Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RECORDS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources
PubMed1992

Physician failure to record alcohol use history when prescribing benzodiazepines.

The purpose of this pilot study was (1) to determine the proportion of patients in an ambulatory medical clinic who have an alcohol history recorded when prescribed benzodiazepines, and (2) to assess the adequacy of the alcohol history when obtained. Medical records of 35 outpatients who obtained prescriptions for benzodiazepines at a large inner-city teaching hospital medical clinic were audited. In none of the records was there evidence that the physician had sufficient knowledge of the patient's alcohol use to safely prescribe a benzodiazepine. In 57% of the records, no information about alcohol use was recorded. In the remaining 15 medical records, the information recorded was limited. The implications of prescribing benzodiazepines without knowledge of drinking status are discussed.

Adult↗
PubMed2006

Muscle activity onset in the lumbar multifidus muscle recorded simultaneously by ultrasound imaging and intramuscular electromyography.

BACKGROUND: Delayed anticipatory muscle activity response in deep abdominal and back muscles has been observed in patients with low back pain, indicative of a pathological condition. Muscle activity onset is traditionally recorded by intramuscular electromyography, but there is a need for a non-invasive and less cumbersome recording method in large clinical studies. An experimental study was carried out to explore whether high-frame rate m-mode ultrasound could measure anticipatory muscle responses ("onset") in the lumbar multifidus muscle reliably and comparably accurate to intramuscular electromyography. METHODS: Muscle activity onset was recorded by ultrasound m-mode and intramuscular electromyography. Ultrasound m-mode with a temporal resolution of 500 s(-1) (frames per second) was used to record rapid movements caused by muscle deformations in multifidus. In ultrasound m-mode, the frequency of each echo signal from 0.15 mm incremental depth levels is analysed. The frequency of these signals is proportional to the velocity of the interrogated tissue. The mean amplitude of the high-pass filtered echo signals within a pre-set depth range was plotted against time, and used to indicate onset. The results were compared to muscle activity onset in the multifidus recorded simultaneously by intramuscular electromyography. FINDINGS: High inter-rater agreement was found for visual determination of onset within both methods. The smallest detectable difference was 21 and 24 ms for electromyography and the ultrasound methods, respectively. The ultrasound m-mode method recorded muscle activity onset in the deep multifidus on average 16 ms (SD 21) later than intramuscular electromyography. For single trials, large variation and thus unacceptable method agreement was found. INTERPRETATION: Ultrasound m-mode imaging at high time resolution can detect onset of muscle activity comparably accurate to intramuscular electromyography, but with a small systematic delay that should be corrected for in onset determination by m-mode ultrasound. Regardless of recording method, onset estimates should be based on averaged values of repeated trials. Further studies are needed to explore the applicability of the ultrasound method in clinical settings.

Adult↗
PubMed2005

Model-based analysis of cortical recording with silicon microelectrodes.

OBJECTIVE: The purpose of this study was to use computational modeling to better understand factors that impact neural recordings with silicon microelectrodes used in brain-machine interfaces. METHODS: A non-linear cable model of a layer V pyramidal cell was coupled with a finite-element electric field model with explicit representation of the microelectrode. The model system enabled analysis of extracellular neural recordings as a function of the electrode contact size, neuron position, edema, and chronic encapsulation. RESULTS: The model predicted spike waveforms and amplitudes that were consistent with experimental recordings. Small (< 1000 microm2) and large (10 k microm2) electrode contacts had similar volumes of recording sensitivity, but small contacts exhibited higher signal amplitudes (approximately 50%) when neurons were in close proximity (50 microm) to the electrode. The model results support the notion that acute edema causes a signal decrease ( approximately 24%), and certain encapsulation conditions can result in a signal increase (approximately 17%), a mechanism that may contribute to signal increases observed experimentally in chronic recordings. CONCLUSIONS: Optimal electrode design is application-dependent. Small and large contact sizes have contrasting recording properties that can be exploited in the design process. In addition, the presence of local electrical inhomogeneities (encapsulation, edema, coatings) around the electrode shank can substantially influence neural recordings and requires further theoretical and experimental investigation. SIGNIFICANCE: Thought-controlled devices using cortical command signals have exciting therapeutic potential for persons with neurological deficit. The results of this study provide the foundation for refining and optimizing microelectrode design for human brain-machine interfaces.

