The semantic deficit in dementia: Connectionist approaches to what goes wrong in picture naming

Abstract

This paper addresses two main issues. First, what is the focus (or foci) of the naming deficit in patients with probable Alzheimer's disease? Secondly, how is semantic memory degraded by dementia? This paper will attempt to answer these questions by emphasizing connectionist modelling of semantic and neuropsychological processes. It will be argued that the loss of semantic microfeatures leads to the observed pattern of performance on naming and semantic memory tasks in dementia. These microfeatures may not represent linguistically simple lexical concepts or attributes, but are components of semantic representations that are relatively abstract. It is hypothesized that word meanings are equivalent to semantic attractors across these microfeatures. It is a central theme of this paper that connectionist modelling reveals how apparently disparate phenomena may in fact be related.     

Naming problems in dementia: Semantic or lexical?

Abstract

The naming behaviour was explored of patients moderately deteriorated with probable Alzheimer's disease (pAD) by analysing responses made on a picture naming and two word-picture matching tasks for the same items. Naming responses were classified into target and non-target and the relationship between non-target responses and their targets were explored. It was found that semantic relatedness influenced these non-target responses but frequency and imageability did not. The pAD participants performed significantly better on the two word-picture matching tasks than the naming task, while there was no difference on these within- and between-category tasks. These findings are explored with reference to a two-stage model of lexical access, which has separate storage of semantic, lexical and phonological information. The participants' difficulties appear to lie largely in retrieving the labels for items they comprehend.     

Evidence-based cognitive rehabilitation: updated review of the literature from 1998 through 2002

OBJECTIVE: To update the previous evidence-based recommendations of the Brain Injury Interdisciplinary Special Interest Group of the American Congress of Rehabilitation Medicine for cognitive rehabilitation of people with traumatic brain injury (TBI) and stroke, based on a systematic review of the literature from 1998 through 2002. DATA SOURCES: PubMed and Infotrieve literature searches were conducted using the terms attention, awareness, cognition, communication, executive, language, memory, perception, problem solving, and reasoning combined with each of the terms rehabilitation, remediation, and training. Reference lists from identified articles were reviewed and a bibliography listing 312 articles was compiled. STUDY SELECTION: One hundred eighteen articles were initially selected for inclusion. Thirty-one studies were excluded after detailed review. Excluded articles included 14 studies without data, 6 duplicate publications or follow-up studies, 5 nontreatment studies, 4 reviews, and 2 case studies involving diagnoses other than TBI or stroke. DATA EXTRACTION: Articles were assigned to 1 of 7 categories reflecting the primary area of intervention: attention; visual perception; apraxia; language and communication; memory; executive functioning, problem solving and awareness; and comprehensive-holistic cognitive rehabilitation. Articles were abstracted and levels of evidence determined using specific criteria. DATA SYNTHESIS: Of the 87 studies evaluated, 17 were rated as class I, 8 as class II, and 62 as class III. Evidence within each area of intervention was synthesized and recommendations for practice standards, practice guidelines, and practice options were made. CONCLUSIONS: There is substantial evidence to support cognitive-linguistic therapies for people with language deficits after left hemisphere stroke. New evidence supports training for apraxia after left hemisphere stroke. The evidence supports visuospatial rehabilitation for deficits associated with visual neglect after right hemisphere stroke. There is substantial evidence to support cognitive rehabilitation for people with TBI, including strategy training for mild memory impairment, strategy training for postacute attention deficits, and interventions for functional communication deficits. The overall analysis of 47 treatment comparisons, based on class I studies included in the current and previous review, reveals a differential benefit in favor of cognitive rehabilitation in 37 of 47 (78.7%) comparisons, with no comparison demonstrating a benefit in favor of the alternative treatment condition. Future research should move beyond the simple question of whether cognitive rehabilitation is effective, and examine the therapy factors and patient characteristics that optimize the clinical outcomes of cognitive rehabilitation.     

Sublethal and transgenerational effects of insecticides in developing Trichogramma galloi (Hymenoptera: Trichogrammatidae)

This study assessed the transgenerational effects of insecticides in developing Trichogramma galloi (Hymenoptera: Trichogrammatidae). Laboratory bioassays were performed in which five insecticides were sprayed on egg-larval, pre-pupal and pupal stages of the parasitoid. The interaction between insecticides and development stages of the parasitoid was not significant for the rate of F0 emergence. All insecticides significantly reduced the emergence of wasps, with the lowest emergence observed when they were applied to the pupal stage. For the sex ratio, only spinosad applied to the pre-pupal stage and triflumuron applied on the egg-larval and pre-pupal stages did not differ from the controls. Triflumuron applied to pre-pupae did not lead to any difference in the parasitism rate of the treated generation (F0) when compared to the control. There were no significant differences among survival curves for females of F0 when all insecticides were sprayed on the egg-larval stage. Both concentrations of lambda-cyhalothrin + thiamethoxam reduced female pre-pupal survival, and all treatments reduced female pupal survival. In addition, we observed a transgenerational effect of the insecticides on emergence and sex ratio of next generation (F1). Lambda-cyhalothrin + thiamethoxam (Min) applied to the pre-pupae and pupae, the maximum rate of the same insecticides applied to the egg-larvae and pre-pupae, and spinosad applied to pre-pupae all significantly reduced the adults emergence of T. galloi F1 generation. Only triflumuron did not alter the F1 sex ratio. These bioassays provide a basis for better understanding the effects of insecticide use on beneficial parasitoids.     

