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Biomedical subjects

A Postma

Publications and source records attributed to A Postma.

At least 37 records · Page 2Linked to original sources
PubMed2000

Spatial memory impairment in patients after tumour resection: evidence for a double dissociation.

Human spatial memory can be divided into multiple, partly separate cognitive processes. In this study, object location memory was studied using a set of tasks that assessed three different spatial memory aspects: positional memory, object location binding, and a combined process. Also, maze learning and spatial span memory were measured. Ten patients who had undergone intracranial tumour resection participated, and their individual results were compared with control data from 24 healthy subjects. Four patients showed selective spatial memory impairments; two patients were impaired at positional memory, and two other patients were impaired on object location binding and the combined process. This double dissociation provides further evidence for the notion that object location memory is not a unitary system, but consists of at least two separate mechanisms. In addition, spatial memory problems were predominantly present in the patients with lesions in either the right hemisphere or in the parietal lobe. These results are in agreement with previous findings on the involvement of the right hemisphere and the posterior parietal cortices in spatial processing.

Adult↗
PubMed2000

The Corsi Block-Tapping Task: standardization and normative data.

This article describes a standardized administration and scoring procedure for the widely used Corsi Block-Tapping Task, designed to assess the visual memory span. This method was applied in a group of healthy participants (n = 70) and a group of patients with cerebral lesions (n = 70), that were categorized on the basis of lesion location (left or right hemisphere, bilateral or subcortical). The percentile distribution as well as cutoff points on the basis of the control data are provided. It was found that 20% of the patients perform in the borderline range on this task, and over 8% have an impaired performance ("retarded"). In addition, right hemisphere patients performed worse than left hemisphere patients. These data show that the Corsi Block-Tapping Task can be effectively used to assess visuospatial short-term memory in patients with brain damage, and is selective for the side of the lesion.

Adolescent↗
PubMed1999

P and M channel-specific interference in the what and where pathway.

It was the purpose of this experiment to study interference effects of colour or luminance peripheral flicker (in order to saturate either the parvocellular or the magnocellular stream) on object identity and spatial location memory. Colour flicker interfered with object identity recognition, whereas luminance flicker affected memory for spatial location. Moreover, overall performance was worse if coloured rather than grey-scaled objects were used in the stimulus display. There was no selective effect of coloured flicker affecting coloured objects and chromatic flicker affecting chromatic objects. These results provide strong evidence for the theoretical position that the what pathway relies heavily on information derived from the P stream and the where pathway on the M stream.

Adult↗
PubMed1999

Protracted and variable latency of acute lymphoblastic leukemia after TEL-AML1 gene fusion in utero.

We report a pair of identical twins with concordant acute lymphoblastic leukemia (ALL). Unusually, their diagnoses were spaced 9 years apart at ages 5 and 14. Leukemic cells in both twins had a TEL-AML1 rearrangement, which was characterized at the DNA level by an adaptation of a long distance polymerase chain reaction (PCR) method. The genomic fusion sequence was identical in the two leukemias, indicative of a single cell origin in one fetus, in utero. At the time twin 1 was diagnosed (aged 5 years), the bone marrow of twin 2 was hematologically normal. However, retrospective scrutiny of the DNA from an archived slide with clonotypic TEL-AML1 primers showed that the presumptive preleukemic clone was present and disseminated 9 years before a clinical diagnosis. These data provide novel insight into the natural history of childhood leukemia and suggest that consequent to a prenatal initiation of a leukemic clone, most probably by TEL-AML fusion itself, the latency of ALL can be both extremely variable and protracted. This, in turn, is likely to reflect the timing of critical secondary events.

Adolescent↗
PubMed1999

The influence of decision criteria upon remembering and knowing in recognition memory.

One may recognise an item as 'old' on basis of a recollective experience or by a feeling of familiarity without specific recollection. The former is called a 'remember' judgement; the latter a 'know' judgement. It has been claimed that remember and know responses reflect qualitatively distinct components of recognition memory, and not just derive from gradual differences in perceived trace strength or subjective certainty (i.e. remember judgments include memories of which one is more confident). Nonetheless, the present study examined the possibility that the distinction does relate to decision criteria placed upon a single familiarity axis (see Donaldson, 1996; Hirshman & Master, 1997). To this purpose, two groups of subjects were compared: one, which was instructed to be very conservative in their old-new judgements, while the other group was stimulated to be very lenient instead. Remember hit rates increased with more lenient criteria, whereas know hit rates did not, but false alarm rates did. While remember sensitivity was equal in the two groups, know sensitivity was lower with liberal criteria. Also it correlated with overall response bias. This lends support to the possibility that subjects not only apply an old-new decision criterion, but also set a remember-know criterion, which is affected in a similar way by liberal versus conservative instructions.

