Functional aspects of evoked alpha and theta responses in humans and cats

A systems theoretical approach was used to compare possible functional roles of theta (4--7 Hz) and alpha (8--15 Hz) response components of brain evoked potentials. These response components were described earlier by Ba\c sar (1980). We recorded EEG and evoked potentials (EPs) from occipital scalp locations in 11 subjects. We used auditory and visual stimuli as inadequate and adequate stimuli, respectively (``cross-modality' measurements). The combined EEG-EP epochs were analysed in frequency domain with fast Fourier transform and adaptive digital filters. Alpha (8--15 Hz) response components turned out to be dependent on whether the stimulus was adequate or not (median amplitude with inadequate vs. adequate stimulation: vs. ). Theta (4--7 Hz) response components were less dependent on stimulus modality (inadequate vs. adequate stimulation: vs. ). In EP recordings the occipital alpha response almost disappeared in the first 250 ms following auditory stimulation. Comparable behaviour was observed in similar experiments with recordings from the cat visual cortex (area 17) and with occipital magnetoencephalographic recordings. Taking into account the above-mentioned previous reports on intracranial recordings in primary sensory areas of the cat brain and preliminary results of magnetoencephalographic measurements, we propose the following hypothesis: alpha responses in a time window of about 250 ms after stimulation might predominantly reflect primary sensory processing whereas the theta responses in the first 250 ms after stimulation might be more involved in supra-modality -- or cross-modality -- associative-cognitive processing. Received: 25 February 1994 / Accepted in revised form: 5 August 1994     

Simultaneous BOLD fMRI and fiber-optic calcium recording in rat neocortex

Functional magnetic resonance imaging (fMRI) based on blood oxygen level-dependent (BOLD) contrast is widely used for probing brain activity, but its relationship to underlying neural activity remains elusive. Here, we combined fMRI with fiber-optic recordings of fluorescent calcium indicator signals to investigate this relationship in rat somatosensory cortex. Electrical forepaw stimulation (1-10 Hz) evoked fast calcium signals of neuronal origin that showed frequency-dependent adaptation. Additionally, slower calcium signals occurred in astrocyte networks, as verified by astrocyte-specific staining and two-photon microscopy. Without apparent glia activation, we could predict BOLD responses well from simultaneously recorded fiber-optic signals, assuming an impulse response function and taking into account neuronal adaptation. In cases with glia activation, we uncovered additional prolonged BOLD signal components. Our findings highlight the complexity of fMRI BOLD signals, involving both neuronal and glial activity. Combined fMRI and fiber-optic recordings should help to clarify cellular mechanisms underlying BOLD signals.     

Ultrasonic communication in concave-eared torrent frogs (Amolops tormotus)

The concave-eared torrent frogs (Amolops tormotus) have highly unusual ear morphology--in males the eardrums are embedded deep inside ear cavities. In collaboration with our colleagues we investigated the functional significance of this morphological feature in hearing. Sound recordings in the field showed that males of A. tormotus produce diverse bird-like melodic calls with pronounced frequency modulations and non-linear phenomena (e.g., frequency jumps, different orders of subharmonics, and chaos) that often contain spectral energy in the ultrasonic range. The audible as well as the ultrasonic components of the species call could effectively evoke males' vocal responses, demonstrating that they can hear and respond to ultrasound. Electrophysiological recordings from the auditory midbrain confirmed the ultrasonic hearing capacity of these frogs. The recessed tympana and extremely thin tympanic membranes are adaptations for hearing ultrasound--this sensitivity may have evolved in response to the intense, predominately low-frequency ambient noise from local streams. Finally, results from the isolated laryngeal preparation in euthanized frogs revealed that the origin of call complexity and diversity lies with having a vocal system with nonlinear properties.     

Scalp,basal epidural and intravascular far-field recordings after median nerve stimulation: evidence for a separate N18a potential

Far-field somatosensory evoked potentials (SSEPs) after median nerve stimulation were recorded from scalp- (Fz), epidural(ED) and intravascular electrodes (basilar artery [Bas]) to study the nature of the controversial N18a component of the widespread N18 potential. In healthy volunteers frequently an N18a potential was recorded at Fz. Simultaneous Fz and ED recordings at the pontomesencephalic junction as well as Bas-recordings at the caudal basilar artery showed N18a components identical in latency and shape. With intravascular recordings the shapes differed between the top of the basilar artery and the caudal artery recordings. These findings support the existence of a separate N18a potential. The generator of the N18a is likely to be localized within the upper brainstem.     

