Influences of cognitive control on number processing: New evidence from switching between two numerical tasks

A growing body of research suggests that basic numerical abilities such as number magnitude and number parity processing are influenced by cognitive control. So far, however, evidence for number processing being influenced by cognitive control came primarily from observed adaptations to stimulus set characteristics (e.g., ratio or order of specific stimulus types) and switches between a numerical and non-numerical task. Complementing this previous research, the present study employed a task switching paradigm exclusively involving numerical tasks (i.e., magnitude comparisons and parity judgements) to examine how cognitive control processes influence number processing. Participants were presented with a single-digit number and had to either judge its parity or compare its magnitude with a standard of 5, depending on a preceding cue. Based on previous results, we expected the numerical distance effect and the spatial-numerical association of response codes (SNARC) effect to be modulated in switch trials requiring the exertion of cognitive control. Partly in line with our expectations, the numerical distance effect was reduced in switch trials. However, no modulation of the SNARC effect was observed. The results pattern suggests that number processing is influenced by cognitive control, depending on task requirements and the type of numerical information (i.e., numerical magnitude vs spatial association of numbers) that is processed. To reconcile the present and previous results, we propose an information prioritisation account, suggesting that cognitive control primarily influences the processing of the information type that requires the most explicit processing.

Cognitive control in number processing: new evidence from number compatibility effects in task-switching

A growing body of research suggests that basic numerical abilities such as number magnitude processing are influenced by cognitive control processes. So far, evidence for number processing being affected by cognitive control processes stems primarily from observed adaptations of numerical effects to stimulus set characteristics (e.g. order or ratio of specific stimulus types). Complementing previous research on adaptation to stimulus set characteristics as an index of influences of cognitive control, the present study employed a task-switching paradigm to examine how cognitive control processes influence number processing. Participants were presented with a two-digit number and had to either judge its parity or compare its magnitude to a standard depending on a preceding cue. We expected numerical congruency effects (i.e. the unit-decade compatibility effect for magnitude comparisons and the parity congruity effect for parity judgements) to be larger in switch trials, as persisting activation of the task set of the preceding trial should increase interference. In contrast to our expectations, both numerical congruity effects were reduced following task switches as compared to repetitions. This interaction of task-switching with numerical congruency effects suggests an influence of cognitive control on basic number processing in form of persisting inhibition of previously abandoned task sets, so that these exert less influence on current number processing demands.

Cognitive control in number processing: new evidence from task switching

Recently, it was demonstrated that even basic numerical cognition such as the processing of number magnitude is under cognitive control. However, evidence so far primarily came from adaptation effects to stimulus characteristics (e.g., relative frequency of specific stimulus categories). Expanding this approach, we evaluated a possible influence of more active exertion of cognitive control on basic number processing in task switching. Participants had to perform a magnitude comparison task while we manipulated the order of compatible and incompatible input–output modalities (i.e., auditory/vocal input–visual/manual output vs. auditory/visual input–manual/vocal output, respectively) on the trial level, differentiating repeat vs. switch trials. Results indicated that the numerical distance effect but not the problem size effect was increased after a switch in input–output modality compatibility. In sum, these findings substantiate that basic number processing is under cognitive control by providing first evidence that it is influenced by the active exertion of cognitive control as required in task switching.

Darstellung und Kristallstruktur des Bis(triethylammonium)octasulfids, [HN(C2 H5)3]2 S8 / Preparation and Crystal Structure of the Bis(triethylammonium)octasulfide, [HN(C2 H5) 3]2S8

The preparation and crystal structure of the first octasulfide is described. The reaction of triethylamine, sulfur and dihydrogen sulfide in a solution of formamide yields orange-red crystals of bis(triethylammonium)octasulfide. The crystals are orthorhombic, space group Pbcn. with 4 molecules per unit cell. The cell constants are a = 23.709(4) Å. b = 13.276(4) Å. c = 7.388(2) Å. The chains of sulfur, S8 2-, do not show the common helical all-trans conformation, but a mixed sequence with the signs of the dihedral angles (++−++ and −−+−−).

