ABSTRACT
How do we see the motion of objects as well as their shapes? The Gaussian Derivative (GD) spatial model is extended to time to help answer this question. The GD spatio-temporal model requires only two numbers to describe the complete three-dimensional space-time shapes of individual receptive fields in primate visual cortex. These two numbers are the derivative numbers along the respective spatial and temporal principal axes of a given receptive field. Nine transformation parameters allow for a standard geometric association of these intrinsic axes with the extrinsic environment. The GD spatio-temporal model describes in one framework the following properties of primate simple cell fields: motion properties, number of lobes in space-time, spatial orientation. location, and size. A discrete difference-of-offset-Gaussians (DOOG) model provides a plausible physiological mechanism to form GD-like model fields in both space and time. The GD model hypothesizes that receptive fields at the first stage of processing in the visual cortex approximate 'derivative analyzers' that estimate local spatial and temporal derivatives of the intensity profile in the visual environment. The receptive fields as modeled provide operators that can allow later stages of processing in either a biological or machine vision system to estimate the motion as well as the shapes of objects in the environment.
Subject(s)
Models, Psychological , Motion Perception/physiology , Space Perception/physiology , Visual Cortex/physiology , Animals , Humans , Normal DistributionABSTRACT
Receptive fields of simple cells in the primate visual cortex were well fit in the space and time domains by the Gaussian Derivative (GD) model for spatio-temporal vision. All 23 fields in the data sample could be fit by one equation. varying only a single shape number and nine geometric transformation parameters. A difference-of-offset-Gaussians (DOOG) mechanism for the GD model also fit the data well. Other models tested did not fit the data as well as or as succinctly, or failed to converge on a unique solution, indicating over-parameterization. An efficient computational algorithm was found for the GD model which produced robust estimates of the direction and speed of moving objects in real scenes.
Subject(s)
Models, Psychological , Motion Perception/physiology , Space Perception/physiology , Visual Cortex/physiology , Animals , Humans , Normal DistributionABSTRACT
A conceptual model and objective scale for measuring resistiveness to care in individuals with advanced dementia of the Alzheimer type (DAT) were empirically generated from the perspective of nursing staff caregivers and through observation of residents with DAT. The resistiveness to care scale (RTC-DAT) was judged to have content validity and reduced to 13 items. Quantifiable scoring procedures and methods for rating videotapes and conducting clinical observations were developed. The RTC-DAT was tested with 68 subjects at three sites. The RTC has a range of 0-156. Initial testing provided reliability estimates of .82-.87 for internal consistency and good to excellent kappas. Criterion-related validity with observed discomfort and construct validity by factor analysis support the RTC-DAT. Measurement issues and recommendations for use in research are discussed.
Subject(s)
Agonistic Behavior , Alzheimer Disease/nursing , Alzheimer Disease/psychology , Geriatric Assessment , Nursing Assessment/methods , Treatment Refusal/psychology , Activities of Daily Living , Aged , Factor Analysis, Statistical , Humans , Models, Nursing , Nursing Methodology Research , Nursing Staff/psychology , Psychometrics , Reproducibility of Results , Sensitivity and Specificity , Videotape RecordingSubject(s)
Emergencies , Legislation, Veterinary , Liability, Legal , Animals , Canada , Emergencies/veterinary , HumansABSTRACT
STUDY OBJECTIVE: To determine whether intracranial hemorrhage is a predictor of occult cervical-spine fracture. DESIGN: A prospective, cross-sectional study. SETTING: University-affiliated Level I trauma center. PARTICIPANTS: Ninety-three blunt trauma victims with a Glasgow Coma Scale score of 12 or less. Exclusion criteria were incomplete radiographic evaluation caused by hemodynamic instability, death, or other reasons. INTERVENTIONS: The study protocol required that all patients undergo a five-view cervical-spine trauma series, head computed tomography (CT), and upper cervical-spine CT. Cervical-spine radiographs and CT scans were read by two radiologists blinded to each other's interpretations. The results were compared with each patient's head CT diagnosis. Medical records were reviewed for demographic information and mechanism of injury. RESULTS: Of the 93 patients, 54 had intracranial hemorrhage noted on CT scan; two of these patients had an upper cervical-spine fracture, but only one was an occult cervical-spine fracture. Thirty-nine patients had no intracranial hemorrhage; two patients had an upper cervical-spine fracture, but only one had an occult cervical-spine fracture. Fisher's exact test showed no significant difference between the rate of occult cervical-spine fracture between patients with and without hemorrhage. CONCLUSION: Despite a high percentage of patients with traumatic intracranial hemorrhage, our study failed to demonstrate that intracranial hemorrhage is predictor of occult cervical-spine fracture.
Subject(s)
Cerebral Hemorrhage/etiology , Cervical Vertebrae/injuries , Spinal Fractures/complications , Adolescent , Adult , Aged , Cerebral Hemorrhage/diagnosis , Cerebral Hemorrhage/diagnostic imaging , Child , Child, Preschool , Cross-Sectional Studies , Female , Glasgow Coma Scale , Hematoma, Epidural, Cranial/complications , Hematoma, Subdural/complications , Humans , Infant , Male , Middle Aged , Probability , Prospective Studies , Radiography , Spinal Fractures/diagnosis , Subarachnoid Hemorrhage/complicationsSubject(s)
Gallstones/etiology , Hemostasis, Surgical/instrumentation , Iatrogenic Disease , Pancreatitis/etiology , Adult , Female , HumansABSTRACT
A 62-year-old woman had symptoms of cough provoked by ingestion of liquids and radiologic changes compatible with repeated bouts of aspiration pneumonitis. A left bronchoesophageal fistula was easily demonstrated by barium esophagogram and fiberoptic bronchoscopy. Division of the fistula resulted in immediate disappearance of the symptoms, gradual resolution of the radiologic abnormalities, and marked improvement in the results of pulmonary function tests. The fistula appeared to be of congenital origin, but the reason that symptoms developed so late in life remains obscure.