Scalp, basal epidural and intravascular far-field recordings after median nerve stimulation: evidence for a separate N18a potential

Far-field somatosensory evoked potentials (SSEPs) after median nerve stimulation were recorded from scalp- (Fz), epidural- (ED) and intravascular electrodes (basilar artery [Bas]) to study the nature of the controversial N18a component of the widespread N18 potential. In healthy volunteers frequently an N18a potential was recorded at Fz. Simultaneous Fz and ED recordings at the pontomesencephalic junction as well as Bas-recordings at the caudal basilar artery showed N18a components identical in latency and shape. With intravascular recordings the shapes differed between the top of the basilar artery and the caudal artery recordings. These findings support the existence of a separate N18a potential. The generator of the N18a is likely to be localized within the upper brainstem.     

Brain-stem auditory evoked potentials (BAEPs) from basal surface of temporal lobe recorded from chronic subdural electrodes

BAEPs were recorded from the basal surface of the temporal lobe by subdural electrodes chronically implanted in 6 patients who were evaluated for surgical management of intractable partial seizures. Near-field recordings were obtained by recording between the subdural electrode closet and most distant to the brain-stem. Far-field recordings were obtained by recording between the subdural electrodes and an indifferent electrode over the spinal process of the seventh cervical vertebrae. The recordings were compared with standard ear-vertex recordings.After ipsilateral ear stimulation, the subdural electrode closet to the brain-stem recorded large amplitude waves I and II, followed by less well-defined waves of longer latencies. Recordings to contralateral stimulation showed no clearly defined waves I and II and a large amplitude wave Vn. Waves III, IV, V, Vn and VI were of opposite polarity after ipsi- and contralateral stimulation. These findings indicate that waves I and II are generated ipsilaterally to the stimulation side, whereas wave Vn has a contralateral origin. Wave Vn may be generated in the brachium of the inferior colliculus, as suggested from latency and from dipole configuration studies. This conclusion is consistent with the classical anatomical observations that the supracollicular auditory pathways are predominantly crossed.     

The origin of the muscle fasciculation caused by funnel-web spider venom

The origin of the fasciculation of skeletal muscle produced by funnel-web spider venom (FSV) has been examined in mouse phrenic nerve hemi-diaphragm preparations, FSV from male spiders at concentrations greater than 10(-6) g/ ml invariably produced muscle fasciculation which could be prevented by d-tubocurarine (14micron), tetrodotoxin (0.3 micron) or by increasing the external magnesium concentration or calcium concentration. Diphenyl hydantoin (3-6 X 10(-5) M) was able to reduce these fasciculations in some experiments. In curarized preparations, multiple end plate potentials (EPPs) in response to single stimuli and bursts of spontaneous EPPs were seen in the presence of FSV (10(-5) g/ml). Extracellular recordings from phrenic nerves in the presence of FSV (10(-5) g/ml) revealed additional components in compound action potentials elicited by single stimuli, and "spontaneous" electrical activity was observed in unstimulated nerves. This spontaneous activity was abolished by raising the divalent cation concentration in the bathing solution. These results suggest that a primary site of action of FSV is the surface membrane of nerve fibres and that muscle fasciculation arises as a consequence of spontaneous action potentials produced by the venom in motor nerves.     

New structure in cell puncture activities by aphid stylets: a dual‐mode EPG study

Intracellular punctures by aphid stylets appear as potential drop (pd) waveforms in DC electrical penetration graph (EPG) recordings. We used a dual‐EPG device that recorded in one channel the ‘full EPG’ with R‐plus emf‐components (i.e., the usual DC EPG) and concurrently in a second channel the ‘R‐EPG’ with R‐components only. The circuit of the latter channel was an optimised amplitude modulation (AM) version derived from early (before 1990) AC systems. We also made some ‘emf‐EPG’ recordings using a separate high input resistance ‘emf‐amplifier’ sensitive to emf‐components only. The intracellular pd waveforms have previously been divided into three subphases, and we aimed to distinguish and separate these subphases more accurately by the dual‐EPG recordings than with the normal full EPG only. In this study, we temporarily distinguished five subphases (α–ε), but unequivocal distinction of only a few of these appeared possible, in spite of the information coming from the two signals. The lack of clearly separable features in R‐EPG signals often provided serious difficulties in pd recognition without the concurrent full EPG, but once located, only subphase II‐2 features were clear and supported the II‐2 data from the full EPG. Consequently, we could not distinguish subphases of complete pd waveforms better with additional R‐EPG information during cell punctures by Aphis gossypii Glover (Hemiptera: Aphididae). In Brevicoryne brassicae (L.) (Hemiptera: Aphididae), however, distinguishing II‐2 subphases in the full EPG was sometimes a problem. Our detailed dual‐EPG observations showed some waveform continuity from halfway into the II‐1 subphase (start of the newly recognised subphase β) until the end of the pd, with a strong but variable emf origin. This waveform tended to overrule other subphase waveforms in B. brassicae more than in A. gossypii and Myzus persicae (Sulzer) (Hemiptera: Aphididae). Subphase waveforms in full EPGs were especially difficult to recognise when pd periods had been interrupted in a virus inoculation experiment and additional R‐EPG information could then be useful. This inoculation experiment showed again that only the first subphase (II‐1) contributes to virus (Cucumber mosaic virus) inoculation by A. gossypii. In B. brassicae, the benefit of concurrent R‐EPG information in such virus experiments is presently under further investigation. Apart from this special application to virus experiments, we do not recommend the routine use of the dual‐EPG device. Furthermore, we do not advocate the distinction of more than the previously recognised three intracellular pd subphases as a feasible option in future studies. Analysis of EPGs with concurrent R‐EPGs requires substantially more analysis work without yielding consistently useful additional insights. This confirms earlier dual‐EPG results from thrips.     

