Cagdas Guducu

Acute Supramaximal Exercise Increases the Brain Oxygenation in Relation to Cognitive Workload

Single bout of exercise can improve the performance on cognitive tasks. However, cognitive responses may be controversial due to different type, intensity, and duration of exercise. In addition, the mechanism of the effect of acute exercise on brain is still unclear. This study was aimed to investigate the effects of supramaximal exercise on cognitive tasks by means of brain oxygenation monitoring. The brain oxygenation of Prefrontal cortex (PFC) was measured on 35 healthy male volunteers via functional near infrared spectroscopy (fNIRS) system. Subjects performed 2-Back test before and after the supramaximal exercise wingate anerobic test (WAnT) lasting 30-s on cycle ergometer. The PFC oxygenation change evaluation revealed that PFC oxygenation rise during post-exercise 2-Back task was considerably higher than those in pre-exercise 2-Back task. In order to describe the relationship between oxygenation change and exercise performance, subjects were divided into two groups as high performers (HP) and low performers (LP) according to their peak power values (PP) obtained from the supramaximal test. The oxy-hemoglobin (oxy-Hb) values were compared between pre- and post-exercise conditions within subjects and also between subjects according to peak power. When performers were compared, in the HP group, the oxy-Hb values in post-exercise 2-Back test were significantly higher than those in pre-exercise 2-Back test. HP had significantly higher post-exercise oxy-Hb change (Δ) than those of LP. In addition, PP of the total group were significantly correlated with Δoxy-Hb.The key findings of the present study revealed that acute supramaximal exercise has an impact on the brain oxygenation during a cognitive task. Also, the higher the anerobic PP describes the larger the oxy-Hb response in post-exercise cognitive task. The current study also demonstrated a significant correlation between peak power (exercise load) and post-exercise hemodynamic responses (oxy-, deoxy- and total-Hb). The magnitude of this impact might be related with the physical performance capacities of the individuals. This can become a valuable parameter for future studies on human factor.

Chemosensory Function in Congenitally Blind or Deaf Teenagers

IntroductionIt may be assumed that congenital absence of a certain sensory function would affect the processing of remaining sensory processes. The purpose of the present study was to evaluate chemosensory brain responsiveness both electrophysiologically and psychophysically in congenitally blind or deaf individuals.MethodsFourteen blind, 13 deaf, and 10 control subjects were recruited to this study. Psychophysical assessment of olfactory function was performed via “Sniffin’ Sticks” test. In this test, olfactory threshold, discrimination, identification, and total scores were compared between blind, deaf, and control subjects. In addition, electrophysiological assessment of olfactory function was performed via event-related potentials to olfactory and trigeminal stimuli.ResultsThe “Sniffin’ Sticks” test indicated frequent hyposmia in the deaf group. Discrimination and total scores of the deaf group were significantly lower than the control group. On the other hand, there were no significant differences between blind and control groups. Threshold and total scores of the deaf group were significantly lower than the blind group. There were no significant differences in amplitudes and latencies of any chemosensory-evoked potential components for both stimuli between the groups.ConclusionsThe deaf subjects appear to have lower olfactory test scores than blind and control subjects. Application of stimulants in a more complex setup may help to disentangle the various changes in chemosensory processing in the absence of other sensory channels.

Olfactory dysfunction in children with Kallmann Syndrome: relation of smell tests with brain magnetic resonance imaging

OBJECTIVEKallmann syndrome (KS) is a genetic disorder with the distinctive features of hyposmia or anosmia and hypogonadotropic hypogonadism. Though hyposmia/anosmia can be evaluated by both objective and subjective smell tests, there is no study comparing these two methods in KS. The aim of the present case series was to discuss the results of objective and subjective smell tests and compare them to volumetric magnetic resonance imaging (MRI).METHODSA total of six adolescent males (aged between 14–18 years) with KS were examined by objective and subjective olfactometry to test smell function and by specific MRI sequences to measure the olfactory bulbs.RESULTSThe objective smell test showed anosmia in all six of the patients. However, the subjective test revealed anosmia in five patients and hyposmia in one patient. Brain MRI showed olfactory bulb aplasia in all six cases.CONCLUSIONMRI provides robust evaluation of the olfactory bulb volume. Our data show excellent compatibility between the results obtained via objective olfactometry and those obtained by measuring olfactory bulb volume as determined by MRI and therefore demonstrate that objective olfactometry remains a highly reliable test. Furthermore, although the number of subjects studied was small, these data also suggest that cheaper and more easily available subjective tests could be used in preference to the more expensive as well as labor-intensive and time-consuming objective smell tests. In the event of doubts as to the validity of the subjective tests, the objective olfactometry tests can confirm the diagnosis. The bulb volumetric MRI may be also used in difficult cases.

