Faculty Bibliography

The neurophysiological footprint of brain activity after cardiac arrest and during near-death experience (NDE) is not well understood. Although a hypoactive state of brain activity has been assumed, experimental animal studies have shown increased activity after cardiac arrest, particularly in the gamma-band, resulting from hypercapnia prior to and cessation of cerebral blood flow after cardiac arrest. No study has yet investigated this matter in humans. Here, we present continuous electroencephalography (EEG) recording from a dying human brain, obtained from an 87-year-old patient undergoing cardiac arrest after traumatic subdural hematoma. An increase of absolute power in gamma activity in the narrow and broad bands and a decrease in theta power is seen after suppression of bilateral hemispheric responses. After cardiac arrest, delta, beta, alpha and gamma power were decreased but a higher percentage of relative gamma power was observed when compared to the interictal interval. Cross-frequency coupling revealed modulation of left-hemispheric gamma activity by alpha and theta rhythms across all windows, even after cessation of cerebral blood flow. The strongest coupling is observed for narrow- and broad-band gamma activity by the alpha waves during left-sided suppression and after cardiac arrest. Albeit the influence of neuronal injury and swelling, our data provide the first evidence from the dying human brain in a non-experimental, real-life acute care clinical setting and advocate that the human brain may possess the capability to generate coordinated activity during the near-death period.

Most textbook definitions recognize only animals as having nervous systems. However, for the past couple decades, botanists have been meticulously studying long-distance signaling systems in plants, and some researchers have stated that plants have a simple nervous system. Thus, an academic conflict has emerged between those who defend and those who deny the existence of a nervous system in plants. This article analyses that debate, and we propose an alternative to answering yes or no: broadening the definition of a nervous system to include plants. We claim that a definition broader than the current one, which is based only on a phylogenetic viewpoint, would be helpful in obtaining a deeper understanding of how evolution has driven the features of signal generation, transmission and processing in multicellular beings. Also, we propose two possible definitions and exemplify how broader a definition allows for new viewpoints on the evolution of plants, animals and the nervous system.

Stroke patients with small central nervous system infarcts often demonstrate an acute dysexecutive syndrome characterized by difficulty with attention, concentration, and processing speed, independent of lesion size or location. We use magnetoencephalography (MEG) to show that disruption of network dynamics may be responsible. Nine patients with recent minor strokes and eight age-similar controls underwent cognitive screening using the Montreal cognitive assessment (MoCA) and MEG to evaluate differences in cerebral activation patterns. During MEG, subjects participated in a visual picture-word matching task. Task complexity was increased as testing progressed. Cluster-based permutation tests determined differences in activation patterns within the visual cortex, fusiform gyrus, and lateral temporal lobe. At visit 1, MoCA scores were significantly lower for patients than controls (median [interquartile range] = 26.0 [4] versus 29.5 [3], P = 0.005), and patient reaction times were increased. The amplitude of activation was significantly lower after infarct and demonstrated a pattern of temporal dispersion independent of stroke location. Differences were prominent in the fusiform gyrus and lateral temporal lobe. The pattern suggests that distributed network dysfunction may be responsible. Additionally, controls were able to modulate their cerebral activity based on task difficulty. In contrast, stroke patients exhibited the same low-amplitude response to all stimuli. Group differences remained, to a lesser degree, 6 mo later; while MoCA scores and reaction times improved for patients. This study suggests that function is a globally distributed property beyond area-specific functionality and illustrates the need for longer-term follow-up studies to determine whether abnormal activation patterns ultimately resolve or another mechanism underlies continued recovery.

A spectroscopic paradigm has been developed that allows the magnetic field emissions generated by the electrical activity in the human body to be imaged in real time. The growing significance of imaging modalities in biology is evident by the almost exponential increase of their use in research, from the molecular to the ecological level. The method of analysis described here allows totally noninvasive imaging of muscular activity (heart, somatic musculature). Such imaging can be obtained without additional methodological steps such as the use of contrast media.

Nothing is more intuitive, yet more complex, than the concepts of space and time. In contrast to spacetime in physics, space and time in neuroscience remain separate coordinates to which we attach our observations. Investigators of navigation and memory relate neuronal activity to position, distance, time point, and duration and compare these parameters to units of measuring instruments. Although spatial-temporal sequences of brain activity often correlate with distance and duration measures, these correlations may not correspond to neuronal representations of space or time. Neither instruments nor brains sense space or time. Neuronal activity can be described as a succession of events without resorting to the concepts of space or time. Instead of searching for brain representations of our preconceived ideas, we suggest investigating how brain mechanisms give rise to inferential, model-building explanations.