棉铃虫雄蛾触角的毛形感器对其性信息素组分及类似物的反应

本文用单细胞电反应的记录方法,测定了棉铃虫Heliothis armigera Hubner雄蛾触角的毛形感器对其性信息素组分及雌蛾腹部提取物的反应,发现顺-11-十六碳烯醛和顺-9-十六碳烯醛能引起反应。对前者发放大脉冲,对后者发放小脉冲,对雌蛾腹部提取物发放大、小两种脉冲,但以大脉冲为主。     

Frequency component selection for an ECoG-based brain-computer interface.

The aim of the present study was to investigate the most significant frequency components in electrocorticogram (ECoG) recordings in order to operate a brain computer interface (BCI). For this purpose the time-frequency ERD/ERS map and the distinction sensitive learning vector quantization (DSLVQ) are applied to ECoG from three subjects, recorded during a self-paced finger movement. The results show that the ERD/ERS pattern found in ECoG generally matches the ERD/ERS pattern found in EEG recordings, but has an increased prevalence of frequency components in the beta range.     

The DC-Recorded Dog Electroretinogram in Ketamine -Medetomidine Anaesthesia

A new selective alpha 2-adre-noreceptor agonist, medetomidine hydrochloride was combined with low dosage ketamine hydrochloride and vecuronium bromide for d.c. (direct current) recordings of fast electroretinographic (ERG) components in nine ophthalmoscopically healthy dark adapted dogs. The dogs were tracheally intubated and manually ventilated. They were given full field single flash stimuli of different intensities starting with near b-wave threshold blue light (tests 1-3), followed by white light (tests 4-6) and 30 Hz photopic flicker (test 7). The a- and b-wave amplitudes and flicker responses were measured from the base line. The latencies were measured from the stimulus moment to the highest point of the different waves. Statistical analysis of results gave individual differencies which had a good constancy. This showed that the dogs had an individual ERG profile according to the standardized method. The latencies varied very little as expected, but the amplitudes differed individually and showed a good constancy as seen by reproducibility tests made nine to ten days later on three of the dogs’ ipsilateral eyes. The combination of drugs used in this study was considered suitable for short term (10-12 minutes) stable d.c.–ERG recordings in dogs as the rod and cone responses had higher amplitudes when compared to an identical examination made with other anaesthetic combinations on the same dogs. Involuntary eye movements and other involuntary muscular activity caused by ketamine in dogs were negligible when using medetomidine premedication and was completely absent when using vecuronium. The anaesthetic method described can be recommended for ambulatory ERG recordings in dogs because of the above mentioned advantages.     

Intracranial recording from the brain-stem and the trigeminal nerve following upper lip stimulation

Short latency evoked potentials following stimulation of the upper lip were recorded intracranially during neurosurgical procedures in 14 patients. In 10 patients, a suboccipital craniectomy provided direct access to the trigeminal root and the pons at the root entry zone. Direct recordings from the trigeminal root were characterized by a large triphasic potential at 2.4–2.7 msec. The latency of this potential increased as a result of moving the recording electrode proximally towards the brain-stem. The same potential could be recorded from the brain-stem surface at a latency suggesting an intra-axial presynaptic origin. A second component, N4.7, was recorded from over the most rostral aspect of the brain-stem in 3 patients and from the tentorium free edge in 4 patients. This potential of smaller amplitude did not show significant difference in latency or polarity at various electrode locations, suggesting a deep diencephalic origin remote from the recording electrode.     

