Istvan Hernadi | University of Pecs (original) (raw)
Papers by Istvan Hernadi
International Journal of Molecular Sciences
Traumatic brain injury (TBI) is among the main causes of sudden death after head trauma. These in... more Traumatic brain injury (TBI) is among the main causes of sudden death after head trauma. These injuries can result in severe degeneration and neuronal cell death in the CNS, including the retina, which is a crucial part of the brain responsible for perceiving and transmitting visual information. The long-term effects of mild–repetitive TBI (rmTBI) are far less studied thus far, even though damage induced by repetitive injuries occurring in the brain is more common, especially amongst athletes. rmTBI can also have a detrimental effect on the retina and the pathophysiology of these injuries is likely to differ from severe TBI (sTBI) retinal injury. Here, we show how rmTBI and sTBI can differentially affect the retina. Our results indicate an increase in the number of activated microglial cells and Caspase3-positive cells in the retina in both traumatic models, suggesting a rise in the level of inflammation and cell death after TBI. The pattern of microglial activation appears distribu...
Traumatic brain injury (TBI) is among the main causes of sudden death after head trauma. These in... more Traumatic brain injury (TBI) is among the main causes of sudden death after head trauma. These injuries can result in severe degeneration and neuronal cell death in the CNS, including the retina which is a crucial part of the brain responsible for perceiving and transmitting visual information. The long-term effects of mild-repetitive TBI (rmTBI) are far less studied thus far, even though damages induced by repetitive injuries occurring in the brain are more common, especially amongst athletes. rmTBI can also have a detrimental effect on the retina and the pathophysiology of these injuries are likely to differ from the severe TBI (sTBI) retinal injury.Here we showed how rmTBI and sTBI can dissimilarly affect the retina. Our results indicate an increase in the number of activated microglial cells and Caspase3-positive cells in the retina in both traumatic models, suggesting a rise in the level of inflammation and cell death after TBI. The pattern of microglial activation appears even...
Songorine (SON) is a diterpenoid alkaloid from Aconitum plants. Preparations of Aconitum roots ha... more Songorine (SON) is a diterpenoid alkaloid from Aconitum plants. Preparations of Aconitum roots have been employed in traditional oriental herbal medicine, however, their mechanisms of action are still unclear. Since GABA-receptors are possible brain targets of SON, we investigated which subtypes of GABA-receptors contribute to the effects of SON, and how SON affects anxiety-like trait behavior and psychomotor cognitive performance of rats. First, we investigated the effects of microiontophoretically applied SON alone and combined with GABA-receptor agents picrotoxin and saclofen on neuronal firing activity in various brain areas. Next, putative anxiolytic effects of SON (1.0-3.0 mg/kg) were tested against the GABA-receptor positive allosteric modulator refer-ence compound diazepam (1.0-5.0 mg/kg) in the elevated zero maze (EOM). Furthermore, basic cognitive effects were assessed in a rodent version of the psychomotor vigilance task (PVT). Local application of SON predominantly inhib...
Scientific Reports
The human mu rhythm has been suggested to represent an important function in information processi... more The human mu rhythm has been suggested to represent an important function in information processing. Rodent homologue rhythms have been assumed though no study has investigated them from the cognitive aspect yet. As voluntary goal-directed movements induce the desynchronization of mu rhythm, we aimed at exploring whether the response-related brain activity during the touchscreen visual discrimination (VD) task is suitable to detect sensorimotor rhythms and their change under cognitive impairment. Different doses of scopolamine or MK-801 were injected subcutaneously to rats, and epidural electroencephalogram (EEG) was recorded during task performance. Arciform ~ 10 Hz oscillations appeared during visual processing, then two characteristic alpha/beta desynchronization-resynchronization patterns emerged mainly above the sensorimotor areas, serving presumably different motor functions. Beyond causing cognitive impairment, both drugs supressed the touch-related upper alpha (10–15 Hz) rea...
