Ariel Schoenfeld

Delayed Striate Cortical Activation during Spatial Attention

Recordings of event-related potentials (ERPs) and event-related magnetic fields (ERMFs) were combined with functional magnetic resonance imaging (fMRI) to study visual cortical activity in humans during spatial attention. While subjects attended selectively to stimulus arrays in one visual field, fMRI revealed stimulus-related activations in the contralateral primary visual cortex and in multiple extrastriate areas. ERP and ERMF recordings showed that attention did not affect the initial evoked response at 60-90 ms poststimulus that was localized to primary cortex, but a similarly localized late response at 140-250 ms was enhanced to attended stimuli. These findings provide evidence that the primary visual cortex participates in the selective processing of attended stimuli by means of delayed feedback from higher visual-cortical areas.

How does attention attenuate target-distractor interference in vision?. Evidence from magnetoencephalographic recordings.

This study used magnetoencephalographic and electroencephalographic recordings to investigate the neural mechanisms that underlie the attentional resolution of ambiguous feature coding in visual search. We addressed this issue by comparing neural activity related to target discrimination under conditions of more versus less feature overlap between the target and distractor items. The results show that increasing feature overlap leads to a focal enhancement of neural activity in ventral occipito-temporal areas, consistent with the larger need to attenuate distractor interference. Furthermore, the results suggest that distractor attenuation proceeds as a stepwise operation, with different spatial locations containing interfering features being suppressed successively. These findings support theories of visual search that emphasize location-based attentional selection as a key mechanism in resolving ambiguous feature coding in vision.

Neural correlates of recognition memory with and without recollection in patients with Alzheimer's disease and healthy controls

To dissociate recognition memory with and without recollection, event-related potentials (ERPs) of patients with Alzheimers disease (AD) and matched controls were recorded in a test of verbal recognition memory accompanied by a source judgement. AD patients who had smaller hippocampi showed a disability to recollect the study context (source). Their ERPs elicited by correctly recognized old words compared to new items were more positive only between 300 and 500 ms with a maximum over the frontal scalp. Controls exhibited a sustained old/new effect over left temporoparietal and frontal sites. The present findings suggest that preserved recognition memory in patients with mild AD is independent of hippocampally mediated processes recollecting episodic memories.

Correlation of hippocampal glucose oxidation capacity and interictal FDG-PET in temporal lobe epilepsy

Summary:  Purpose: Interictal [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) demonstrates temporal hypometabolism in the epileptogenic zone of 60–90% of patients with temporal lobe epilepsy. The pathophysiology of this finding is still unknown. Several studies failed to show a correlation between hippocampal FDG‐PET hypometabolism and neuronal cell loss. Because FDG is metabolized by hexokinase bound to the outer mitochondrial membrane, we correlated the glucose‐oxidation capacity of hippocampal subfields obtained after surgical resection with the corresponding hippocampal presurgical FDG‐PET activity.

Sonography of the median nerve in CMT1A, CMT2A, CMTX, and HNPP

Introduction: In this study we compare the ultrasound features in the median nerve in patients with different types of Charcot–Marie–Tooth (CMT) disease and hereditary neuropathies with liability to pressure palsies (HNPP) as a typical entrapment neuropathy. Methods: Median nerve ultrasound and conduction studies were performed in patients with CMT1A (n = 12), MFN2‐associated CMT2A (n = 7), CMTX (n = 5), and HNPP (n = 5), and in controls (n = 28). Results: Median nerve cross‐sectional area (CSA) was significantly increased in CMT1A, whereas, in axonal CMT2A, fascicle diameter (FD) was enlarged. CSA correlated with nerve conduction slowing in CMT1A and with axonal loss, as shown by motor and sensory nerve amplitudes in both CMT1A and CMT2A. A relatively low wrist‐to‐forearm‐ratio (WFR <0.8) or a relatively high WFR (>1.8) appeared to be unlikely in MFN2 and Cx32 mutations of CMT2A and CMTX, respectively. Conclusion: Differences in CSA, FD, and WFR of the median nerve can be helpful in defining subtypes of hereditary neuropathies. Muscle Nerve 47:385‐395, 2013

Hippocampal N-acetyl aspartate levels do not mirror neuronal cell densities in creatine-supplemented epileptic rats

For neuroprotective therapy of neurodegenerative diseases creatine treatment has gained special interest because creatine has been shown to cross the blood–brain barrier, accumulate in the human brain in vivo and cause delayed neuronal cell death in a large number of animal models. Here, we used the pilocarpine model of temporal lobe epilepsy to determine whether creatine administration is able to attenuate the epilepsy‐associated decrease in hippocampal N‐acetyl aspartate (NAA) concentrations, impairment of mitochondrial function and neuronal cell loss. In vivo1H‐NMR spectroscopy showed, in epileptic rats after creatine administration, higher hippocampal NAA concentrations, suggesting improved neuronal survival. However, in vitro observation of hippocampal slices from creatine‐treated epileptic rats revealed a more pronounced loss of pyramidal neurons and decrease in activity of mitochondrial enzymes in hippocampal subfields. This indicates that NAA concentrations measured by in vivo1H‐NMR spectroscopy reflect alterations of metabolism rather than neuronal cell densities. Our data indicate an adverse effect of creatine on neuronal survival under conditions of enhanced neuronal activity.

