A NWB-based dataset and processing pipeline of human single-neuron activity during a declarative memory task.

A challenge for data sharing in systems neuroscience is the multitude of different data formats used. Neurodata Without Borders: Neurophysiology 2.0 (NWB:N) has emerged as a standardized data format for the storage of cellular-level data together with meta-data, stimulus information, and behavior. A key next step to facilitate NWB:N adoption is to provide easy to use processing pipelines to import/export data from/to NWB:N. Here, we present a NWB-formatted dataset of 1863 single neurons recorded from the medial temporal lobes of 59 human subjects undergoing intracranial monitoring while they performed a recognition memory task. We provide code to analyze and export/import stimuli, behavior, and electrophysiological recordings to/from NWB in both MATLAB and Python. The data files are NWB:N compliant, which affords interoperability between programming languages and operating systems. This combined data and code release is a case study for how to utilize NWB:N for human single-neuron recordings and enables easy re-use of this hard-to-obtain data for both teaching and research on the mechanisms of human memory.

Neuronal spiking in the pedunculopontine nucleus in progressive supranuclear palsy and in idiopathic Parkinson's disease.

The pedunculopontine nucleus (PPN) is engaged in posture and gait control, and neuronal degeneration in the PPN has been associated with Parkinsonian disorders. Clinical outcomes of deep brain stimulation of the PPN in idiopathic Parkinson's disease (IPD) and progressive supranuclear palsy (PSP) differ, and we investigated whether the PPN is differentially affected in these conditions. We had the rare opportunity to record continuous electrophysiological data intraoperatively in 30 s blocks from single microelectrode contacts implanted in the PPN in six PSP patients and three IPD patients during rest, passive movement, and active movement. Neuronal spikes were sorted according to shape using a wavelet-based clustering approach to enable comparisons between individual neuronal firing rates in the two disease states. The action potential widths showed a bimodal distribution consistent with previous findings, suggesting spikes from noncholinergic (likely glutamatergic) and cholinergic neurons. A higher PPN spiking rate of narrow action potentials was observed in the PSP than in the IPD patients when pooled across all three conditions (Wilcoxon rank sum test: p = 0.0141). No correlation was found between firing rate and disease severity or duration. The firing rates were higher during passive movement than rest and active movement in both groups, but the differences between conditions were not significant. PSP and IPD are believed to represent distinct disease processes, and our findings that the neuronal firing rates differ according to disease state support the proposal that pathological processes directly involving the PPN may be more pronounced in PSP than IPD.

The benefit of cesarean section in acute myocardial infarction complicated by premature labor.

A 42-year-old woman with no known risk factors had an acute myocardial infarction at 32 weeks' gestation and went into premature labor. She required invasive hemodynamic monitoring and inotropic support. Congestive heart failure improved dramatically after cesarean section. During the acute infarction, ventricular dysfunction was out of proportion to the ultimate ventricular damage. The concept of the stunned myocardium is used to explain this finding and to justify early cesarean section. Another complication of her infarction, left ventricular thrombosis, has not previously been described in pregnancy.

Human cutaneous leishmaniasis acquired in Texas.

Four cases of autochthonous human cutaneous leishmaniasis have been identified in south-central Texas since 1980. The patients presented with chronic ulcerating papules on the face, earlobe, and lateral thigh. In two patients, the infections healed without treatment. In the other two patients, the lesions healed following treatment with intramuscular sodium stibogluconate or topical antimony potassium tartrate. Serologic testing of family members, using four different techniques, indicates that asymptomatic infections may occur. These are the first reported cases of cutaneous leishmaniasis acquired in Texas since 1974. Organisms isolated from patients in 1974 and 1980 belonged to the Leishmania mexicana complex when tested by the isoenzyme technique. Although no animal reservoir or insect vector has been identified, six species of sand flies belonging to the genus Lutzomyia do inhibit this part of Texas. Accumulated evidence strongly suggests that cutaneous leishmaniasis is endemic in south-central Texas.

Controlling conditioning-related emesis in children undergoing bone marrow transplantation.

