Can activated long-term memory maintain serial order information?

Does the extension of free time trigger spontaneous elaborative strategies in working memory?

Elaboration has emerged as a potential maintenance mechanism involved in the substantial contribution of long-term memory (LTM) to working memory (WM) performance. The objective of the current study was to determine whether elaborative strategies could be spontaneously implemented under favorable conditions. Across four experiments, the distribution of free-time periods was manipulated in a complex span task, while keeping the total amount of free time and cognitive load constant. As elaboration requires time to be set up, Experiment 1 elicited better WM performance in a condition with fewer long free-time periods compared to a condition with many short free-time periods. However, because this benefit did not persist during delayed recall, the following experiments aimed to further investigate this effect by manipulating factors supposed to modulate elaboration. In Experiment 2, half of the participants received no specific instructions regarding strategies whereas the other half were encouraged to use elaborative strategies. In Experiment 3, the to-be-maintained stimuli did or did not have LTM representations that are essential for elaboration (i.e., words or pseudowords). Finally, the last experiment used a self-strategy report to better understand the nature of the WM maintenance strategies spontaneously employed by participants. Despite a consistent effect of free time manipulation on WM recall, the explanatory assumption of elaboration was challenged by the unexpected lack of effect on LTM recall and on the type of strategy reported. Alternative explanations stemming from well-known factors influencing WM performance are discussed, and emphasis is placed on the potential contribution of direct semantic maintenance in WM.

Lexico-syntactic constraints influence verbal working memory in sentence-like lists

We test predictions from the language emergent perspective on verbal working memory that lexico-syntactic constraints should support both item and order memory. In natural language, long-term knowledge of lexico-syntactic patterns involving part of speech, verb biases, and noun animacy support language comprehension and production. In three experiments, participants were presented with randomly generated dative-like sentences or lists in which part of speech, verb biases, and animacy of a single word were manipulated. Participants were more likely to recall words in the correct position when presented with a verb over a noun in the verb position, a good dative verb over an intransitive verb in the verb position, and an animate noun over an inanimate noun in the subject noun position. These results demonstrate that interactions between words and their context in the form of lexico-syntactic constraints influence verbal working memory.

Phonological Working Memory Representations in the Left Inferior Parietal Lobe in the Face of Distraction and Neural Stimulation

The neural basis of phonological working memory (WM) was investigated through an examination of the effects of irrelevant speech distractors and disruptive neural stimulation from transcranial magnetic stimulation (TMS). Embedded processes models argue that the same regions involved in speech perception are used to support phonological WM whereas buffer models assume that a region separate from speech perception regions is used to support WM. Thus, according to the embedded processes approach but not the buffer approach, irrelevant speech and TMS to the speech perception region should disrupt the decoding of phonological WM representations. According to the buffer account, decoding of WM items should be possible in the buffer region despite distraction and should be disrupted with TMS to this region. Experiment 1 used fMRI and representational similarity analyses (RSA) with a delayed recognition memory paradigm using nonword stimuli. Results showed that decoding of memory items in the speech perception regions (superior temporal gyrus, STG) was possible in the absence of distractors. However, the decoding evidence in the left STG was susceptible to interference from distractors presented during the delay period whereas decoding in the proposed buffer region (supramarginal gyrus, SMG) persisted. Experiment 2 examined the causal roles of the speech processing region and the buffer region in phonological WM performance using TMS. TMS to the SMG during the early delay period caused a disruption in recognition performance for the memory nonwords, whereas stimulations at the STG and an occipital control region did not affect WM performance. Taken together, results from the two experiments are consistent with predictions of a buffer model of phonological WM, pointing to a critical role of the left SMG in maintaining phonological representations.