Adolescent↗
PubMed1999

Sex differences and menstrual cycle effects in human spatial memory.

A typical test of spatial memory requires subjects to relocate a number of objects in their original, previously studied positions. It has been argued that this test includes multiple separate processing components (Postma, A., De Haan, E.H.F., 1996. Quarterly Journal of Experimental Psychology 48A (1), 178-199; Postma, A., Izendoorn, R., De Haan, E.H.F., 1998. Brain and Cognition 36, 334-345). One has to encode the precise positions occupied, assign the various objects to the correct (relative) locations, and achieve an integration of both types of spatial information. The present study examined the presence of sex differences and the role of hormonal factors for these selective components of spatial memory. A computerised, immediate (working) memory version of the test was used, comparing 23 males and 34 females on three experimental conditions: positions only, object-to-position-assignment, and the combined condition, requiring integration of the other two components. In line with previous research (Postma et al., 1998) males showed a selective advantage for fine-grained, metric positional reconstruction (i.e. positions-only). Interestingly, a within-subjects comparison in the females only revealed a menstrual cycle effect for exactly the same dimension of spatial memory. In the nonmenstrual phase, females were better than during menstruation. This clearly implies a role for sex hormones in spatial memory, even though a subsequent analysis of testosterone samples in saliva did not reveal a significant correlation with measures of spatial memory in both males and females.

Adolescent↗
PubMed1999

Object Relocation: a program for setting up, running, and analyzing experiments on memory for object locations.

Object Relocation is a computer program for Windows 95, with which experiments on spatial memory for object locations can be designed, run, and analyzed. Because of its clear graphical user interface, no long and complex command syntax is needed. Basically, a stimulus consists of a frame that contains a chosen number of locations (i.e., the actual spatial layout) to which objects can be assigned. When the experiment is run, these stimuli are presented to the subject for a variable period of time. Subsequently (either with or without a delay), the objects are presented in a row above the frame and have to be relocated to the correct positions. Finally, the raw data can be analyzed efficiently, using various error scores, and an SPSS-ready output file can be produced. Object Relocation is a very flexible program: New objects and positions can easily be added, and various options for presentation and relocation are present.

Computer Graphics↗
PubMed1998

Sex differences in object location memory.

The ability to remember where objects were is thought to require multiple separate processes. One has to encode the precise positions occupied, assign the various objects to the correct (relative) locations, and achieve an integration of both types of spatial information. This study examined whether sex differences exist for these selective components of object location memory. Twenty males and 20 females participated in the following task. On a PC screen, they were shown a square with 10 different objects for 30 s. Subsequently, the objects disappeared from the screen, reappeared in a row above the square, and subjects were asked to relocate them in three different conditions. In the object-to-position-assignment condition, the original positions were premarked in the square, so subjects needed only to assign the correct object to the correct position. In the positions-only condition, all objects assumed the same identity. Therefore, subjects had only to reproduce the precise positions. Finally, in the combined condition, subjects were required to replace all the different objects in the square without any of object positions premarked. The absolute displacements between an object's original and its relocated position reflect the integration mechanism. Females did as well as males in the object-to-position-assignment condition and on the absolute displacements in the combined condition, but they were less efficient than males in positional reconstruction per se. Thus, it seems that the male advantage in spatial memory is not a general effect but applies only to certain specific processing components. Moreover, the employment of a dual task during encoding, concurrent articulatory suppression, yielded no significant interactions with sex. This suggests that females' weaker positional encoding does not derive from the use of an inefficient verbal strategy.

Adult↗
PubMed1996

Late cardiotoxicity after treatment for a malignant bone tumor.

Cardiac function was assessed in long-term survivors of malignant bone tumors who were treated according to Rosen's T5 or T10 protocol, both including doxorubicin. Thirty-one patients, age 10-45 years (median age 17.8 years) were evaluated 2.3-14.1 years (median 8.9 years) following completion of treatment. Cumulative doses of doxorubicin were 225-550 mg/m2 (median dose 360). The evaluation consisted of a history, physical examination, electrocardiogram (ECG), signal averaged ECG, 24-hour ambulatory ECG, echocardiography and radionuclide angiography. Eighteen of 31 (58%) patients showed cardiac toxicity, defined as having one or more of the following abnormalities: late potentials, complex ventricular arrhythmias, left ventricular dilation, decreased shortening fraction, or decreased ejection fraction. The incidence of cardiac abnormalities increased with length of follow-up (P< or = .05). No correlation could be demonstrated between cumulative dose of doxorubicin and cardiac status, except for heart rate variability. When adjusted to body surface area, the left ventricular posterior wall thickness (LVPW index) was decreased in all patients. The incidence of doxorubicin-induced cardiotoxicity is high and increases with follow-up, irrespective of cumulative dose. Life-long cardiac follow-up in these patients is warranted. The results of our study suggest that heart rate variability and LVPW index could be sensitive indicators for cardiotoxicity.

