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P F Liddle

Publications and source records attributed to P F Liddle.

84 records · Page 5Linked to original sources
PubMed1987

Schizophrenic syndromes, cognitive performance and neurological dysfunction.

In a sample of chronic schizophrenic patients, a group of symptoms which included poverty of speech and lack of spontaneous movement was found to be associated with poor performance in tests of conceptual thinking, object naming and long-term memory, and also with cortical neurological signs. A second group of symptoms which included formal thought disorder and inappropriate affect was associated with poor performance in tests of concentration, immediate recall and word learning, and with cortical neurological signs. The findings suggest that these two syndromes are associated with dysfunction at two different sites within the frontal lobes. A third group of symptoms, comprising various delusions and hallucinations, was associated with poor figure-ground perception, and might reflect temporal lobe dysfunction.

Adult↗
PubMed1987

The symptoms of chronic schizophrenia. A re-examination of the positive-negative dichotomy.

The relationships between symptoms in 40 schizophrenic patients, selected for persistence of symptoms, were examined. The symptoms segregated into three syndromes: psychomotor poverty (poverty of speech, lack of spontaneous movement and various aspects of blunting of affect); disorganisation (inappropriate affect, poverty of content of speech, and disturbances of the form of thought); and reality distortion (particular types of delusions and hallucinations). Both the psychomotor poverty and disorganisation syndromes were associated with social and occupational impairment; in particular, the psychomotor poverty syndrome was associated with impairment of personal relationships, and the disorganisation syndrome with poor self-care and impersistence at work.

Adult↗
PubMed1984

Age disorientation in chronic schizophrenia is associated with global intellectual impairment.

From a population of long-stay patients with a diagnosis of schizophrenia according to the St Louis criteria, a group of 21 patients with 'age disorientation' was selected, and compared on a series of tests of intellect and learning capacity with a matched control group of 21 schizophrenic patients without this feature. The age-disorientated patients demonstrated substantial impairments on tests of orientation and general knowledge, associational learning, the 'famous personality' test, tests of vocabulary and aphasia, Raven's matrices, the digit-symbol substitution test and the mental test score. We conclude that profound 'organic-type' psychological deficits (global impairment of intellectual function associated with temporal disorientation) undoubtedly occur in chronic schizophrenia. The findings on the 'famous personality' test and the Peabody vocabulary test did not exclude the possibility that such impairment arises early in life, at a time preceding the onset of the illness which leads to hospital admission.

Chronic Disease↗
PubMed1977

The isolation and characterization of differentially phosphorylated fractions of phosphofructokinase from rabbit skeletal muscle.

A preparation of phosphofructokinase from rabbit skeletal muscle is described which exploits the association-dissociation properties of the enzyme. Phosphofructokinase to prepared is partially phosphorylated and may be fractioned into three distinct species with sedimentation coefficients of 30 S, 18 S and 13 S by chromatography of agarose gels, hydroxyapatite or DEAE-cellulose. Measurements of alkali-labile phosphate content (phosphoserine and/or phosphothreonine) show that fractions consisting almost exclusively of 30-S species and fractions consisting predominantly of 18-S and 13-S species contain approximately 0.15 and 0.29 mol of phosphate per phosphofructokinase monomer (Mr = 80000) respectively. The results are interpreted in terms of at least two 13-S components which differ in their phosphate contents and also in their self-association properties. The possible significance of phosphorylation is discussed.

Animals↗
PubMed1974

The preparation and properties of pyruvate kinase from yeast.

A new method is described for the preparation of pyruvate kinase from yeast. This eliminates proteolysis during the preparation. The molecular weight of yeast pyruvate kinase is 215000, and it is composed of four subunits. Such properties of the enzyme as its extinction coefficient, cold-lability, thiol-group reactivity and binding of Mn(2+) ions are compared with those previously reported for yeast pyruvate kinase prepared by different methods. The specific activity is significantly higher than previously observed, but otherwise the enzyme is similar, apart from its molecular weight and Mn(2+)-binding characteristics, to preparations from Saccharomyces cerevisiae obtained in this laboratory (e.g. Fell et al., 1972, and references therein) and that of C. H. Suelter (e.g. Kuczenski & Suelter, 1971, and references therein), and is different from the enzyme isolated from Saccharomyces carlsbergensis by B. Hess and his co-workers (e.g. Wieker & Hess, 1972, and references therein).