Diagnosis and management after life threatening events in infants and young children who received cardiopulmonary resuscitation.

OBJECTIVE--To determine the mechanisms and thereby appropriate management for apparent life threatening events treated with cardiopulmonary resuscitation in infants and young children. DESIGN--Prospective clinical and physiological study. SETTING--Royal Brompton Hospital or in patients'' homes, or both. SUBJECTS--157 Patients referred at median age 2.8 months (range 1 week to 96 months), 111 (71%) had recurrent events, 44 were born preterm, 19 were siblings of infants who had died suddenly and unexpectedly, and 18 were over 12 months old. INTERVENTIONS--Multichannel physiological recordings, including oxygenation, in hospital (n = 150) and at home (n = 61). Additional recordings with electroencephalogram, video, or other respiratory measures were used to confirm diagnoses. Management involved monitoring of oxygen at home, additional inspired oxygen, anticonvulsant treatment, or child protection procedures. MAIN OUTCOME MEASURES--Abnormalities on recordings compared to published normal data and their correlation with clinical events; sudden death. RESULTS--53 of 150 patients had abnormalities of oxygenation on hospital recordings, 28 of whom had an accompanying clinical event. Home recordings produced physiological data from 34 of 61 patients during subsequent clinical events. Final diagnoses were reached in 77 patients: deliberate suffocation by a parent (18), hypoxaemia induced by epileptic seizure (10), fabricated history and data (Munchausen syndrome by proxy; seven), acute hypoxaemia of probable respiratory origin (40), and changes in peripheral perfusion and skin colour without hypoxaemia (two). Four patients died: three suddenly and unexpectedly (none on home oxygen monitors) and one from pneumonia. CONCLUSIONS: Identification of mechanisms is essential to the appropriate management of infants with apparent life threatening events.     

Glossopharyngeal taste responses of the channel catfish to binary mixtures of amino acids

This study examines the neural processing of binary mixtures in the glossopharyngeal (IX) taste system of the channel catfish, Ictalurus punctatus, and finds that the nature of the components of a mixture determines the intensity of the neural response to it. Taste buds in fish innervated by IX are located along the gill rakers of the first gill arch and rostral floor of the oral cavity, and function primarily in the consummatory phase of feeding behavior; however, few studies of IX taste responses have been reported in any species of teleost. Here, we report IX taste responses to eight different binary mixtures of amino acids whose components were adjusted to be approximately equipotent in electrophysiological recordings. Four binary (group I) mixtures whose components were indicated from prior electrophysiological cross-adaptation experiments to bind to independent receptor sites resulted in significantly larger (22% average increase) integrated IX taste activity than four other (group II) binary mixtures whose components were indicated to bind to the same or highly cross-reactive receptor sites. These results are similar to those observed previously from facial nerve recordings in channel catfish, and to olfactory and taste responses in other vertebrate and invertebrate species. The group I results help to explain behavioral observations that chemical mixtures of chemosensory stimuli are often more stimulatory than their individual components.     

Evaluation of fitness components in strains of Drosophila mulleri carrying different genotypes for an esterase

Several fitness components in strains of Drosophila mulleri carrying the slow or the fast alleles for the major beta esterase (esterase-4) found in this species, as well as in heterozygous flies in which the slow or fast alleles came from one of the parents, were evaluated. Twelve components were analysed including longevity of both virgins and mated males and females, productivity, viability, including the egg-larva, egg-pupa, egg-imago and pupa-imago periods. These parameters were used to estimate the total fitness for each genotype. The best score was reached by individuals having the Est-4S/Est-4S genotype (scored at 1.000), followed by a fitness value of 0.892 presented by the Est-4F/Est-4S genotype (with the fast allele from maternal origin), 0.863 for the Est-4F/Est-4F and 0.842 for the Est-4S/Est-4Fgenotypes (with Est-4F of maternal origin). These results suggested a higher relative adaptability of the Est-4S/Est-4S genotype followed by the Est-4F/Est-4S hybrid that possessed the allele Est-4S of maternal origin, which was incompatible with predictions of neutral polymorphism.     