PURPOSE/OBJECTIVES: To compare the efficacy of two antiemetic regimens, ondansetron alone versus perphenazine with diphenhydramine, on emesis control in children undergoing conditioning therapy for bone marrow transplantation (BMT). DESIGN: Single-center, prospective, open, randomized, crossover study. SETTING: Pediatric BMT unit in an urban area in the northeastern United States. SAMPLE: 28 children, ages 4-17, undergoing BMT for a variety of underlying diseases. METHODS: After randomization to one of the two antiemetic regimens, emesis control was evaluated during conditioning therapy. If a participant experienced more than five episodes of emesis during any 12-hour period, he or she was crossed over to the other antiemetic regimen. If emesis control still was not achieved, the participant was removed from the study and other medications were administered to control vomiting. MAIN RESEARCH VARIABLES: Number of emetic episodes and incidence of side effects. FINDINGS: 10 of 15 patients (67%) who received ondansetron experienced major emesis control (no more than two episodes) compared with 0 of 13 patients (0%) who received perphenazine with diphenhydramine (p = 0.044, Fisher exact test). Of those who crossed over to ondansetron after failure with perphenazine and diphenhydramine, 38% were able to achieve major emesis control. CONCLUSIONS: Ondansetron offers superior antiemetic control over the combination of perphenazine and diphenhydramine for children undergoing high-dose chemotherapy with or without total body irradiation for BMT. IMPLICATIONS FOR NURSING PRACTICE: Oncology nurses must develop an understanding of the etiology of therapy-induced emesis and the mechanisms of action of the various classes of antiemetic agents designed to control it. Implementing documentation to describe events of emesis will help to tailor antiemetic therapy to a patient's specific situation. Further research is necessary to determine alternate strategies, including different combinations or sequences of antiemetics to provide optimum emetic control during acute and delayed phases of emesis. The higher cost of ondansetron therapy must be considered within the context of superior efficacy.

Intelligibility of frequency-lowered speech produced by a channel vocoder.

Frequency lowering is a form of signal processing designed to match speech to the residual auditory capacity of a listener with a high frequency hearing loss. A vocoder-based frequency-lowering system similar to one studied by Lippmann was evaluated in the present study. In this system, speech levels in high frequency bands modulated one-third-octave bands of noise at low frequencies, which were then added to unprocessed speech. Results obtained with this system indicated, in agreement with Lippmann, that processing improved the recognition of stop, fricative, and affricate consonants when the listening bandwidth was restricted to 800 Hz. However, results also showed that processing degraded the perception of nasals and semivowels, consonants not included in Lippmann's study. Based on these results, the frequency-lowering system was modified so as to suppress the processing whenever low frequency components dominated the input signal. High and low frequency energies of an input signal were measured continuously in the modified system, and the decision to process or to leave the signal unaltered was based on their relative levels. Results indicated that the modified system maintained the processing advantage for stops, fricatives, and affricates without degrading the perception of nasals and semi-vowels. The results of the present study also indicated that training is an important consideration when evaluating frequency-lowering systems.

Preliminary results of speech-reception tests obtained with the synthetic Tadoma system.

In the Tadoma method of speech reception used by some deaf-blind individuals, speech is understood by placing a hand on the face of the talker and feeling certain mechanical actions of the face associated with speech production. The synthetic Tadoma system is a computer-driven artificial face that simulates these mechanical actions. This paper reports some preliminary data on the discrimination of nonsense syllables with the synthetic system. Although further work is required to produce an accurate simulation, the results suggest that such a goal is indeed achievable.

Automatic speech recognition to aid the hearing impaired: prospects for the automatic generation of cued speech.

Although great strides have been made in the development of automatic speech recognition (ASR) systems, the communication performance achievable with the output of current real-time speech recognition systems would be extremely poor relative to normal speech reception. An alternate application of ASR technology to aid the hearing impaired would derive cues from the acoustical speech signal that could be used to supplement speechreading. We report a study of highly trained receivers of Manual Cued Speech that indicates that nearly perfect reception of everyday connected speech materials can be achieved at near normal speaking rates. To understand the accuracy that might be achieved with automatically generated cues, we measured how well trained spectrogram readers and an automatic speech recognizer could assign cues for various cue systems. We then applied a recently developed model of audiovisual integration to these recognizer measurements and data on human recognition of consonant and vowel segments via speechreading to evaluate the benefit to speechreading provided by such cues. Our analysis suggests that with cues derived from current recognizers, consonant and vowel segments can be received with accuracies in excess of 80%. This level of performance is roughly equivalent to the segment reception accuracy required to account for observed levels of Manual Cued Speech reception. Current recognizers provide maximal benefit by generating only a relatively small number (three to five) of cue groups, and may not provide substantially greater aid to speechreading than simpler aids that do not incorporate discrete phonetic recognition. To provide guidance for the development of improved automatic cueing systems, we describe techniques for determining optimum cue groups for a given recognizer and speechreader, and estimate the cueing performance that might be achieved if the performance of current recognizers were improved.

