EXPRESS:Spatial Organisation in the Human Mind as a Function of the Distance Between Stimuli.

Studies investigating serial order in working memory have shown that participants from Western cultures are faster at responding to items presented at the beginning of a sequence using their left hand and faster at responding to items at the end with their right hand. This is known as the spatial positional association of response codes (SPoARC) effect. The SPoARC effect provides evidence that recently presented information is spatially organised in the cognitive system along a horizontal axis. This study investigated the flexibility of spatialisation by testing the effect that distance between items presented on a screen has on the magnitude of the SPoARC effect. It was hypothesised that by increasing the distance between items on a screen a larger SPoARC effect would be found. We used three conditions: central, narrow, and wide. In central, four random letters were presented sequentially at the centre of the screen, in narrow the letters were presented from left to right on the screen, wide was the same as narrow but the separation between the letters was larger. Participants consisted of 64 adults aged 18-55 years old. Participants were presented with four random letters, followed by single probe letter, participants had to indicate, by pressing a key on a normal keyboard, if the probe had been in the sequence. We analysed the data with multilevel modelling. We found evidence for the SPoARC effect in all three conditions. But no evidence that the effect varied between conditions.

Perceptual Clauses as Units of Production in Visual Descriptions.

Describing our visual environments is challenging because although an enormous amount of information is simultaneously available to the visual system, the language channel must impose a linear order on that information. Moreover, the production system is at least moderately incremental, meaning that it interleaves planning and speaking processes. Here, we address how the operations of these two cognitive systems are coordinated given their different characteristics. We propose the concept of a perceptual clause, defined as an interface representation that allows the visual and linguistic systems to exchange information. The perceptual clause serves as the input to the language formulator, which translates the representation into a linguistic sequence. Perceptual clauses capture speakers' ability to describe visual scenes coherently while at the same time taking advantage of the incremental abilities of the language production system.

Comparative Roles of the Caudate and Putamen in the Serial Order of Behavior: Effects of Striatal Glutamate Receptor Blockade on Variable versus Fixed Spatial Self-Ordered Sequencing in Marmosets.

Self-ordered sequencing is an important executive function involving planning and executing a series of steps to achieve goal-directed outcomes. The lateral frontal cortex is implicated in this behavior, but downstream striatal outputs remain relatively unexplored. We trained marmosets on a three-stimulus self-ordered spatial sequencing task using a touch-sensitive screen to explore the role of the caudate nucleus and putamen in random and fixed response arrays. By transiently blocking glutamatergic inputs to these regions, using intrastriatal CNQX microinfusions, we demonstrate that the caudate and putamen are both required for, but contribute differently to, flexible and fixed sequencing. CNQX into either the caudate or putamen impaired variable array accuracy, and infusions into both simultaneously elicited greater impairment. We demonstrated that continuous perseverative errors in variable array were caused by putamen infusions, likely due to interference with the putamen's established role in monitoring motor feedback. Caudate infusions, however, did not affect continuous errors, but did cause an upward trend in recurrent perseveration, possibly reflecting interference with the caudate's established role in spatial working memory and goal-directed planning. In contrast to variable array performance, while both caudate and putamen infusions impaired fixed array responding, the combined effects were not additive, suggesting possible competing roles. Infusions into either region individually, but not simultaneously, led to continuous perseveration. Recurrent perseveration in fixed arrays was caused by putamen, but not caudate, infusions. These results are consistent overall with a role of caudate in planning and flexible responding and the putamen in more rigid habitual or automatic responding.

Cortical network and projection neuron types that articulate serial order in a skilled motor behavior.

