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PubMedDate not supplied

A comparison of two single-headed and two multi-headed allergen skin test devices.

Given the potential differences in performance of skin test devices, the purpose of this study was to prospectively assess the performance of two single-headed and two multiheaded devices for allergy skin testing in terms of wheal size, sensitivity, specificity, intradevice variability, and pain level. Two single-headed devices (Greer Pick, Duotip-Test) and two multiheaded devices (Multi-Test II, OMNI) were tested in 15 subjects in a prospective partially blind fashion looking at wheal reactions and pain using histamine and glycerol-saline on the arms and back. Differences among devices in wheal size and pain were noted. Sensitivity, specificity, and intradevice variability were calculated. Differences between corner and interior heads in multiheaded devices were analyzed. No significant differences were observed in wheal size between Greer Pick (7.1+/-1.4 mm) and Duotip-Test (7.2+/-1.6 mm). Multiheaded devices were significantly different in wheal size compared with each other and to the single-headed devices (Multi-Test II, 5.4+/-1.7 mm; OMNI, 3.3+/-1.2 mm). Single-headed devices were more sensitive (100% each, 95% CI of 92-100%) than the multiheaded devices. Multi-Test II was significantly more sensitive (83%, 95% CI of 78-87%) than OMNI (57%, 95% CI of 51-62%). There was significant intradevice variability for the multiheaded devices with corner heads being significantly more sensitive than interior heads. Specificities for all devices were equally good (-97%). Pain was greater for multiheaded devices than single-headed devices but was generally mild. In conclusion, this study supports the idea that single-headed devices may be more sensitive and consistent than multiheaded devices. Multi-Test II is more sensitive than OMNI. In multiheaded devices, corner heads are more sensitive than interior heads.

Adolescent↗
PubMed1989

The role of the long head of biceps brachii in the stabilization of the head of the humerus.

The role of the tendon of the long head of the biceps in the stabilization of the head of the humerus was studied in 15 freely hanging anatomic specimen shoulders. Upward migration of the humeral head was measured by noting any reduction in the acromiohumeral distance in roentgenograms of the shoulder. There was a statistically significant decrease in the acromiohumeral interval on tensing the short head of biceps, but there was no significant change in the interval on tensing either the long head or both heads of the biceps brachii. Severing the tendon of the long head while both the heads were tensed caused a significant upward migration of the head of the humerus. One of the important functions of the long head of the biceps is to stabilize the humeral head in the glenoid during powerful elbow flexion and forearm supination by the main muscle. Sacrifice of the intraarticular segment of this tendon in surgical procedures of the shoulder may produce instability and dysfunction.

Arm↗
PubMed1989

[Analysis of the work of the head nurse and a work model for the head nurse in university hospitals in Korea].

When the head nurse who is pivotal in the nursing service administration of the hospital performs efficiently as a first-line manager, the effectiveness of the nursing unit, which includes the quality of nursing care, the job satisfaction of staff members, and the cohesiveness of staff members is increased. With this point of view in mind, the researcher carried out a study to determine the actual work (the content of the work, the work process, the role of the head nurse, the activity media, and the purpose of the work) of the head nurse in a university hospital in Korea. In addition, this study was also carried out for the purpose of preparing an ideal model for the work of the head nurse. The research subjects were 39 head nurses. This included all the head nurses in two university hospitals except those who were working in outpatient care, operating rooms, central supply, nursing administration, in-service education and emergency care. Data were collected from September 24th to October 21st, 1987 and April 4th to 12th, 1988. A work activity record on which the head nurse recorded directly in a chronological narrative form, was used as the research instrument. The 234 work activity records, 39 head nurse's continuous recording over 6 days (from Monday to Saturday) were collected and analysed. The results were as follows: 1. With regard to the work content for the total daily work of the head nurse, 45.2% of the activities were managerial activities but 58.1% of the head nurse's time was spent in direct patient care. 2. With regard to the work process of the head nurse, specifically the location, the size and membership of groups contacted, the results were as follows: 1) Of the total daily work activities 92.4% were carried out in the nursing unit and this occupied 84. 5% of total daily work time. Direct patient care was generally performed on the nursing unit and managerial work was performed in other areas. 2) Of the total daily work activities, 73% was with one or more persons and 51.2% of total daily work time was spent in groups. 3) A total of 51 persons, working in different capacities were contacted. These included 21 persons giving patient care, 19 persons working in nursing unit management, and 7 persons working in human resource management.(ABSTRACT TRUNCATED AT 400 WORDS)

Hospitals, University↗
PubMed1994

Head surface digitization and registration: a method for mapping positions on the head onto magnetic resonance images.