Development and testing of artificial low-frequency speech codes.

In a new approach to the frequency-lowering of speech, artificial codes were developed for 24 consonants (C) and 15 vowels (V) for two values of lowpass cutoff frequency F (300 and 500 Hz). Each individual phoneme was coded by a unique, nonvarying acoustic signal confined to frequencies less than or equal to F. Stimuli were created through variations in spectral content, amplitude, and duration of tonal complexes or bandpass noise. For example, plosive and fricative sounds were constructed by specifying the duration and relative amplitude of bandpass noise with various center frequencies and bandwidths, while vowels were generated through variations in the spectral shape and duration of a ten-tone harmonic complex. The ability of normal-hearing listeners to identify coded Cs and Vs in fixed-context syllables was compared to their performance on single-token sets of natural speech utterances lowpass filtered to equivalent values of F. For a set of 24 consonants in C-/a/ context, asymptotic performance on coded sounds averaged 90 percent correct for F = 500 Hz and 65 percent for F = 300 Hz, compared to 75 percent and 40 percent for lowpass filtered speech. For a set of 15 vowels in /b/-V-/t/ context, asymptotic performance on coded sounds averaged 85 percent correct for F = 500 Hz and 65 percent for F = 300 Hz, compared to 85 percent and 50 percent for lowpass filtered speech. Identification of coded signals for F = 500 Hz was also examined in CV syllables where C was selected at random from the set of 24 Cs and V was selected at random from the set of 15 Vs. Asymptotic performance of roughly 67 percent correct and 71 percent correct was obtained for C and V identification, respectively. These scores are somewhat lower than those obtained in the fixed-context experiments. Finally, results were obtained concerning the effect of token variability on the identification of lowpass filtered speech. These results indicate a systematic decrease in percent-correct score as the number of tokens representing each phoneme in the identification tests increased from one to nine.

Effects of rate of presentation on the reception of American Sign Language.

Previous research on the visual reception of fingerspelled English suggests that communication rates are limited primarily by constraints on production. Studies of artificially accelerated fingerspelling indicate that reception of fingerspelled sentences is highly accurate for rates up to 2 to 3 times those that can be produced naturally. The current paper reports on the results of a comparable study of the reception of American Sign Language (ASL). Fourteen native deaf ASL signers participated in an experiment in which videotaped productions of isolated ASL signs or ASL sentences were presented at normal playback speed and at speeds of 2, 3, 4, and 6 times normal speed. For isolated signs, identification scores decreased from 95% correct to 46% correct across the range of rates that were tested; for sentences, the ability to identify key signs decreased from 88% to 19% over the range of rates tested. The results indicate a breakdown in processing at around 2.5-3 times the normal rate as evidenced both by a substantial drop in intelligibility in this region and by a shift in error patterns away from semantic and toward formational. These results parallel those obtained in previous studies of the intelligibility of the auditory reception of time-compressed speech and the visual reception of accelerated fingerspelling. Taken together, these results suggest a modality-independent upper limit to language processing.

A novel approach to the detection of synchronisation in EEG based on empirical mode decomposition.

Transient neural assemblies mediated by synchrony in particular frequency ranges are thought to underlie cognition. We propose a new approach to their detection, using empirical mode decomposition (EMD), a data-driven approach removing the need for arbitrary bandpass filter cut-offs. Phase locking is sought between modes. We explore the features of EMD, including making a quantitative assessment of its ability to preserve phase content of signals, and proceed to develop a statistical framework with which to assess synchrony episodes. Furthermore, we propose a new approach to ensure signal decomposition using EMD. We adapt the Hilbert spectrum to a time-frequency representation of phase locking and are able to locate synchrony successfully in time and frequency between synthetic signals reminiscent of EEG. We compare our approach, which we call EMD phase locking analysis (EMDPL) with existing methods and show it to offer improved time-frequency localisation of synchrony.