Skilled motor behaviors require orderly coordination of multiple constituent movements with sensory cues towards achieving a goal, but the underlying brain circuit mechanisms remain unclear. Here we show that target-guided reach-grasp-to-drink (RGD) in mice involves the ordering and coordination of a set of forelimb and oral actions. Cortex-wide activity imaging of multiple glutamatergic projection neuron (PN) types uncovered a network, involving the secondary motor cortex (MOs), forelimb primary motor and somatosensory cortex, that tracked RGD movements. Photo-inhibition highlighted MOs in coordinating RGD movements. Within the MOs, population neural trajectories tracked RGD progression and single neuron activities integrated across constituent movements. Notably, MOs intratelencephalic, pyramidal tract, and corticothalamic PN activities correlated with action coordination, showed distinct neural dynamics trajectories, and differentially contributed to movement coordination. Our results delineate a cortical network and key areas, PN types, and neural dynamics therein that articulate the serial order and coordination of a skilled behavior.

Sequential syntactic knowledge supports item but not order recall in verbal working memory.

Previous studies have shown that psycholinguistic effects such as lexico-semantic knowledge effects mainly determine item recall in verbal working memory (WM). However, we may expect that syntactic knowledge, involving knowledge about word-level sequential aspects of language, should also impact serial-order aspects of recall in WM. Evidence for this assumption is scarce and inconsistent and has been conducted in language with deterministic syntactic rules. In languages such as French, word position is determined in a probabilistic manner: an adjective is placed before or after a noun, depending on its lexico-semantic properties. We exploited this specificity of the French language for examining the impact of syntactic positional knowledge on both item and serial order recall in verbal WM. We presented lists with adjective-noun pairs for immediate serial recall, the adjectives being in regular or irregular position relative to the nouns. We observed increased recall performance when adjectives occurred in regular position; this effect was observed for item recall but not order recall scores. We propose an integration of verbal WM and syntactic processing models to account for this finding by assuming that the impact of syntactic knowledge on serial-order WM recall is indirect and mediated via syntax-dependent item-retrieval processes.

The effect of abstract inter-chunk relationships on serial-order control.

Hierarchical control is often thought to dissect a complex task space into isolated subspaces in order to eliminate interference. Yet, there is also evidence from serial-order control tasks that our cognitive system can make use of abstract relationships between different parts (chunks) of a sequence. Past evidence in this regard was limited to situations with ordered stimuli (e.g., numbers or positions) that may have aided the detection of relationships and allowed gradual learning and hypothesis testing. Therefore, we used a modified task-span paradigm (with no ordered elements between tasks) in which participants performed memorized sequences of tasks that were encoded in terms of separate chunks of three tasks each. To allow examination of learning effects, each sequence was "cycled" through repeatedly. Importantly, we compared sequences whose chunks were governed by a common, abstract grammar with sequences whose chunks were governed by different grammars. Experiment 1 examined the effect of relationships between shared-element chunks (e.g., ABB-BAA vs. ABB-BAB), Experiment 2 and 3 between different-element chunks (e.g., ABA-CDC vs. ABA-CCD), and Experiment 4 examined second-order relationships (e.g., ABA-ABB--CDC-CDD vs. ABA-ABB--CDC-CCD). Robust evidence in favor of beneficial effects of abstract inter-chunk relationships was obtained across all four experiments. Importantly, these effects were at least as strong in initial cycles of performing a given sequence as during later cycles, suggesting that the cognitive system operates with an "expectation of abstract relationships," rather than benefitting from them through gradual learning. We discuss the implications of these results for models of hierarchical control.

Serial attention to serial memory: The psychological refractory period in forward and backward cued recall.

Guided by the conjecture that memory retrieval is attention turned inward, we examined serial attention in serial memory, combining the psychological refractory period (PRP) procedure from attention research with cued recall of two items from brief six-item lists. We report six experiments showing robust PRP effects in cued recall from memory (1-4) and cued report from perceptual displays (5-6), which suggest that memory retrieval requires the same attentional bottleneck as "retrieval" from perception. There were strong direction effects in each memory experiment. Response time (RT) was shorter and accuracy was higher when the cues occurred in the forward direction (left-to-right, top-to-bottom, first-to-last), replicating differences between forward and backward serial recall. Cue positions had strong effects on RT and accuracy in the memory experiments (1-4). The pattern suggested that subjects find cued items in memory by stepping through the list from the beginning or the end, with a preference for starting at the beginning. The perceptual experiments (5-6) showed weak effects of position that were more consistent with direct access. In all experiments, the distance between the cues in the list (lag) had weak effects, suggesting that subjects searched for each cue from the beginning or end of the list more often than they moved through the list from the first cue to the second. Direction, distance, and lag effects on RT and inter-response interval changed with SOA in a manner that suggested they affect bottleneck or pre-bottleneck processes that create and execute a plan for successive retrievals. We conclude that sequential retrieval from memory and sequential attention to perception engage the same computations and we show how computational models of memory can be interpreted as models of attention focused on memory.

