Biology subjects

Alizadeh, S.

Publications and source records attributed to Alizadeh, S..

5 recordsLinked to original sources

bioRxiv2023

The Effects of Physical and Mental Fatigue on Time Perception

The subjective perception of time holds a foundational significance within the realm of human psychology and our conceptualizations of reality and how we elucidate the chronological progression of events within our lives. While there have been some studies examining the effects of exercise on time perception during the exercise period, there are no studies investigating the effects of fatiguing exercise on time perception after the exercise intervention. This study aimed to investigate the effects of physical and mental fatigue on time estimates over 30-seconds (5-, 10-, 20-, and 30-seconds) immediately after exercise and 6-minutes after the post-test. Seventeen healthy and recreationally active volunteers (14 males, 3 females) were subjected to three conditions: physical fatigue, mental fatigue, and control. All participants completed a familiarization and three 30-minute experimental conditions (control, physical fatigue (cycling at 65% peak power output), and mental fatigue (Stroop task for 1100 trials) on separate days. Heart rate and body temperature were recorded at the pre-test, start, 5-, 10-, 20-, 30-seconds of the interventions, post-test, and 6-min follow-up. Rating of perceived exertion (RPE) was recorded four times during the intervention. Time perception was measured prospectively (at 5-, 10-, 20-, and 30-seconds) at the pre-test, post-test, and 6-minute follow-up. Physical fatigue significantly (p=0.001) underestimated time compared to mental fatigue and control conditions at the post-test and follow-up, with no significant differences between mental fatigue and control conditions. Heart rate, body temperature, and RPE were significantly (all p=0.001) higher with physical fatigue compared to mental fatigue and control conditions during the intervention and at the post-test. This study demonstrated that cycling-induced fatigue led to time underestimation compared to mental fatigue and control conditions. It is crucial to consider that physical fatigue has the potential to lengthen an individuals perception of time estimates in sports or work environments.

neuroscience↗

bioRxiv2020

Effect of An Inverted Seated Position with Upper Arm Blood Flow Restriction on Measures of Elbow Flexors Neuromuscular Performance

PurposeThe objective of the investigation was to determine the concomitant effects of upper arm blood flow restriction (BFR) and inversion on elbow flexors neuromuscular responses. MethodsRandomly allocated, 13 volunteers performed four conditions in a within-subject design: rest (control, 1-min upright position without BFR), control (1-min upright with BFR), 1-min inverted (without BFR), and 1-min inverted with BFR. Evoked and voluntary contractile properties, before, during and after a 30-s maximum voluntary contraction (MVC) exercise intervention were examined as well as pain scale. ResultsInversion induced significant pre-exercise intervention decreases in elbow flexors MVC (21.1%, [Formula], p=0.02) and resting evoked twitch (29.4%, [Formula], p=0.03) forces. The 30-s MVC induced significantly greater pre- to post-test decreases in potentiated twitch force ([Formula], p<0.0009) during inversion ({downarrow}75%) than upright ({downarrow}65.3%) conditions. Overall, BFR decreased MVC force 4.8% ([Formula], p=0.05). For upright position, BFR induced 21.0% reductions in M-wave amplitude ([Formula], p=0.04). There were no significant differences for electromyographic activity or voluntary activation as measured with the interpolated twitch technique. For all conditions, there was a significant increase in pain scale between the 40-60 s intervals and post-30-s MVC (upright<inversion, and without BFR<BFR). ConclusionThe concomitant application of inversion with elbow flexors BFR only amplified neuromuscular performance impairments to a small degree. Individuals who execute forceful contractions when inverted or with BFR should be cognizant that force output may be impaired.

physiology↗

bioRxiv2020

The missing role of gray matter in studying brain controllability

1Brain controllability properties are normally derived from the white matter fiber tracts in which the neural substrate of the actual energy consumption, namely the gray matter, has been widely ignored. Here, we study the relationship between gray matter volume of regions across the whole cortex and their respective control property derived from the structural architecture of the white matter fiber tracts. The data suggests that the ability of white fiber tracts to exhibit control at specific nodes not only depends on the connection strength of the structural connectome but additionally strongly depends on gray matter volume at the host nodes. Our data indicates that connectivity strength and gray matter volume interact with respect to the brains control properties, such that gray matter exerts the great impact in regions with high structural connectivity. Disentangling effects of the regional gray matter volume and connectivity strength, we found that frontal and sensory areas play crucial roles in controllability. Together these results suggest that structural and regional properties of the white matter and gray matter provide complementary information in studying the control properties of the intrinsic structural and functional architectural of the brain.

neuroscience↗

bioRxiv2020

Evidence for modulation of EEG microstate sequence by vigilance level

The momentary global functional state of the brain is reflected in its electric field configuration and cluster analytical approaches have consistently shown four configurations, referred to as EEG microstate classes A to D. Changes in microstate parameters are associated with a number of neuropsychiatric disorders, task performance, and mental state establishing their relevance for cognition. However, the common practice to use eye-closed resting state data to assess the temporal dynamics of microstate parameters might induce systematic confounds related to vigilance levels. Here, we studied the dynamics of microstate parameters in two independent data sets and showed that the parameters of microstates are strongly associated with vigilance level assessed both by EEG power analysis and fMRI global signal. We found that the duration and contribution of microstate class C, as well as transition probabilities towards microstate class C were positively associated with vigilance, whereas the sign was reversed for microstate classes A and B. Furthermore, in looking for the origins of the correspondence between microstates and vigilance level, we found Granger-causal effects of vigilance levels on microstate sequence parameters. Collectively, our findings suggest that duration and occurrence of microstates have a different origin and possibly reflect different physiological processes. Finally, our findings indicate the need for taking vigilance levels into consideration in resting-sate EEG investigations.

neuroscience↗

bioRxiv2020

Replicative aging is associated with loss of genetic heterogeneity from extrachromosomal circular DNA in Saccharomyces cerevisiae

Circular DNA of chromosomal origin form from all parts of eukaryotic genomes. In yeast, circular rDNA accumulates as cells divide, contributing to replicative aging. However, little is known about how other chromosome-deri ved circles segregate and contribute to geneticvariation as cells age. We identified circular DNA across the genome of young S. cerevisiae populations and their aged descendants. Young cells had highly diverse circular DNA populations, but lost 94% of the different circular DNA after 20 divisions. Circles present in both young and old cells were characterized by replication origins and included circles from unique regions of the genome, rDNA circles and telomeric Y circles. The loss in genetic heterogeneity in aged cells was accompanied by massive accumulation of rDNA circles >95% of all circular DNA. We discovered circles had flexible inherence patterns. Glucose limited conditions selected for cells with glucose-transporter gene circles, [HXT6/7circle], and up to 50% of cells in a population carried them. [HXT6/7circle] cells were eventually substituted by cells carrying stable chromosomal HXT6 HXT6/7 HXT7 amplifications, suggesting circular DNA were intermediates in chromosomal amplifications. In conclusion, DNA circles can offer a flexible adaptive solution but cells lose genetic heterogeneity from circular DNA as they undergo replicative aging.

cell biology↗