Markers of foamy virus infections in monkeys, apes, and accidentally infected humans: appropriate testing fails to confirm suspected foamy virus prevalence in humans

Foamy viruses (FVs) persist in healthy individuals of various mammalian species, including nonhuman primates. Laboratory markers of FV infection are (1) virus in throat epithelium or peripheral blood lymphocytes (PBLs), (2) proviral DNA sequences in PBLs and various solid organs, and (3) antibodies reactive to viral antigens on Western blots, in radioimmunoprecipitation tests, and in immunofluorescence assays. Using PCR and serological tests, we readily detected FV markers in naturally infected African green monkeys, rhesus monkeys, and chimpanzees, as well as in accidentally infected humans. Transmission of simian foamy viruses to humans (by bite or inadvertent laboratory infection) leads to viral markers, without affecting the recipient. Reports on FV-associated clinical disorders (e.g., thyroid or neurological) have remained controversial. In this study we failed to detect, by PCR, viral sequences in the samples from 223 patients, including 16 HIV-infected Africans, 46 Graves' disease patients, and 28 patients with the de Quervain's thyroiditis. Evaluation of 2688 sera from suspected high-risk areas (e.g., Central and East Africa, or high-risk groups such as HIV-infected individuals and patients with AIDS, thyroid, and neurological disorders) did not reveal FV-specific antibodies in a single case. Previously reported FV seroprevalence in various populations has never been verified by appropriate confirmatory tests. The strain of "human foamy virus" has remained a unique isolate. In conclusion, FVs are unlikely--at present--to circulate in human populations.

Coronavirus induced encephalomyelitis: an immunodominant CD4(+)-T cell site on the nucleocapsid protein contributes to protection

In this communication we present clear evidence, that the N-protein of MHV-JHM contains immunodominant CD4+ T-cell sites. These sites were recognized by the immune system of virus infected Lewis rats. In previous investigations we have shown, that CD4+ T-cell lines with specificity for defined viral proteins can be selected from diseased Lewis rats and mediate protection, if transferred to otherwise lethally infected animals. To define regions of the N-protein, which are immunodominant for the T-cell response, we employed bacterially expressed N-protein and truncated subfragments of N as an antigen. We demonstrate, that T-cells from MHV-JHM infected, diseased Lewis rats recognized with high prevalence the carboxyterminal subfragment C4-N (95 aa) and to some extent the adjacent C3-N protein. The same results were obtained with T-cells derived from rats immunized with bacterially expressed N-protein or from animals vaccinated by a stable N-protein expressing vaccinia recombinant. Finally, transfer of CD4+ line T-cells to MHV-JHM infected rats specific for C4-N mediated protection against acute disease.

An immunodominant CD4+ T cell site on the nucleocapsid protein of murine coronavirus contributes to protection against encephalomyelitis

The murine coronavirus neurotropic strain JHM (MHV-JHM) nucleocapsid (N) protein induces a strong T-helper cell response in Lewis rats. It has been shown previously that N-specific CD4+ T cells can confer protection against acute disease upon transfer to otherwise lethally infected rats. To define the major antigenic regions that elicit this T cell response, truncated fragments of N protein were expressed from a bacterial expression vector and employed as T cell antigens. Lymphocytes from either MHV-JHM-infected or immunized rats were stimulated in culture with virus antigen, grown and tested for their specificity to the N protein fragments. The carboxy-terminally located C4-N fragment (95 amino acids) induced the most pronounced proliferative response irrespective of whether the lymphocyte culture was derived from immunized or MHV-JHM-infected rats. We established T cell lines specific for the truncated N protein fragments and tested their potential to mediate protection by transfer experiments. Only the T cell line C4-N and the T cell line specific for the full-length N protein were protective. By contrast, all truncated N protein fragments elicited a humoral immune response and contained antigenic sites recognized by antibodies from diseased rats.