Heterogeneity of short-term memory deficits in children with dyslexia.

Many studies have highlighted short-term memory (STM) impairment in dyslexic individuals. Several studies showed deficits for both item and serial order aspects of verbal STM in dyslexic individuals. These group-based studies, however, do not inform us about the prevalence of these deficits and, importantly, their potential heterogeneity at the individual level. The present study examined both group-level and individual STM profiles in dyslexic and age-matched non-dyslexic children. While confirming previous group-based results of both item and serial order STM deficits, individual analyses indicated two distinct profiles: one profile was associated with verbal item STM and phonological impairment while another profile showed selective serial STM deficits in both verbal and visual domains. Our results highlight the need for practitioners to consider the heterogeneous nature of STM impairment in dyslexia and to adapt STM and reading treatment strategies accordingly.

What's so hard about hierarchical control? Pinpointing processing constraints within cue-based and serial-order control structures.

Most task spaces require a hierarchical structure, where decisions on one level are contingent on previous decisions made on one or more higher levels. While it is a truism that increasing the number of hierarchical levels makes it harder to solve a given task, the exact nature of this "number-of-levels" effect is not clear. On the one hand, processing costs might be strictly "local," incurred only when higher-level settings need to be updated, while otherwise lower-level decisions are insulated from the presence of higher-level settings (local updating costs with ballistic control). On the other hand, maintaining and integrating more complex hierarchical structures could require overall greater representational resources, negatively affecting each individual decision within the represented task space (global integration/maintenance costs). Further, navigation through hierarchical structures can be guided either through prompts in the environment (cue-based), or through sequential plans (serial-order based), with potentially distinct maintenance and updating demands. In two experiments, we assessed performance as a function of hierarchical level and format (serial-order vs. cue-based). Model comparisons showed that the pattern of costs in the serial-order format was consistent with a global maintenance/integration account. In contrast, in the cue-based format, costs arose at updating points and when one additional relevant level beyond the current decision was relevant, while additional levels produced no further costs. This overall constellation of costs can be explained by assuming that each decision requires checking the immediately relevant higher-level context for that decision. For cue-based control, this context involves the "next-level-up" rule, whereas in the serial-order format, each trial requires updating of the current position within the sequence, which in turn requires integration across all relevant hierarchical levels.

Effect of Spatial Contiguity on Learning Sequences of Positions / Efecto de la contigüidad espacial sobre el aprendizaje de secuencias de posiciones

Abstract Four conditions of spatial contiguity of positions were used to assess sequence learning. Two sequences of 16 and 25 positions presented in two matrices of 4x4 and 5x5 respectively were used. Within each matrix, 4 (in the 4x4 matrix) or 6 positions (in the 5x5 matrix) presented spatial contiguity. The place at the sequence in which contiguous positions occurred varied across groups. In this way, spatial contiguity of the 4 or 6 positions was presented at the beginning of the sequence (Group 1), in the middle part (Group 2), at the end of the sequence (Group 3) or it was presented a sequence in which all positions occurred without spatial contiguity (Group 4). 28 undergraduate students participated. Results showed no differences among groups in the number of trials required to reproduce the sequence correctly. Number of errors was lower when contiguous positions were presented at the beginning of the sequence. These findings are explained as a possible effect of accentuation of primacy given by the occurrence of contiguous positions at the beginning of the sequence.

