Massive pulmonary thromboembolism in six horses.

This report involves 6 cases in which medical records and post mortem findings were reviewed leading to the diagnosis of massive pulmonary thromboembolism (MPTE). All horses were mature and MPTE has not been recognised previously as a sequel to generalised systemic illness in mature horses. The clinical data and pathological findings of the cases are reported and the authors conclude that MPTE is an uncommon but important complication of medical and surgical disorders in mature horses. In 3 of the cases, the condition was nonfatal suggesting that some horses having developed PTE survive and the condition may not be recognised in such cases. The incidence of the condition might be higher than supposed.

Magnetic resonance imaging of the brain of normal neonatal foals.

Magnetic resonance imaging (MRI) was performed on the brain of 5 normal, anesthetized, neonatal (age 3-to-6 days) Quarter Horse foals. The objectives of the study were to develop a technique for imaging the brain of neonatal foals, and to ascertain their normal brain anatomy. Intravenous propofol was administered for induction and maintenance of general anesthesia. Using spin echo MR techniques, T1 weighted sagittal and transverse views, and spin density and T2 weighted transverse views were successfully made of each foal. MR images provided excellent visualization of many anatomic structures of the brain and head. MRI of the brain is feasible for selected neonatal equine patients.

Parasitic dermatoses that cause pruritus in horses.

Insect hypersensitivity is the most common cause of equine pruritus. It is a seasonal, highly pruritic dermatosis that is caused by the salivary antigens of biting insects. The most common insects are discussed in terms of the area of the horse affected, clinical signs, therapy, and preventative strategies.

Fifty months of memory: a longitudinal study in early childhood.

Three studies were conducted to evaluate long-term memory longitudinally. In Study 1, 10-month-olds (N = 20) were taught to operate a toy in their homes and were tested at home after four months, as were age-matched (14 months) inexperienced controls (N = 20). Experienced infants were more willing to remain in the play situation, relearned faster than controls, and one operated the toy spontaneously. In Study 2, conducted 18 months thereafter, two subgroups (N = 5) of Study 1 groups and an age-matched (32 months) control group (N = 5) were observed in a lab playroom. Only the children with experiences at both 10 months and 14 months operated the toys without being shown. Children with a single 14-month experience made equivalent numbers of toy contacts and successful responses, however, and both groups exceeded controls. In Study 3, conducted 2+ years after Study 2, 36 children played in a novel playroom. Subgroups differed in amount and timing of experience (in Studies 1 and 2); a naive age-matched (60 months) control group (N = 6) was added. Controls took longer to make the toy work than children in the combined experience groups. Only experienced children elected to operate the toys later in the session. Two children verbally recalled part of the 10-month event. The findings are discussed in the light of their relevance to the assessment and description of memory during early childhood.

Object representation guides infants' reaching in the dark.

Infants were presented with two sounding objects of different sizes in light and dark, in which sound cued the object's identity. Reaching behavior was assessed to determine if object size influenced preparation for grasping the object. In both light and dark, infants aligned their hands when contacting the large object compared with the small object, which resulted in a reach with both hands extended for the large object and reach with one hand more extended for the small object. Infants contacted the large object more frequently on the bottom and sides rather than the top, where the sound source was located. Reaching in the dark by 6 1/2-month-olds is not merely directed toward a sound source but rather shows preparation in relation to the object's size. These findings were interpreted as evidence that mental representation of previously seen objects can guide subsequent motor action by 6 1/2-month-old infants.

Long-term memory for a single infancy experience.

Children's memory of a single infant experience was evaluated. Children in the experimental groups (N = 16 for 2.5-year-olds; N = 8 for 1.5-year-olds) had participated at 6.5 months in a study of auditory localization where they reached in the light and dark for a sounding object. They were reintroduced to the laboratory and the dark procedure they had experienced on that one occasion either 1 or 2 years previously. The first 5 trials were uninstructed; for the remaining 5 trials, children were instructed to find the sounding object. For half of the older group, a potential reminder of the infant procedure was introduced. The original infant rattle was sounded for 3 sec out of reach in the dark one-half hour prior to test trials. Equal numbers of age-matched inexperienced control subjects were also tested. The older children with infant experience reached and grasped the sounding object significantly more overall, and on instructed trials, than age-matched control children. Experienced 2.5-year-olds were also more likely to remain in the testing situation than children in the control group. The reminder facilitated uninstructed performance of the experienced children. Instructions to reach were helpful to all subjects. We conclude that children remembered aspects of a single experience that occurred when they were 6.5 months of age.

Stimulus duration and repetition rate influence newborns' head orientation toward sound.

Three experiments evaluated the effects of stimulus duration and repetition rate on newborns' head orientation responses. In Experiment 1, 28 infants turned toward a 20-sec continuous rattle sound but not toward 14- and 500-msec rattle sounds. Signal energy as a possible explanation for the infants' difficulty orienting toward brief sounds was explored in Experiment 2. Twenty neonates did not turn toward a single 90 dB, 14-msec rattle sound, although a longer duration (10 sec) sound containing less energy (70 dB) did elicit reliable head orientation. In Experiment 3, 16 neonates heard trains of repeated 14-msec rattle sounds (2/sec, 1.3/sec, and 1/sec) lasting 10 sec as well as a 10-sec continuous rattle sound. They turned toward the most rapidly repeating brief sound and the continuous one, while the slowly repeating sounds elicited little head movement in any direction. These results suggest that newborns' head orientation is selectively deficient for brief sounds, that the difficulty does not result from lessened energy in the brief sounds, and that the efficacy of repeated brief sounds depends upon their repetition rates.

Categorization and memory retrieval by three-month-olds.

84 3-month-olds were tested in 3 studies of the acquisition and long-term retention of category-specific information. Infants who were trained with a perceptibly different member of an alphanumeric category on each of 3 days generalized responding to a novel instance of the original training category but not a novel member of a novel category during a 24-hour novelty test. 2 weeks later, when infants displayed no evidence of remembering their prior training experience, categorization was reinstated if a novel exemplar from the original training category was used as the retrieval cue in a memory reactivation procedure. A novel exemplar from a novel category was not an effective retrieval cue. The effectiveness of the category-specific retrieval cue was a function of its physical similarity to the individual exemplars encountered during training, not testing. The background against which the alphanumeric exemplars were displayed during training was not an effective retrieval cue in either the 24-hour novelty test or the memory reactivation procedure, indicating that all invariant stimulus attributes do not contribute equally as category cues. These data are the first to document retention of category-specific information after extended intervals. A popular account of categorization holds that infants abstract invariant features from individual exemplars and form a schema or distinctive memory representation of these shared features against which subsequent exemplars are compared. The present data provide support for a more parsimonious account of categorization, based on the retrieval of information about individual exemplars, that does not require an assumption of prototype formation.