Working Memory

Visual events are structured in space and time, yet models of visual working memory have largely relied on tasks emphasizing spatial aspects. Here, we show that temporal properties of visual events are incidentally encoded along with spatial properties. Across several experiments, participants performed a colour-change-detection task, in which each item had unique but task-irrelevant spatial and temporal coordinates at encoding. The key manipulation concerned the retrieval context: The test array was identical to the memory array in terms of either its entire spatiotemporal structure, or only its spatial or temporal structure. Removing spatial or temporal information at retrieval resulted in performance costs, indicating that memory relied to some degree on both spatial and temporal contexts in which items were initially perceived. No comparable costs were observed for a different task-irrelevant feature dimension (size). Encoding of the spatiotemporal structure occurred incidentally, not strategically, as it was robust even when the retrieval context was perfectly predictable. However, spatial and temporal inter-item spacings influenced the weighting of spatial and temporal information: It favoured the domain in which items were more widely spaced, likely facilitating their individuation and thereby access to memory representations. Across individuals, the weighting of spatial and temporal information varied substantially, but it remained consistent across days, suggesting stable preferences for coding in the spatial or temporal domain. We propose that time serves a similar function as space in the representational architecture of visual working memory, providing a reference frame in which objects are bound.

When memorizing the locations of multiple objects in visual working memory, these locations are not represented individually but based on the global spatial configuration formed by the memorized objects. We performed multiple experiments studying the reorganizing of spatial configurations in visual working memory based on an informative retro-cue within a location change detection task. We observed that participants could reorganize the global spatial configuration into a partial configuration containing the retro-cued objects during maintenance. Further, reorganization occurred across a wide range of different set sizes even up to 16 objects. Finally, our data suggests that the organization of visual working memory based on spatial configurations seems to depend on eye movements. That is, the influence of spatial configurations on change detection performance was stronger when participants were allowed to move their eyes than when we enforced fixation using an eye-tracker. We discuss our findings in the context of the potential memory representation underlying spatial configurations in visual working memory.

o Only certain sounds disturb certain cognitive functions. Verbal serial recall of unrelated verbal items (e.g. numbers, consonants, or words) has been proven to be significantly reduced by certain task-irrelevant background sounds (Irrelevant Sound Effect), e.g. speech. So-called changing-state sounds, characterized by successively differing auditory-perceptual tokens (e.g. "beh, tie, peh, buh, ..."), disturb verbal short-term memory significantly more than so-called steady-state sounds, which are constituted by a repeating auditory-perceptual token (e.g. "bah, bah, bah, ..."). It is still subject of debate, whether phonological interferences between automatic processing of the background speech signal and volitional processing of the verbal memory material are decisive for the disruptive effect to occur. Thus, reducing the phonological content of background speech should diminish its disturbance impact on verbal serial recall. In one experiment (n=30), we compared the effects of changing-state and steady-state syllable sequences on verbal serial recall. These background sounds were either presented as the original speech signal, or as its modified version through sinewave synthesis (sinewave speech). Sinewave synthesis largely preserves the temporal-spectral complexity of the speech sound (and thus the changing-state content), while the phonological content is greatly reduced. As expected, changing-state sounds were more disturbing than steady-state sounds in both sinusoidal and natural speech. However, the changing- and steady-state sinewave speech sequences reduced performance less than the corresponding original speech sounds. We conclude that despite comparable temporal-spectral complexity, the original speech reduced verbal short-term memory to a greater extent than the phonologically degraded sinewave speech due to its higher phonological content.

The development of the four basic arithmetic operation skills is the main objectives of the primary school mathematics (math) curricula. Recent research shows that these skills are related to working memory capacity of the students. In line with these findings, the purpose of this research is to determine the impacts of the working memory components on the multiplication skills of 3rd graders. The study was carried out with 60 third grade students (23 female and 37 male) at a private primary school in Istanbul. In order to measure the participants’ capacity of working memory due to its components, the tasks named as the counting recall test, digit span test, block recall test were designed and administered on computer programs. In addition, participants’ multiplication skills were measured by multiplication tests. Linear multiple regression was used to analyze the data. The results of analysis revealed that the best predictor variable of multiplication skills was the central executive component of working memory. However, the phonological loop (PL) and the visuo-spatial sketchpad (VSSP) components of the working memory were not significant predictors for multiplication skills of the 3rd grade students.

Previous work has shown bidirectional interactions of Working Memory (WM) and perception, in that the contents of WM can alter what we perceive and vice versa. However, from a decision-theoretic perspective, subjective perceptual reports can be altered through at least two separate mechanisms (i) multiplicative modulations of perceptual sensitivity (that are expressed e.g., in the local slope of the psychometric function) and (ii) additive shifts of the response criterion (that are expressed e.g., in parallel displacement of the psychometric function). Here, using a novel spatiotemporal sampling paradigm and reverse correlation analysis of psychometric weight, we demonstrate both types of interaction and show that they are functionally dissociable. Concurrent WM content modulated local perceptual sensitivity, consistent with a low-level bias of visuospatial attention. However, this effect was ephemeral and dissipated quickly with perceptual task engagement. Independently, we observed a strong additive response bias that was lasting and bidirectional, indicating a locus of interference at a late decisional processing stage. Together, these findings indicate that WM and perception may interact at distinct stages of the cortical processing hierarchy and at different levels of abstraction, consistent with a dynamically distributed view of WM storage.