INTRODUCTION: Oxygen (O2 ) nanobubbles offer a new method for tissue oxygenation. The effects of O2 nanobubbles on transmission at neuromuscular junctions (NMJs) and muscle function were explored in murine diaphragm. METHODS: Electrophysiological parameters, NMJ ultrastructure, muscle force, and muscle fatigue were studied during superfusion with solutions with different oxygen levels or oxygen nanobubbles. RESULTS: High frequency nerve stimulation of muscles superfused with O2 nanobubble solution slowed neurotransmission decline over those with either control or hyperoxic solution. O2 nanobubble solution increased the amplitude of evoked excitatory junction potentials and quantal content but did not affect spontaneous activity. Electron microscopy of stimulated O2 nanobubble treated NMJs showed accumulation of large synaptic vesicles and endosome-like structures. O2 nanobubble solution had no effects on isometric muscle force, but it significantly decreased fatigability and maximum force recovery time in nerve stimulated muscles. CONCLUSIONS: O2 nanobubbles increase neurotransmission and reduce the probability of neurotransmission failure in muscle fatigue

1-octanol is a therapeutic candidate for disorders involving the abnormal activation of the T-type calcium current since it blocks this current specifically. Such disorders include essential tremor and a group of neurological and psychiatric disorders resulting from thalamocortical dysrhythmia (TCD). For example, clinically, the observable phenotype in essential tremor is the tremor itself. The differential diagnostic of TCD is not based only on clinical signs and symptoms. Rather, TCD incorporates an electromagnetic biomarker, the presence of abnormal thalamocortical low frequency brain oscillations. The effect of 1-octanol on brain activity has not been tested. As a preliminary step to such a TCD study, we examined the short-term effects of a single dose of 1-octanol on resting brain activity in 32 healthy adults using magnetoencephalograpy. Visual inspection of baseline power spectra revealed that the subjects fell into those with strong low frequency activity (set 2, n = 11) and those without such activity, but dominated by an alpha peak (set 1, n = 22). Cross-validated linear discriminant analysis, using mean spectral density (MSD) in nine frequency bands as predictors, found overall that 82.5% of the subjects were classified as determined by visual inspection. The effect of 1-octanol on the MSD in narrow frequency bands differed between the two subject groups. In set 1 subjects the MSD increased in the 4.5-6.5Hz and 6.5-8.5 Hz bands. This was consistent with a widening of the alpha peak toward lower frequencies. In the set two subjects the MSD decrease in the 2.5-4.5 Hz and 4.5-6.5 Hz bands. This decreased power is consistent with the blocking effect of 1-octanol on T-type calcium channels. The subjects reported no adverse effects of the 1-octanol. Since stronger low frequency activity is characteristic of patients with TCD, 1-octanol and other T-type calcium channel blockers are good candidates for treatment of this group of disorders following a placebo-controlled study.

Brain tauopathies are characterized by abnormal processing of tau protein. While somatodendritic tau mislocalization has attracted considerable attention in tauopathies, the role of tau pathology in axonal transport, connectivity and related dysfunctions remains obscure. We have previously shown using the squid giant synapse that presynaptic microinjection of recombinant human tau protein (htau42) results in failure of synaptic transmission. Here, we evaluated molecular mechanisms mediating this effect. Thus, the initial event, observed after htau42 presynaptic injection, was an increase in transmitter release. This event was mediated by calcium release from intracellular stores and was followed by a reduction in evoked transmitter release. The effect of htau42 on synaptic transmission was recapitulated by a peptide comprising the phosphatase-activating domain of tau, suggesting activation of phosphotransferases. Accordingly, findings indicated that htau42-mediated toxicity involves the activities of both GSK3 and Cdk5 kinases.

A crucial pathophysiological issue concerning central neuropathic pain is the modification of sensory processing by abnormally increased low-frequency brain rhythms. Here we explore the molecular mechanisms responsible for such abnormal rhythmicity and its relation to neuropathic pain syndrome. Toward this aim, we investigated the behavioral and electrophysiological consequences of trigeminal neuropathic pain following infraorbital nerve ligations in CaV3.1 T-type Ca(2+) channel knockout and wild-type mice. CaV3.1 knockout mice had decreased mechanical hypersensitivity and reduced low-frequency rhythms in the primary somatosensory cortex and related thalamic nuclei than wild-type mice. Lateral inhibition of gamma rhythm in primary somatosensory cortex layer 4, reflecting intact sensory contrast, was present in knockout mice but severely impaired in wild-type mice. Moreover, cross-frequency coupling between low-frequency and gamma rhythms, which may serve in sensory processing, was pronounced in wild-type mice but not in CaV3.1 knockout mice. Our results suggest that the presence of CaV3.1 channels is a key element in the pathophysiology of trigeminal neuropathic pain.