Redundancy and synergy arising from pairwise correlations in neuronal ensembles

Multielectrode arrays allow recording of the activity of many single neurons, from which correlations can be calculated. The functional roles of correlations can be revealed by measures of the information conveyed by neuronal activity; a simple formula has been shown to discriminate the information transmitted by individual spikes from the positive or negative contributions due to correlations (Panzeri et al., 1999). Here, this analysis, previously applied to recordings from small ensembles, is developed further by considering a model of a large ensemble, in which correlations among the signal and noise components of neuronal firing are small in absolute value and entirely random in origin. Even such small random correlations are shown to lead to large possible synergy or redundancy, whenever the time window for extracting information from neuronal firing extends to the order of the mean interspike interval. In addition, a sample of recordings from rat barrel cortex illustrates the mean time window at which such corrections dominate when correlations are, as often in the real brain, neither random nor small. The presence of this kind of correlations for a large ensemble of cells restricts further the time of validity of the expansion.     

Mixture interactions in moth olfactory physiology: examining the effects of odorant mixture, concentration, distal stimulation, and antennal nerve transection on sensillar responses

The insect olfactory system is challenged to decipher valid signals from among an assortment of chemical cues present in the airborne environment. In the moth, Heliothis virescens, males rely upon detection and discrimination of a unique blend of components in the female sex pheromone to locate mates. The effect of variable odor mixtures was used to examine physiological responses from neurons within sensilla on the moth antenna sensitive to female sex pheromone components. Increasing concentrations of heliothine sex pheromone components applied in concert with the cognate stimulus for each neuronal type resulted in mixture suppression of activity, except for one odorant combination where mixture enhancement was apparent. Olfactory receptor neuron (ORN) responses were compared between moths with intact and transected antennal nerves to determine whether specific instances of suppression might be influenced by central mechanisms. Type A sensilla showed little variation in response between transected and intact preparations; however, recordings from type B sensilla with transected antennal nerves exhibited reduced mixture suppression. Testing by parallel stimulation of distal antennal segments while recording and stimulating proximal segments dismissed the possibility of interneuronal or ephaptic effects upon sensillar responses. The results indicate that increasing concentrations of "noncognate" odorants in an odor mixture or antennal nerve transection can produce variation in the intensity and temporal dynamics of physiological recordings from H. virescens ORNs.     

Slow-wave fluctuations in craniosacral space: hemo-liquorodynamic conception of origin

In the paper, the mechanism of forming of rhythmic slow-wave fluctuations in craniospinal cavity was investigated. In five young healthy persons, at rest and under voluntary respiration arrest test, the bioimpedansograms of head and lumbosacral part of vertebral column were synchronously registered as these recordings reflect the changes of relationships between blood/CSF volumes in cranial and lumbosacral regions, respectively. The recordings were subjected to frequency and spectral computer analysis (PC Macintosh G-4, Chart 5.2. software). The rapid (pulsatile) as well as slow and counter-directed waves (frequency 6-10 cycles/min) of these processes were revealed in cranial and lumbosacral regions. The data obtained suggest the CSF dynamic concept of origin of the craniosacral rhythm. The pulse and slow-frequency oscillations of the cerebral vessels tone initiate corresponding intracranial pressure waves, and the latter are the motivating forces for to-and-fro CSF shifts in caudal direction. This mechanism is accompanied by tonic contractions of lumbar muscles and sacrum movements, and it is manually perceptible as a craniosacral rhythm.     

Circadian and ultradian activity rhythms in manatee (Trichechus manatus manatus) in captivity

In this study, we show temporal organization of activity patterns in larger temporal series recording. The objective of this study was to determine the temporal pattern of the rest-activity rhythm in manatee (Trichechus manatus manatus) in captivity. Activity recordings were programmed from August 2010 to September 2011 with actimetry devices, and behavior recordings were conducted in dry and rainy seasons. We showed that the marine manatee presents a complex temporal organization, in which the rest-activity rhythm comprises several frequencies with a predominant circadian component and multiple ultradian components. Our results indicate that the animals were more active during the day with respect to the night. The temporal organization of this cycle entails multiple frequencies that include ultradian rhythms, which may be expressions generated by physiological needs, such as food availability and thermoregulatory requirements. These patterns should be taken into consideration for future studies of biological rhythms in manatee.     

Detection of sex pheromone components in Manduca sexta (L.).

The ability of olfactory receptor neurons to detect female-produced sex pheromone components and a limited sample of potential host plant odours was studied by single-sensillum recordings from olfactory sensilla present on male and female antennae in Manduca sexta. The majority of pheromone-sensitive receptor neurons examined in males was specialized for detection of the two major pheromone components, E10,Z12-hexadecadienal and E10,E12,Z14-hexadecatrienal or E10,E12,E14-hexadecatrienal. New olfactory receptor neurons tuned to the minor components E10,E12-hexadecadienal and Z11-hexadecenal were found. In females, olfactory receptor neurons specific to Z11-hexadecanal were discovered. Pheromone components and host volatiles were detected by separate sets of receptor neurons.