We have developed a method for mapping positions on the head, such as anatomical landmarks, electrode locations, and stimulation sites, onto magnetic resonance (MR) images of the head. This method is based on the registration of two representations of the head surface: a series of contours obtained from MR images and a set of points measured from the head. The three-dimensional coordinates of each head point were acquired with the use of a magnetic digitizer, whose source was removed from the equipment and mounted on top of the subject's head. This arrangement seemed less uncomfortable for the subject than head immobilization and allowed the acquisition of many points without compromising the precision of the measurements. The digitized head surface was registered to MR image head contours using a surface registration algorithm. The registration provided the rotation and translation parameters needed for mapping head positions onto MR images. The precision of this mapping method has been estimated to be in the range of 3 to 8 mm. This method has been used to map dipole sources in electroencephalography and magneto-encephalography and to impose maps of scalp sites used in transcranial magnetic stimulation onto MR and PET images of the brain.

Adult↗
PubMed1999

Preoperative assessment of cervical lymph nodes in head and neck cancer with fluorine-18 fluorodeoxyglucose using a dual-head coincidence camera: a pilot study.

The aim of this study was to investigate whether in patients with head and neck cancer, staging is possible with fluorine-18 fluorodeoxyglucose (18F-FDG) using a dual-head positron emission tomography (PET) camera. Twenty patients (ten men, ten women; mean age: 60 years) were studied using 185 MBq (5 mCi) 18F-FDG. Two of these patients who were suspected of having recurrence in the neck were restaged 19 and 12 months, respectively, after the resection of the primary tumour. The images were visually analyzed and the results were correlated with computed tomography (CT) (n = 18), ultrasonography (n = 17) and pathological findings. With respect to the primary tumour, FDG dual-head PET and CT revealed a sensitivity of 100% and 59%, respectively (P < 0.001). In seven patients lymph node metastases were found in the neck specimen. Two of them had bilateral metastases. FDG dual-head PET correctly identified all nine pathological neck sides whereas CT and ultrasonography depicted eight of nine and seven of eight pathological sides, respectively. In three patients, false-positive FDG uptake was seen, which was due to a preceding biopsy in two cases. The sensitivity of FDG dual-head PET, CT and ultrasonography in the identification of pathological neck sides was 100%, 89% and 87%, respectively, and the specificity was 90%, 93% and 50%, respectively. With knowledge of the preceding biopsies, the specificity of FDG dual-head PET would have been 97%. The smallest lymph node metastasis detected by FDG dual-head PET that was missed by CT had a diameter of 0.6 cm. Measurement of 18F-FDG with a dual-head PET camera is very sensitive in the detection of primary head and neck cancers and accurate in the preoperative assessment of lymph node metastases. The results justify a prospective study on the identification of metastases in patients with head and neck cancer. In addition, it is justified to start a study on the detection of unknown primary tumours in patients with cervical metastases.

Carcinoma, Squamous Cell↗
PubMed2002

Consequences of head size following trauma to the human head.

The objective of the present study was to evaluate whether variation of human head size results in different outcome regarding intracranial responses following a direct impact. Finite Element models representing different head sizes and with various element mesh densities were created. Frontal impacts towards padded surfaces as well as inertial loads were analyzed. The variation in intracranial stresses and intracranial pressures for different sizes of the geometry and for various element meshes were investigated. A significant correlation was found between experiment and simulation with regard to intracranial pressure characteristics. The maximal effective stresses in the brain increased more than a fourfold, from 3.6kPa for the smallest head size to 16.3kPa for the largest head size using the same acceleration impulse. When simulating a frontal impact towards a padding, the head injury criterion (HIC) value varies from the highest level of 2433 at a head mass of 2.34kg to the lowest level of 1376 at a head mass of 5.98kg, contradicting the increase in maximal intracranial stresses with head size. The conclusion is that the size dependence of the intracranial stresses associated with injury, is not predicted by the HIC. It is suggested that variations in head size should be considered when developing new head injury criteria.

Brain↗
PubMed2003

Head-elevated laryngoscopy position: improving laryngeal exposure during laryngoscopy by increasing head elevation.