Adolescent↗
PubMed1996

Renal function after unilateral nephrectomy for Wilms' tumour: the influence of radiation therapy.

The effect of therapy on renal function after unilateral nephrectomy for Wilms' tumour was studied. In the second year following unilateral nephrectomy, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were estimated simultaneously by measuring 125I-iothalamate clearance and 131I-hippurate clearance. Of 41 evaluable patients, 29 received chemotherapy as sole treatment modality following nephrectomy (group 1); 12 patients additionally received radiation therapy to a field that included the remaining kidney (group 2). Results were expressed as standard deviation scores (z-scores). In group 1, mean z-score for GFR was -0.27 (94.6% of normal) and in group 2 mean z-score was -1.51 (72.7% of normal for two kidneys) (P = 0.022, Mann-Whitney U-test). Mean z-score for ERPF was -0.09 (97.0%) in group 1 and -1.53 (73.8%) in group 2 (P = 0.039). It was concluded that the combination of chemotherapy and radiation therapy, in contrast to chemotherapy alone, negatively affects the ability of the remaining kidney to adjust its function after the loss of its counterpart.

Child↗
PubMed1996

What was where? Memory for object locations.

Three experiments are reported on short-term memory for object location. Stimulus displays containing different numbers and types of objects were presented for 30 seconds, after which subjects were required to relocate the various objects within the display, merely to reconstruct positions, or to assign objects correctly to an equal number of premarked positions. In all experiments half the trials were performed with concurrent articulatory suppression. The results support the hypothesis that two processes can be distinguished: one that underlies the construction of a positional map and one that assigns objects to positions. These processes are differentially affected by object numbers and articulatory suppression. This hypothesis is discussed in terms of Baddeley's (1986) working memory model and Kosslyn's (1987) distinction between "categorical" and "coordinate" spatial relations.

Adult↗
PubMed1994

Development and test of an extendable endoprosthesis for bone reconstruction in the leg.

A malignant bone tumour may develop in the femur of a child. In the majority of cases it will be necessary to resect the bone involved, growth plate and adjacent tissues. A modular endoprosthetic system has been developed which can be extended non-invasively to bridge the defect resulting from such a resection. Elongation is achieved by using an external magnetic field. In vitro tests with a prototype showed that the lengthening element met all requirements. Six animal experiments showed that the lengthening element also functioned in vivo.

Animals↗
PubMed1993

The covert repair hypothesis: prearticulatory repair processes in normal and stuttered disfluencies.

Self-repairing of speech errors demonstrates that speakers possess a monitoring device with which they verify the correctness of the speech flow. There is substantial evidence that this speech monitor not only comprises an auditory component (i.e., hearing one's own speech), but also an internal part: inspection of the speech program prior to its motoric execution. Errors thus may be detected before they are actually articulated. In the covert repair hypothesis of disfluency, this internal error detection possibility has been extended with an internal correction counterpart. Basically, the covert repair hypothesis contends that disfluencies reflect the interfering side-effects of covert, prearticulatory repairing of speech programming errors on the ongoing speech. Internally detecting and correcting an error obstructs the concurrent articulation in such manner that a disfluent speech event will result. Further, it is shown how, by combining a small number of typical overt self-repair features such as interrupting after error detection, retracing in an utterance, and marking the correction with editing terms, one can parsimoniously account for the specific forms disfluencies are known to take. This reasoning is argued to apply to both normal and stuttered disfluency. With respect to the crucial question concerning what makes stuttering speakers so greatly disfluent, it is hypothesized that their abilities to generate error-free speech programs are disordered. Hence, abundant stuttering derives from the need to repeatedly repair one's speech programs before their speech motor execution.

Auditory Perception↗
PubMed1992

Quality of life in bone tumor patients comparing limb salvage and amputation of the lower extremity.

In 33 long-term survivors of lower extremity bone cancer quality-of-life data were studied following limb salvage compared to amputation. Self-report questionnaires, semistructured interviews and visual analog scales were used to measure psychoneurotic and somatical distress, activities of daily living, self-esteem, and adjustment to illness. Fourteen patients with limb salvage (age 13-56 years, median 24) and 19 patients with an amputation (age 21-53 years, median 27) were evaluated 2-17 years (median 10 years) after surgery. The differences between the two groups were not statistically significant. However, physical complaints were reported more often by limb salvage patients, whereas the amputees showed a trend toward lower self-esteem and isolation in social life, due to their disability. Both groups felt equal diminution of quality of life and disability as measured on the visual analog scale. These findings could support the cosmetic advantage of limb salvage compared to amputation.

Adolescent↗