Biomedical subjects

M E Calkins

Publications and source records attributed to M E Calkins.

6 recordsLinked to original sources

PubMed2001

Saccadic disinhibition in schizophrenia patients and their first-degree biological relatives. A parametric study of the effects of increasing inhibitory load.

Several studies have reported that patients with schizophrenia and their relatives perform poorly on antisaccade tasks and have suggested that this deficit represents saccadic disinhibition. If this proposition is correct, then varying task parameters that specifically increase the difficulty with which unwanted saccades can be inhibited should exacerbate deficits. Forty-two schizophrenia patients, 42 of their first-degree biological relatives, 21 psychotic affective disorder patients, and 38 nonpsychiatric comparison subjects were given fixation and antisaccade tasks. The introduction of distracters and the presence of visible fixation stimuli were parameters used to vary the difficulty in suppressing unwanted saccades (inhibitory load). It is known that the presence of a fixation stimulus at the time when a saccade must be inhibited results in fewer reflexive errors on antisaccade tasks. Performance on fixation tasks without (low load) vs with distracters (high load) and antisaccade tasks that had fixation stimuli still visible (low load) vs already extinguished (high load) at the time when the reflexive saccade must be inhibited was compared. The schizophrenia patients and their first-degree biological relatives showed evidence of increased saccadic disinhibition that was most pronounced during high inhibitory load conditions. These data indicate that dysfunctional inhibitory processes, at least in the oculomotor domain, are associated with the liability to schizophrenia. Results also suggest that this genetic liability may be related to dysfunctional prefrontal cortical areas that provide top-down inhibitory control over reflexive saccade generation.

Adult↗

PubMed2001

Saccadic disinhibition in patients with acute and remitted schizophrenia and their first-degree biological relatives.

OBJECTIVE: Performance on measures of saccadic inhibition and control was investigated in a large family study of schizophrenia to evaluate the utility of using antisaccade task performance as an endophenotypic marker of genetic liability for schizophrenia. METHOD: Ninety-five patients with acute schizophrenia and 116 of their first-degree biological relatives, 13 schizophrenia patients whose illness was in full remission, 35 patients with acute psychotic affective disorder, and 109 nonpsychiatric comparison subjects were administered antisaccade and prosaccade tasks. RESULTS: Both schizophrenia patient groups had a greater number of errors on the antisaccade task than did the first-degree relatives and the affective disorder group, which both had more errors than the comparison subjects. Among the first-degree relatives of the probands with acute schizophrenia, relatives of poor-performing patients performed worse on the antisaccade task than relatives of patients with good performance. Reflexive errors were not likely the result of interfering psychotic symptoms, medication, or medication side effects. Although the schizophrenia patients demonstrated other signs of saccadic abnormalities, these problems, which were not observed in their relatives even though they had high antisaccade error rates, seem unlikely to account for the higher antisaccade error rate of the schizophrenia patients. CONCLUSIONS: These findings suggest that saccadic disinhibition is strongly associated with the genetic liability for schizophrenia.

Acute Disease↗

PubMed2001

The misclassification of blinks as saccades: implications for investigations of eye movement dysfunction in schizophrenia.

It is important to have a simple. accurate method for recording eye movements. Of the two popular approaches commonly adopted, electro-oculography (EOG) and infrared oculography (IROG), IROG is often accepted as the more accurate, and it is the method that is currently used most frequently to examine eye movements in schizophrenia. This study investigated whether the misclassification of blinks as saccades affects saccade rates when the presence of a blink is determined using only IROG recordings of eye position. Both vertical electro-oculography (VEOG), which can be used to objectively identify blinks, and IROG were recorded while 17 schizophrenia patients and 19 healthy controls were presented with sinusoidal stimuli. Of the blinks identified with the VEOG for the total group of participants, a substantial number (37%) were misclassified as catch-up and anticipatory saccades when only the IROG was used. Furthermore, in the schizophrenia group, but not in the healthy control group, the use of the IROG led to a significant misclassification of blinks as anticipatory saccades. Therefore, when IROG alone is used to identify blinks, the misclassification of blinks as saccades is likely to introduce measurement error into estimates of saccade rates, particularly estimates of anticipatory saccade rates in schizophrenia patients.

Adult↗

PubMed2000

Eye movement dysfunction in schizophrenia: a heritable characteristic for enhancing phenotype definition.

The occurrence of ocular motor dysfunction in schizophrenia patients and their first-degree biological relatives is remarkably consistent, suggesting that abnormal smooth pursuit and saccadic oculomotion are heritable characteristics that can be used to identify gene carriers for schizophrenia. Saccadic system dysfunction probably reflects a generalized deficit in prefrontal cortical functioning, rather than a specific deficit in saccade system functioning. Although abnormal smooth pursuit has also been associated with impaired frontal functioning, it is unclear whether these two types of dysfunction arise from the same neural pathology. Therefore, deviant smooth pursuit and saccadic oculomotion may constitute unrelated factors identifying two different types of genetic risk. Alternatively, they may derive from a single risk factor that causes (a) both types of deficits to be expressed together or (b) each type to be expressed separately as pleiotropic manifestations of the underlying genotype. Although a full complement of pursuit and saccade measures has not been examined together in family studies of schizophrenia, there is obvious value in determining how these measures relate to one another in schizophrenia families and whether they can be used in combination to enhance phenotype definition to facilitate the search for schizophrenia susceptibility genes.

Biomarkers↗

PubMed1996

Pathophysiology of congestive heart failure in ESRD.

Congestive heart failure (CHF) represents the inability of the heart to pump enough blood to meet tissue requirements for oxygen, resulting in a discrepancy between myocardial oxygen supply and demand. It can result from any clinical situation that alters myocardial performance, including end stage renal disease (ESRD). The purpose of this article is to describe the pathophysiology of CHF, major signs and symptoms, medical management, and nursing interventions in patients with ESRD.

Decision Trees↗

PubMed1993

Ethical issues in the elderly ESRD patient.

The fastest growing population group in the United States is the over 65 years old group. In 1985, 59% of all new patients to chronic dialysis were age 55 years or older. Quality of life has been a health care issue in the past and is more so now with decreasing health care resources. The rationing of health care resources has become an increasingly important issue in determining and defining the quality of life, especially for the chronically ill elderly. This article does not support either dialysis treatment or no dialysis treatment for the elderly, but assists readers to consider the implications to the health care system and the limited health care resources that are present. This bioethical dilemma will be with the health care system for years to come.

Age Factors↗