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Biomedical subjects

J I Campbell

Publications and source records attributed to J I Campbell.

15 recordsLinked to original sources
PubMed1996

Inhibitory processes in sequential retrieval: evidence from variable-lag repetition priming.

Performance of simple mental arithmetic provides a sensitive measure of subtle inhibitory and excitatory processes operating in sequential retrieval. Specifically, the probability that an error (e.g., 6 x 7 = 36) matches an earlier answer is below chance for the preceding trial (negative error priming), greater-than-chance for intermediate lags (positive error priming), and returns to chance after about 10 intervening trials (approximately 60 sec) (Campbell & Clark, 1989). Negative error priming suggests that inhibitory processes initially suppress just-produced items and temporarily mask excitatory effects of recent retrievals. To test further the inhibition hypothesis of negative error priming, we examined repetition priming effects at variable lags. The results demonstrate similar non-monotonic functions for error priming and repetition priming as a function of lag, consistent with the hypothesized decay of inhibitory memory processes.

Adolescent↗
PubMed1996

Retrieval processes in arithmetic production and verification.

To investigate whether arithmetic production and verification involve the same retrieval processes, we alternated multiplication production trials (e.g., 9 x 6 = ?) with verification trials (4 x 9 = 36, true or false?) and analyzed positive error priming. Positive error priming is the phenomenon in which errors frequently match correct answers from preceding problems. Production errors were strongly primed by previous production trials (the error-answer matching rate was about 90% greater than expected by chance), but production errors were not strongly primed by previous verification trials (approximately 13% above chance). Conversely, false-verification errors were primed by previous verification trials (approximately 25% above chance), but not by production trials. The results indicated that arithmetic production and verification were mediated by different memory processes and suggest a familiarity-based over a retrieval-based model of arithmetic verification.

Adolescent↗
PubMed1994

Architectures for numerical cognition.

Current theories of numerical cognition differ in assumptions about the componential architecture of number processing and about the extent of notation-specific processes. To investigate these issues, 64 adult subjects were tested on simple addition and multiplication problems presented in Arabic digit or English number-word format. Overall, response times and error rates were much higher with the word format, but more importantly, presentation format interacted with arithmetic operation and problem size. Operation errors (2 + 4 = 8), operand-naming errors (2 + 8 = 8), and operand-intrusion errors (9 x 6 = 36) were each characterized by a different format x operation interaction, and analysis of inter-trial error priming showed selective interference from preceding trials as a function of number format. These types of format-specific retrieval interference and operation-specific effects of format are problematic for models that hypothesize notation-independent memory processes for arithmetic. Furthermore, analyses of operand-naming errors, operand-intrusion errors, and other operand-priming effects, revealed strong interactions of number reading and number-fact retrieval processes; processes that are typically posited to be functionally independent. The results suggest a complex encoding architecture that incorporates notation-dependent activation of addition and multiplication facts, as well as interpenetration of number reading and number-fact retrieval processes.

Adult↗
PubMed1992

Network interference and number-fact retrieval: evidence from children's alphaplication.

The origins of several phenomena of number-fact retrieval were investigated by having children in Grades 3 and 4 memorize alphaplication facts (arithmetic-like memory items composed of letters instead of numbers). Alphaplication performance paralleled memory for arithmetic facts in several important respects: Results showed (a) a large performance advantage for tie (e.g., E, E = j) over nontie problems (E, I = p), (b) that most errors involved answers from the correct alpha-table, (c) that response times and error rates were strongly correlated across problems, (d) that the correct answers to poorly learned problems tended to be the most common error responses, and (e) that performance was lower for problems introduced later in the learning sequence. Taken together, these findings support a network-interference approach (Campbell & Graham, 1985) to memory for arithmetic facts.

Attention↗
PubMed1991

Integrated versus modular theories of number skills and acalculia.

This paper contrasts two views of the cognitive architecture underlying numerical skills and acalculia. According to the abstract-modular theory (e.g., McCloskey, Caramazza, & Basili, 1985), number processing is comprised of independent comprehension, calculation, and production subsystems that communicate via a single type of abstract quantity code. The alternative, specific-integrated theory (e.g., Campbell & Clark, 1988), proposes that visuospatial, verbal, and other modality-specific number codes are associatively connected as an encoding complex and that different facets of number processing generally involve common, rather than independent, processes. The hypothesis of specific number codes is supported by conceptual inadequacies of abstract codes, format-specific phenomena in calculation, the diversity of acalculias and individual differences in number processing, lateralization issues, and the role of format-specific codes in working memory. The integrated, associative view of number processing is supported by the dependence of modular views on abstract codes and other conceptual inadequacies, evidence for integrated associative networks in calculation tasks, acalculia phenomena, shortcomings in modular architectures for number-processing dissociations, close ties between semantic and verbal aspects of numbers, and continuities between number and nonnumber processing. These numerous logical and empirical considerations challenge the abstract-modular theory and support the encoding-complex view that number processing is effected by integrated associative networks of modality-specific number codes.

Humans↗
PubMed1991

Conditions of error priming in number-fact retrieval.

Analysis of errors in simple multiplication has shown that answers retrieved on previous trials are initially inhibited (negative error priming) but later are promoted as errors to subsequent problems (positive error priming). Two experiments investigated whether error priming is associated either with problem-specific retrieval processes or with representations of answers that can be manipulated independently of problems. In Experiment 1, answers were primed by visually presenting products for 200 msec prior to problems. Correct-answer primes facilitated retrieval, related-incorrect primes interfered with retrieval more than unrelated primes, and both effects were greater for more difficult problems. Primes affected only the trial on which they were presented, however, whereas both negative and positive error priming from previous problems were observed across trials. In Experiment 2, subjects named and retrieved multiplication products on alternating trials. Just-named products were inhibited as errors to the following multiplication problem (i.e., negative error priming), but, compared to positive priming from previous retrieved products, positive error priming from previously named numbers was weak. The results indicate that positive error priming is due mainly to an encoding or retrieval bias produced by previous problems, whereas negative error priming entails suppression, or de-selection, of answer representations.

