Biology subjects

Gordleeva, S.

Publications and source records attributed to Gordleeva, S..

3 recordsLinked to original sources

bioRxiv2025

Transcranial Magnetic Stimulation Reduces Non-Decision Time in Perceptual Decisions

Perceptual decision-making enables humans to process sensory information and translate it into goal-directed actions. A critical component of this process is response time, which declines with age due to the slowing of both non-decision processes and evidence accumulation. While perceptual learning has been shown to counteract these declines, it remains unclear whether non-decision processes can be accelerated through direct neural stimulation, bypassing the need for long training sessions. Here, we propose that Transcranial Magnetic Stimulation (TMS) can enhance perceptual decision-making by specifically reducing non-decision time. To test this hypothesis, we tracked response times during a perceptual learning task while recording brain activity. Using the Drift Diffusion Model, we quantified the effects of TMS on mental speed and non-decision time. Our findings reveal that perceptual learning decreases response time by simultaneously increasing mental speed and reducing non-decision time. Crucially, TMS application to brain regions associated with perceptual learning further shortened non-decision time without altering mental speed. These results demonstrate that TMS can selectively accelerate non-decision processes, offering a promising intervention for mitigating age-related cognitive slowing and enhancing decision efficiency. Significance StatementPerceptual decision-making is a fundamental cognitive process that slows with age due to declines in both non-decision processes and mental speed. While perceptual learning can mitigate these declines through practice, we propose that non-decision time can also be reduced by directly stimulating neural ensembles using Transcranial Magnetic Stimulation (TMS). Our study demonstrates that TMS applied to task-relevant brain areas decreases non-decision time, thereby accelerating response speed without affecting mental speed. These findings reveal a novel mechanism for enhancing perceptual decision-making efficiency and highlight TMS as a potential tool for counteracting age-related cognitive slowing.

neuroscience↗

bioRxiv2021

A BCI-based vibrotactile neurofeedback training improves motor cortical excitability during motor imagery

In this study, we address the issue of whether vibrotactile feedback can enhance the motor cortex excitability translated into the plastic changes in local cortical areas during motor imagery (MI) BCI-based training. For this purpose, we focused on two of the most notable neurophysiological effects of MI - the event-related-desynchronization (ERD) level and the increase in cortical excitability assessed with navigated transcranial magnetic stimulation (nTMS). For TMS navigation, we used individual high-resolution 3D brain MRIs. Ten BCI-naive and healthy adults participated in this study. The MI (rest or left/right hand imagery using Graz-BCI paradigm) tasks were performed separately in the presence and absence of feedback. To investigate how much the presence/absence of vibrotactile feedback in MI BCI-based training could contribute to the sensorimotor cortical activations, we compared the MEPs amplitude during MI after training with and without feedback. In addition, the ERD levels during MI BCI-based training were investigated. Our findings provide evidence that applying vibrotactile feedback during MI training leads to (i) an enhancement of the desynchronization level of mu-rhythm EEG patterns over the contralateral motor cortex area corresponding to the MI of the non-dominant hand; (ii) an increase in motor cortical excitability in hand muscle representation corresponding to a muscle engaged by the MI.

neuroscience↗

bioRxiv2018

Morphological profile determines the frequency of spontaneous calcium events in astrocytic processes

Astrocytes express a complex repertoire of intracellular Ca2+ transients (events) that represent a major form of signaling within individual cells and in the astrocytic syncytium. These events have different spatiotemporal profiles, which are modulated by neuronal activity. Spontaneous Ca2+ events appear more frequently in distal astrocytic processes and independently from each other. However, little is known about the mechanisms underlying such subcellular distribution of the Ca2+ events. Here we identify the initiation points of the Ca2+ events within the territory of single astrocytes expressing genetically encoded Ca2+ indicator GCaMP2 in culture or in hippocampal slices. We found that most of the Ca2+ events start in thin distal processes. Our mathematical model demonstrated that a high surface-to-volume (SVR) of the thin processes leads to increased amplitude of baseline Ca2+ fluctuations caused by a stochastic opening of Ca2+ channels in the plasma membrane. Suprathreshold fluctuations trigger Ca2+-induced Ca2+ release (CICR) from the Ca2+ stores by activating inositol 1,4,5-trisphosphate (IP3) receptors. In agreement with the model prediction, the spontaneous Ca2+ events frequency depended on the extracellular Ca2+ concentration. Astrocytic depolarization by high extracellular K+ increased the frequency of the Ca2+ events through activation of voltage-gated Ca2+ channels (VGCC) in cultured astrocytes. Our results suggest that the morphological profile of the astrocytic processes is responsible for tuning of the Ca2+ event frequency. Therefore, the structural plasticity of astrocytic processes can be directly translated into changes in astrocytic Ca2+ signaling. This may be important for both physiological and pathological astrocyte remodeling.\n\nMain pointsO_LIMajority of spontaneous Ca2+ events start in thin astrocytic processes\nC_LIO_LIHigher surface-to-volume ratio of the process is responsible for larger intracellular Ca2+ fluctuations\nC_LIO_LILarger intracellular Ca2+ fluctuations trigger Ca2+-dependent Ca2+ release\nC_LI

neuroscience↗