STUDY OBJECTIVE: The objective of this study was to determine the effect of increasing head elevation and neck flexion on the quality of laryngeal view during laryngoscopy. METHODS: Laryngoscopy with a straight blade was performed on 7 fresh human cadavers. Laryngeal views were recorded with the direct laryngoscopy video system, and the laryngoscopy angle was measured throughout the procedure with an angle finder attached to the handle of the laryngoscope. Each cadaver had laryngoscopy initiated with the head lying flat on the table and with atlanto-occipital extension. The head was then progressively elevated as much as possible (the head-elevated laryngoscopy position), increasing neck flexion and the laryngoscopy angle. Three physicians blinded to the laryngoscopy angle graded the quality of laryngeal view using the percentage of glottic opening (POGO) score. RESULTS: The laryngoscopy angle ranged from a mean of 32 degrees +/-8 degrees (1 SD) with the head flat on the table to a mean of 67 degrees +/-8 degrees with the head-elevated laryngoscopy position. The mean midposition laryngoscopy angle was 49 degrees +/-6 degrees. Comparing the 3 positions, mean POGO scores+/-1 SD significantly increased from 31%+/-10% (flat position) to 64%+/-12% (midposition) to 87%+/-13% (head-elevated laryngoscopy position). Both the midposition and the head-elevated laryngoscopy position compared with the flat position were statistically significant at a P value of less than.0001. The midposition also differed significantly from the head-elevated laryngoscopy position (P <.0007). Additionally, there was a significant linear relationship among the 3 positions (P <.0001). CONCLUSION: Increasing head elevation and laryngoscopy angle (neck flexion) significantly improves POGO scores during laryngoscopy on fresh human cadavers.

Cadaver↗
PubMed1995

Natural head position and natural head orientation: basic considerations in cephalometric analysis and research.

Natural head position (NHP) provides the key for meaningful cephalometric analysis because an extracranial reference line is used instead of intracranial reference lines, known to be subject to considerable biological variation in their inclination. Although the principle of natural head position is being recognized in the orthodontic literature, its registration may contain an element of unavoidable error that requires correction. A new concept of natural head orientation (NHO) has been introduced to maximize the contribution of NHP to cephalometrics. It is defined as the head orientation of the subject perceived by the clinician, based on general experience, as the natural head position in a standing, relaxed body and head posture, when the subject is looking at a distant point at eye level. The present study was designed to determine the accuracy and validity of NHO, using lateral profile photographs cut in a circular shape, obtained from 27 orthodontic patients, 10-14 years old. Findings among four investigators showed a high correlation (r = 0.82-0.96), in orientating these profile photographs in estimated natural head position (NHP). Moreover, investigators showed good correlation (r = 0.57-0.84) in head orientation after a 3-week interval. Mean differences for the same period varied between 0.1 and 2.9 degrees. The validity of NHO was supported also by a panel investigation. Clinicians as well as auxiliary personnel can be trained to make a critical judgement of the recorded natural head position and correct head orientation, whenever indicated, to enhance the reliability of cephalometric analysis in clinical practice and research.

Adolescent↗
PubMed2005

Impact of patient race on receiving head CT during blunt head injury evaluation.

OBJECTIVES: Prior evidence suggests that physicians may alter process of care based on race/ethnicity. The objective of this study was to determine whether race/ethnicity predicts whether a patient receives computed tomography of the head (head CT) during evaluation of blunt head injury. METHODS: This was a nonconcurrent cohort study set in an emergency department of a Level 1 trauma center in a university medical center. Consecutive patients presenting with blunt head injury from January 2000 to December 2000 were enrolled. The main outcome measure was whether or not a patient received head CT during evaluation of blunt head injury. RESULTS: The unadjusted probability of receiving head CT was similar among minority (33.9%; 95% confidence interval [CI] = 30.0% to 38.1%) and non-Hispanic white patients (36.4%; 95% CI = 33.5% to 39.3%). After adjusting for important clinical and socioeconomic predictors, minority patients had a probability of receiving head CT 0.84 times as high as that of non-Hispanic whites, but this result was not statistically significant (95% CI = 0.67 to 1.09). CONCLUSIONS: Minority and non-Hispanic white patients may not have significantly different rates of receiving head CT during evaluation of blunt head injury. A multicenter prospective study is necessary to confirm these preliminary findings.

Adult↗
PubMed2003

Linear and angular head accelerations during heading of a soccer ball.