Benzoates↗
PubMedDate not supplied

Dysphoric and depressive symptoms in chronic schizophrenia.

This study suggests that depressive symptoms are less common in severe, chronic, schizophrenic inpatients than would be predicted if these symptoms were manifestations of negative symptoms or drug-induced parkinsonism. The findings further suggest that depressive symptoms in such patients are independent phenomena which conform to a depressive syndrome. This depression does not represent a misidentification of the negative symptoms affective flattening and alogia, as measured by the SANS, or parkinsonism or akathisia. The study findings fail to support the view that long-term depot antipsychotic medication plays an important role in the genesis of depression and dysphoria in chronic schizophrenic patients. Depressive symptoms were found to occur as frequently, and dysphoria more frequently, in schizophrenic patients in the year after drug withdrawal compared with patients continuing on maintenance drug treatment for the same period.

Administration, Oral↗
PubMedDate not supplied

Entropy and cortical activity: information theory and PET findings.

Functional segregation requires convergence and divergence of neuroanatomical connections. Furthermore, the nature of functional segregation suggests that (1) signals in convergent afferents are correlated and (2) signals in divergent efferents are uncorrelated. The aim of this article is to show that this arrangement can be predicted mathematically, using information theory and an idealized model of cortical processing. In theory, the existence of bifurcating axons limits the number of independent output channels from any small cortical region, relative to the number of inputs. An information theoretic analysis of this special (high input:output ratio) constraint indicates that the maximal transfer of information between inputs, to a cortical region, and its outputs will occur when (1) extrinsic connectivity to the area is organized such that the entropy of neural activity in afferents is optimally low and (2) connectivity intrinsic to the region is arranged to maximize the entropy measured at the initial segments of projection neurons. Under the constraints of the model, a low entropy is synonymous with high correlations between axonal firing rates (and vice versa). Consequently this antisymmetric arrangement of functional activity in convergent and divergent connections underlying functional segregation is exactly that predicted by the principle of maximum preservation of information, considered in the context of axonal bifurcation. The hypothesis that firing in convergent afferents is correlated (has low entropy) and spatially coherent was tested using positron emission tomographic measurements of cortical synaptic function in man. This hypothesis was confirmed.

Afferent Pathways↗
PubMedDate not supplied

Functional topography: multidimensional scaling and functional connectivity in the brain.

In neuroimaging, functional mapping usually implies mapping function into an anatomical space, for example, using statistical parametric mapping to identify activation foci, or the characterization of distributed changes with spatial modes (eigenimages or principal components) (Friston et al., 1993a). This article is about a complementary approach, namely, mapping anatomy into a functional space. We describe a simple variant of multidimensional scaling (principal coordinates analysis; Gower, 1966) that uses functional connectivity as its metric. The scaling transformation maps anatomy into a functional space. The topography, or proximity relationships, in this space embody the functional connectivity among brain regions. The higher the functional connectivity, the closer the regions. Functional connectivity is defined here as the correlation between remote neurophysiological events. The technique represents a descriptive characterization of anatomically distributed changes in the brain that reveals the structure of corticocortical interactions in terms of functional correlations. To illustrate the approach we have analyzed data from normal subjects and schizophrenic patients obtained with PET during the performance of word generation tasks. In particular, we focus on prefrontotemporal integration in normal subjects and show that, in schizophrenia, the left temporal regions and prefrontal cortex evidence abnormal functional connectivity.

Brain↗
PubMedDate not supplied

Plastic transformation of PET images.

A theory and technique are presented that allow nonlinear resampling of positron emission tomography data to remove nonlinear differences in brain shape. The resampling is determined empirically by a function relating the observed image and a desired template. The validity, reliability, and precision of the plastic transformation are compared with linear rescaling alone, within, and between subjects.

Brain↗