Biology subjects

Hramov, A. E.

Publications and source records attributed to Hramov, A. E..

3 recordsLinked to original sources

bioRxiv2020

Age-related changes in the motor planning strategy slow down motor initiation in elderly adults

Age-related changes in the human brain functioning crucially affect the motor system, causing increased reaction time, low ability to control and execute movements, difficulties in learning new motor skills. The lifestyle and lowered daily activity of elderly adults, along with the deficit of motor and cognitive brain functions, might lead to the developed ambidexterity, i.e. the loss of dominant limb advances. Despite the broad knowledge about the changes in cortical activity directly related to the motor execution, less is known about age-related differences in the motor initiation phase. We hypothesize that the latter strongly influences the behavioral characteristics, such as reaction time, the accuracy of motor performance, etc. Here, we compare the neuronal processes underlying the motor planning of fine motor tasks between elderly and young subjects. We demonstrate that aging significantly reduces the speed of motor initiation in the dominant hand task due to the different motor planning strategies employed by elderly and young adults. Based on the results of the whole-scalp electroencephalography (EEG) analysis, we suggest that young adults tend to use the efficient and fast mechanism of motor working memory. In contrast, elderly adults involve a more demanding sensorimotor integration process similar to the non-dominant hand task.

neuroscience↗

bioRxiv2020

Neuronal adaptation during the prolonged cognitive task improves visual stimulus processing

Brain optimally utilizes resources to resist mental fatigue during the prolonged period of cognitive activity. Neural mechanisms underlying long-term cognitive performance remain unknown. We show that during the 40-minutes visual stimuli classification task, subjects improve behavioral performance in terms of response time and correctness. We observe that the prestimulus{theta} and power grows during the experiment manifesting the mental fatigue. The prestimulus {beta} power, in its turn, increases locally in the region, engaged in the ongoing stimulus processing, that may reflect the neuronal adaptation. Our results evidence that the neuronal adaptation is enhanced in the course of the experiment reducing the cognitive demands required to activate the stimulus-related brain regions.

neuroscience↗

bioRxiv2020

Estimating voluntary and involuntary attention in bistable visual perception: A MEG study

We introduce a method for measuring human attention when performing a visual task consisting in different interpretations of a bistable image. The Necker cube with flickering faces was presented to nine conditionally healthy volunteers. The pixels intensity in the front and rear cube faces were modulated by a sinusoidal signal with 6.67-Hz (60/9) and 8.57-Hz (60/7) frequencies, respectively. The tags of these frequencies and their second harmonics were clearly identified in the average Fourier spectra of the magnetoencephalographic (MEG) data recorded from the occipital cortex. In the first part of the experiment, the subjects were asked to voluntary control their attention by interpreting the cube orientation as either left- or right-orientated. Accordingly, we observed the dominance of the corresponding spectral component and voluntary attention performance was measured. In the second part of the experiment, the subjects were just asked to observe the cube image without any effort in its interpretation. The alternation of the dominant spectral energies at the second harmonic tag frequencies was treated as changes in the cube orientation. Based on the results of the first experimental stage and using wavelet analysis, we developed a novel method which allowed us to identify currently perceived cube orientations. Finally, we characterized involuntary attention using the dominance time distribution and related it to voluntary attention performance and brain noise. In particular, we have shown that higher attention performance is associated with stronger brain noise.

neuroscience↗