Short-term memory is implicated in a range of cognitive abilities and is critical for understandi... more Short-term memory is implicated in a range of cognitive abilities and is critical for understanding primate cognitive evolution. To investigate the effects of phylogeny, ecology and sociality on short-term memory ability, we tested 421 non-human primates across 41 species in a pre-registered, experimental delayed-response task. Our results confirm previous findings that longer delays decrease memory performance across species and taxa. Our analyses demonstrate a considerable contribution of phylogeny over ecological and social factors on the distribution of short-term memory performance in primates; closely related species had more similar short-term memory abilities. However, interdependencies between phylogeny and socioecology of a given species present an obstacle to disentangling the effects of each of these factors on the evolution of short-term memory capacity. The dataset corresponding to the study is freely accessible and constitutes an important resource for studying the ev...
Frontiers in Neuroscience, 2020
Although mobile phone (MP) use has been steadily increasing in the last decades and similar posit... more Although mobile phone (MP) use has been steadily increasing in the last decades and similar positive trends are expected for the near future, systematic investigations on neurophysiological and cognitive effects caused by recently developed technological standards for MPs are scarcely available. Here, we investigated the effects of radiofrequency (RF) fields emitted by new-generation mobile technologies, specifically, Universal Mobile Telecommunications System (UMTS) and Long-Term Evolution (LTE), on intrinsic scalp EEG activity in the alpha band (8–12 Hz) and cognitive performance in the Stroop test. The study involved 60 healthy, young-adult university students (34 for UMTS and 26 for LTE) with double-blind administration of Real and Sham exposure in separate sessions. EEG was recorded before, during and after RF exposure, and Stroop performance was assessed before and after EEG recording. Both RF exposure types caused a notable decrease in the alpha power over the whole scalp tha...
Repetitive mild traumatic brain injuries (TBI) impair cognitive abilities and increase risk of ne... more Repetitive mild traumatic brain injuries (TBI) impair cognitive abilities and increase risk of neurodegenerative disorders in humans. We developed two repetitive mild TBI models in rats with different time intervals between successive weight-drop injuries, and assessed cognitive performance and biomarker profiles. Rats were subjected to repetitive Sham (no injury), single mild (mTBI), repetitive mild (rmTBI – 5 hits, 24 h apart), rapid repetitive mild (rapTBI – 5 hits, 5 min apart) and single severe (sTBI) TBI. We assessed cognitive performance 2 and 8 weeks after TBI in the novel object recognition test (NOR), and 6-7 weeks after TBI in the water maze (MWM). Acute immunohistochemical markers were checked 24 h after TBI, and blood biomarkers were measured with ELISA 8 weeks after TBI. In the NOR, both rmTBI and rapTBI showed poor performance at 2 weeks post-injury. At 8 weeks post-injury, the rmTBI group still performed worse than the Sham and mTBI groups, while the rapTBI group rec...
Radiation research, Jan 24, 2015
Mobile equipment use of wireless fidelity (Wi-Fi) signal modulation has increased exponentially i... more Mobile equipment use of wireless fidelity (Wi-Fi) signal modulation has increased exponentially in the past few decades. However, there is inconclusive scientific evidence concerning the potential risks associated with the energy deposition in the brain from Wi-Fi and whether Wi-Fi electromagnetism interacts with cognitive function. In this study we investigated possible neurocognitive effects caused by Wi-Fi exposure. First, we constructed a Wi-Fi exposure system from commercial parts. Dosimetry was first assessed by free space radiofrequency field measurements. The experimental exposure system was then modeled based on real geometry and physical characteristics. Specific absorption rate (SAR) calculations were performed using a whole-body, realistic human voxel model with values corresponding to conventional everyday Wi-Fi exposure (peak SAR10g level was 99.22 mW/kg with 1 W output power and 100% duty cycle). Then, in two provocation experiments involving healthy human volunteers ...
