestational age auditory-evoked responses showed a dramatic change characterized by the disappearance of auditory-evoked delta-brushes and the emergence of low-amplitude auditory-evoked cortical potentials. “Click” and voice evoked auditory responses differentiated in their frequencypower topography starting from 34 weeks onwards. Along with findings in other sensory modalities (visual and somatosensory), these findings suggest that sensory driven delta-brushes represent a ubiquitous feature of the human sensory cortex during fetal stages thus probably contributing to the formation of cortical sensory maps by amplifying sensory input. Sensory evoked delta-brushes provide a test of functional cortical maturation during fetal development.