Adolescent↗
PubMed1990

A recombinant fowlpox virus expressing the hemagglutinin-neuraminidase gene of Newcastle disease virus (NDV) protects chickens against challenge by NDV.

The hemagglutinin-neuraminidase (HN) gene from the Beaudette C strain of Newcastle disease virus (NDV) has been expressed in a recombinant fowlpox virus vector. The HN gene, under the control of the vaccinia p7.5 promoter, was inserted into a nonessential gene in the terminal inverted repeats of fowlpox virus. Expression was demonstrated in tissue culture, a protein of the correct size for fully glycosylated HN protein being recognized by an HN-specific monoclonal antibody on Western blots. When the recombinant fowlpox virus was inoculated into chickens by intravenous or wing-web routes, antibody which recognizes HN from purified NDV virions was produced. Protective immunity to NDV was generated in the chickens; at the highest dose of vaccine 100% of the chickens tested were protected against challenge with a virulent strain of NDV.

Animals↗
PubMed1990

A fowlpox virus vaccine vector with insertion sites in the terminal repeats: demonstration of its efficacy using the fusion gene of Newcastle disease virus.

In this paper we report the development and testing of a fowlpox virus vector system. Insertion sites in non-essential regions within the terminal inverted repeats of the virus have been characterised. Foreign genes inserted into these sites are shown to be present in two copies in the resultant recombinant virus. To test the potential use of this vector as a live vaccine the fusion gene of Newcastle disease virus (NDV) has been inserted into a vaccine strain of fowlpox virus, and inoculated into chickens. The experiments demonstrate the ability of the recombinant to protect chickens against challenge by a virulent strain of NDV and to elicit the formation of anti-fusion protein antibody.

Animals↗
PubMed1990

Insertion of the fusion gene from Newcastle disease virus into a non-essential region in the terminal repeats of fowlpox virus and demonstration of protective immunity induced by the recombinant.

In this paper we report on the identification of non-essential genes in the terminal repeats of the avipox-virus fowlpox virus and the use of these as insertion sites in a vector system. Foreign genes inserted into these sites are shown to be present in two copies in the resultant recombinant virus. To test the potential use of this vector as a live vaccine the fusion gene of Newcastle disease virus has been inserted into a vaccine strain of fowlpox virus and inoculated into chickens. The experiments demonstrate the ability of the recombinant to protect chickens against challenge by a virulent strain of Newcastle disease virus and to elicit the formation of an anti-fusion protein antibody.

Animals↗
PubMed1989

The phototrophic bacterium Rhodopseudomonas capsulata sp108 encodes an indigenous class A beta-lactamase.

The nucleotide sequence of a 2.37 kb DNA fragment derived from cloning a total DNA digest of Rhodopseudomonas capsulata sp108 was determined. The DNA codes for a beta-lactamase, a protein showing sequence similarity to the ampR protein of Enterobacter cloacae and an unidentified open reading frame. Hybridization experiments with a probe carrying DNA from within the beta-lactamase gene suggests a chromosomal location for the coding sequences in strain sp108 and in sp109, a penicillin-sensitive revertant of sp108 in which the enzyme is not inducible. A protein-sequence comparison of the deduced amino acid sequence of the Rps. capsulata beta-lactamase indicates that it is a Class A enzyme and that its sequence can be aligned with those of the characterized beta-lactamases from Staphylococcus aureus, Bacillus licheniformis and the Escherichia coli plasmid (R-TEM enzyme), with only a few insertions or deletions. The corresponding DNA sequence is, however, characteristically rhodopseudomonad, suggesting that it is not a recently transposed gene.

Amino Acid Sequence↗
PubMed1989

Tandem repeated sequences within the terminal region of the fowlpox virus genome.

A 6.2 kb BamHI terminal fragment from fowlpox virus has been cloned and the nucleotide sequence was determined. The fragment was cloned by S1 digestion of viral DNA and therefore does not contain the covalently closed terminal loop. The cloned sequences comprise a short (230 bp) unique region at the terminal end, which is adjacent to a 3.87 bp long, AT-rich region consisting of sets of short tandemly repeated units, 32 and 56 bp long. The remainder of the fragment is composed of a 2.18 kb unique region containing three major open reading frames. The amino acid sequence encoded by one of these has some similarity to that of platelet-derived growth factor.

Amino Acid Sequence↗
PubMed1988

Non-essential genes in the vaccinia virus HindIII K fragment: a gene related to serine protease inhibitors and a gene related to the 37K vaccinia virus major envelope antigen.

The complete nucleotide sequence of a cloned copy of the HindIII K fragment of the WR strain of vaccinia virus has been determined. Eight open reading frames (ORFs) have been identified, on the basis of size and codon usage. The predicted amino acid sequences of the putative genes have been compared to the Protein Identification Resource and to published vaccinia virus sequences. One gene, predicted to encode a 42.2K protein, is highly related to the family of serine protease inhibitors. It shows approximately 25% identity to human antithrombin III and 19% identity to the cowpox virus 38K protein gene which is also related to serine protease inhibitors. The product of another gene shows a similar high level of identity to the 37K vaccinia virus major envelope antigen. The existence of viable deletion mutants and recombinants containing foreign DNA inserted into both these genes indicates that they are non-essential.

Amino Acid Sequence↗