Regulatory Peptides, 2002
Intracerebroventricular injections of 10-20-mg orexin-A induce food intake in rats for about 30 m... more Intracerebroventricular injections of 10-20-mg orexin-A induce food intake in rats for about 30 min, or enhance fasting-induced hyperphagia. In thermoregulatory studies, an amount of 2 mg of the peptide causes hypometabolism and hypothermia in the same period. The thermoregulatory reaction can be demonstrated at moderately cool environments, mainly after slight food deprivation. Both the ingestive and the thermoregulatory reactions are more pronounced in cold-adapted animals. Pretreatment with D-Tyr 27,36 ,D-Thr 32-NPY(27-36), a peptideantagonist of NPY, prevents the hypothermia. It is concluded that, probably through NPY activation, orexin-A is involved primarily in the regulation of energy status of the body (as an anabolic agent), and not simply in the regulation of either food intake or body temperature. This anabolic response is followed by a late and more sustained catabolic phase characterized by absence of food intake, increased metabolism and dose-dependent hyperthermia, which hyperthermia cannot be suppressed by the NPY-antagonist. In contrast to orexin-A, neither hyperphagia nor suppression of refeeding hyperphagia, but dose-dependent hyperthermia follows injections of orexin-B, suggesting that this peptide has neither coordinated anabolic nor coordinated catabolic effects on energy balance.
Neuroscience Research, 2011
The prefrontal cortex is credited with contributing to relational reasoning, or the ability to in... more The prefrontal cortex is credited with contributing to relational reasoning, or the ability to integrate multiple acquired associations to generate new relationships. We have recorded single-unit activity from the lateral prefrontal cortex (LPFC) and the striatum while the monkeys performed a sequential paired-association task with asymmetric reward schedule. In the task, the monkeys learned two sequences of associated stimuli: A1-B1-C1 and A2-B2C2. The asymmetric reward rule was instructed by pairing C1 (or C2) with large (or small) reward block by block. The monkey also learned associations between new stimuli (e.g. N1, N2) and B1 and B2. The new stimuli were presented as the first cue in sequential paired-association trials instead of the old stimuli (A1 and A2). The findings from single-unit activity suggest that the LPFC can use an internal model of category to transfer reward information associated with one stimulus to other stimuli, even to new stimuli that had never been paired with different amount of reward. The striatum only uses direct experience between conditioned stimuli and reward to predict reward. One prediction from this hypothesis is that if the LPFC is inactivated, the monkey still correctly predicts reward for old stimuli through the striatal pathway, but has deficits in predicting reward for new stimuli. We injected muscimol to locally inactivate the LPFC, and also saline into the LPFC as control. In saline sessions, the monkey had significantly higher choice accuracy for new stimuli in large than in small reward trials, but this difference disappeared in muscimol session, consistent with the prediction. Together with single-unit activity data, our results suggest that the LPFC play a critical role in category-based reward inference.
Neuroscience Research, 2009
Retrieval of contextual fear memory by re-exposure to conditioned stimulus (CS) initiates two pro... more Retrieval of contextual fear memory by re-exposure to conditioned stimulus (CS) initiates two processes; reconsolidation and extinction. Previous our studies showed that short re-exposure to the CS inducing memory reconsolidation activated CREBdependent gene expression in hippocampus, while prolonged re-exposure inducing memory extinction inhibited this gene expression, suggesting that hippocampus plays distinct roles in reconsolidation and extinction of contextual fear memory. As a first step to understand the mechanism by which hippocampal gene expression are oppositely regulated in response to short and long re-exposure, we here performed biochemical analyses of glutamate receptors in hippocampus following short and long re-exposure. We found that long re-exposure to the CS inducing extinction decreased in expression of NMDA receptors including NR1, NR2A and NR2B and phosphorylation of GluR1 subunit of AMPA receptors at S831 and S845. These down-regulations of glutamate receptors might play critical roles in extinction of contextual fear memory by inhibiting hippocampal gene expression.
