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Biomedical subjects

S M Rivera

Publications and source records attributed to S M Rivera.

8 recordsLinked to original sources
PubMed2000

Dissociating prefrontal and parietal cortex activation during arithmetic processing.

Lesion and brain-imaging studies have implicated the prefrontal and parietal cortices in arithmetic processing, but do not exclude the possibility that these brain areas are also involved in nonarithmetic operations. In the present study, we used functional magnetic resonance imaging to explore which brain areas contribute uniquely to numeric computation. Task difficulty was manipulated in a factorial design by varying the number of operands and the rate of stimulus presentation. Both manipulations increased the number of operations to be performed in unit time. Manipulating the number of operands allowed us to investigate the specific effect of calculation, while manipulating the rate of presentation allowed us to increase task difficulty independent of calculation. We found quantitative changes in activation patterns in the prefrontal and parietal cortices as well as the recruitment of additional brain regions, including the caudate and midcerebellar cortex, with increasing task difficulty. More importantly, the main effect of arithmetic complexity was observed in the left and right angular gyrus, while the main effect of rate of stimulus presentation was observed in the left insular/orbitofrontal cortex. Our findings indicate a dissociation in prefrontal and parietal cortex function during arithmetic processing and further provide the first evidence for a specific role for the angular gyrus in arithmetic computation independent of other processing demands.

Adolescent↗
PubMed2000

Functional optimization of arithmetic processing in perfect performers.

Lesion and imaging studies to date have not clarified which sub-regions of the parietal lobe are specialized for arithmetic processing, and which perform supporting functions. We used functional magnetic resonance imaging to investigate parietal lobe function during arithmetic processing. Functional optimization was examined by analyzing regional differences in brain activation between perfect (100% accuracy) and imperfect performers. Perfect performers had significantly less activation only in the left angular gyrus, a finding that may be associated with skill mastery and long-term practice effects. The present results provide the first direct evidence of localized functional optimization for arithmetic processing in the human brain.

Adolescent↗
PubMed2000

Patients' own reasons and patient-perceived recommendations for orthognathic surgery.

In an attempt to learn more about patients' decision-making processes, an analysis was performed to examine patients' reasons for undergoing orthognathic surgery and their understanding of the reasons surgery was recommended. Before surgery, 105 females and 38 males completed an open-ended questionnaire in which they listed their reasons for choosing orthognathic surgery and their perceptions of their orthodontists' recommendations. Three raters classified the responses into 7 categories: esthetics, psychosocial, functional, TMJ/pain, authority, prevention, and other. Rater agreement ranged from a kappa of.55 to 1.00. Patients reported undergoing orthognathic surgery primarily for esthetic, functional, and TMJ improvements, 71%, 47%, and 28%, respectively. Females reported more TMJ-related reasons than males (P <.05). Patients reporting function (P <. 05), TMJ (P <.05), and prevention of future problems (P <.05) were older than patients not reporting these reasons. Mexican American patients indicated more psychosocial reasons (P <.05) than European Americans. Patients understood that orthognathic surgery was recommended primarily for esthetic, functional, and TMJ improvements, 52%, 44%, and 18%, respectively. Males reported receiving more preventative recommendations (23%) than females (10%). Mexican American patients reported receiving more psychosocial recommendations (P <.05) than European Americans. Agreement between each paired patient/patient-perceived reason was highest for TMJ problems (kappa = 0.588). In conclusion, patients underwent orthognathic surgery to improve esthetic, functional and TMJ problems and interpreted orthodontists' recommendations for similar reasons. On a case-to-case basis, agreement between patient and orthodontist-represented reasons was modest, suggesting differences between patients' own reasons and their perceptions of orthodontists' recommendations.

Adolescent↗
PubMed2000

Psychosocial predictors of satisfaction among orthognathic surgery patients.

