Biology subjects

Ahnine, H.

Publications and source records attributed to Ahnine, H..

4 recordsLinked to original sources

bioRxiv2019

Functional ultrasound imaging of deep visual cortex in awake non-human primates

Deep regions of the brain are not easily accessible to investigation at the mesoscale level in awake animals or humans. We have recently developed functional Ultrasound (fUS) imaging fUS imaging technique to uncover deep hemodynamic functional responses. Applying fUS imaging on two awake non-human primates performing a passive fixation task, we reconstructed their retinotopic maps down to the deep calcarine and lunate sulci on visual areas (V1, V2 and V3). These maps were acquired in a single hour session with very few stimuli presentation. The spatial resolution of the technology is illustrated by mapping of Ocular Dominance (OD) columns within superficial and deep layers of the primary visual cortex. These acquisitions showed that OD selectivity is mostly present in layer IV but with evidence also in layers II/III and V. The fUS imaging technology therefore provides a new mesoscale approach to map brain activities at high spatiotemporal resolution in awake subjects within the whole depth of the cortex.

neuroscience↗

bioRxiv2018

Ultrasound functional neuroimaging reveals propagation of task-related brain activity in behaving primates

In recent decades, neuroimaging has played an invaluable role in improving the fundamental understanding of the brain. At the macro scale, neuroimaging modalities such as MRI, EEG, and MEG, exploit a wide field of view to explore the brain as a global network of interacting regions. However, this comes at the price of either limited spatiotemporal resolution or limited sensitivity. At the micro scale, electrophysiology is used to explore the dynamic aspects of neuronal activity with a very high temporal resolution. However, this modality requires a statistical averaging of several tens of single task responses. A large-scale neuroimaging modality of sufficient spatial and temporal resolution and sensitivity to study brain region activation dynamically would open new territories of possibility in neuroscience\n\nWe show that neurofunctional ultrasound imaging (fUS) is both able to assess brain activation during single cognitive tasks within superficial and deeper areas of the frontal cortex areas, and image the directional propagation of information within and between these regions. Equipped with an fUS device, two macaque rhesus monkeys were instructed before a stimulus appeared to rest (fixation) or to look towards (saccade) or away (antisaccade) from a stimulus. Our results identified an abrupt transient change in activity for all acquisitions in the supplementary eye field (SEF) when the animals were required to change a rule regarding the task cued by a stimulus. Simultaneous imaging in the anterior cingulate cortex and SEF revealed a time delay in the directional functional connectivity of 0.27 {+/-} 0.07 s and 0.9 {+/-} 0.2 s for animals S and Y, respectively. These results provide initial evidence that recording cerebral hemodynamics over large brain areas at a high spatiotemporal resolution and sensitivity with neurofunctional ultrasound can reveal instantaneous monitoring of endogenous brain signals and behavior.

animal behavior and cognition↗

bioRxiv2018

Non-invasive ultrasonic modulation of visual evoked response by GABA delivery through the blood brain barrier

We demonstrate the feasibility of non-invasively modulating the visual cortex activity of non-human primates by local ultrasound-induced delivery of an inhibitory neurotransmitter (GABA). GABA was injected intravenously after the blood brain barrier (BBB) was transiently disrupted with focused ultrasound (FUS) coupled with ultrasound contrast agents (UCA). Visual evoked potentials exhibited a significant and progressive decrease of the activity. Combined effects of neuromodulation and BBB opening were shown to be 8.7 times less important than GABA-induced inhibition. During the sonication, the UCA harmonic response was monitored to estimate the level of stable cavitation (signature of BBB opening efficiency) and to avoid damages due to inertial cavitation (automatic shutdown of the sonication when detected). As recent developments in beam forming have shown that ultrasound beams can be focused non-invasively in deep-seated human brain locations, our results hold promise to explore and treat the brain with a non-invasive, controllable, repeatable and reversible method.

neuroscience↗

bioRxiv2018

Offline impact of transcranial focused ultrasound on cortical activation in primates

To understand brain circuits it is necessary both to record and manipulate their activity. Despite increased availability of techniques for manipulating neural activity in rodents, manipulating neural activity in primates remains difficult. Here we show that a minimally invasive technique, transcranial focused ultrasound stimulation (TUS), induced offline changes to activity of circumscribed brain regions in the macaque. Applying TUS to the supplementary motor area or frontal polar cortex resulted in spatially specific patterns of activity change measurable with functional magnetic resonance imaging. In each case changes reflected each areas known network of interactions with the rest of the brain. Independent of these specific neural effects, TUS over these regions also induced widespread signal changes that might have a non-neuronal origin possibly mediated by the cerebral spinal fluid compartment. Although sustained for more than one hour beyond the 40s stimulation period, TUS effects were reversible and not associated with histological changes.\n\nHighlights O_LIMany studies of ultrasound neuromodulation focus on online effects in rodents.\nC_LIO_LIWe use fMRI connectivity to investigate its offline impact in the primate brain.\nC_LIO_LI40 s of ultrasound leads to a sustained, specific, reversible neural modulation.\nC_LIO_LIUltrasound caused a sharpening of the stimulated regions connectivity profile.\nC_LI\n\nIn BriefA new application of focused ultrasound safely modulates brain activation in primates for up to 2 hours after 40 seconds of stimulation. Ultrasound caused the stimulated area to interact more selectively with the rest of the brain.

neuroscience↗