Catechol-O-Methyltransferase Polymorphism Influences Outcome After Ischemic Stroke A Prospective Double-Blind Study

Background. To explore whether a polymorphism in dopamine metabolism influences the effectiveness of neurological rehabilitation and the outcome after ischemic stroke. Methods. The Barthel Index (BI) and the Rivermead Motor Assessment (RMA) were assessed in 78 moderately affected stroke patients (1) after they had entered a neurological inpatient rehabilitation, (2) after 4 weeks of rehabilitation therapy, and (3) 6 months later. Polymorphisms of the gene encoding catechol-O-methyltransferase (COMT) were determined. BI and RMA results were analyzed with respect to the genetic profiles of COMT. Results. Carriers of COMT Val/Val alleles showed better results in BI and RMA than COMT Met/Met carriers at all 3 time points. Val/Met carriers exhibited results in between the homozygotes, suggesting a gene–dose relationship. Altogether, BI and RMA results were highly correlated. Conclusion. Stroke patients with COMT Val/Val alleles had higher motor functions and abilities of activities of daily living even at the beginning of the rehabilitation period. All patient groups improved during the rehabilitation period to a similar degree, suggesting that physical therapy is comparably effective in all polymorphism subtypes.

Polymorphismus des „brain derived neurotrophic factor“ und Erholung nach Schlaganfall

ZusammenfassungHintergrundDie Funktionsrestitution nach einem Schlaganfall wird von vielen Faktoren beeinflusst. Insbesondere das Alter des Patienten, die initiale Ausprägung der Symptomatik, das Vorhandensein kognitiver oder neuropsychologischer Defizite zählen dazu. In dieser Studie wurde untersucht, ob ein Polymorphismus im für den „brain derived neurotrophic factor“ (BDNF) kodierenden Gen Einfluss auf die Verbesserung von motorischen Funktionen und Alltagsaktivitäten nimmt.MethodenPatienten mit subakutem ischämischem Hirninfarkt (n = 67) wurden zu Beginn einer stationären neurologischen Rehabilitation, nach 4-wöchiger Behandlung und 6 Monate später mittels Barthel-Index (BI) und Rivermead Motor Assessment (RMA) untersucht. Je nach BDNF-Polymorphismus im Codon 66 erfolgte die Einteilung in Gruppen (Valin [Val]/Valin, Val/Methionin[Met] oder Met/Met).ErgebnisseDie 3 Gruppen (Val/Val, n = 34 Patienten; Val/Met, n = 26; Met/Met, n = 7) wiesen im BI und im RMA sowohl nach 4 Wochen als auch nach 6 Monaten eine signifikante Verbesserung zum jeweils vorhergehenden Untersuchungsergebnis auf. BI und RMA waren hoch miteinander korreliert. Es gab keinen Unterschied in Bezug auf den BDNF-Polymorphismus.DiskussionNach Hirninfarkt kommt es über mindestens 6 Monate zu kontinuierlichen Verbesserungen der motorischen Funktionen und der Alltagsfunktionen. Der BDNF-Polymorphismus beeinflusste diese Entwicklung nicht.SummaryBackgroundAfter ischemic stroke, many factors influence the restitution of functions. In particular they include the patient age, the initial stroke severity and the presence of cognitive and neuropsychological deficits. In this study we investigated whether a polymorphism in the gene encoding for brain derived neurotrophic factor (BDNF) influences improvements of motor functions and everyday activities.MethodsPatients with subacute ischemic stroke (n = 67) were examined at the beginning of an inpatient neurological rehabilitation, after 4 weeks of treatment and after 6 months. The Barthel index (BI) and the Rivermead motor assessment (RMA) were used to measure motor functions and everyday activities. Patients were allocated to three groups (valine [Val]/valine, val/methionine [Met] and Met/Met) depending on the BDNF polymorphism at codon 66.ResultsThe 3 groups (Val/Val, n = 34 patients, Val/Met, n = 26 and Met/Met, n = 7) showed significant improvements in BI and RMA after 4 weeks and after 6 months as compared to the preceding measurements. The BI and RMA were positively correlated. The three groups did not differ with respect to the extent of improvement.ConclusionAfter ischemic stroke, motor functions and everyday activities improved continuously over a period of at least 6 months. The BDNF polymorphism did not influence this development.BACKGROUND After ischemic stroke, many factors influence the restitution of functions. In particular they include the patient age, the initial stroke severity and the presence of cognitive and neuropsychological deficits. In this study we investigated whether a polymorphism in the gene encoding for brain derived neurotrophic factor (BDNF) influences improvements of motor functions and everyday activities. METHODS Patients with subacute ischemic stroke (n = 67) were examined at the beginning of an inpatient neurological rehabilitation, after 4 weeks of treatment and after 6 months. The Barthel index (BI) and the Rivermead motor assessment (RMA) were used to measure motor functions and everyday activities. Patients were allocated to three groups (valine [Val]/valine, val/methionine [Met] and Met/Met) depending on the BDNF polymorphism at codon 66. RESULTS The 3 groups (Val/Val, n = 34 patients, Val/Met, n = 26 and Met/Met, n = 7) showed significant improvements in BI and RMA after 4 weeks and after 6 months as compared to the preceding measurements. The BI and RMA were positively correlated. The three groups did not differ with respect to the extent of improvement. CONCLUSION After ischemic stroke, motor functions and everyday activities improved continuously over a period of at least 6 months. The BDNF polymorphism did not influence this development.

