WP1: Piloting and developing of the experimental setup for the high-resolution 7T fMRI experiment in human subjects during visual, auditory and tactile motion stimulation. Three different set of motion direction manipulation stimuli, one for sensory modality, have been designed and implemented in Psychopy. For the visual condition, three set of stimuli were employed (full field random dots and two sine wave gratings at low and high spatial frequency respectively, see Figure 1). The same set of stimuli was reproduced in the auditory sensory domain using a special audio setup developed in collaboration with Prof. Collignon, University of Louvain, Belgium. For the tactile stimulation a magneto-compatible tactile device was used. The device consists in a lubricated pad slowly moved by a slide. Three different pads were employed: two pads exhibited a pattern of parallel ridges and grooves at high and low spatial frequency respectively and a third circle dots (see Figure 1).
Implementation of the 2D BOLD MRI sequence (2D-EPI sequence, multiband (R=3), spatial resolution=1.5x1.5x1.5 mm 3 and TR=1500 ms). Sequence currently used in the CIBM AIT team and shared across scientists. Due to coils available we were not able to achieve 0.8mm spatial resolution therefore we implemented a sequence with highest spatial resolution as described in the risk management plan section.
WP2: Experiments were conducted on 15 healthy human volunteers using a 7T MRI scanner (Siemens Healthineers). Each motion block had either visual or auditory stimuli moving from left to right and right to left for 10 sec. For the visual condition, three set of stimuli were employed (see wp1). Each condition was randomly interleaved in a single run ending with 3 trials per condition per run. The second session consisted of 5 runs for the tactile stimulation. Each run consisted of three motion blocks of 10s per pad in which the pad moved up and down along the right palm of each participant. Preliminary results: During the visual motion localizer, subjects consistently exhibited positive BOLD responses in the human MT complex (hMT+) and early visual cortex. As expected, the random condition during the visual stimulation task elicited strong activation in hMT+ and early visual cortices (Figure 2). Using the same motion stimulation in the auditory domain we found two clusters of significant activations, one located in the primary auditory cortex A1 and the second located in the third visual cortex V2/V3 (Figure 2). Using univariate analysis, we did not find an engagement of hMT+ during auditory motion conditions. Further analyses are currently in progress. Preliminary results presented in the LINE Retreat in Nendaz (October 2022) and an abstract for IMRF 2023 has been submitted.
WP3: TMS Training was done at the University of Bern. Due to technical issues with the equipment, it was not possible to perform the TMS experiment at the host institution in CHUV. An agreement was made with the EPFL Biotech research center and the Human Neuroscience Platform in Geneva in order to use the neuromodulation facility.
We applied double pulse TMS on hMT+ of each single subject (same subjects who performed the MRI experiment) during visual or auditory motion stimulation using two different spatial frequencies. Functional visual localizer acquired at 7T was used to successfully localized hMT+. The subject was asked to detect first the presence of motion than the direction of motion (left to right or right to left). Results in the visual domain showed a reduction of the percentage of corrected responses to motion stimulation vs no motion stimulation as a consequence of the TMS pulse. The pilot did not show any differences in the auditory motion domain. This might be due to the interference of the TMS pulse noise with the auditory stimulation. Further studies need to be implemented.
WP4: Due to Covid there were no patients available from the HUG hospital in Geneva. We actively engaged in a collaboration with the UMC Utrecht in The Netherlands. We used previously collected data in 4 patients that underwent electrocorticography ECoG measurements to investigate the neuronal responses to visual motion in response to different spatial and temporal frequencies. We found that hMT+ encode motion via two different mechanisms. The first allows for distinct and independent selectivity for the spatial and temporal frequencies of the visual motion stimuli; the second implies pure tuning for the speed of motion. We show that both mechanisms occur different neuronal groups within hMT+, with the largest subregion of the complex showing separable tuning for the spatial and temporal frequency of the visual stimuli. Paper was published in Human Brain Mapping last year:
https://pubmed.ncbi.nlm.nih.gov/36637226/(s’ouvre dans une nouvelle fenêtre). Results were presented in different talk and at Human Brain Mapping conference 2021 and 2022.