PURPOSE: Cognitive deficits observed in professional soccer players may be related to heading of a soccer ball. To assess the severity of a single instance of heading a soccer ball, this study experimentally and theoretically evaluated the linear and angular accelerations experienced by the human head during a frontal heading maneuver. METHODS: Accelerations were measured using a set of three triaxial accelerometers mounted to the head of each of four adult male subjects. These measurements (nine signals) were used to estimate the linear acceleration of the mass center and the angular acceleration of the head. Results were obtained for ball speeds of 9 and 12 m.s(-1) (approximately 20 and 26 mph). A simple mathematical model was derived for comparison. RESULTS: At 9 m.s(-1), peak linear acceleration of the head was 158 +/- 19 m.s(-2) (mean +/- standard deviation) and peak angular acceleration was 1302 +/- 324 rad.s(-2); at 12 m.s(-1), the values were 199 +/- 27 m.s-2 and 1457 +/- 297 rad.s-2, respectively. The initial acceleration pulses lasted approximately 25 ms. Measured head accelerations confirmed laboratory headform measurements reported in the literature and fell within the ranges predicted by the theoretical model. CONCLUSIONS: Linear and angular acceleration levels for a single heading maneuver were well below those thought to be associated with traumatic brain injury, as were computed values of the Gadd Severity Index and the Head Injury Criterion. However, the effect of repeated acceleration at this relatively low level is unknown.

Acceleration↗
PubMed2000

[Transposition of muscular skeletal flap pedicled with straight head of rectus femoris for treatment of avascular necrosis of femoral head].

OBJECTIVE: To investigate the clinical results of transposition of muscular skeletal flap pedicled with straight head of rectus femoris for treatment of avascular necrosis of adult femoral head. METHODS: Eight patients with avascular necrosis of femoral head were adopted in this study. There were 6 males and 2 females, the ages were ranged from 24 to 56 years. According to the criteria of Ficat, there were 5 cases in stage II and 3 cases in stage III. The Smith-Peterson incision was used to expose the capsule of the hip. After complete curettage of the necrotic bone from the femoral head, the muscular skeletal flap pedicled with straight head of rectus femoris was resected and transposited into femoral head. Finally, conventional decompression of head was performed. RESULTS: All the cases were followed up for 1 to 3 years. There were excellent results in 5 cases, good in 2 cases and moderate in 1 case. The rate of excellent and good results were 87.5%. CONCLUSION: Comparing with other pedicled bony flaps, the muscular skeletal flap pedicled with straight head of rectus femoris is characterized by its convenience and efficacy. It is suitable for the treatment of avascular necrosis of femoral head in stage II or III, but the contour of the femoral head should be nearly normal.

Adult↗
PubMed2004

Dissociation of double-headed cytoplasmic dynein into single-headed species and its motile properties.

Cytoplasmic dynein is a minus-end directed microtubule motor and plays important roles in the transport of various intracellular cargoes. Cytoplasmic dynein comprises two identical heavy chains and forms a dimer (double-headed dynein); the total molecular weight of the cytoplasmic dynein complex is about 1.5 million. The dynein motor domain is structurally very different from those of kinesin and myosin, and our understanding of the mechanisms of dynein energy transduction is limited mainly because of the difficulty in obtaining a sufficient quantity of purified and active cytoplasmic dynein. We purified cytoplasmic dynein, which was free from dynactin and other dynein-associated proteins. The purified cytoplasmic dynein was active in an in vitro motility assay. The controlled dialysis of the purified dynein against 4 M urea resulted in its complete dissociation into monomeric species (single-headed dynein). The separation of the dynein heads by the treatment was reversible. The MgATPase activities of the single-headed and reconstituted double-headed dynein were comparable to that of intact dynein. The double-headed dynein bundled microtubules in the absence of ATP; the single-headed dynein did not. The single-headed dynein produced in vitro microtubule-gliding motility at velocities very similar to those of double-headed dynein at various ATP concentrations. These results indicate that a single cytoplasmic dynein heavy chain is sufficient to produce robust microtubule motility. Application of the double- and single-headed dynein molecules in various assay systems will elucidate the mechanism of action of the cytoplasmic dynein.

Animals↗
PubMed2002

Holding two heads together: stability of the myosin II rod measured by resonance energy transfer between the heads.

