Detection threshold differences to crossed and uncrossed disparities

Using a sample of 85 subjects measurements were made of minimum stimulus durations necessary for detection of crossed and uncrossed disparity stimuli which were presented in five positions in the visual field: centre, lower, upper, right, and left field. The results indicated large detection duration differences between the two disparity conditions, with a marked superiority for crossed disparity detection at all positions. A left-right visual field anisotropy was demonstrated for crossed disparity stimuli.     

Prospective study of outcome of infants with infantile spasms treated during controlled studies of ACTH and prednisone

We report the long-term outcome of 64 infants with infantile spasms, followed prospectively, using controlled treatment schedules and objective techniques (24-hour EEG and video monitoring) to determine response. Average age at follow-up was 50 months. Of the 64 infants, three (5%) died; of the others, 41 (67%) had developmental retardation of 50% or more or an IQ of 50 or less. Eight patients (13%) composed our cryptogenic study group and were so classified on the basis of normal CT scan, normal development prior to onset of infantile spasms, and undetermined cause. These patients had the better outcome; 38% had normal development or were only mildly retarded. Both the responders and nonresponders in our symptomatic group had a poor outcome; only 5% had normal development or mild impairment. Outcome was not significantly influenced by short versus long treatment lag or by response to therapy. Other types of seizures occurred in 34 patients (53%). In summary, the overall prognosis for long-term outcome in these 64 patients with infantile spasms was poor.     

Little Rock Lake (Wisconsin): Perspectives on an experimental ecosystem approach to seepage lake acidification

Ecosystem-level experiments are essential in assessing the effects of environmental perturbations like acidification. To date in North America, such experiments have been rare and geographically limited to drainage lakes in south-western Ontario and to streams in the northeastern US. Seepage lakes, which are the dominant hydrologic type in large regions of the US, have received limited attention from many perspectives, including whole-system manipulation. The Little Rock Lake Acidification Project was initiated to expand insights from previous acidification experiments with whole drainage lakes to a seepage lake system. It involves the gradual acidification of a small (18 ha), seepage lake in northcentral Wisconsin. The lake has been divided into a treatment and reference basin using a flexible, inert barrier; and the treatment basin is being acidified in steps of 0.5 pH units/2 yr period from a starting pH of 6.1 to a final pH of 4.6 (roughly the average pH of rain in this region). The goals are to document the biological and chemical changes which occur, to identify the direct and indirect mechanisms which regulate responses, and to expand insights to a class of lakes previously understudied. In this paper, we describe the history and rationale of the project and we discuss in general terms the utility and constraints of whole-ecosystem manipulations.