This study assessed the usefulness of selected psychosocial tests and demographic measures in identifying satisfied versus dissatisfied patients who received orthognathic surgery. Data were collected prior to placement of orthodontic appliances, 1 to 2 weeks presurgery, and at 1 week, 8 weeks, 6 months, 12 months and and 2 years postsurgery. The Revised Symptom Checklist-90 (SCL-90-R) scales, the Eysenck Personality Inventory (EPI), the Sickness Impact Profile (SIP), and the Oral Health Status Questionnaire (OHSQ) were used as independent variables. Indicators from the Post-Surgical Patient Satisfaction Questionnaire (PSPSQ), which assesses patient satisfaction regarding psychosocial issues, oral functioning, and esthetics, served as a postsurgical dependent measure of patient satisfaction. Thirty-one male and 86 female subjects participated in the multisite randomized trial comparing rigid and wire fixation. Patient age was significantly correlated with patient satisfaction from 8 weeks postsurgery through 2 years postsurgery. Older patients appear to report greater postsurgical satisfaction in comparison to younger patients. The postsurgical OHSQ (esthetics subscale) and postsurgical PSPSQ (satisfaction) were significantly related at 8 weeks, 6 months, 12 months, and 2 years postsurgery. Additionally, PSPSQ (satisfaction) and postsurgical OHSQ (general oral health scale) were correlated at 12 months. The EPI, SIP, and SCL-90-R were not significantly associated with postsurgical satisfaction when assessing the entire study sample. Postsurgical qualitative data from the PSPSQ indicated that 50% of the patients reported positive outcomes in oral functioning. Sixty-five percent reported esthetic improvements, and 37% reported neurosensory loss.

Adult↗
PubMed1999

The drawbridge phenomenon: representational reasoning or perceptual preference?

Two experiments investigated whether infants would look longer at a rotating "drawbridge" that appeared to violate physical laws because they knew that it was causally impossible, as claimed by R. Baillargeon, E. S. Spelke, and S. Wasserman (1985) and R. Baillargeon (1987a). Using a habituation paradigm, they reported that infants looked longer at a display that appeared impossible (rotated 180 degrees while an obstructing box was behind it) than at one that appeared possible (rotated only 112 degrees, appearing to stop at the box). Experiment 1 eliminated habituation to 180 degree screen rotations. Still, infants looked longer at the 180 degree impossible rotations. Critically, however, infants also looked longer at possible 180 degree rotations in Experiment 2, in which no obstruction was present. Moreover, no difference in effect size was found between the 2 experiments. These findings indicate that infants' longer looking at 180 degree rotations is due to simple perceptual preference for more motion. They question R. Baillargeon's (1987a) claim that it is due to infants' representational reasoning about physically impossible object permanence events.

Cognition↗
PubMed1999

Psychosocial predictors of high-risk patients undergoing orthognathic surgery.

The purpose of this analysis was to identify a set of predictor variables that are prospectively related to postsurgical outcomes. Specifically, psychosocial characteristics were sought to predict postsurgical outcomes. The 5 Revised Symptom Checklist-90 (SCL-90-R) scales, the neuroticism score of the Eysenck Personality Inventory (EPI), the psychosocial domain score from the Sickness Impact Profile (SIP), and 4 scales from the Oral Health Status Questionnaire (OHSQ) were used as the predictors. A total of 31 male and 86 female subjects participated in this multicenter randomized trial, which compared rigid and wire fixation. Data were collected prior to placement of orthodontic appliances, 1 to 2 weeks presurgery, and at 1 week, 8 weeks, 6 months, and 2 years after surgery. Baseline oral health was used as an indicator of postsurgical oral health functioning. A path analytic model of influences on presurgical oral health was estimated (R2 = 0.43). The results suggest that presurgical screening of demographic characteristics (age, sex, and ethnicity), oral health (the OHSQ), quality of life issues (SIP), and personality features (SCL-90-R), accounts for 23% to 39% of the variance in postsurgical oral health outcomes. The path analysis conducted suggests that a patient's age, ethnicity, gender, and elevated scores on the EPI have indirect effects on postsurgical health. As determined by a 2-stage least squares regression model, 3 variables--the patient's presurgical oral health (per the OHSQ), pre- and postsurgical Global Severity Index (GSI) score from the SCL-90-R, and the psychosocial scale score from the SIP--were found to have a statistically significant impact on postsurgical outcomes. Additionally, the GSI, SIP, and OHSQ are reliable measures in predicting oral health outcomes.

Adult↗