Publication Alert
May 14 2024
Check out the new pre-print publication from Tobias Teichert et al., titled "Volumetric mesoscopic electrophysiology: a new imaging modality for the non-human primate" which was recently published in bioRxiv. This study presents an approach for recording local field potentials (LFPs) across an entire monkey hemisphere, providing a unique functional profile that combines high temporal resolution with a wide field of view.
The researchers developed a method to record from 992 electrode contacts distributed across 62 multi-electrode shafts, forming a three-dimensional grid. This allowed stable, hemisphere-wide LFP recordings over months, offering new insights into large-scale brain networks and their responses to external stimuli.
Background summary:
- The temporal resolution of fMRI is limited by the relatively slow hemodynamic response.
- Electrophysiological approaches have either 1) limited spatial resolution (e.g., scalp EEG) or (2) a limited field of view (e.g., microscopic single-cell recordings).
Solution:
- MePhys yields hemisphere-wide spatial maps of any LFP-based feature, such as sound-evoked electric fields, response-related beta-band desynchronization or resting-state spectra.
- MePhys simultaneously records data from more than 300,000 pairs of electrodes distributed across the entire hemisphere.
- By combining the best features of both EEG and fMRI into a single method in the non-human primate, MePhys will be able to facilitate the comparison between macroscopic findings in humans and microscopic single-cell recordings non-human primates, and thus the translation of findings from rodents, via monkeys to humans, and vice versa.
Plexon products in this study include:
- The Intracranial Probes (T-Probes): The researchers utilized custom-designed T-Probes, multi-contact probes distributed by Plexon. Their specifications were based on a CT scan obtained after the MePhys platform implantation, with individual electrode layouts determined for each of the 62 grid holes according to the underlying anatomy.
Fig. 1: Figure 1Mesoscopic Electrophysiology (MePhys).
(A) Exploded design of the MePhys platform with the main structural and functional elements: crown, spider, wall, grid, baseplate, headstage and cap. (B) Schematic of the electrode – guidepin – grid system. (C) The intracranial contacts (blue dots) of the MePhys prototype are arranged in 14 coronal slices from posterior to anterior in the panels from bottom right to top left. The antero-posterior position of the slices is indicated by horizontal lines in the top-down schematic of the monkey brain. Slices #1 and #2 were omitted, because they do not contain any currently functional electrode contacts.
Fig. 2: Spatial distribution of auditory evoked electric fields.
(A–C) Hemisphere-wide auditory evoked electric fields. The top of each panel features a butterfly plot with time-resolved activity of all channels; the red line indicates the time-point displayed in each panel. The mapping of color to potential is indicated on the y-axis of the butterfly plot. The first activation of auditory cortex occurs ∼9 ms after sound onset (slice #7). Activity in motor and pre-frontal cortex reaches its first surface-positive peak 17 ms after sound onset (slices #8&9). A second peak with inverted polarity emerges around 38 ms after sound onset. Note the dipole-like structure of the fields in auditory and motor cortex. For visualization purposes, the evoked potentials at the EEG electrodes were multiplied by a factor of 2. (D) A map of the strength of the evoked fields measured as the standard deviation of the time-resolved evoked responses over the first 250 ms of the response. The inset depicts the distribution of evoked field strength across the hemisphere and defines the relationship between color and field strength (0uV: gray, 200uV: red). (E) The attenuation of evoked responses after administration of a subanesthetic dose of Ketamine. Note that responses in auditory cortex are not attenuated. (F) Attenuation of responses after a subanesthetic dose of midazolam is much more pronounced (note different color scale) and strongly attenuates responses in auditory cortex.
For further inquiries about Plexon products or to learn more about our commitment to advancing neuroscience research, please visit our website or contact our dedicated team at info@plexon.com