Algorithms↗
PubMed2006

Agreement between maternal report and antenatal records for a range of pre and peri-natal factors: the influence of maternal and child characteristics.

BACKGROUND: Events during pregnancy and labour may influence the future health and well-being of offspring. Many studies rely on maternal reports of pre and peri-natal factors. Both maternal and child characteristics may potentially influence the reliability and accuracy of maternal recall. However, this has not been previously examined. AIMS: To examine agreement between information from maternally reported questionnaires and medical records for a range of pre and peri-natal factors. To examine whether maternal and child characteristics influence the level of agreement with medical records. METHODS: A survey of women who had school aged children born following in vitro fertilization (IVF) was carried out. Mothers completed a postal questionnaire booklet which included the Lewis and Murray scale which asks about antenatal and obstetric complications and the Strengths and Difficulties Questionnaire which assesses child behaviour problems. Antenatal case notes were also reviewed. Multi-centre ethical approval was obtained. Complete data were available for 126 women. RESULTS: The agreement between maternal report and medical records was very good for the majority of outcomes examined (infant birth weight, infant admission to special care baby unit, method of delivery, smoking during pregnancy, high blood pressure/oedema during pregnancy). Exceptions were length of labour and alcohol use during pregnancy. However, alcohol use during pregnancy was not routinely recorded in medical records. Maternal characteristics did not substantially influence level of agreement for the majority of outcomes examined. Exceptions were that agreement for length of labour was better in women with more educational qualifications and that agreement for pre-natal smoking was worse in women from higher socio-occupational groups. There was little evidence that child behaviour problems influenced the level of agreement between maternal recall and medical records. CONCLUSIONS: For the majority of pre and peri-natal events examined, mothers can provide accurate reports in comparison to information from medical records.

Alcohol Drinking↗
PubMed2004

On compensation of mismatched recording conditions in the Bayesian approach for forensic automatic speaker recognition.

This paper deals with a procedure to compensate for mismatched recording conditions in forensic speaker recognition, using a statistical score normalization. Bayesian interpretation of the evidence in forensic automatic speaker recognition depends on three sets of recordings in order to perform forensic casework: reference (R) and control (C) recordings of the suspect, and a potential population database (P), as well as a questioned recording (QR) . The requirement of similar recording conditions between suspect control database (C) and the questioned recording (QR) is often not satisfied in real forensic cases. The aim of this paper is to investigate a procedure of normalization of scores, which is based on an adaptation of the Test-normalization (T-norm) [2] technique used in the speaker verification domain, to compensate for the mismatch. Polyphone IPSC-02 database and ASPIC (an automatic speaker recognition system developed by EPFL and IPS-UNIL in Lausanne, Switzerland) were used in order to test the normalization procedure. Experimental results for three different recording condition scenarios are presented using Tippett plots and the effect of the compensation on the evaluation of the strength of the evidence is discussed.

Bayes Theorem↗
PubMed2004

Utility of event loop recorders for the management of arrhythmias in young ambulatory patients.

We evaluated the diagnostic yield of event loop recorders in ambulatory patients referred for palpitations, dizziness or syncopal events and in whom a previous Holter recording was not diagnostic. A total of 96 patients were studied, 50 (52%) were men and 46 (48%) were women with a mean age of 37+/-10 years. Mean duration of the recording was 5.2+/-2.3 days. During the recording period, 24 of the 96 patients (25%) remained asymptomatic. Automatic recordings revealed significant arrhythmias in four (16.7%) patients, which included two (8.3%) cases of atrial fibrillation, one (4.2%) non-sustained ventricular tachycardia (VT) and one (4.2%) second degree atrio-ventricular (AV) block. The manual function of the recorder was used by 72 (75%) patients while they were symptomatic. Palpitations were the most common symptom, which corresponded most frequently to normal sinus rhythm (43.1%), followed by sinus tachycardia (16.7%). An arrhythmic substrate was found in 29 (40.3%) patients, including 13 (18.1%) with isolated ectopic beats of supraventricular and/or ventricular origin, 14 (19.4%) with supraventricular tachycardia (SVT) and 2 (2.8%) with second degree AV block. The data of our study showed that the ambulatory use of an event loop recorder in young patients during a mean period of 5 days was highly useful to elucidate the potential cause of their symptoms. The particular use of the manually triggered function during symptoms allowed to establish a clear correlation between symptoms and arrhythmic events including sinus tachycardia in 75% of patients.