Identification of pol-related gene products of human foamy virus

Human foamy virus pol gene fragments were molecularly cloned into a procaryotic expression vector. The expression pattern of the cloned fragments and nucleotide sequence analysis of the 5' pol gene region revealed that in HFV the protease (PR) is located in the pol open reading frame. Purified recombinant proteins were used to generate antibodies in rats. In immunoblot assay, using infected cells as antigen, a precursor protein with an apparent molecular mass (M(r)) of 127K was identified by antibodies directed against the reverse transcriptase (RT), RNaseH, or integrase (IN) domains of pol. With concentrated virus as antigen, the RT and RNaseH antibodies recognized a protein of 80K, the IN antiserum recognized a protein of 40K, and the PR antiserum detected a protein of approximately 10K.

Search for retrovirus in the chronic fatigue syndrome

AIM

To examine peripheral blood and skeletal muscle from patients with chronic fatigue syndrome for exogenous retrovirus.

METHODS

Blood samples from 30 patients and muscle biopsy specimens of 15 patients were examined for retroviral sequences by DNA extraction, polymerase chain reaction (PCR), and Southern blotting hybridisation. Sera were examined for human foamy virus by western immunoblotting and indirect immunofluorescence techniques.

RESULTS

No differences between the patient and control populations was found for any of the PCR primer sets used (gag, pol, env, and tax regions of HTLV I/II). An endogenous gag band was observed in both the patient and control groups. All sera were negative for antibody to human foamy virus.

CONCLUSION

The results indicate that there is no evidence of retroviral involvement in the chronic fatigue syndrome.

Nucleocapsid or spike protein-specific CD4+ T lymphocytes protect against coronavirus-induced encephalomyelitis in the absence of CD8+ T cells

To investigate the antiviral CD4+ T cell response in coronavirus MHV-JHM-induced encephalomyelitis, spleen and thymic lymphocytes from diseased rats were stimulated in culture with virus Ag, expanded and tested for their specificity to viral proteins and nucleocapsid (N) and spike (S) proteins that had been expressed in bacteria. A strong T cell response specific for N was measurable during acute disease, whereas S-specific T cells were only detectable in rats with a later onset of disease. CD4+ T cell lines with specificity for virus and either N or S protein were established and their influence on the course of a mouse hepatitis virus-JHM infection was investigated. All lines were of the CD4+ phenotype. Both N and S protein-specific CD4+ T cells conferred protection to infected Lewis rats and reduced the amount of infectious virus in the central nervous system. After transfer of CD4+ T cells and challenge with virus, an increase in the antiviral IgM response occurred, but neutralizing antibodies were not detectable during the period of virus clearance. Previous CD8+ cell depletion did not abrogate protection mediated by CD4+ T cell line transfer.

Nucleocapsid or spike protein-specific CD4+ T lymphocytes protect against coronavirus-induced encephalomyelitis in the absence of CD8+ T cells

To investigate the antiviral CD4+ T cell response in coronavirus MHV-JHM-induced encephalomyelitis, spleen and thymic lymphocytes from diseased rats were stimulated in culture with virus Ag, expanded and tested for their specificity to viral proteins and nucleocapsid (N) and spike (S) proteins that had been expressed in bacteria. A strong T cell response specific for N was measurable during acute disease, whereas S-specific T cells were only detectable in rats with a later onset of disease. CD4+ T cell lines with specificity for virus and either N or S protein were established and their influence on the course of a mouse hepatitis virus-JHM infection was investigated. All lines were of the CD4+ phenotype. Both N and S protein-specific CD4+ T cells conferred protection to infected Lewis rats and reduced the amount of infectious virus in the central nervous system. After transfer of CD4+ T cells and challenge with virus, an increase in the antiviral IgM response occurred, but neutralizing antibodies were not detectable during the period of virus clearance. Previous CD8+ cell depletion did not abrogate protection mediated by CD4+ T cell line transfer.