International Journal of Molecular Sciences
Traumatic brain injury (TBI) is among the main causes of sudden death after head trauma. These in... more Traumatic brain injury (TBI) is among the main causes of sudden death after head trauma. These injuries can result in severe degeneration and neuronal cell death in the CNS, including the retina, which is a crucial part of the brain responsible for perceiving and transmitting visual information. The long-term effects of mild–repetitive TBI (rmTBI) are far less studied thus far, even though damage induced by repetitive injuries occurring in the brain is more common, especially amongst athletes. rmTBI can also have a detrimental effect on the retina and the pathophysiology of these injuries is likely to differ from severe TBI (sTBI) retinal injury. Here, we show how rmTBI and sTBI can differentially affect the retina. Our results indicate an increase in the number of activated microglial cells and Caspase3-positive cells in the retina in both traumatic models, suggesting a rise in the level of inflammation and cell death after TBI. The pattern of microglial activation appears distribu...
Traumatic brain injury (TBI) is among the main causes of sudden death after head trauma. These in... more Traumatic brain injury (TBI) is among the main causes of sudden death after head trauma. These injuries can result in severe degeneration and neuronal cell death in the CNS, including the retina which is a crucial part of the brain responsible for perceiving and transmitting visual information. The long-term effects of mild-repetitive TBI (rmTBI) are far less studied thus far, even though damages induced by repetitive injuries occurring in the brain are more common, especially amongst athletes. rmTBI can also have a detrimental effect on the retina and the pathophysiology of these injuries are likely to differ from the severe TBI (sTBI) retinal injury.Here we showed how rmTBI and sTBI can dissimilarly affect the retina. Our results indicate an increase in the number of activated microglial cells and Caspase3-positive cells in the retina in both traumatic models, suggesting a rise in the level of inflammation and cell death after TBI. The pattern of microglial activation appears even...
Songorine (SON) is a diterpenoid alkaloid from Aconitum plants. Preparations of Aconitum roots ha... more Songorine (SON) is a diterpenoid alkaloid from Aconitum plants. Preparations of Aconitum roots have been employed in traditional oriental herbal medicine, however, their mechanisms of action are still unclear. Since GABA-receptors are possible brain targets of SON, we investigated which subtypes of GABA-receptors contribute to the effects of SON, and how SON affects anxiety-like trait behavior and psychomotor cognitive performance of rats. First, we investigated the effects of microiontophoretically applied SON alone and combined with GABA-receptor agents picrotoxin and saclofen on neuronal firing activity in various brain areas. Next, putative anxiolytic effects of SON (1.0-3.0 mg/kg) were tested against the GABA-receptor positive allosteric modulator refer-ence compound diazepam (1.0-5.0 mg/kg) in the elevated zero maze (EOM). Furthermore, basic cognitive effects were assessed in a rodent version of the psychomotor vigilance task (PVT). Local application of SON predominantly inhib...
Scientific Reports
The human mu rhythm has been suggested to represent an important function in information processi... more The human mu rhythm has been suggested to represent an important function in information processing. Rodent homologue rhythms have been assumed though no study has investigated them from the cognitive aspect yet. As voluntary goal-directed movements induce the desynchronization of mu rhythm, we aimed at exploring whether the response-related brain activity during the touchscreen visual discrimination (VD) task is suitable to detect sensorimotor rhythms and their change under cognitive impairment. Different doses of scopolamine or MK-801 were injected subcutaneously to rats, and epidural electroencephalogram (EEG) was recorded during task performance. Arciform ~ 10 Hz oscillations appeared during visual processing, then two characteristic alpha/beta desynchronization-resynchronization patterns emerged mainly above the sensorimotor areas, serving presumably different motor functions. Beyond causing cognitive impairment, both drugs supressed the touch-related upper alpha (10–15 Hz) rea...
