Biology subjects

Moreau, T.

Publications and source records attributed to Moreau, T..

3 recordsLinked to original sources

bioRxiv2021

Causal contributions of neural noise to left frontal networks subtending the modulation of conscious visual perception in the human brain

For several decades, the field of human neurophysiology has focused on the role played by cortical oscillations in enabling brain function underpinning behaviors. In parallel, a less visible but robust body of work on the stochastic resonance phenomenon has also theorized contributions of neural noise - hence more heterogeneous, complex and less predictable activity - in brain coding. The latter notion has received indirect causal support via improvements of visual function during non-regular or random brain stimulation patterns. Nonetheless, direct evidence demonstrating an impact of brain stimulation on direct measures of neural noise is still lacking. Here we evaluated the impact of three non frequency-specific TMS bursts, compared to a control pure high-beta TMS rhythm, delivered to the left FEF during a visual detection task, on the heterogeneity, predictability and complexity of ongoing brain activity recorded with scalp EEG. Our data showed surprisingly that the three non frequency-specific TMS patterns did not prevent a build-up of local high-beta activity. Nonetheless, they increased power across broader or in multiple frequency bands compared to control purely rhythmic high-beta bursts tested along. Importantly, non frequency-specific patterns enhanced signal entropy over multiple time-scales, suggesting higher complexity and an overall induction of higher levels of cortical noise than rhythmic TMS bursts. Our outcomes provide indirect evidence on a potential modulatory role played by sources of stochastic noise on brain oscillations and synchronization. Additionally, they pave the way towards the development of novel neurostimulation approaches to manipulate cortical sources of noise and further investigate their causal role in neural coding.

neuroscience↗

bioRxiv2021

Mapping the biogenesis of forward programmed megakaryocytes from induced pluripotent stem cells

Platelet deficiency, known as thrombocytopenia, can cause haemorrhage and is treated with platelet transfusions. We developed a system for the production of platelet precursor cells, megakaryocytes, from pluripotent stem cells. These cultures can be maintained for >100 days, implying culture renewal by megakaryocyte progenitors (MKPs). However, it is unclear whether the MKP state in vitro mirrors the state in vivo, and MKPs cannot be purified using conventional surface markers. We performed single cell RNA sequencing throughout in vitro differentiation and mapped each state to its equivalent in vivo. This enabled the identification of 5 surface markers which reproducibly purify MKPs, allowing us an insight into their transcriptional and epigenetic profiles. Finally, we performed culture optimisation, increasing MKP production. Altogether, this study has mapped parallels between the MKP states in vivo and in vitro and allowed the purification of MKPs, accelerating the progress of in vitro-derived transfusion products towards the clinic.

developmental biology↗

bioRxiv2019

Perturbation-based mapping of natural frequencies with direct intracranial stimulation of the human brain

Theoretical and experimental evidence suggest that the induction of oscillatory activity by an external rhythmic source on a specific brain area is maximally efficient if the input pattern matches its so-called natural frequency, defined as the predominant neural rhythm at which the activity of this area tends to fluctuate spontaneously. Based on this principle, single pulse Transcranial Magnetic Stimulation (TMS) coupled to scalp electroencephalography (EEG) has provided evidence of frequency-specific power increases within a unique natural frequency band, considered common to the whole lobe.\n\nIn an attempt to gain deeper insight into this phenomenon and set the basis for a finer-grained atlas of natural frequencies, here we analyzed intracranial EEG (iEEG) signals modulated by single pulses of direct electrical brain stimulation in human patients implanted with depth multielectrodes. Our analyses revealed changes in local EEG activity emerging from local oscillators and contributing to a complex distribution of frequency-specific natural rhythmic responses throughout cortical regions. Moreover, challenging the notion of natural oscillations featuring a predominant frequency band characteristic for an entire lobe, our data support a rich diversity of spectral fingerprints (narrowband, vs. broadband or multiband) with single or multiple frequency peaks, often encompassing contiguous frequency bands, operating at a very local scale.\n\nOur findings contribute novel insights on which specific brain areas could be more likely to be synchronized at a given frequencies band and their preferred coupling frequencies, features that could ultimately inform on their structural and functional organization. Our results may also increase our mechanistic understanding of invasive and noninvasive brain stimulation and promote further developments of these approaches for the manipulation of brain oscillations subtending normal and impaired cognition.

neuroscience↗