Dye coupling in the muscles controlling squid chromatophore expansion.

Dye coupling between the cone-shaped radial muscle fibres, which control the expansion and closing of a squid chromatophore organ, was investigated in the squid Loligo vulgaris. Particular attention was paid to the role of the myomuscular junctions located between the muscle fibres. Lucifer Yellow was injected ionophoretically into single muscle fibres under normal artificial sea water (ASW) and under various concentrations of calcium in ASW. Under ASW, 44% of muscle fibres examined were dye-coupled, 82% were coupled under calcium-free sea water and 67% were coupled under sea water containing high concentrations of calcium. Dye transfer was blocked by octanol. Muscle fibres were never seen to link adjacent chromatophore organs. Results are discussed in terms of the role of the myomuscular junctions in the regulation of chromatophore expansion in the living animal.

The ultrastructure and innervation of muscles controlling chromatophore expansion in the squid, Loligo vulgaris.

Squid chromatophores are organs of colour change, consisting of a pigment sac opened by contraction of 10-24 radial muscle fibres. The ultrastructure and innervation of these muscle fibres were examined by electron microscopy and diagramatic reconstructions made on the basis of serial ultra-thin sections. At the proximal end of the fibre, nearest the pigment sac a cortical myofilament zone surrounds 2 cores containing mitochrondria; further along the fibre these merge to form one central core. The myofilament zone forms a groove containing a nerve bundle consisting of 2 to 4 axons per muscle fibre. The axons are surrounded by glial cell processes, and either originate from a neighbouring fibre, or join the fibre at some point along its length. Axons twist around each other, forming a series of synapses with the muscle fibre. As many as 6-37 synapses exist along the length of each muscle fibre; the mean synapse interval is 9.05 microm, but the largest may be 123 microm. At the distal end of the muscles, the nerve is located towards the middle of the fibre, which it penetrates as the muscle splits up. Electron-lucent vesicles are present in all synaptic regions, but electron-dense vesicles are only found towards the distal end of the fibre. There is thus a possibility that more than one neurotransmitter is present in the nerves innervating chromatophores. Electron-lucent and dense-cored vesicles are not colocalised.

A comparison of the effects of filtering and sensorineural hearing loss on patients of consonant confusions.

It has been found that listeners with sensorineural hearing loss who show similar patterns of consonant confusions also tend to have similar audiometric profiles. The present study determined whether normal listeners, presented with filtered speech, would produce consonant confusions similar to those previously reported for the hearing-impaired listener. Consonant confusion matrices were obtained from eight normal-hearing subjects for four sets of CV and VC nonsense syllables presented under six high-pass and six-low pass filtering conditions. Patterns of consonant confusion for each condition were described using phonological features in sequential information analysis. Severe low-pass filtering produced consonant confusions comparable to those of listeners with high-frequency hearing loss. Severe high-pass filtering gave a result comparable to that of patients with flat or rising audiograms. And, mild filtering resulted in confusion patterns comparable to those of listeners with essentially normal hearing. An explanation in terms of the spectrum, the level of speech, and the configuration of this individual listener's audiogram is given.

Discrimination and identification of frequency-lowered speech in listeners with high-frequency hearing impairment.

The effects of frequency lowering on consonant perception were studied in four listeners with high-frequency sensorineural loss. Frequency lowering, accomplished by pitch-invariant nonuniform compression of the short-term spectral envelope, included lowering to bandwidths of 2500 and 1250 Hz. Performance on frequency lowering was compared to that obtained with linear amplification using uniform or high-frequency emphasis. Results of pairwise discrimination tests indicated that performance on lowering to 1250 Hz was inferior to that obtained with linear amplification. After training, performance on consonant identification with lowering to bandwidths of 2500 or 1250 Hz was equivalent or inferior to that obtained with linear amplification, depending on the subject. In most cases, the performance of the impaired subjects on a given lowering condition was inferior to that obtained by normal subjects, except for one impaired subject whose performance on two lowering conditions was similar to normal.