Precise Electrolytic Lesioning Through Chronically Implanted Multielectrode Arrays Enables Causal Investigations of Neuronal Circuit Function

核心概念

A novel electrolytic lesioning technique through chronically implanted multielectrode arrays enables precise, controlled lesions while maintaining stable electrophysiological recordings before and after the lesion.

摘要

The content describes the development and validation of a novel electrolytic lesioning technique that can be used in conjunction with chronically implanted multielectrode arrays. The key highlights are:

1. The authors created a custom current source circuit that allows for controlled, repeatable electrolytic lesions through the same multielectrode array used for neuronal activity recordings. This enables stable electrophysiological recordings before and after the lesion.

2. Ex vivo testing in sheep and pig brains, as well as in vivo testing in anesthetized pigs, demonstrated that the size and extent of the lesion can be controlled by adjusting the amplitude and duration of the current passed through the electrodes. Smaller, more focal lesions were achieved by reducing the current intensity and duration.

3. The technique was validated in vivo in sedated and awake-behaving rhesus macaques, showing that it can be safely used in primates without compromising the ability to record neuronal activity.

4. Analysis of the recorded neuronal activity before and after the lesions revealed changes in the proportions of recorded neurons, likely reflecting neuron loss or silencing within the lesioned area.

5. The authors show that this electrolytic lesioning technique can be used with different types of multielectrode probes, demonstrating its flexibility and cross-compatibility.

6. This novel lesioning method provides a powerful tool for establishing causal links between neuronal circuit activity and behavior, while also enabling the study of local reorganization and recovery after neuron loss.

統計資料

Electrolytic lesions created in ex vivo sheep cortex using 250 μA current for 10 minutes resulted in a spheroidal cavitation of approximately 1.5 mm in diameter.
Reducing the current to 180 μA for 1 minute in ex vivo pig cortex created a smaller spheroidal cavitation of around 0.5 mm in diameter.
In vivo lesions in pig cortex using 150 μA current for 1 minute resulted in a well-demarcated region of parenchymal damage, 3.5 mm wide at the surface and extending 2 mm deep, with widespread coagulative necrosis and perivascular microhemorrhage.
The authors performed a total of 14 lesions across two awake-behaving rhesus macaques, using 150 μA current for 30-45 seconds.

引述

"Electrolytic lesioning leads to cell death through heat, electroporation, and local changes in pH."
"Even if the closest, cleanly separable neurons were terminated by the lesion, the recorded signal would still be comprised of the remaining, surviving neurons in that vicinity."
"This electrolytic lesioning method avoids disruptive procedures, provides millimeter precision over the extent and submillimeter precision over the location of the injury, and permits electrophysiological recording of single-unit activity from the remaining neuronal population after lesioning."

從以下內容提煉的關鍵洞見

Neuroelectrophysiology-Compatible Electrolytic Lesioning

by Bray,I. E., ... 於 www.biorxiv.org 11-13-2022

https://www.biorxiv.org/content/10.1101/2022.11.10.516056v2

深入探究

How could this electrolytic lesioning technique be further refined or optimized to create even more precise and controlled lesions?

The electrolytic lesioning technique can be further refined and optimized in several ways to enhance precision and control over the lesions created:

Fine-tuning Current Parameters: Experimentation with different current amplitudes and durations can help identify the optimal combination for creating precise lesions. By systematically varying these parameters and analyzing the resulting lesion sizes, researchers can establish a more detailed understanding of the relationship between current delivery and lesion characteristics.

Exploration of Electrode Configurations: Investigating different electrode configurations, such as spacing between electrodes and electrode shapes, can influence the shape and size of the lesions. By testing various electrode arrangements, researchers can determine the most effective setup for creating targeted and consistent lesions.

Automation and Feedback Control: Implementing automation and feedback control mechanisms in the lesioning device can enhance the accuracy and repeatability of lesion creation. Real-time monitoring of current delivery and lesion formation, coupled with automated adjustments based on predefined parameters, can ensure precise and consistent lesioning outcomes.

Integration with Imaging Techniques: Combining the electrolytic lesioning technique with imaging modalities, such as MRI or CT scans, can provide real-time visualization of lesion formation. This integration can enable researchers to monitor the progression of the lesion in situ and make adjustments as needed to achieve the desired lesion size and shape.

