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Biomedical subjects

R G Ross

Publications and source records attributed to R G Ross.

27 records · Page 2Linked to original sources
PubMed1998

Familial transmission of two independent saccadic abnormalities in schizophrenia.

Difficulties with inhibiting inappropriate responses, i.e. disinhibition, and problems with spatial memory are both presumed to be a part of the phenotypic expression of the genetic risk for schizophrenia. Schizophrenic probands are impaired on saccadic eye movement tasks which require (a) response inhibition to prepotent stimuli and (b) generation of an accurate response to a remembered or calculated spatial location, but it is unknown how these deficits are inherited. Sixteen schizophrenic probands, their 32 parents, and two normal control groups completed a delayed oculomotor response and an antisaccade task. The parents with a positive ancestral family history for chronic psychosis (n = 8) were presumed to be more likely than their family history-negative spouses to be genetic carriers for schizophrenia. Probands and their positive family history parents had more failures of response inhibition than did normal control groups. However, it was the probands and their negative family history spouses who demonstrated impaired accuracy of the remembered- or antisaccades. Disinhibition may be closely tied to a specific genetic risk for schizophrenia. However, a second familial factor related to the maintenance or manipulation of spatial information may also contribute to the genetic risk of the full clinical disorder.

Adult↗
PubMed1998

Improvement in smooth pursuit eye movements after cigarette smoking in schizophrenic patients.

This study examined whether schizophrenics' cigarette smoking normalized smooth pursuit eye movement abnormalities. Fifteen schizophrenic and 15 nonschizophrenic subjects abstained from their usual cigarette smoking for an average of 10 h. Their baseline performance during a constant velocity smooth pursuit task was then assessed. The subjects smoked as much as they desired in a 10-min period and then were retested immediately postsmoking, and 10 and 20 min later. Smooth pursuit gain and the percentage of total eye movement due to various saccadic subtypes were computed using infrared oculography and computerized pattern recognition software. After smoking, smooth pursuit gain increased and the percentage of total eye movements due to leading saccades decreased significantly in the schizophrenic patients. There were no changes in the gain or leading saccades of nonschizophrenic subjects after smoking. Nicotinic receptor dysfunction may be a candidate mechanism for smooth pursuit eye movement abnormalities in schizophrenia.

Adult↗
PubMed1996

Early expression of smooth-pursuit eye movement abnormalities in children of schizophrenic parents.

OBJECTIVE: Disordered smooth-pursuit eye movements (SPEM) and, specifically, small anticipatory saccades that disrupt SPEM have been hypothesized to be a marker of genetic vulnerability to schizophrenia. This study compares SPEM in children of schizophrenic parents with normally developing control children to assess whether SPEM abnormalities are also present in a subset of at-risk children. METHOD: With infrared oculography, SPEM was examined in 13 children of schizophrenic parents and 19 normally developing controls (aged 6 to 15 years). Measures of smooth-pursuit gain and root mean square error were used in addition to more specific measures of catch-up saccades and anticipatory saccades. RESULTS: Children of schizophrenic parents differed from normally developing controls on gain and root mean square error, but not on catch-up saccades. Small anticipatory saccades were significantly more frequent in the at-risk group. The percentage of total eye movements due to anticipatory saccades identified 54% of the at-risk group (compared with none of the control group) as performing more than two standard deviations above (worse than) the control mean. CONCLUSIONS: The presence of increased anticipatory saccades is evidence for an oculomotor dysfunction that may be a phenotype of the genetic risk for schizophrenia, expressed years prior to the possible development of clinical illness.

Adolescent↗
PubMed1994

Saccadic eye movements in normal children from 8 to 15 years of age: a developmental study of visuospatial attention.

This cross-sectional study used saccadic eye movements, as measured by infrared occulography, to assess several aspects of visuospatial attention in normal children ages 8-15 years. Saccadic latency (a global measure of the ability to shift visuospatial attention), the ability to suppress extraneous saccades during fixation, and the ability to inhibit task-provoked anticipatory saccades all improve with age. However, the pattern of development differs for different tasks; saccadic latency shortens at a linear rate across the age range 8-15 years, while the capacity to inhibit anticipatory saccades matures by 12-13 years of age, and the ability to suppress saccades matures by 10 years of age. Analyses of age-related changes in oculomotor measures of attention may provide a novel approach in the study of children with attentional difficulties.