Short-term memory is implicated in a range of cognitive abilities and is critical for understandi... more Short-term memory is implicated in a range of cognitive abilities and is critical for understanding primate cognitive evolution. To investigate the effects of phylogeny, ecology and sociality on short-term memory ability, we tested 421 non-human primates across 41 species in a pre-registered, experimental delayed-response task. Our results confirm previous findings that longer delays decrease memory performance across species and taxa. Our analyses demonstrate a considerable contribution of phylogeny over ecological and social factors on the distribution of short-term memory performance in primates; closely related species had more similar short-term memory abilities. However, interdependencies between phylogeny and socioecology of a given species present an obstacle to disentangling the effects of each of these factors on the evolution of short-term memory capacity. The dataset corresponding to the study is freely accessible and constitutes an important resource for studying the ev...
Frontiers in Neuroscience, 2020
Although mobile phone (MP) use has been steadily increasing in the last decades and similar posit... more Although mobile phone (MP) use has been steadily increasing in the last decades and similar positive trends are expected for the near future, systematic investigations on neurophysiological and cognitive effects caused by recently developed technological standards for MPs are scarcely available. Here, we investigated the effects of radiofrequency (RF) fields emitted by new-generation mobile technologies, specifically, Universal Mobile Telecommunications System (UMTS) and Long-Term Evolution (LTE), on intrinsic scalp EEG activity in the alpha band (8–12 Hz) and cognitive performance in the Stroop test. The study involved 60 healthy, young-adult university students (34 for UMTS and 26 for LTE) with double-blind administration of Real and Sham exposure in separate sessions. EEG was recorded before, during and after RF exposure, and Stroop performance was assessed before and after EEG recording. Both RF exposure types caused a notable decrease in the alpha power over the whole scalp tha...
Repetitive mild traumatic brain injuries (TBI) impair cognitive abilities and increase risk of ne... more Repetitive mild traumatic brain injuries (TBI) impair cognitive abilities and increase risk of neurodegenerative disorders in humans. We developed two repetitive mild TBI models in rats with different time intervals between successive weight-drop injuries, and assessed cognitive performance and biomarker profiles. Rats were subjected to repetitive Sham (no injury), single mild (mTBI), repetitive mild (rmTBI – 5 hits, 24 h apart), rapid repetitive mild (rapTBI – 5 hits, 5 min apart) and single severe (sTBI) TBI. We assessed cognitive performance 2 and 8 weeks after TBI in the novel object recognition test (NOR), and 6-7 weeks after TBI in the water maze (MWM). Acute immunohistochemical markers were checked 24 h after TBI, and blood biomarkers were measured with ELISA 8 weeks after TBI. In the NOR, both rmTBI and rapTBI showed poor performance at 2 weeks post-injury. At 8 weeks post-injury, the rmTBI group still performed worse than the Sham and mTBI groups, while the rapTBI group rec...
Radiation research, Jan 24, 2015
Mobile equipment use of wireless fidelity (Wi-Fi) signal modulation has increased exponentially i... more Mobile equipment use of wireless fidelity (Wi-Fi) signal modulation has increased exponentially in the past few decades. However, there is inconclusive scientific evidence concerning the potential risks associated with the energy deposition in the brain from Wi-Fi and whether Wi-Fi electromagnetism interacts with cognitive function. In this study we investigated possible neurocognitive effects caused by Wi-Fi exposure. First, we constructed a Wi-Fi exposure system from commercial parts. Dosimetry was first assessed by free space radiofrequency field measurements. The experimental exposure system was then modeled based on real geometry and physical characteristics. Specific absorption rate (SAR) calculations were performed using a whole-body, realistic human voxel model with values corresponding to conventional everyday Wi-Fi exposure (peak SAR10g level was 99.22 mW/kg with 1 W output power and 100% duty cycle). Then, in two provocation experiments involving healthy human volunteers ...