Adult↗
PubMed2004

Information content in Medline record fields.

BACKGROUND: The authors have been conducting text mining analyses (extraction of useful information from text) of Medline records, using Abstracts as the main data source. For literature-based discovery, and other text mining applications as well, all records in a discipline need to be evaluated for determining prior art. Many Medline records do not contain Abstracts, but typically contain Titles and Mesh terms. Substitution of these fields for Abstracts in the non-Abstract records would restore the missing literature to some degree. OBJECTIVES: Determine how well the information content of Title and Mesh fields approximates that of Abstracts in Medline records. APPROACH: Select historical Medline records related to Raynaud's Phenomenon that contain Abstracts. Determine the information content in the Abstract fields through text mining. Then, determine the information content in the Title fields, the Mesh fields, and the combined Title-Mesh fields, and compare with the information content in the Abstracts. RESULTS: Four metrics were used to compare the information content related to Raynaud's Phenomenon in the different fields: total number of phrases; number of unique phrases; content of factors from factor analyses; content of clusters from multi-link clustering. The Abstract field contains almost an order of magnitude more phrases than the other fields, and slightly more than an order of magnitude more unique phrases than the other fields. Each field used a factor matrix with 14 factors, and the combination of all 56 factors for the four fields represented 27 separate, but not unique, themes. These themes could be placed in two major categories, with two sub-categories per major category: Auto-immunity (antibodies, inflammation) and circulation (peripheral vessel circulation, coronary vessel circulation). All four sub-categories included representation from each field. Thus, while the focus of the representation of each field in each sub-category was moderately different, the four sub-category structure could be identified by analyzing the total factors in each field. In the cluster comparison phase of the study, the phrases used to create the clusters were the most important phrases identified for each factor. Thus, the factor matrix served as a filter for words used for clustering. While clusters were generated for all four fields, the Title hierarchy tended to be fragmented due to sparsity of the co-occurrence matrix that underlies the clusters. Therefore, the Title clusters were examined at only the lower levels of aggregation. The Abstract, Mesh, and Mesh + Title fields had the same first level taxonomy categories, auto-immunity and circulation. At the second level, the Abstract, Mesh, and Mesh + Title fields had the autoimmune diseases and antibodies sub-category in common. The Abstract and Mesh fields shared fascia inflammation as the other auto-immunity sub-category, while the other Mesh + Title sub-category focuses on vinyl chloride poisoning from industrial contact, and consequences of antineoplastic agents. However, in both cases, even though the words may be different, inflammation may be the common theme. CONCLUSIONS: For taxonomy generation, especially at the higher levels, each of the four fields has a similar thematic structure. At very detailed levels, the Mesh and Title fields run out of phrases relative to the Abstract field. Therefore, selection of field (s) to be employed for taxonomy generation depends on the objectives of the study, particularly the level of categorization required for the taxonomy. For information retrieval, or literature-based discovery, selection of the appropriate field again depends on the study objectives. If large queries, or large numbers of concepts or themes are desired, then the field with the largest number of technical phrases would be desirable. If queries or concepts represented by the more accepted popular terminology is adequate, then the smaller fields may be sufficient. Because of its established and controlled vocabulary, the Mesh field lags the Title or Abss the Title or Abstract fields in currency. Thus, the Title or Abstract fields would retrieve records with the most explicitly stated current concepts, but the Mesh field would capture a larger swath of fields that contained a concept of interest but perhaps had a wider range of specific terminology in the Abstract or Title text. In addition, this study provides the first validated estimate of the disparity in information retrieved through text mining limited to Titles and Mesh terms relative to entire Abstracts. As much of the older biomedical literature was entered into electronic databases without associated Abstracts, literature-based discovery exercises that search the older medical literature may miss a substantial proportion of relevant information. On the basis of this study, it may be estimated that up to a log order more information may be retrieved when complete Abstracts are searched.

