Biomedical subjects

J S Freeman

Publications and source records attributed to J S Freeman.

At least 19 recordsLinked to original sources

PubMed1996

The accuracy and precision of timing of self-paced, repetitive movements in subjects with Parkinson's disease.

In separate experiments, we studied the temporal accuracy and precision of self-paced, repetitive finger-tapping in two groups of 12 patients with Parkinson's disease and a group of 12 controls matched to the patients with respect to age and general cognitive state. One group (I) of patients was studied initially following 12-15 h abstinence from normal levodopa medication ('off') and again, subsequently, approximately 1 h after ingestion of a single normal dose ('on'). A second group (II) of patients, each of whom had bilaterally asymmetrical neurological signs, was tested using 'worse' and 'better' hands separately. Within each session, subjects were tested repeatedly on a tapping task during which they were required to produce a regular series of self-timed inter-tap intervals, the target duration (550 ms) of which had been established previously during an initial period of tapping in synchrony with the beats of a regular metronome. We employed Wing and Kristofferson's (1973) model of control of motor timing to partition the total variance (TV) about the mean inter-response interval (IRI) produced during the self-paced phase of each run into separate components ['clock' variance (CV) and 'motor-delay' variance (MDV)] attributable to hypothetical 'clock' and 'motor-implementation' processes. Although the mean self-paced IRI of parkinsonian patients was generally shorter than that of controls, only during the 'on' medication condition (Group I) was it significantly so. By comparison with control values, and those observed during the 'on' medication condition, values of TV, CV and MDV in Group I were all significantly higher when subjects were 'off' medication. During the 'on' medication condition, only CV was significantly higher than the control value. In Group II, values of TV, CV and MDV associated with use of the 'worse' hand were all significantly higher than both control values and those associated with use of the 'better' hand. Values of these variables when subjects used the 'better' hand did not, however, differ significantly from control values. The theoretical import of these results is discussed in the light of several important procedural, statistical and computational issues and we conclude that TV, CV, and MDV may all vary significantly as a function of the efficacy of dopaminergic transmission in the basal ganglia.

Aged↗

PubMed1996

Arguing along the slippery slope of human embryo research.

One frequent argument in the debate over federal funding of human embryo research is the slippery slope argument. Slope arguments can be of several types: either logical, empirical, or full (a combination of logical and empirical slope arguments, with an additional psychological premise). A full slope argument against human embryo research suggests that funding embryo research could undermine current protections for human subjects research, erode respect for persons with disabilities, and encourage eugenics practices. While the Panel commissioned by the National Institutes of Health to issue funding guidelines regarding human embryo research acknowledges some slippery slope concerns, the Panel's final report fails to address such concerns in any depth. Given this failure seriously to address these valid concerns, federal funding of embryo research should not proceed at this time.

Advisory Committees↗

PubMed1993

The influence of external timing cues upon the rhythm of voluntary movements in Parkinson's disease.

The ability of patients with Parkinson's disease (PD) and healthy subjects to synchronise finger tapping, produced by rhythmic wrist movements, with auditory signals of target frequencies (range 1-5 Hz) and to sustain such rhythms following sudden withdrawal of auditory cues was studied. Healthy subjects were able, in the presence of auditory cues, to duplicate target frequencies accurately over the range investigated both in terms of mean tapping rate and in regularity of tapping. PD patients were less accurate under these conditions and on average tended to tap too rapidly at the lower (1-3 Hz) target frequencies and too slowly at the highest (5 Hz) target frequency. In addition, the variability of their tapping rhythms was generally greater. Healthy subjects were able to sustain tapping rhythms well following suppression of auditory signals. By contrast, withdrawal of external timing cues resulted in marked impairment of the patients' rhythm generation. At lower frequency targets (1-3 Hz) patients' tapping rates increased over rates which were already elevated in the presence of external cues. Conversely, at higher target frequencies (4-5 Hz), the average tapping rate tended to decline further from previously depressed levels. The accuracy of almost all patients fell outside the normal range. Two patterns of tapping errors were found. The first was hastening of tapping which was most evident at intermediate target frequencies. The second was faltering which occurred mainly at the higher target frequencies. These forms of behaviour may result from inherent abnormalities of internal rhythm generation since they occurred both in the presence and absence of external timing signals. Overall, our findings are consistent with the view that the basal ganglia have a role in the internal cueing of repetitive voluntary movements.

Aged↗

PubMed1992

Empty sella syndrome associated with partial hypopituitarism (visualized on MRI scan).

The empty sella syndrome has become a rather frequent finding in magnetic resonance imaging (MRI) scanning. The usual presentation of empty sella syndrome involves an incidental finding on a computed tomography scan or an MRI scan. It is unusual to find empty sella syndrome associated with hypopituitarism. The authors describe such an unusual finding in a 54-year-old nulliparous woman.

Empty Sella Syndrome↗

PubMed1991

A new lethal sclerosing bone dysplasia.

A neonate is described with a lethal sclerosing bone dysplasia associated with prenatal fractures and craniofacial abnormalities including microcephaly, exophthalmos, hypoplastic nose and mid-face, small jaw and nodular hyperplasia of the gums. Parental consanguinity suggests that an autosomal recessive mutation is the likely aetiology.

Bone Diseases, Developmental↗

PubMed1988