Resumen Cuatro condiciones de contigüidad espacial de posiciones fueron empleadas para evaluar el aprendizaje de secuencias. Se emplearon dos secuencias de 16 y 25 posiciones presentadas en dos matrices de 4x4 y 5x5, respectivamente. Dentro de cada matriz, 4 (en la matriz de 4x4) o 6 posiciones (en la matriz de 5x5) presentaron contigüidad espacial. Entre grupos, se varió el punto de la secuencia en el que se presentaron las posiciones contiguas. De este modo, la contigüidad espacial de las 4 o 6 posiciones se presentó al inicio de la secuencia (Grupo 1), en la parte media (Grupo 2), al final de la secuencia (Grupo 3), o bien, se presentó una secuencia en la que todas las posiciones ocurrieron sin contigüidad espacial (Grupo 4). Participaron 28 estudiantes de licenciatura. Los resultados no mostraron diferencias entre grupos en cuanto al número de ensayos requeridos para reproducir la secuencia correctamente. El número de errores fue menor cuando las posiciones contiguas se presentaron al inicio de la secuencia. Los hallazgos se explican a partir de un posible efecto de acentuación de la primacía, dado por la ocurrencia de posiciones contiguas al inicio de la secuencia.

Choice between decision-making strategies in human route-following.

To follow a prescribed route, we must decide which way to turn at intersections. To do so, we can memorize either the serial order of directions or the associations between spatial cues and directions ("at the drug store, turn left"). Here, we investigate which of these two strategies is used if both are available. In Task S, all intersections looked exactly alike, and participants therefore had to use the serial order strategy to decide which way their route continued. In Task SA, each intersection displayed a unique spatial cue, and participants therefore could use either strategy. In Task A, each intersection displayed a unique cue, but the serial order of cues varied between trips, and participants therefore had to use the associative cue strategy. We found that route-following accuracy increased from trip to trip, was higher on routes with 12 rather than 18 intersections, and was higher on Task SA than on the other two tasks, both with 12 and with 18 intersections. Furthermore, participants on Task SA acquired substantial knowledge about the serial order of directions as well as about cue-direction associations, both with 12 and with 18 intersections. From this we conclude that, when both strategies were available, participants did not pick the better one but rather used both. This represents dual encoding, a phenomenon previously described for more elementary memory tasks. We further conclude that dual encoding may be implemented even if the memory load is not very high (i.e., even with only 12 intersections).

Effect of visual presentation format and recall direction on letter span and error patterns in Deaf signing and hearing adults.

Deaf signers consistently show shorter memory spans than hearing nonsigners, but the scope and nature of this difference remain unclear. The present study tested whether Deaf signers are biased toward flexible use of visual aspects of linguistic items. Matched samples of adult Deaf signers (N = 33) and hearing nonsigners (N = 32) performed a letter-span task with visual serial presentation, to bias phonological processing, and a simultaneous presentation, to bias visuospatial processing. We also manipulated short-term memory by varying recall direction (forward, backward). Analyses revealed reduced spans for Deaf signers compared with hearing nonsigners, backward compared with forward recall, and sequential compared with simultaneous presentation. Item-level responses indicated that Deaf signers made more errors than hearing nonsigners across three error types. Deaf signers also showed reduced item position binding compared with hearing nonsigners, which indicates differences related to item order and sequencing in tasks with printed, linguistic stimuli. Deaf signers were the only group who demonstrated reduced omission errors when switching from sequential to simultaneous presentation, suggesting flexible processing mechanisms. No group differences were found for a secondary spatial span test, indicating the scope of group differences for ordered information was limited to verbal items. Overall, results are consistent with flexible use of different memory cues in Deaf signers. A core area for future research includes evaluating reduced activation of phonological representations of linguistic items in Deaf signers. These results amplify a novel M3 model approach for evaluating how errors contribute to short-term memory differences in Deaf signers.

Sequential versus simultaneous presentation of memoranda in verbal working memory: (How) does it matter?