Abstracting and Indexing↗
PubMedDate not supplied

Digitized infrared segmental thermometry: time requirements for stable recordings.

OBJECTIVES: Digitized infrared segmental thermometry (DIST) is a method for measuring and recording skin surface body temperatures. The project evaluated the required length of time for patients to acclimatize their core body temperature to ambient conditions to obtain stable DIST readings. METHODS: Seventeen subjects were allowed a 20-minute acclimatizing period in a temperature-controlled room. The bilateral DIST temperature was measured with thermistors in combination with infrared cameras (IRCs) at the C4 and L4 levels. All IRC temperatures were recorded after a 20-minute stabilization period. The room temperature and relative humidity were recorded throughout all trials. The acclimatization trend was computed from the 20- to 24-minute period for the IRCs, and the acclimatization trend was computed continuously for a total of 30 minutes (at 2-minute intervals) for 5 days. RESULTS: We discovered a stabilization trend in the early trial stages, with the thermistor recordings between 8 and 16 minutes. The IRC trend was also conclusive for the core temperature requirements. CONCLUSIONS: This study determined a core body temperature acclimatization trend tested among patients using thermistor recordings in a controlled environment. Based on these findings, we recommend acclimatization in a temperature- and humidity-controlled environment for a minimum 8-minute period, followed by an 8-minute maximum recording period with the patient in a prone position to obtain accurate DIST recordings.

Acclimatization↗
PubMed2004

Intrinsic signal recording from a monkey whose behavior was maintained by a schedule of reinforcement.

Optical recording of cortical activity in awake monkeys has enhanced our understanding of the functional anatomy of the primary visual cortex (V1). However, cortical representation of visual cognition has not been studied by optical recording, even though the greatest merit of using awake animals is that they can offer advantages in studying cognitive function that anesthetized animals cannot. Thus far, the optical recording method has not been combined with tasks that accompany body movements because of concern about movement noise, although behavioral tasks are helpful in the study of animal cognition. Here, I tested the influence of body movements during the signal acquisition period on the resultant images. I recorded the intrinsic signals associating with different orientations from V1 of a monkey who was emitting behavior during the signal acquisition period. Although the monkey's behavior was maintained on a variable-interval schedule that typically induces a high rate of response, orientation maps were consistently obtained. Therefore, a successful recording under this operant regimen implies the applicability of the optical recording method to other behavioral tasks. Several constraints in applying optical recording to studies using behaving animals are also discussed.

Analysis of Variance↗
PubMed2006

Whole-cell recordings in freely moving rats.

Intracellular recording, which allows direct measurement of the membrane potential and currents of individual neurons, requires a very mechanically stable preparation and has thus been limited to in vitro and head-immobilized in vivo experiments. This restriction constitutes a major obstacle for linking cellular and synaptic physiology with animal behavior. To overcome this limitation we have developed a method for performing whole-cell recordings in freely moving rats. We constructed a miniature head-mountable recording device, with mechanical stabilization achieved by anchoring the recording pipette rigidly in place after the whole-cell configuration is established. We obtain long-duration recordings (mean of approximately 20 min, maximum 60 min) in freely moving animals that are remarkably insensitive to mechanical disturbances, then reconstruct the anatomy of the recorded cells. This head-anchored whole-cell recording technique will enable a wide range of new studies involving detailed measurement and manipulation of the physiological properties of identified cells during natural behaviors.

Animals↗
PubMed2005

Quantitative measures of cluster quality for use in extracellular recordings.