Myosin, similar to many molecular motors, is a two-headed dimer held together by a coiled-coiled rod. The stability of the coiled coil has implications for head-head interactions, force generation, and possibly regulation. Here we used two different resonance energy transfer techniques to measure the distances between probes placed in the regulatory light chain of each head of a skeletal heavy meromyosin, near the head-rod junction (positions 2, 73, and 94). Our results indicate that the rod largely does not uncoil when myosin is free in solution, and at least beyond the first heptad, the subfragment 2 rod remains relatively intact even under the relatively large strain of two-headed myosin (rigor) binding to actin. We infer that uncoiling of the rod likely does not play a role in myosin II motility. To keep the head-rod junction intact, a distortion must occur within the myosin heads. This distortion may lead to different orientations of the light-chain domains within the myosin dimer when both heads are attached to actin, which would explain previously puzzling observations and require reinterpretation of others. In addition, by comparing resonance energy transfer techniques sensitive to different dynamical time scales, we find that the N terminus of the regulatory light chain is highly flexible, with possible implications for regulation. An intact rod may be a general property of molecular motors, because a similar conclusion has been reached recently for kinesin, although whether the rod remains intact will depend on the relative stiffness of the coiled coil and the head in different motors.

Actins↗
PubMed2004

Perception of the vertical with a head-mounted visual frame during head tilt.

This study addressed the question of potential disorienting effects associated to head-mounted displays, by investigating the influence of a head-fixed visual frame on the perception of the vertical when the head is tilted in the frontal plane. Subject performance in indicating the vertical was contrasted with the effect of an earth-fixed visual frame as well as with the effect of tilting the head without a frame. With the tilted frames, subjects set the rod in an intermediate direction between the gravitational vertical and the orientation of the frame. Errors were strikingly larger with a head-fixed visual frame during head tilt than with a tilted earth-based frame. The increased effect cannot be attributed to the addition of a postural effect, due to the head being tilted. Moreover, continuous vision of the frame when its orientation changed improved performance only when the head and the frame were dissociated, i.e., with an earth-based frame. Those results suggest that integrating visual information in the head-centric reference frame is crucial for spatial orientation. This property of the perceptual system should be taken into account in the design of head-mounted displays for aeronautics.

Adult↗
PubMed2003

The need for head computed tomography in patients sustaining loss of consciousness after mild head injury.

BACKGROUND: Many management schemes have incorporated mandatory head computed tomography (HCT) to evaluate a patient sustaining blunt head trauma with a history of loss of consciousness (LOC). Commonly, this is despite physical examination findings warranting such a workup. This study is intended to better identify the significance of selective criteria, a set of constitutional signs and symptoms (CSS) for head injury, to screen patients sustaining blunt head trauma and LOC. METHODS: Over a 141/2-month period, data were prospectively collected on adults with a history of LOC and a Glasgow Coma Scale score of 14 to 15. Patients were screened for the presence of 10 typical CSS for head injury at admission before undergoing computed tomography of the head. Data collected also included mechanism of injury and alcohol intoxication. RESULTS: Three hundred thirty-one patients met criteria, of which 195 showed no CSS for head injury. Eleven (5.6%) of these patients were found to have HCT evidence of intracranial injury but resulted in no acute medical intervention. One hundred thirty-six patients had CSS, of which 29 (21.3%) had HCT evidence of injury and resulted in a lengthier hospital stay. CONCLUSION: The liberal use of HCT in patients without CSS for head injury did not influence patient care, with no increase in morbidity or mortality. These results suggest that LOC alone is not predictive of significant head injury and is not an absolute indications for HCT. More objective criteria, such as CSS, should be used before initiating a costly workup where further diagnostic and therapeutic intervention is unlikely after mild head injury.

Adult↗
PubMed2006

Why olanzapine beats risperidone, risperidone beats quetiapine, and quetiapine beats olanzapine: an exploratory analysis of head-to-head comparison studies of second-generation antipsychotics.