To-be-memorized information in verbal working memory (WM) can be presented sequentially, like in oral language, and simultaneously, like in written language. Few studies have addressed the importance and implications for verbal WM processing of these two presentation modes. While sequential presentation may favor discrete, temporal encoding processes, simultaneous presentation may favor spatial encoding processes. We compared immediate serial recall tasks for sequential versus simultaneous word list presentation with a specific focus on serial position curves of recall performance, transposition gradients, and the nature of serial order errors. First, we observed higher recall performance in the simultaneous compared to the sequential conditions, with a particularly large effect at end-of-list items. Moreover, results showed more transposition errors between non-adjacent items for the sequential condition, as well as more omission errors especially for start-of-list items. This observation can be explained in terms of differences in refreshing opportunities for start-of-list items during encoding between conditions. This study shows that the presentation mode of sequential material can have a significant impact on verbal WM performance, with an advantage for simultaneous encoding of sequence information.

The domain-specificity of serial order working memory.

Making a turn while driving is simple: turn on the indicator, check for cars, then turn. Two types of information are required to perform this sequence of events: information about the items (e.g., the correct indicator), and the serial order of those items (e.g., checking before turning rather than vice-versa). Previous research has found distinct working memory capacities (WMCs) for item and serial order information in both verbal and nonverbal domains. The current study investigates whether the serial order WMC is shared for sequences from different content domains. One hundred and fifty-three participants performed sequence matching tasks with verbal (letters and words) and nonverbal (locations and arrows) stimuli. The accuracy of detecting mismatched item-identity and serial order information in sequences was used to operationalize item and order WMC. Using structural equation modeling analyses, we directly compared models that included either domain-specific or domain-general serial order WMC latent variables, finding that models with domain-specific serial order WMC latent variables for verbal and nonverbal materials fit the data better than models with domain-general latent variables. The findings support the hypothesis that there are separate capacities for serial order working memory depending on the type of material being ordered.

When A is greater than B: Interactions between magnitude and serial order.

Processing ordinal information is an important aspect of cognitive ability, yet the nature of such ordinal representations remains largely unclear. Previously, it has been suggested that ordinal position is coded as magnitude, but this claim has not yet received direct empirical support. This study examined the nature of ordinal representations using a Stroop-like letter order judgment task. If ordinal position is coded as magnitude, then letter ordering and font size should interact. Experiments 1 and 2 identified a significant interaction between letter size and ordering. Specifically, a facilitation effect was observed for alphabetically ordered sequences with decreasing font size (e.g., ). This suggests an overlap in the mechanisms for order and magnitude processing. The finding also suggests that earlier ranks may be represented as "more" in such a magnitude-based code, and vice versa for later ranks.

Temporal grouping effects in verbal and musical short-term memory: Is serial order representation domain-general?

The question of the domain-general versus domain-specific nature of the serial order mechanisms involved in short-term memory is currently under debate. The present study aimed at addressing this question through the study of temporal grouping effects in short-term memory tasks with musical material, a domain which has received little interest so far. The goal was to determine whether positional coding-currently the best account of grouping effect in verbal short-term memory-represents a viable mechanism to explain grouping effects in the musical domain. In a first experiment, non-musicians performed serial reconstruction of 6-tone sequences, where half of the sequences was grouped by groups of three items and the other half presented at a regular pace. The overall data pattern suggests that temporal grouping exerts on tone sequences reconstruction the same effects as in the verbal domain, except for ordering errors which were not characterised by the typical increase of interpositions. This pattern has been replicated in two additional experiments with verbal material, using the same grouping structure as in the musical experiment. The findings support that verbal and musical short-term memory domains are characterised by similar temporal grouping effects for the recall of 6-item lists grouped by three, but it also suggests the existence of boundary condition to observe an increase in interposition errors predicted by positional theories.

Eye-movements reveal the serial position of the attended item in verbal working memory.