A longitudinal immunologic evaluation of hemophiliac patients

Over an average span of one year, we performed a prospective clinical and immunologic evaluation of 30 patients with hemophilia. No patient developed life-threatening opportunistic infection or malignancy; however, the immunologic abnormalities and lymphadenopathy initially present in nine patients (lymphadenopathy group) persisted. In addition, five patients, representing 24% of the initial group without lymphadenopathy, developed generalized lymphadenopathy (converter group). One episode of idiopathic thrombocytopenia (ITP) and one episode of staphylococcal sepsis occurred in this "converter" group; one episode of ITP also occurred in the lymphadenopathy group. Sixteen patients remained asymptomatic. At the time of the follow-up evaluation, those differences in mononuclear cell (MNC) percentages and numbers noted initially among the three hemophiliac groups were no longer present. Natural killer cell function alone or in the presence of biologic response modifiers was not different among hemophiliac and control groups. Before developing lymphadenopathy, the converter group of patients had significantly better lymphocyte mitogenic function than did the other two groups of patients with hemophilia. However, lymphocyte mitogenic responses of all groups of patients with hemophilia significantly deteriorated over the course of the study. The abnormal mitogenic responses noted in these patients was explained in part by higher levels of spontaneous suppressor cell activity in mononuclear cell preparations from patients with hemophilia. We conclude that long-term immunologic studies of this patient population requires both quantitative and qualitative evaluations. Our data show that patients with hemophilia have progressive dysfunction of cell- mediated immunity.     

Ricin inhibition of in vitro protein synthesis by plant ribosomes

In vitro translation systems were prepared with supernatant factors from wheat germ and 80S ribosomes from wheat germ, barley embryos, watermelon cotyledons, pea cotyledons, and castor bean endosperm. Ricin A-chain, which strongly inhibits protein synthesis by mammalian ribosomes, inhibited all of the plant ribosomal systems by 50% when present at 25-45 μg/ml—≈23,000 times the concentration needed to inhibit mammalian systems. Ricinus communis agglutinin A-chain, a protein similar to ricin A-chain, inhibited translation by the plant systems 50% at concentrations 5-10 times those of the ricin A-chain. Ribosomes from castor bean endosperm, the source of ricin and the agglutinin, were just as susceptible to the inhibitors as were ribosomes from the other four plants. Compartmentation of the inhibitors within vacuoles derived from protein bodies of the endosperm appears to be responsible for protecting cytoplasmic protein synthesis during germination of castor beans.     

In vitro characterization of the human recombinant soluble granulocyte- macrophage colony-stimulating factor receptor

We have cloned, expressed, and partially purified a naturally occurring, truncated, soluble form of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor alpha subunit to investigate its biochemical and biologic properties. The soluble receptor species lacks the transmembrane and cytoplasmic domains that are presumably removed from the intact receptor cDNA by a mechanism of alternative splicing. The resulting soluble 55- to 60-kD glycosylated receptor species binds GM-CSF with a dissociation constant (kd) of 3.8 nmol/L. The soluble GM-CSF receptor successfully competes for GM-CSF binding not only with the transmembrane-anchored GM-CSF receptor alpha subunit but also with the native oligomeric high-affinity receptor complex. In addition, in human bone marrow colony-forming assays, the soluble GM-CSF receptor species can antagonize the activity of GM-CSF. Our data suggest that the soluble GM-CSF receptor may be capable of acting in vivo as a modulator of the biologic activity of GM-CSF.     

Primary structure of human corticosteroid binding globulin, deduced from hepatic and pulmonary cDNAs, exhibits homology with serine protease inhibitors.

We have isolated and sequenced cDNAs for corticosteroid binding globulin (CBG) prepared from human liver and lung mRNAs. Our results indicate that CBG mRNA is relatively abundant in the liver but is also present in the lung, testis, and kidney. The liver CBG cDNA contains an open reading frame for a 405-amino acid (Mr 45,149) polypeptide. This includes a predominantly hydrophobic, leader sequence of 22 residues that precedes the known NH2-terminal sequence of human CBG. We, therefore, predict that the mature protein is composed of 383 amino acids and is a polypeptide of Mr 42,646. A second, in-frame, 72-base-pair cistron of unknown significance exists between the TAA termination codon for CBG and a possible polyadenylylation signal (AATAAA) located 16 nucleotides before the polyadenylylation site. The deduced amino acid sequence of mature CBG contains two cysteine residues and consensus sequences for the attachment of six possible N-linked oligosaccharide chains. The sequences of the human lung and liver CBG cDNAs differ by only one nucleotide within the proposed leader sequence, and we attribute this to a point mutation. No sequence homology was found between CBG and other steroid binding proteins, but there is a remarkable similarity between the amino acid sequences of CBG and of alpha 1-antitrypsin, and this extends to other members of the serpin (serine protease inhibitor) superfamily.