Polymorphismus des „brain derived neurotrophic factor“ und Erholung nach Schlaganfall@@@Polymorphism of brain derived neurotrophic factor and recovery of functions after ischemic stroke

ZusammenfassungHintergrundDie Funktionsrestitution nach einem Schlaganfall wird von vielen Faktoren beeinflusst. Insbesondere das Alter des Patienten, die initiale Ausprägung der Symptomatik, das Vorhandensein kognitiver oder neuropsychologischer Defizite zählen dazu. In dieser Studie wurde untersucht, ob ein Polymorphismus im für den „brain derived neurotrophic factor“ (BDNF) kodierenden Gen Einfluss auf die Verbesserung von motorischen Funktionen und Alltagsaktivitäten nimmt.MethodenPatienten mit subakutem ischämischem Hirninfarkt (n = 67) wurden zu Beginn einer stationären neurologischen Rehabilitation, nach 4-wöchiger Behandlung und 6 Monate später mittels Barthel-Index (BI) und Rivermead Motor Assessment (RMA) untersucht. Je nach BDNF-Polymorphismus im Codon 66 erfolgte die Einteilung in Gruppen (Valin [Val]/Valin, Val/Methionin[Met] oder Met/Met).ErgebnisseDie 3 Gruppen (Val/Val, n = 34 Patienten; Val/Met, n = 26; Met/Met, n = 7) wiesen im BI und im RMA sowohl nach 4 Wochen als auch nach 6 Monaten eine signifikante Verbesserung zum jeweils vorhergehenden Untersuchungsergebnis auf. BI und RMA waren hoch miteinander korreliert. Es gab keinen Unterschied in Bezug auf den BDNF-Polymorphismus.DiskussionNach Hirninfarkt kommt es über mindestens 6 Monate zu kontinuierlichen Verbesserungen der motorischen Funktionen und der Alltagsfunktionen. Der BDNF-Polymorphismus beeinflusste diese Entwicklung nicht.SummaryBackgroundAfter ischemic stroke, many factors influence the restitution of functions. In particular they include the patient age, the initial stroke severity and the presence of cognitive and neuropsychological deficits. In this study we investigated whether a polymorphism in the gene encoding for brain derived neurotrophic factor (BDNF) influences improvements of motor functions and everyday activities.MethodsPatients with subacute ischemic stroke (n = 67) were examined at the beginning of an inpatient neurological rehabilitation, after 4 weeks of treatment and after 6 months. The Barthel index (BI) and the Rivermead motor assessment (RMA) were used to measure motor functions and everyday activities. Patients were allocated to three groups (valine [Val]/valine, val/methionine [Met] and Met/Met) depending on the BDNF polymorphism at codon 66.ResultsThe 3 groups (Val/Val, n = 34 patients, Val/Met, n = 26 and Met/Met, n = 7) showed significant improvements in BI and RMA after 4 weeks and after 6 months as compared to the preceding measurements. The BI and RMA were positively correlated. The three groups did not differ with respect to the extent of improvement.ConclusionAfter ischemic stroke, motor functions and everyday activities improved continuously over a period of at least 6 months. The BDNF polymorphism did not influence this development.BACKGROUND After ischemic stroke, many factors influence the restitution of functions. In particular they include the patient age, the initial stroke severity and the presence of cognitive and neuropsychological deficits. In this study we investigated whether a polymorphism in the gene encoding for brain derived neurotrophic factor (BDNF) influences improvements of motor functions and everyday activities. METHODS Patients with subacute ischemic stroke (n = 67) were examined at the beginning of an inpatient neurological rehabilitation, after 4 weeks of treatment and after 6 months. The Barthel index (BI) and the Rivermead motor assessment (RMA) were used to measure motor functions and everyday activities. Patients were allocated to three groups (valine [Val]/valine, val/methionine [Met] and Met/Met) depending on the BDNF polymorphism at codon 66. RESULTS The 3 groups (Val/Val, n = 34 patients, Val/Met, n = 26 and Met/Met, n = 7) showed significant improvements in BI and RMA after 4 weeks and after 6 months as compared to the preceding measurements. The BI and RMA were positively correlated. The three groups did not differ with respect to the extent of improvement. CONCLUSION After ischemic stroke, motor functions and everyday activities improved continuously over a period of at least 6 months. The BDNF polymorphism did not influence this development.