The problem of how the mind can retain sequentially organized information has a long research tradition that remains unresolved. While various computational models propose a mechanism of binding serial order information to position markers, the representational nature and processes that operate on these position markers are not clear. Recent behavioral work suggests that space is used to mark positions in serial order and that this process is governed by spatial attention. Based on the assumption that brain areas controlling spatial attention are also involved in saccadic planning, we continuously tracked the eye-movements as a direct measure of the spatial attention during retrieval from a verbal WM sequence. Participants memorized a sequence of auditory numbers. During retention, they heard a number-cue that did or did not belong to the memorized set. After this number-cue, a target-beep could be presented to which they had to respond if the number-cue belonged to the memorized sequence. In Experiment 1, the target-beep was either presented to the left or right ear, and in Experiment 2 bilaterally (removing any spatial aspect). We tested the hypothesis that systematic eye-movements are made when people retrieve items of sequences of auditory words and found that the retrieval of begin items resulted in leftward eye-movements and the retrieval of end items in rightward eye-movements. These observations indicate that the oculomotor system is also involved in the serial order processes in verbal WM thereby providing a promising novel approach to get insight into abstract cognitive processes.

The Neural Representation of Ordinal Information: Domain-Specific or Domain-General?

Ordinal processing allows for the representation of the sequential relations between stimuli and is a fundamental aspect of different cognitive domains such as verbal working memory (WM), language and numerical cognition. Several studies suggest common ordinal coding mechanisms across these different domains but direct between-domain comparisons of ordinal coding are rare and have led to contradictory evidence. This fMRI study examined the commonality of ordinal representations across the WM, the number, and the letter domains by using a multivoxel pattern analysis approach and by focusing on triplet stimuli associated with robust ordinal distance effects. Neural patterns in fronto-parietal cortices distinguished ordinal distance in all domains. Critically, between-task predictions of ordinal distance in fronto-parietal cortices were robust between serial order WM, alphabetical order judgment but not when involving the numerical order judgment tasks. Moreover, frontal ROIs further supported between-task prediction of distance for the luminance judgment control task, the serial order WM, and the alphabetical tasks. These results suggest that common neural substrates characterize processing of ordinal information in WM and alphabetical but not numerical domains. This commonality, particularly in frontal cortices, may however reflect attentional control processes involved in judging ordinal distances rather than the intervention of domain-general ordinal codes.

Space modulates cross-domain transfer of abstract rules in infants.

Developmental studies have shown that infants exploit ordinal information to extract and generalize repetition-based rules from a sequence of items. Within the visual modality, this ability is constrained by the spatial layout within which items are delivered given that a left-to-right orientation boosts infants' rule learning, whereas a right-to-left orientation hinders this ability. Infants' rule learning operates across different domains and can also be transferred across modalities when learning is triggered by speech. However, no studies have investigated whether the transfer of rule learning occurs across different domains when language is not involved. Using a visual habituation procedure, we tested 7-month-old infants' ability to extract rule-like patterns from numerical sequences and generalize them to non-numerical sequences of visual shapes and whether this ability is affected by the spatial orientation. Infants were first habituated to left-to-right or right-to-left oriented numerical sequences instantiating an ABB rule and were then tested with the familiar rule instantiated across sequences of single geometrical shapes and a novel (ABA) rule. Results showed a transfer of learning from number to visual shapes for left-to-right oriented sequences but not for right-to-left oriented ones (Experiment 1) even when the direction of the numerical change (increasing vs. decreasing) within the habituation sequences violated a small-left/large-right number-space association (Experiment 2). These results provide the first demonstration that visual rule learning mechanisms in infancy operate at a high level of abstraction and confirm earlier findings that left-to-right oriented directional cues facilitate infants' representation of order.

Russian-German five-year-olds: What omissions in sentence repetition tell us about linguistic knowledge, memory skills and their interrelation.

In error analyses using sentence repetition data, most authors focus on word types of omissions. The current study considers serial order in omission patterns independent of functional categories. Data was collected from Russian and German sentence repetition tasks performed by 53 five-year-old bilingual children. Number and positions of word omissions were analyzed. Serial order effects were found in both languages: medial errors made up the largest percentage of errors. Then, the position of omissions was compared to visuo-verbal n-back working memory and non-verbal visual forward short-term memory scores using stepwise hierarchical linear regression models, taking into account demographic variables and receptive language. The interaction differed between languages: there was a significant negative association between omissions in the medial position in German and the final position in Russian and the visuo-verbal n-back memory score. Our study contributes to the understanding of how working memory and language are intertwined in sentence repetition.