Adolescent↗
PubMed1993

A developmental study of smooth pursuit eye movements in normal children from 7 to 15 years of age.

OBJECTIVE: To examine age-related changes in smooth pursuit tracking. METHOD: Using infrared occulography, smooth pursuit eye movements are examined in 53 normal 7- to 15-year-old children during 6 degrees and 12 degrees/second visual pursuit. In addition to smooth pursuit gain and saccadic frequency, measures of mean amplitude per second are introduced to facilitate comparison across age and target speed. RESULTS: The 6 degrees/second task is found to be easier than the 12 degrees/second task. Age is correlated with smooth pursuit system performance but not saccadic system performance during 12 degrees/second pursuit. No measure correlates with age during 6 degrees/second pursuit. CONCLUSIONS: Eye movements improve as children age. The future use of smooth pursuit eye movements to study children and adolescents with and at risk for schizophrenia must control for developmental changes.

Adolescent↗
PubMedDate not supplied

Age diminishes performance on an antisaccade eye movement task.

Tthe antisaccade eye movement task, which has been linked to frontal lobe function, presents a target in one visual field and asks subjects to move their eyes to the same location in the opposite field. The task requires inhibition of the reflexive prosaccade to the cue, initiation of the antisaccade to the opposite field, and visuo-spatial memory of the cue location. Forty-two subjects from 19-79 years of age performed this task and a control task, visually guided saccades to the cue itself, to determine which functions are affected by aging. The time to initiate antisaccades increased linearly with age at a rate greater than the time to initiate visually guided saccades. This difference suggests that the processing time to inhibit the incorrect movement to the cue is selectively increased with age. Older subjects also made more incorrect prosaccadic movements to the cue, a finding consistent with the loss of inhibitory processing capacity. The accuracy of movements did not change, which suggests that visuo-spatial memory is unaffected by aging.

Adolescent↗
PubMedDate not supplied

How controlled stress affects healing tissues.

Restoration of a patient's full range of motion, strength, and function are the primary goals of occupational and physical therapy. Immobilization of normal connective tissue leads to biochemical, biomechanical, and physiologic changes within a week. These changes are magnified in the presence of trauma or edema, and they may create permanent damage if not addressed swiftly and properly. This is best accomplished by applying specific types of stress to the involved and associated structures at optimal intervals during the rehabilitation process. Load must be applied at adequate intensity and duration to successfully affect the viscous property of connective tissue. This is necessary to effect permanent elongation of the restricted tissues. Early controlled motion is vital to prevent the negative changes associated with immobilization and to maintain normal viscoelasticity and homeostasis of connective tissue. Hand therapists must have a thorough understanding of the changes associated with injured structures. Only then can they provide optimal stress delivery to facilitate restoration of function.

Connective Tissue↗
PubMedDate not supplied

Eye movement task related to frontal lobe functioning in children with attention deficit disorder.

OBJECTIVE: Attention-deficit hyperactivity disorder (ADHD) has been postulated to be related to dysfunction of the prefrontal cortex. In the oculomotor delayed response task, a subject is cued as to where he or she should look (shift visual gaze to) but must delay a short period and then shift gaze to the location where the cue previously existed but no longer exists (a memory-guided saccade). Dependent measures from this task provide information on three functions tentatively tied to prefrontal cortex functioning: the ability to inhibit response (during the delay period), preparation of motor response (inversely tied to the latency of shifting visual gaze), and accuracy of working visuospatial memory (accuracy of the memory-guided saccade). METHOD: Thirteen children with ADHD and 10 normal controls, aged 9 to 12 years, were tested using an 800-msec delay period. RESULTS: Children with ADHD showed, relative to normal controls, deficits on inhibiting response during the delay period but no differences in latency (preparation of motor response) or accuracy of visuospatial memory. CONCLUSIONS: These results support the hypothesis that the primary deficit in ADHD is difficulty in inhibition of response. This deficit may be associated with pathology located outside the dorsolateral prefrontal cortex.

Adolescent↗