Long-term Studies and Histological Analysis: Conducting long-term studies to assess the stability and permanence of the lesions over time can provide valuable insights into the efficacy of the technique. Histological analysis of the lesioned tissue at different time points post-lesion can help evaluate the extent of neuronal loss and tissue reorganization, guiding further refinements in the technique.

By incorporating these refinements and optimizations, the electrolytic lesioning technique can be advanced to create highly precise, controlled, and reproducible lesions for a wide range of research applications in neuroscience.

What are the potential limitations or drawbacks of using electrolytic lesions compared to other inactivation methods, such as optogenetics or chemogenetics?

While electrolytic lesions offer unique advantages in creating permanent and localized inactivation of neuronal populations, they also have limitations and drawbacks compared to other inactivation methods like optogenetics or chemogenetics:

Non-specificity: Electrolytic lesions can damage not only the targeted neurons but also surrounding tissue, leading to potential off-target effects. This lack of specificity can limit the precision of the inactivation compared to optogenetics, which allows for more selective manipulation of specific neuronal populations.

Inability for Temporal Control: Unlike optogenetics, which enables precise temporal control over neuronal activity, electrolytic lesions result in permanent inactivation of the targeted neurons. This lack of temporal specificity can hinder the ability to investigate dynamic changes in neural circuits and behaviors over time.

Limited Reversibility: Electrolytic lesions cause irreversible damage to the neurons, making it challenging to study the potential recovery or plasticity of the neural circuit post-inactivation. In contrast, optogenetics and chemogenetics offer reversible inactivation methods that allow for dynamic modulation of neuronal activity.

Invasive Nature: The process of creating electrolytic lesions involves physical damage to the brain tissue, which can induce inflammatory responses and tissue scarring. This invasiveness may introduce confounding factors in the interpretation of results and can impact the overall health of the experimental subjects.

Lack of Cell-Type Specificity: Electrolytic lesions do not provide cell-type specificity in inactivation, as they affect all neurons in the lesioned area indiscriminately. Optogenetics and chemogenetics offer the ability to target specific neuronal subtypes, allowing for more precise dissection of neural circuits and functions.

While electrolytic lesions have been valuable in establishing causal relationships between brain regions and behaviors, researchers must consider these limitations when choosing the most appropriate inactivation method for their specific research objectives.

How might the insights gained from combining this lesioning technique with chronic electrophysiology recordings be leveraged to develop novel therapeutic interventions for neurological disorders involving localized neuronal loss?

The integration of electrolytic lesioning with chronic electrophysiology recordings offers unique insights into the functional consequences of localized neuronal loss, which can be leveraged to develop novel therapeutic interventions for neurological disorders involving such loss:

Identification of Critical Neural Circuits: By selectively lesioning specific brain regions and monitoring the resulting changes in neuronal activity, researchers can identify critical neural circuits involved in various neurological disorders. Understanding the functional impact of localized neuronal loss can pinpoint key brain areas that contribute to disease pathology.

Validation of Therapeutic Targets: The combination of lesioning and electrophysiology recordings can validate potential therapeutic targets within the identified neural circuits. By demonstrating the causal relationship between neuronal activity in specific regions and disease symptoms, researchers can prioritize targets for intervention.

Development of Circuit-Based Therapies: Insights from chronic electrophysiology recordings post-lesion can inform the development of circuit-based therapies for neurological disorders. Targeted interventions, such as deep brain stimulation or optogenetic modulation, can be designed to restore normal neural activity patterns in affected brain regions.

Personalized Treatment Approaches: The detailed mapping of neural circuits and functional changes following electrolytic lesions can enable the development of personalized treatment approaches for patients with neurological disorders. Tailoring interventions based on individual circuit abnormalities can enhance treatment efficacy and minimize side effects.

Exploration of Neural Plasticity Mechanisms: Studying the reorganization and compensatory mechanisms in neural circuits post-lesion can provide insights into neural plasticity and adaptive changes in the brain. This knowledge can guide the development of interventions that promote neuroplasticity and functional recovery in patients with neuronal loss.

Overall, the combination of electrolytic lesioning and chronic electrophysiology recordings offers a powerful platform for understanding the neural basis of neurological disorders and designing innovative therapeutic strategies that target specific brain circuits involved in localized neuronal loss.