Serial Recall Order and Semantic Features of Category Fluency Words to Study Semantic Memory in Normal Ageing

Background: Category Fluency Test (CFT) is a common measure of semantic memory (SM). Test performance, however, is also influenced by other cognitive functions. We here propose a scoring procedure that quantifies the correlation between the serial recall order (SRO) of words retrieved during the CFT and a number of linguistic features, to obtain purer SM measures. To put this methodology to the test, we addressed a proof-of-concept hypothesis whereby, in alignment with the literature, older adults would show better SM.Methods: Ninety participants (45 aged 18–21 years; 45 aged 70–81 years) with normal neurological and cognitive functioning completed a 1-min CFT. SRO was scored as an ordinal variable incrementing by one unit for each valid entry. Each word was also scored for 16 additional linguistic features. Participant-specific normalised correlation coefficients were calculated between SRO and each feature and were analysed with group comparisons and graph theory.Results: Younger adults showed more negative correlations between SRO and “valence” (a feature of words pleasantness). This was driven by the first five words generated. When analysed with graph theory, SRO had significantly higher degree and lower betweenness centrality among older adults.Conclusion: In older adults, SM relies significantly less on pleasantness of entries typically retrieved without semantic control. Moreover, graph-theory metrics indicated better optimised links between SRO and linguistic features in this group. These findings are aligned with the principle whereby SM processes tend to solidify with ageing. Although additional work is needed in support of an SRO-based item-level scoring procedure of CFT performance, these initial findings suggest that this methodology could be of help in characterising SM in a purer form.

Transplant Tissue: Cryolife Human Soft Tissue Implants Recalled

In a rare step, the U.S. Food and Drug Administration (FDA) in August ordered Cryolife Corporation to recall all human soft tissue it had processed since October of last year, stating that the safety of Cryolife products could not be assured. Although a subsequent agreement between the FDA and Cryolife led to a limited relaxation on the recall order for “medically urgent uses when alternative therapies are exhausted or unavailable,” the sale of Cryolife soft tissue remains severely restricted. Cryolife insists that its procedures are safe and that its overall rates of infection are extremely low, and is appealing the FDA recall?Cryolife is the nation’s largest processor of donated human tissue, and supplies 15 to 20 percent of the market for soft tissue implants. Such implants are widely used in elective orthopedic surgery: about 650,000 Americans have surgery involving soft tissue implants each year. Cryolife also processes 70 percent of the country’s heart valves.

Effect of Recall Order on Long-Term Recency

The effect of recall order on long-term recency effects in the continuous-distractor paradigm was investigated. Each list contained a series of pairs, each of a word and a number. In a recall session, subjects were given the numbers as probes and recalled the words paired with the numbers. Long-term recency effects were largely reduced when subjects recalled words from the primacy portion prior to other words, as in the case of short-term recency effects observed in the immediate-recall paradigm. These results suggest that the same mechanisms underlie the short-term and the long-term recency effects.

Separating Central Mechanisms by POCs: Evidence for an Input—Output Buffer

Four experiments were performed, in each of which two sub-lists of items were presented for later recall, with varying priorities for success on each of the lists. All showed a trade-off, indicating that at some point the two lists were using the same mechanisms. In the two cases where presentation was simultaneous, however, the effects of priority interacted with those of recall order—that is, the items recalled first showed a larger effect of priority than did those recalled second. In the two cases where one sub-list arrived after the other, the low-priority items gave just as large an effect of recall order as the high-priority items. The second list presented did, however, show a larger effect of recall order than the first list presented. It is argued that the systems shared between two sublists involve some representations that are not disturbed by output, as well as an input—output buffer. The latter can hold a little extra information temporarily, but is disturbed by output; for successive lists it is dedicated largely to the most recently received list, but for simultaneous lists it is shared between the two lists in proportion to priority.