OBJECTIVE: In many parts of the world, second-generation antipsychotics have largely replaced typical antipsychotics as the treatment of choice for schizophrenia. Consequently, trials comparing two drugs of this class--so-called head-to-head studies--are gaining in relevance. The authors reviewed results of head-to-head studies of second-generation antipsychotics funded by pharmaceutical companies to determine if a relationship existed between the sponsor of the trial and the drug favored in the study's overall outcome. METHOD: The authors identified head-to-head comparison studies of second-generation antipsychotics through a MEDLINE search for the period from 1966 to September 2003 and identified additional head-to-head studies from selected conference proceedings for the period from 1999 to February 2004. The abstracts of all studies fully or partly funded by pharmaceutical companies were modified to mask the names and doses of the drugs used in the trial, and two physicians blinded to the study sponsor reviewed the abstracts and independently rated which drug was favored by the overall outcome measures. Two authors who were not blinded to the study sponsor reviewed the entire report of each study for sources of bias that could have affected the results in favor of the sponsor's drug. RESULTS: Of the 42 reports identified by the authors, 33 were sponsored by a pharmaceutical company. In 90.0% of the studies, the reported overall outcome was in favor of the sponsor's drug. This pattern resulted in contradictory conclusions across studies when the findings of studies of the same drugs but with different sponsors were compared. Potential sources of bias occurred in the areas of doses and dose escalation, study entry criteria and study populations, statistics and methods, and reporting of results and wording of findings. CONCLUSIONS: Some sources of bias may limit the validity of head-to-head comparison studies of second-generation antipsychotics. Because most of the sources of bias identified in this review were subtle rather than compelling, the clinical usefulness of future trials may benefit from minor modifications to help avoid bias. The authors make a number of concrete suggestions for ways in which potential sources of bias can be addressed by study initiators, peer reviewers of studies under consideration for publication, and readers of published studies.

Antipsychotic Agents↗
PubMed2004

Fractures of the radial head and neck treated with radial head excision.

BACKGROUND: The reported long-term outcomes of the treatment of radial head and neck fractures with excision of the radial head have been mixed. The purpose of the present study was to evaluate the long-term outcomes of primary or delayed radial head excision for the treatment of these fractures. METHODS: Sixty-one individuals (mean age, forty-four years) with thirty-nine Mason type-II, ten Mason type-III, and twelve Mason type-IV fractures were evaluated subjectively, objectively, and radiographically at a mean of eighteen years (range, eleven to thirty-three years) after treatment. Forty-three fractures were treated with primary radial head excision, and the remaining eighteen were treated with delayed radial head excision at a median of five months (range, one to 238 months) after the injury. RESULTS: At the time of follow-up, twenty-eight individuals had no symptoms, twenty-seven had occasional elbow pain, and six had daily pain. Four individuals with daily pain had had a Mason type-IV fracture. The range of motion of the formerly injured upper extremities was slightly less than that of the uninjured upper extremities in terms of flexion (139 degrees +/- 11 degrees compared with 142 degrees +/- 8 degrees ), extension (-7 degrees +/- 12 degrees compared with -1 degrees +/- 6 degrees ), and supination (77 degrees +/- 20 degrees compared with 85 degrees +/- 10 degrees ) (all p < 0.01). A higher percentage of formerly injured elbows than uninjured elbows had cysts, sclerosis, and osteophytes (73% compared with 7%; p < 0.001), but none had a reduced joint space. No differences were found between the outcomes for individuals treated with a primary radial head excision and those for individuals treated with a delayed excision. CONCLUSIONS: Following a displaced radial head or neck fracture, excision of the radial head often leads to a good or fair result. We found no differences in outcome between primary and delayed radial head excisions following a Mason type-II, III, or IV fracture. The outcomes are associated with the type of fracture, with Mason type-IV fractures having the worst results, rather than with the timing of the radial head excision (primary or delayed).

Adolescent↗
PubMed2000

Comparing extraocular motoneuron discharges during head-restrained saccades and head-unrestrained gaze shifts.

Burst neurons (BNs) in the paramedian pontine reticular formation provide the primary input to the extraocular motoneurons (MNs) during head-restrained saccades and combined eye-head gaze shifts. Prior studies have shown that BNs carry eye movement-related signals during saccades and carry head as well as eye movement-related signals during gaze shifts. Therefore MNs receive signals related to head motion during gaze shifts, yet they solely drive eye motion. Here we addressed whether the relationship between MN firing rates and eye movements is influenced by the additional premotor signals present during gaze shifts. Neurons in the abducens nucleus of monkeys were first studied during saccades made with the head stationary. We then recorded from the same neurons during voluntary combined eye-head gaze shifts. We conclude that the activity of MNs, in contrast to that of BNs, is related to eye motion by the same dynamic relationship during head-restrained saccades and head-unrestrained gaze shifts. In addition, we show that a standard metric-based analysis [i.e., counting the number of spikes (NOS) in a burst] yields misleading results when applied to the same data set. We argue that this latter approach fails because it does not properly consider the system's dynamics or the strong interactions between eye and head motion.

Animals↗