Biology subjects

Pakhomov, A.

Publications and source records attributed to Pakhomov, A..

4 recordsLinked to original sources

bioRxiv2024

Improved Temporal and Spatial Focality of Non-invasive Deep-brain Stimulation using Multipolar Single-pulse Temporal Interference with Applications in Epilepsy

Temporal Interference (TI) is an emerging method to non-invasively stimulate deep brain structures. This innovative technique is increasingly recognized for its potential applications in the treatment of various neurological disorders, including epilepsy, depression, and Alzheimers disease. However, several drawbacks to the TI method exist that we aim to improve upon. To begin, the applied electric field in the TI target is not much higher than what non-invasive transcranial alternating current stimulation (TACS) provides in the cortex. Additionally, the TI stimulation onset is dependent on the envelope of the amplitude modulated (AM) signal, where for example 1 Hz and 100 Hz envelopes have significantly different rise times to reach maximum envelope amplitude - unlike square biphasic pulses. This limitation in turn prevents classic TI, from applying bursts of pulses. Finally, the electric field intensity of TI cannot be increased or decreased at the target without dramatically altering the spatial profile of the stimulation focus. In the work presented here, we efficiently address all three of these limitations. First, we performed two-photon calcium imaging to show that individual neurons selectively respond to the TI envelope frequency, providing evidence that TI modulates neural activity with temporal specificity. This marks a significant advancement, representing the first empirical demonstration of neuronal activation at the {Delta}f frequency within the context of TI and in an imaging modality. Subsequently, we compared the AM signals of TI with phase-shift keying (PSK) modulated signals to highlight the superior effectiveness of noninvasive pulses in contrast to the traditional TI method, particularly in inducing epileptic activity (after-discharges) in mice. We also added a multipolar configuration to create a significant increase in the electric field at the target without significantly altering the spatial profile and applied Fourier components to replicate classic biphasic bursts of square pulses - all transcranially, without the use of penetrating electrodes. These innovations aim to enhance the precision and efficacy of TI stimulation, to advance its application in neurological research and therapy. Key Points / HighlightsO_LINon-invasive temporal interference stimulation modulates the activity of individual neurons at the envelope frequency. C_LIO_LIA non-invasive multi-pulse TI stimulation paradigm improves both temporal and spatial focality in the deep target neural tissue when compared to traditional continuous wave (amplitude-modulated) TI stimulation. C_LIO_LIPulse TI paradigms can stimulate deep neural targets with reduced amplitude of the topical high-frequency stimulation, decreasing off-target stimulation when compared to continuous wave TI patterns. As a consequence, pulse TI stimulation reduces the risk of undesired side effects such as high-frequency conduction block in off-target tissues or cortical areas. C_LIO_LIBoth temporal and spatial focality of the TI stimulation pattern positively correlate with the efficacy of the stimulation to induce seizures in the mouse hippocampus. C_LI

neuroscience↗

bioRxiv2023

Orientation tests and long-term movement phenology establish the red admiral Vanessa atalanta as an applicable model for navigation research in migratory butterflies

Animal migrations are disappearing globally, while insect populations are on alarming declines. Both ecosystem degradations, influenced by unpredictable impacts of climate change, are also exacerbated by human activities such as intensified land use and various forms of environmental pollution. Butterfly migrations may serve as sensitive indicator phenomena of these broader environmental changes. While the transcontinental journeys of one of the most famous Lepidopteran species, the North American monarch butterfly, Danaus plexippus, are documented in depth, they are a geographically restricted phenomenon. Comprehensive studies from other areas and on other migratory butterflies like the European red admiral, Vanessa atalanta, are notably sparse. In addition, the details of their navigational capacities and how they might be affected by the aforementioned changes remain largely enigmatic. Against this backdrop, we seek to establish the red admiral as a model for insect movement phenology and navigation behaviour which both might be impacted by environmental changes. Employing a combination of orientation tests, utilizing flight-simulators and free-flight trials during late summer, together with a 23-year study on movement phenology at a coastal migration flyway, the Baltic Sea coast, we offer broad insights into red admiral migration. In our experiments, butterflies exhibited a southwestern orientation on the Courish Spit and chose a south-southeastern trajectory in free-flight trials after translocation at the Latvian Baltic Sea coast. Directional records from decades-long trapping data, based on more than 16,000 individuals, match these findings. Nevertheless, we also found reverse movements to occur under some circumstances. At the same time, the observed estimated median dates of red admiral passages did change by one day only between decades, however, generally more butterflies were recorded in recent years. Our data thus suggest a certain degree of adaptability in the butterflies movement behaviour, indicating an innate migration schedule, possibly supported by a flexible navigational capacity. As the world is facing biodiversity loss at a high rate, long-term monitorings of indicator species become important. By establishing the red admirals as a model for butterfly migration, we expect insights into broader movement patterns and navigational strategies in Lepidoptera negotiating human-dominated environments, filling a crucial gap in our current understanding of these interdependent aspects of insect biology.

zoology↗

bioRxiv2023

Birds are easier to trick: an effect of magnetic field manipulation on migratory orientation of Nathusius's pipistrelle in the circular release box

Bats, like birds, are capable of long annual migrations; however, a very limited number of studies are devoted to the role of the Earths magnetic field in bat navigation. We aimed to perform a series of experiments on Nathusius pipistrelle (Pipistrellus nathusii) to ensure that they are able to use the geomagnetic field for orientation. Bats were tested under two different conditions: in the geomagnetic field and the field, rotated 120{degrees} CW. To determine the takeoff direction and analyse behaviour in different magnetic conditions, we used the modified circular release box (CRBox) and a mini camera with IR LEDs. Helmholtz magnetic coils were used to manipulate the magnetic field. Bats were captured during migration through the Curonian spit (Kaliningrad region, Russia). Totally 53 bats were tested during August and September 2021-2022. During the second year, we recorded post-release bats behaviour using a thermal camera. Although results from 2021 are ambiguous, data obtained in 2022 suggests that under given conditions bats, unlike birds, could prefer local audible landmarks and wind direction prior to global cues. However, the recordings of released bats clearly show that they have some specific directional preferences, which correspond to their migratory orientation.

animal behavior and cognition↗

bioRxiv2023

Migratory birds are able to choose the appropriate migratory direction under dim yellow monochromatic light

Previously it has been shown that migratory birds were oriented in the appropriate migratory direction under UV, blue and green monochromatic lights (short-wavelength) and were unable to use their magnetic compass in total darkness and under yellow and red light (long-wavelength). Currently, it is generally assumed that the magnetic compass of birds works correctly only under short-wavelength light. However, it also been suggested that the magnetic compass has two sensitivity peaks: in the short and long wavelengths, but with different intensities. In this project, we aimed to study the orientation of long-distance migrants, pied flycatchers (Ficedula hypoleuca), in different monochromatic lights during autumn migration. The birds were tested in the natural magnetic field (NMF) and 120{degrees} CCW shifted magnetic field (CMF) under green and yellow light (intensity 1 mW m-2). All tests were performed in a specially constructed wooden laboratory equipped with magnetic coils to manipulate the magnetic field. We showed that (1) pied flycatchers were completely disoriented under green light both in the NMF and CMF but (2) showed the migratory direction in NMF and the appropriate response to CMF under yellow light. Our data contradict results of previous experiments under monochromatic yellow light and might indicate the previously proposed hypothesis of two different mechanisms in avian magnetoreception (a high-sensitive short-wavelength mechanism and a low-sensitive mechanism in the long-wavelength spectrum) has a right to exist.

zoology↗