While the use of multi-channel electrodes (stereotrodes and tetrodes) has allowed for the simultaneous recording and identification of many neurons, quantitative measures of the quality of neurons in such recordings are lacking. In multi-channel recordings, each spike waveform is discriminated in a high-dimensional space, making traditional measures of unit quality inapplicable. We describe two measures of unit isolation quality, Lratio and Isolation Distance, and evaluate their performance using simulations and tetrode recordings. Both measures quantified how well separated the spikes of one cluster (putative neuron) were from other spikes recorded simultaneously on the same multi-channel electrode. In simulations and tetrode recordings, both Lratio and Isolation Distance discriminated well- and poorly-separated clusters. In data sets from the rodent hippocampus in which neurons were simultaneously recorded intracellularly and extracellularly, values of Isolation Distance and Lratio were related to the correct identification of spikes.

Animals↗
PubMed1996

Uterine contractility as assessed by abdominal surface recording of electromyographic activity in rats during pregnancy.

OBJECTIVES: The primary aim of this study was to develop a noninvasive method for recording uterine contractile activity during pregnancy by systematically evaluating whether abdominal surface electromyography is representative of uterine electrical and contractile events. A secondary purpose was to use these techniques to determine when the uterus is in a state of preparedness for labor. STUDY DESIGN: Electrical activity was acquired by use of unipolar electrodes attached simultaneously to the uterine wall and to the abdominal surface of pregnant rats. Intrauterine pressure was recorded with a pressure transducer inserted in the uterine cavity. Computer-acquired records of electrical events (electromyography) and pressure were compared on different days of gestation, during spontaneous labor at term, or during preterm birth induced with an antiprogestin. Similarly, electrical activity was assessed after administration of agents that either stimulate (oxytocin) or inhibit (isoproterenol) contractility. Correlation analyses were performed between uterine electromyographic activity, surface electromyographic activity, and concomitant intrauterine pressure. The effects of vaginal wall stimulation were also evaluated at different times of pregnancy. RESULTS: The electrical activity recorded early in pregnancy (day 18) from the uterus consisted of irregular electrical bursts with little correspondence to the signals recorded from the surface (R2=0.006). Later in gestation (days 19 through 21) the electrical activity of the uterus became more regular, consisting of frequent bursts with accordance between the signals recovered from the uterus and those collected from the surface (R2=0.95). During labor (preterm or term) bursts recorded from either the uterus or the abdominal surface were of large amplitude and corresponded to ample changes in intrauterine pressure. Correlation coefficients between uterus and surface and uterus and pressure were R2=1 and 0.96, respectively. Similarly, during preterm labor the coefficients were R2=1 for uterine electromyographic activity versus surface electromyographic activity and R2=0.99 for uterine electromyographic activity versus intrauterine pressure. Vaginal stimulation in early gestation was not followed by subsequent signal conduction to the uterus, whereas during delivery activity induced in the vagina propagated to the uterus and consequently to the abdominal surface. CONCLUSIONS: Abdominal surface recording of uterine electrical events are representative of the activity generated by the muscle cells of the uterus. During term and preterm labor uterine electrical activity and intrauterine pressure achieve maximum activity. Electromyographic monitoring with vaginal stimulation of the uterus may allow prediction of when the uterus is in a state required for labor.

Abdomen↗
PubMed1993

Home event recordings of oxygenation, breathing movements, and heart rate and rhythm in infants with recurrent life-threatening events.

For an evaluation of the usefulness of event recording in identifying mechanisms for apparent life-threatening events, 94 infants (median age, 3.1 months; range, 0.5 to 12 months) with a history of two or more apparent life-threatening events of hitherto unknown cause underwent event recording of transcutaneous oxygen pressure, arterial oxygen saturation, (not recorded in all patients), breathing movements, pulse waveforms, electrocardiogram, and instantaneous heart rate. Recordings were triggered by a fall in transcutaneous oxygen pressure to less than 20 mm Hg. During a median duration of event recording of 1.3 months (0.1 to 10 months), 52 events were recorded in 34 patients; 7 of the events had to be excluded because of uninterpretable signals. The following mechanisms were identified in the remaining 30 patients (45 events): a sudden change in skin perfusion but without hypoxemia (6 in 5 patients), hypoxemia induced by an epileptic seizure (6 in 5 patients), hypoxemia induced by suffocation by a parent (4 in 4 patients), and parental fabrication of events and medical history (7 in 6 patients). In the remaining 22 events in 12 patients, the precise mechanism of events could not be identified. Analysis of these as-yet-unexplained events showed prolonged abnormal hypoxemia (a fall in transcutaneous oxygen pressure to between 4 and 18 mm Hg and a fall in arterial oxygen saturation to 5% to 75%), lasting for 40 to 500 seconds in all. Only five of these events involved prolonged (> 20 seconds) apneic pauses, and only four an episode of bradycardia (heart rate < 80 or 60 beats/min). Thus event recording identified various mechanisms of apparent life-threatening events. In the events that remained unexplained, prolonged apneic pauses or episodes of bradycardia were found in only a minority. The identification of hypoxemia therefore may be more relevant to the early detection of these events than the identification of apnea or bradycardia or both. The relevance of these findings with regard to sudden infant death syndrome remains to be determined.

