Projects | Mihály Vöröslakos

Brain-body relationships

Sat, 01 Jul 2023 03:00:00 +0000

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Circuit Resonance

Tue, 04 Jul 2023 00:00:00 +0000

Resonance is a notable phenomenon observed in neuronal systems, referring to the peak response of a network to a periodic input within a specific frequency range. Such resonance can manifest at both the cellular and network levels. At the cellular level, spikes may occur in response to specific frequencies of oscillatory input, resulting in what is known as spiking resonance. At the network level, interactions between recurrently coupled excitatory and inhibitory neurons generate resonant behavior.

Transcranial Alternating Current Stimulation (tACS) has the potential to modulate network activity through stochastic resonance, neural activity entrainment, or the imposition of specific patterns.

Given that a substantial portion of the extracellularly recorded Local Field Potential (LFP) signal originates from the combined activity of time-overlapping transmembrane potentials, influenced by spike-induced postsynaptic currents (known as synapsembles), any non-physiological alterations in the coordination of neuronal assemblies can be deduced from in-depth analysis of LFP patterns. Although LFP is most commonly used to detect epileptic activity, it can also offer insights into various psychiatric conditions characterized by “oscillopathy” or “rhythmopathy.”

The relationship between spike assemblies and synapsembles can also find practical applications in controlling computers, robots, or other artificial actuators. Measuring spatially distributed LFP features offers the advantage of long-term stability compared to multisite recording of single units, which are sensitive to microscopic movements.

TES-fMRI in rats

Tue, 04 Jul 2023 00:00:00 +0000

Using single-unit recordings is more effective for studying specific and localized aspects of neuronal assemblies in particular areas of interest, rather than assessing brain-wide activity. When using Transcranial Electrical Stimulation (TES), the electric fields are stronger near the stimulation electrode, but they decrease rapidly with depth. However, modeling studies suggest that deep areas, such as the brainstem, can also be affected due to the effects of cerebrospinal fluid and the less explored inhomogeneities in brain tissue.

Integrating TES with MR imaging techniques allows researchers not only to study how stimulation affects targeted brain regions but also to understand its impact on anatomical and functional connectivity. TES-fMRI can offer crucial insights into the most effective ways, locations, and timing for stimulation.

Applying results from rodent studies to human applications is challenging because our brains differ in size (number of neurons and connections) and the presence of gyri (folds) in humans. Moreover, animal studies usually involve placing stimulation electrodes beneath the skin and applying much higher electric fields compared to humans. To bridge this gap between rodents and humans, I combined neurostimulation with MRI. MRI is a safe tool that works for both species and provides information about the brain’s structure and functions.

In this project, I developed an MRI compatible and artifact-free stimulation setup to deliver electrical stimulation in rats. To avoid metal-induced artifacts during MRI scans, a deuterium-filled (5% NaCl) compartment, invisible in proton MR, and a watertight pocket system were used for the stimulation electrodes.

ThermoMaze

Fri, 30 Jun 2023 00:00:00 +0000

In mammals, two fundamental brain states can be readily identified by basic electrophysiological monitoring: “preparative” and “consummatory” states. Consummatory behaviors include eating, drinking, and resting – including non-rapid eye movement sleep. Revealing the significance of switching between these states for cognition requires collecting a sufficient amount of brain data and the experimental control of consummatory classes of behavior.

In this project, we developed the ThermoMaze, a behavioral paradigm that allows the experimenter to guide small rodents to multiple positions in a two-dimensional environment.

Decreasing the maze floor temperature induces heat seeking behavior and after finding a warm spot the animal will stay immobile at that spot for extended periods of time, allowing for recording large amounts of neurophysiological data in immobility-related brain states. The paradigm exploits natural behavior.

A location that provides a warm shelter needs to be remembered and generalized for future strategies. Our paradigm offers means to investigate exploratory-consummatory transitions, wake-sleep continuity in the same physical location and, in the reverse direction, the physiological processes that evaluate discomfort levels, motivate behavioral transition from rest to exploration and the decision-making circuit mechanisms that gives rise to overt behaviors.

Our novel behavioral paradigm exploits natural learning patterns in rodents. The ThermoMaze will allow for detailed studies of brain correlates of preparatory-consummatory transitions and open new options for studying temperature homeostasis.