neurophysiology recordings in cortical tissue of marmoset

Udvikling af et X-Y-elektrodetrin til præcis neural optagelse i silkeaber

The common marmoset (Callithrix jacchus) has quickly grown in popularity as a model to study brain function in recent years. This growing popularity is due to the accessibility of the marmoset&#39;s smooth cortex, the similarities in neural functional organization with humans and other primates, and the small size and fast breeding rate1. As this model organism has grown in popularity, there has been rapid development in the neurophysiological techniques suited for use in the marmoset brain. Electrophysiology methods are widely used in neuroscience to study the activity of single neurons in the cortex of both rodents and primates, resulting in unparalleled temporal resolution and location access. Due to the relative novelty of the marmoset monkey as a model of visual neuroscience, the optimization of awake-behaving electrophysiology techniques is still evolving. Previous studies have shown the establishment of robust protocols for electrophysiology in anesthetized preparations2, and early awake-behaving neurophysiology studies have shown the reliability of single-channel tungsten electodes3. In recent years, researchers have established the use of silicon-based microelectrode arrays for awake-behaving neurophysiology4. However, the marmoset poses unique targeting challenges due to its small brain size and lack of anatomical landmarks. This protocol outlines how to construct and use a micro-drive recording system suitable for the marmoset that allows for the recording of large populations of neurons with silicon linear arrays while producing minimal tissue damage.
Working with the marmoset poses a challenge due to the smaller scale of the retinotopic maps in the visual cortex as compared to larger primates. A slight shift of the electrodes by just 1 mm can result in significant changes in the maps. Moreover, researchers often need to alter the placement of the electrodes between the recording sessions to obtain a broader range of retinotopic positions in the visual cortex. Current semi-chronic preparations do not allow for the adjustment of the electrode positioning daily or with enough precision to target specific locations at sub-millimeter scales5. With this in mind, the proposed micro-drive system utilizes an X-Y electrode stage that mounts a lightweight micro-drive to a recording chamber and allows for the sub-millimeter targeting of cortical sites. The moveable X-Y stage components allow for vertical and horizontal movement of the linear array in order to traverse the cortical areas systematically, which is required to identify areas of interest (via retinotopy and tuning properties). Across recording sessions, researchers can also manually adjust the X-Y stage to shift the targeted sites within the area. This is a key advantage over alternative techniques using semi-chronic recording preparations, which do not have easy electrode targeting mechanisms.
The micro-drive is a versatile tool that enables the attachment of various silicon arrays to be mounted for lowering into the cortex. In this protocol, a custom probe with two 32-channel linear arrays spaced 200 &#181;m apart was used for the investigation of laminar circuits spanning the cortical depth. Most methods for probing the neural circuitry typically sample the electrical potentials or single units averaged across all the layers of the cerebral cortex. However, recent research has revealed intriguing findings about cortical laminar microcircuits6. By utilizing the micro-drive, researchers can use laminar probes and make fine adjustments to the recording depth to ensure comprehensive sampling across all the layers.
This system can be constructed with commercially available components and is easily modified for different experimental techniques or probes. The key advantages of this preparation are the ability to change the X-Y recording position with sub-millimeter precision and to control the depth of the recording within the cortex. This protocol presents step-by-step instructions for constructing the X-Y stage micro-drive and neurophysiology recording techniques.

Forfatter Spotlight: Optimering af mikrodrevsystemer til præcis elektrodepositionering i silkeaber

Elektrofysiologi af laminær kortikal aktivitet i den fælles marmoset

The common marmoset poses unique challenges for neurophysiology due to its small size and lack of gyre as anatomical landmarks. A slight shift of the electrode by just a millimeter can result in significant changes in the retinotopy map. The proposed micro drive system utilizes an XY electrode stage that allows for vertical and horizontal movement on a sub millimeter scale.Due to the relative novelty of the marmoset monkey as a model for visual neuron sign, awake behaving electrophysiology techniques are still evolving. Current preparations often use semi chronic probes that do not allow access for the positioning mechanisms. This protocol demonstrates a lightweight micro drive for useful linear array recordings, which allow flexible positioning across sessions to map out retinotopy within the chamber.Long-term cortical damage can be avoided in the preparation when used correctly with the secure drive, slow penetration of tissue, and avoidance of major blood vessels. Additionally, the use of silastic in the craniotomies to avoid infections has been optimized in this technique.

Neurofysiologi optagelser i kortikalt væv af silkeaber

Til at begynde med skal du fastgøre mikrodrevet på en hovedhætte. Fastgør alle tre skruer på mikrodrevsystemet. Brug skruestyringen på mikrodrevet til at sænke siliciumsonden, og lav en drejning hvert 1. til 2. sekund, indtil enheder observeres ved array-spidsen.Når neuronerne er observeret, skal du trække mikrodrevets ene drejning tilbage for at reducere elektrodens indgangshastighed, når den bevæger sig gennem silastisk og dura ind i det kortikale væv. Fortsæt langsomt med at køre arrayet ind i cortex og gå frem 4 til 6 omdrejninger over 20 til 30 minutter, indtil neuroner er jævnt fordelt over sondens længde. Derefter trækkes arrayet langsomt tilbage med 1 til 2 omdrejninger for at reducere trykket på vævet.Når optagelsen er færdig, skal du langsomt trække arrayet tilbage fra cortex med en hastighed svarende til den oprindelige indsættelse. Når der ikke er flere neuroner synlige på sonden, skal du trække arrayet hurtigere tilbage, indtil det vender tilbage til den fuldt tilbagetrukne startposition. Når sonden er taget ud af optagekammeret, lægges den i blød i kontaktlinseopløsning i 20 minutter for at rense væv eller blod.Anbring sonden i alkohol i et minut for at fjerne kontaktlinseopløsningen og lade elektroden tørre. De spike-sorterede array-data, der blev opnået gennem Kilosort, afslørede, at de vigtigste komponentfunktioner for udvalgte pigge i en klynge adskilte sig fra baggrundsspidser, hvilket bekræftede optagelsens stabilitet over tid. Pålideligheden af X-Y-positioneringen viste en overlapning på 70,8 % i gennemsnitlige RF-placeringer mellem to sessioner med en uges mellemrum.Præcise nethinden emne rumbevægelser blev observeret i en række optagelsessessioner, der krydsede MT- og MTC-grænserne ved hjælp af mindre positioneringsændringer.

Research

JoVE Journal

Neuroscience

Neurophysiology Recordings in Cortical Tissue of Marmoset

Electrophysiology of Laminar Cortical Activity in the Common Marmoset

The marmoset monkey provides an ideal model for examining laminar cortical circuits due to its smooth cortical surface, which facilitates recordings with ...

Construction of the Electrode Micro-Drive and Polytrode Plating of Electrodes for Neurophysiology Recordings

Konstruktion af elektrodemikrodrev og polytrodebelægning af elektroder til neurofysiologiske optagelser 