Apnea↗
PubMed2005

Chronic multiunit recordings in behaving animals: advantages and limitations.

By simultaneous recording from neural responses at many different loci at the same time, we can understand the interaction between neurons, and thereby gain insight into the network properties of neural processing, instead of the functioning of individual neurons. Here we will discuss a method for recording in behaving animals that uses chronically implanted micro-electrodes that allow one to track neural responses over a long period of time. In a majority of cases, multiunit activity, which is the aggregate spiking activity of a number of neurons in the vicinity of an electrode tip, is recorded through these electrodes, and occasionally single neurons can be isolated. Here we compare the properties of multiunit responses to the responses of single neurons in the primary visual cortex. We also discuss the advantages and disadvantages of the multiunit signal as opposed to a signal of single neurons. We demonstrate that multiunit recording provides a reliable and useful technique in cases where the neurons at the electrodes have similar response properties. Multiunit recording is therefore especially valuable when task variables have an effect that is consistent across the population of neurons. In the primary visual cortex, this is the case for figure-ground segregation and visual attention. Multiunit recording also has clear advantages for cross-correlation analysis. We show that the cross-correlation function between multiunit signals gives a reliable estimate of the average single-unit cross-correlation function. By the use of multiunit recording, it becomes much easier to detect relatively weak interactions between neurons at different cortical locations.

Animals↗
PubMed2001

Recording of electroneurograms from the nerves innervating the pancreas of a dog.

Electroneurograms (ENGs) from the vagus, splanchnic and pancreatic nerves innervating the pancreas of a dog, were recorded with chronically implanted silicone multi-electrode circular cuffs in an intact pancreas and in a pancreas partly disabled with alloxan. The cuffs contained 33 platinum electrodes (0.6x1.5 mm) arranged in three parallel circular groups integrated into the inner surface of the cuff. Each circular group contained 11 electrodes at a distance of 0.5 mm apart, with 6 mm between the circular groups. The cuffs had an inner diameter of 2.5 mm and the length of 18 mm. In a 2-year study, the cuffs were implanted into two adult Beagle dogs (one female and one male). In the vagus nerve, the cuff was installed on the nerve at the neck, whilst in the splanchnic nerve, the cuff was installed on the nerve before the celiac ganglion, and in the pancreatic nerve, the cuff was installed on the nerve just before it enters the pancreas. In each of the three implanted cuffs, the electrodes of the central circular group were connected to each other and this signal provided one input to a multi-channel ENG amplifying system. The electrodes of each of the two outer spiral groups were connected to each other and then both these groups were short-circuited. This signal then provided another input to the multi-channel ENG amplifying system. The ENG amplifying system was designed to amplify the ENGs 100000 times and to pass frequencies of between 500 and 10 kHz. In our study, three recordings in each animal were conducted. Recordings in the intact pancreas were conducted 2 and 6 months after the implantation, while the recording in the partly disabled pancreas, was conducted 10 months after the implantation and 10 days after the disablement. Due to the fact that the results obtained in both animals were actually quite similar, we present the results of the recordings obtained in one animal. In both animals the cuffs were left implanted for more than 1 year and were used for pancreatic stimulation, although this is not in this paper. The results show that cuffs implanted chronically on the nerves innervating the pancreas of a dog could reliably record the ENGs. This information could be used effectively in further study of pancreatic innervation and its function. Moreover, the results suggest that cuffs could also be useful in recording the ENGs from other nerves of the autonomic nervous system that innervate various glands and internal organs.