Regulatory Peptides, 2002
Intracerebroventricular injections of 10-20-mg orexin-A induce food intake in rats for about 30 m... more Intracerebroventricular injections of 10-20-mg orexin-A induce food intake in rats for about 30 min, or enhance fasting-induced hyperphagia. In thermoregulatory studies, an amount of 2 mg of the peptide causes hypometabolism and hypothermia in the same period. The thermoregulatory reaction can be demonstrated at moderately cool environments, mainly after slight food deprivation. Both the ingestive and the thermoregulatory reactions are more pronounced in cold-adapted animals. Pretreatment with D-Tyr 27,36 ,D-Thr 32-NPY(27-36), a peptideantagonist of NPY, prevents the hypothermia. It is concluded that, probably through NPY activation, orexin-A is involved primarily in the regulation of energy status of the body (as an anabolic agent), and not simply in the regulation of either food intake or body temperature. This anabolic response is followed by a late and more sustained catabolic phase characterized by absence of food intake, increased metabolism and dose-dependent hyperthermia, which hyperthermia cannot be suppressed by the NPY-antagonist. In contrast to orexin-A, neither hyperphagia nor suppression of refeeding hyperphagia, but dose-dependent hyperthermia follows injections of orexin-B, suggesting that this peptide has neither coordinated anabolic nor coordinated catabolic effects on energy balance.
Neuroscience Research, 2011
The prefrontal cortex is credited with contributing to relational reasoning, or the ability to in... more The prefrontal cortex is credited with contributing to relational reasoning, or the ability to integrate multiple acquired associations to generate new relationships. We have recorded single-unit activity from the lateral prefrontal cortex (LPFC) and the striatum while the monkeys performed a sequential paired-association task with asymmetric reward schedule. In the task, the monkeys learned two sequences of associated stimuli: A1-B1-C1 and A2-B2C2. The asymmetric reward rule was instructed by pairing C1 (or C2) with large (or small) reward block by block. The monkey also learned associations between new stimuli (e.g. N1, N2) and B1 and B2. The new stimuli were presented as the first cue in sequential paired-association trials instead of the old stimuli (A1 and A2). The findings from single-unit activity suggest that the LPFC can use an internal model of category to transfer reward information associated with one stimulus to other stimuli, even to new stimuli that had never been paired with different amount of reward. The striatum only uses direct experience between conditioned stimuli and reward to predict reward. One prediction from this hypothesis is that if the LPFC is inactivated, the monkey still correctly predicts reward for old stimuli through the striatal pathway, but has deficits in predicting reward for new stimuli. We injected muscimol to locally inactivate the LPFC, and also saline into the LPFC as control. In saline sessions, the monkey had significantly higher choice accuracy for new stimuli in large than in small reward trials, but this difference disappeared in muscimol session, consistent with the prediction. Together with single-unit activity data, our results suggest that the LPFC play a critical role in category-based reward inference.
Neuroscience Research, 2009
Retrieval of contextual fear memory by re-exposure to conditioned stimulus (CS) initiates two pro... more Retrieval of contextual fear memory by re-exposure to conditioned stimulus (CS) initiates two processes; reconsolidation and extinction. Previous our studies showed that short re-exposure to the CS inducing memory reconsolidation activated CREBdependent gene expression in hippocampus, while prolonged re-exposure inducing memory extinction inhibited this gene expression, suggesting that hippocampus plays distinct roles in reconsolidation and extinction of contextual fear memory. As a first step to understand the mechanism by which hippocampal gene expression are oppositely regulated in response to short and long re-exposure, we here performed biochemical analyses of glutamate receptors in hippocampus following short and long re-exposure. We found that long re-exposure to the CS inducing extinction decreased in expression of NMDA receptors including NR1, NR2A and NR2B and phosphorylation of GluR1 subunit of AMPA receptors at S831 and S845. These down-regulations of glutamate receptors might play critical roles in extinction of contextual fear memory by inhibiting hippocampal gene expression.