Biomedical subjects

P A Higham

Publications and source records attributed to P A Higham.

8 recordsLinked to original sources

PubMed2000

Beyond dissociation logic: evidence for controlled and automatic influences in artificial grammar learning.

Evidence for unconscious learning has typically been based on dissociations between direct and indirect tests of learning. Because of some inherent problems with dissociation logic, we applied the logic of opposition to 2 artificial grammar learning experiments. In Experiment 1, participants were exposed to 2 different sets of letter strings, generated from 2 different grammars, and later rated test strings for grammaticality with either in-concert (rate grammatical strings consistent with either structure) or opposition (rate grammatical only strings from 1 of the structures) instructions. Manipulating response deadline affected controlled, but not automatic influences. In Experiment 2, after similar training, a source-monitoring test was administered from which the in-concert and opposition conditions were derived. The test indicated that varying the retention interval affected controlled, but not automatic, influences. The results are discussed in terms of awareness, knowledge representation, and metacognitive processing.

Adolescent↗

PubMed2000

The controlled application of a strategy can still produce automatic effects: reply to Redington (2000).

The deliberate application of a strategy can have unintended discriminative effects. It is argued that these effects or influences on discriminative responding are the source of automatic influences and can be dissociated from controlled influences under appropriate circumstances. Such automatic influences are often latent in the interaction between the memory structures and the strategies that participants bring to bear in many implicit learning tasks.

Decision Making↗

PubMed2000

Judgment heuristics and recognition memory: prime identification and target-processing fluency.

In three experiments, the effect of identification of a briefly presented word (prime) on a subsequent recognition response to that word (target) was investigated. Theories of current processing fluency (e.g., Jacoby & Whitehouse, 1989) suggest that prime identification should reduce P(old) relative to prime misidentification because awareness of the prime provides a source to which to attribute target fluency, rendering attributions to prior presentation less likely. However, counter to these predictions, Experiment 1 demonstrated that prime identification increased P(old) relative to misidentified primes. It is hypothesized that this reversed effect was due to participants' using a heuristic that related prime identification success to prior presentation but was not based on current processing fluency. In Experiment 2, participants were induced to avoid using this heuristic by making an alternate source for prime identification success (display duration) highly available. Under these circumstances, prime identification reduced P(old) relative to prime misidentification, suggesting that participants now relied on current processing fluency rather than on prime identification success. Experiment 3 replicated the results of Experiments 1 and 2, but with fixed rather than variable prime displays.

Adult↗

PubMed1999

Effectiveness of bone cement containing tobramycin. An in vitro susceptibility study of 99 organisms found in infected joint arthroplasty.

We used 99 strains of organisms representative of orthopaedic infections to examine the effectiveness of a bone cement containing tobramycin, employing a modified in vitro Kirby-Bauer susceptibility model. The spectrum was broad, including Gram-positive and Gram-negative aerobic organisms, anaerobes and mycobacteria. Simplex P with added tobramycin was effective against most of the strains, including those which are resistant to typical systemic levels of tobramycin. Although direct correlation between in vitro and in vivo results is difficult, the study showed that tobramycin is stable to the exothermic polymerisation of the cement, and that it is released from the surface of the cement at concentrations high enough to inhibit the growth of most organisms which may be encountered after joint arthroplasty.

Anti-Bacterial Agents↗

PubMed1997

Dissociations of grammaticality and specific similarity effects in artificial grammar learning.

Three artificial grammer learning experiments investigated the memory processes underlying classification judgments. In Experiment 1, effects of grammatically, specific item similarity, and chunk frequency were analogous between classification and recognition tasks. In Experiments 2A and 2B, instructions to exclude "old" and "similar" test items, under conditions that limited the role of conscious recollection, dissociated grammaticality and similarity effects in classification. Dividing attention at test also produced a dissociation in Experiment 3. It is concluded that a dual-process model of classification, whereby the grammaticality and specific similarity effects are based mostly on automatic and intentional memory processes, respectively, is consistent with the results, whereas a unitary mechanism account is not. This conclusion is further supported by evidence indicating that chunk frequency had both implicit and explicit influences on classification judgments.

Humans↗

PubMed1997

Learning the experimenter's design: tacit sensitivity to the structure of memory lists.

Two experiments are reported that draw an analogy between experiments on verbal memory and experiments on tacit learning. Rules that experimenters use to select words for memory experiments, such as frequency, length, and grammatical class, produce consistencies to which subjects can become sensitive. Replicating the key results from the tacit learning literature, subjects in our experiments discriminated new words consistent with the experimenters' selection rules from inconsistent words, even when they could not describe those rules. The results also reveal a close relation between the information underlying both recognition memory and classification judgements. In particular, a "mirror effect" (Glanzer & Bowles, 1976) is found with both tasks. Implications for research on memory and learning are discussed.

Humans↗

PubMed1996

The artificial disc: theory, design and materials.

Low back pain is one of the most common medical conditions in the Western world. Disc degeneration, an inevitable process of aging, of variable rate and degree, is one of the major causes of low back pain. Currently, there are two major surgical interventions for treating conditions related to the degenerative disc: discectomy and fusion. Although discectomy and fusion produce a relatively good short-term clinical result in relieving pain, both these surgical treatments alter the biomechanics of the spine, possibly leading to further degeneration of the surrounding tissues and the discs at adjacent levels. Over the past 35 years, a tremendous effort has been made to develop an artificial disc to replace the degenerated disc. The goal is the restoration of the natural biomechanics of the segment after disc excision, thus relieving pain and preventing further degeneration at adjacent segments. However, the artificial disc faces a complex biomechanical environment which makes replication of the biomechanics difficult and long-term survival challenging to designs and materials. The purpose of this article is to examine the factors of importance in designing a disc replacement. Topics covered include the structure and function of the natural disc, the changes that occur with disc degeneration and existing methods of treatment for the degenerative spine. The progress in achieving a functional, long-lasting disc replacement is outlined.

Humans↗

PubMed1993

A histomorphometric and histologic analysis of the implant interface in five successful, autopsy-retrieved, noncemented porous-coated knee arthroplasties.

Five clinically successful, primary uncemented porous-coated anatomic knee implants were retrieved postmortem, 13-56 months after implantation, and were sectioned and evaluated histologically and histomorphometrically for bone ingrowth. The prosthesis-bone interface was divided into the following four zones: (1) the tissue prosthetic surface interface; (2) the beaded area; (3) the immediate beadless area; and (4) the marrow space. Although fibroosseous ingrowth was present in all cases, it varied quantitatively with each case and component. Average component bone ingrowth for the prosthesis interface (Zones 1 and 2) of patellae was 29%; tibias, 6%; and femora, 8%. In Zone 3, the percentage of bone apposed to the prosthesis for the patellae was 53%; tibias 36%; and femora, 32%. Zone 4, the marrow space, was not quantitated. The fibrous tissue filling nonbone-ingrown porous space in Zone 2 appeared "ligamentoid," connecting bone to beads within Zone 2 and between Zones 2 and 3. Zone 3 exhibited a bony plate formation parallel to the prostheses. No significant inflammation was noted. Overall there was more bone ingrowth into Zone 3 than Zones 1 and 2 with greater bone ingrowth found in the patellar components. The implant interface in clinically successful noncemented porous-coated prostheses of this design is characterized histologically by a noninflammatory fibroosseous ingrowth of varying degrees, and the fibrous component of this composite structure exhibits a highly organized pattern.

Aged↗