Action Potentials↗
PubMed2003

A simple and effective process for noise reduction of multichannel cortical field potential recordings in freely moving rats.

Simple and useful steps, i.e. placing a grounded plate under the recording chamber as well as using multiple reference electrodes, are introduced here for obtaining reliable low-noise recordings of brain activity in freely moving rats. A general circuit model was built to analyze the electrical interference of both single-grounded and two-reference ground-free recording configurations. In both simulated and realistic conditions under two recording states, 60-Hz magnitude was in the microvolt range. Moreover, the noise was significantly reduced by shortening the distance between the subject and the grounded plate under the recording chamber. Furthermore, in chronically implanted rats, average 60-Hz interference of multichannel electroencephalograms of two-reference ground-free recordings (3.74 +/- 0.18 microV) was significantly smaller than that of the single-grounded condition (9.03 +/- 1.98 microV). Thus, we demonstrated that a lower-noise recording can be achieved by a two-reference configuration and a closely-placed metal grounded plate in an open-field circumstance. As compared to the use of a Faraday cage, this simple procedure is of benefit for long-term behavioral tracking with a video camera and for pharmacological experiments.

Action Potentials↗
PubMed2003

A micromachined silicon multielectrode for multiunit recording.

A 16-channel multielectrode was used to record propagating action potentials from multiple units in the ventral nerve cord of the cricket Gryllus bimaculatus. The multielectrode was fabricated using photolithographic and bulk silicon etching techniques. The fabrication differs from standard methods in its use of deep reactive ion etching (DRIE) to form the bulk electrode structure. This technique enables the fabrication of relatively thick (>100 microm), rigid structures whose top surface can have any form of thin film electronics. The multielectrode tested in this paper consists of 16 narrow silicon bridges, 150 microm wide and 350 microm tall, spaced evenly over a centimeter, with passive rectangular gold recording sites on the top surface. The nerve cord was placed perpendicularly across the bridges. In this geometry, the nerve spans a 350 microm deep, 450 microm wide trench between each recording site, permitting adequate isolation of recording sites from each other and a platinum ground plane. Spike templates for eight neurons were formed using principle component analysis and clustering of the concatenated multichannel waveforms. Clean templates were generated from a 40 s recording of stimulus evoked activity. Conduction velocities ranged from 2.59+/-0.05 to 4.99+/-0.12 m/s. Two limitations of extracellular electrode arrays are the resolution of overlapping spikes and relation of discriminated units to known anatomy. The high density, precise positioning, and controlled impedance of recording sites achievable in microfabricated devices such as this one will aid in overcoming these limitations. The rigid devices fabricated using this process offer stable positioning of recording sites over relatively large distances (several millimeters) and are suitable for clamping or squeezing of nerve cords.

Action Potentials↗
PubMed2003

Magnetic resonance image-guided implantation of chronic recording electrodes in the macaque intraparietal sulcus.

The implantation of chronic recording electrodes in the brain has been shown to be a valuable method for simultaneously recording from many neurons. However, precise placement of these electrodes, crucial for successful recording, is challenging if the target area is not on the brain surface. Here we present a stereotaxic implantation procedure to chronically implant bundles of recording electrodes into macaque cortical sulci, employing magnetic resonance (MR) imaging to determine stereotaxic coordinates of target location and sulcus orientation. Using this method in four animals, we recorded simultaneously the spiking activity and the local field potential from the parietal reach region (PRR), located in the medial bank of the intraparietal sulcus (IPS), while the animal performed a reach movement task. Fifty percent of all electrodes recorded spiking activity during the first 2 post-operative months, indicating their placement within cortical gray matter. Chronic neural activity was similar to standard single electrode recordings in PRR, as reported previously. These results indicate that this MR image-guided implantation technique can provide sufficient placement accuracy in cortical sulci and subcortical structures. Moreover, this technique may be useful for future cortical prosthesis applications in humans that require implants within sulci.

Anesthesia, General↗