Temporal Encoding During Unimodal and Bimodal Odor Processing in the Human Brain

IntroductionIn daily life, people encounter a wide range of odors, most of which contain multiple chemical substances. So-called bimodal odors stimulate both the olfactory and trigeminal nerve, and the interaction between these two systems shapes the perception of the odor. However, temporal encoding of these sensory systems during bimodal odor processing has received limited scientific attention.MethodsTo investigate this, we recorded the electrophysiological response in 17 participants to relatively unimodal olfactory (strawberry), trigeminal (l-isopulegol) and strongly bimodal (strawberry and l-isopulegol) stimuli.ResultsERP amplitudes and intensity ratings were significantly bigger for bimodal stimulation, as compared to unimodal stimulations. No significant difference was observed between N1 and P2 response latencies to olfactory and bimodal stimuli while responses to both stimuli showed longer latencies compared to the response of the trigeminal stimulus.ConclusionsResults provide further evidence of interaction between olfactory and trigeminal systems; additional activation of the olfactory system results in more vigorous electrophysiological responses and the experience of higher intensity. In addition, results indicate that the trigeminal system is faster to react to stimulation.ImplicationsThe current study offers a view on the temporal processing of bimodal odorants that are most likely to be encountered in the environment. We link the more vigorous electrophysiological response to a more complex odorant with activation of different neural structures.

Brain activity characterization by entropic clustering of EEG signals

25th Signal Processing and Communications Applications Conference, SIU 2017; Antalya; Turkey; 15 May 2017 through 18 May 2017In this study, two novel entropy and mutual information based algorithms have been proposed to characterize the stimulus specific brain activity. In the first method, inter-channel mutual information of electroencephalography signals has been calculated and the channels that exhibit synchronized behaivour during stimulus. In the second method, the responsiveness of the individual channels has been characterized in an entropic manner and then, the channels which demonstrates stimulus specific entropic behavior have been obtained. The performance of the proposed methods has been simulated on a real dataset obtained from Dokuz Eylul University Brain Biophysics laboratory. The results demonstrate that different regions of the brain exhibit a coherent activity during stimulus.

Investigating the responses of brain to taste stimuli via electrophysiological methods and frequency analysis: Preliminary results

Spontaneous potentials occur during the brains activities. In addition, some potentials occur depending on receptor activations during the stimulated state. The aim of this study is to investigate bioelectrical changes of the brain against taste stimuli. Bioelectrical changes were recorded and measured objectively via electroencephalograhpy (EEG). Five healthy volunteers (2 females; mean age: 24.6 years) participated to the study. Current study was conducted in Dokuz Eylul University Biophysics Department, Five Senses Laboratory. Taste stimuli were delivered via Gustometer (Burghart MT, Germany). These tastes were bitter, sour, sweet, salty, and umami. As a result of EEG data analysis amplitude-time graphs were obtained for all participants. Continuous wavelet transform was applied to brain responses to taste stimuli for detailed analysis. These responses were investigated on scalogram. The highest peak to peak maximum amplitude value was measured on sour taste (11.46 µV). The aim of the future studies is to topologically demonstrate the brain responsiveness to five basic taste, and also to make contributions to literature about the activations in frequency-time domain.

Delta oscillatory responses to somatosensory stimuli in blind humans

The aim of this study was to investigate the delta oscillatory responses to non-painful tactile stimuli for the blind subjects. The measurements were performed with thirteen blind subjects (15.07 age ±1.65, 10 male) and thirteen healthy subjects (15.92 age ± 2.90, 8 male). One type of tactile stimuli, were applied to middle finger and index finger of the right hand. The electroencephalogram (EEG) was recorded from 64 channels, 3 of which (C<inf>Z</inf>, C<inf>3</inf>, C<inf>4</inf>) were primarily analyzed. Peak-to-peak maximum amplitudes and durations of delta (0.5–3.5 Hz) were measured in 1000 ms following stimuli. For the statistical analysis Wilcoxon test was used. In this present study, increases in delta (0.5–3.5 Hz) responses for non-painful tactile stimuli in blind subjects were compared with the control group. In each electrode area (C<inf>Z</inf>, C<inf>3</inf>, C<inf>4</inf>) the amplitude measurements of the blind group found higher than the control group and the difference found statistically significant in C4 electrode area (p≪0.05).The durations in each electrode area (C<inf>Z</inf>, C<inf>3</inf>, C<inf>4</inf>) for the blind group found statistically longer than the control group ( for each one p≪0.05).