No position-specific interference from prior lists in cued recognition: A challenge for position coding (and other) theories of serial memory.

Position-specific intrusions of items from prior lists are rare but important phenomena that distinguish broad classes of theory in serial memory. They are uniquely predicted by position coding theories, which assume items on all lists are associated with the same set of codes representing their positions. Activating a position code activates items associated with it in current and prior lists in proportion to their distance from the activated position. Thus, prior list intrusions are most likely to come from the coded position. Alternative "item dependent" theories based on associations between items and contexts built from items have difficulty accounting for the position specificity of prior list intrusions. We tested the position coding account with a position-cued recognition task designed to produce prior list interference. Cuing a position should activate a position code, which should activate items in nearby positions in the current and prior lists. We presented lures from the prior list to test for position-specific activation in response time and error rate; lures from nearby positions should interfere more. We found no evidence for such interference in 10 experiments, falsifying the position coding prediction. We ran two serial recall experiments with the same materials and found position-specific prior list intrusions. These results challenge all theories of serial memory: Position coding theories can explain the prior list intrusions in serial recall and but not the absence of prior list interference in cued recognition. Item dependent theories can explain the absence of prior list interference in cued recognition but cannot explain the occurrence of prior list intrusions in serial recall.

The gated cascade diffusion model: An integrated theory of decision making, motor preparation, and motor execution.

This article introduces an integrated and biologically inspired theory of decision making, motor preparation, and motor execution. The theory is formalized as an extension of the diffusion model, in which diffusive accumulated evidence from the decision-making process is continuously conveyed to motor areas of the brain that prepare the response, where it is smoothed by a mechanism that approximates a Kalman-Bucy filter. The resulting motor preparation variable is gated prior to reaching agonist muscles until it exceeds a particular level of activation. We tested this gated cascade diffusion model by continuously probing the electrical activity of the response agonists through electromyography in four choice tasks that span a variety of domains in cognitive sciences, namely motion perception, numerical cognition, recognition memory, and lexical knowledge. The model provided a good quantitative account of behavioral and electromyographic data and systematically outperformed previous models. This work represents an advance in the integration of processes involved in simple decisions and sheds new light on the interplay between decision and motor systems. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The Role of a Dopamine-Dependent Limbic-Motor Network in Sensory Motor Processing in Parkinson Disease.

Limbic and motor integration is enabled by a mesial temporal to motor cortex network. Parkinson disease (PD) is characterized by a loss of dorsal striatal dopamine but relative preservation of mesolimbic dopamine early in disease, along with changes to motor action control. Here, we studied 47 patients with PD using the Simon conflict task and [18F]fallypride PET imaging. Additionally, a cohort of 16 patients participated in a single-blinded dextroamphetamine (dAMPH) study. Task performance was evaluated using the diffusion model for conflict tasks, which allows for an assessment of interpretable action control processes. First, a voxel-wise examination disclosed a negative relationship, such that longer non-decision time is associated with reduced D2-like binding potential (BPND) in the bilateral putamen, left globus pallidus, and right insula. Second, an ROI analysis revealed a positive relationship, such that shorter non-decision time is associated with reduced D2-like BPND in the amygdala and ventromedial OFC. The difference in non-decision time between off-dAMPH and on-dAMPH trials was positively associated with D2-like BPND in the globus pallidus. These findings support the idea that dysfunction of the traditional striatal-motor loop underlies action control deficits but also suggest that a compensatory parallel limbic-motor loop regulates motor output.

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.

The distinction between long-term knowledge and short-term control processes is valid and useful.

The binary distinction De Neys questions has been put forward many times since the beginnings of psychology, in slightly different forms and under different names. It has proved enormously useful and has received detailed empirical support and careful modeling. At heart the distinction is that between knowledge in long-term memory and control processes in short-term memory.

Serial order depends on item-dependent and item-independent contexts.

We address four issues in response to Osth and Hurlstone's (2022) commentary on the context retrieval and updating (CRU) theory of serial order (Logan, 2021). First, we clarify the relations between CRU, chains, and associations. We show that CRU is not equivalent to a chaining theory and uses similarity rather than association to retrieve contexts. Second, we fix an error Logan (2021) made in accounting for the tendency to recall ACB instead of ACD in recalling ABCDEF (fill-in vs. in-fill errors, respectively). When implemented correctly, the idea that subjects mix the current context with an initial list cue after the first order error correctly predicts that fill-in errors are more frequent than in-fill errors. Third, we address position-specific prior-list intrusions, suggesting modifications to CRU and introducing a position-coding model based on CRU representations to account for them. We suggest that position-specific prior-list intrusions are evidence for position coding on some proportion of the trials but are not evidence against item coding on other trials. Finally, we address position-specific between-group intrusions in structured lists, agreeing with Osth and Hurlstone that reasonable modifications to CRU cannot account for them. We suggest that such intrusions support position coding on some proportion of the trials but do not rule out CRU-like item-based codes. We conclude by suggesting that item-independent and item-dependent coding are alternative strategies for serial recall and we stress the importance of accounting for immediate performance. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The spotlight turned inward: the time-course of focusing attention on memory.

Guided by the idea that memory retrieval is selective attention turned inward, we report four experiments examining the time-course of focusing attention on memory. We used a novel episodic flanker task that turns the famous perceptual flanker task inward, presenting memory lists followed by probes that asked whether a cued letter had appeared in the same position in the memory list. Like the perceptual flanker task, we manipulated distance to measure the sharpness of the focus of attention on memory, and compatibility to measure the resistance to distraction. To measure the time-course of focusing, we presented a cue indicating the probed position in the interval between the list and the probe and varied the interval between the cue and the probe (0, 250, 500, 750 ms). The main questions were whether the focus would become sharper and resistance to distraction would become stronger as cue-probe delay increased. Experiments 1a and 1b showed strong distance effects and strong cue-probe interval effects but no reliable interaction between them. Experiments 2a and 2b showed robust compatibility effects and cue-probe interval effects but no interaction between them. Thus, there is no evidence that the sharpness of the focus increases and little evidence that the resistance to distraction improves over time. The robust reduction in response time and slight increase in accuracy with cue-probe interval may reflect the time-course of orienting to the cued position in the memory list prior to focusing on the item it contains.

Partial Repetition Costs are Reduced but not Eliminated with Practice.

Often, we depart from an intended course of events to react to sudden situational demands (an intervening event) before resuming the originally planned action. Executing an action to an intervening event can be delayed if the features of this action plan partly overlap with an action plan retained in working memory (WM) compared to when they completely overlap or do not overlap. This delay is referred to as a partial repetition cost (PRC). PRCs are typically attributed to code confusion between action plans in WM. We tested this by training the component action plans extensively to reduce their reliance on WM. If PRCs are caused by code confusion within WM, then PRCs should be reduced and possibly eliminated with extensive practice. To test this, participants performed a partial repetition (PR) task after 0, 4 and 8.5 sessions of stimulus-response (S-R) training. In the PR task, participants saw two visual events. They retained an action to the first event while executing a speeded action to a second (intervening) event; afterwards, they executed the retained action. The two action plans either partly overlapped or did not overlap. Results showed that extensive (S-R and PR task) practice reduced but did not eliminate PRCs. A reduction in PRCs (code confusion) with practice is compatible with memory models that assume action events become more specific and less reliant on WM with practice. These findings merit expansions of PR tasks to other domains and broader conceptions of action plans that incorporate the formal structure of memory models.

Salience by competitive and recurrent interactions: Bridging neural spiking and computation in visual attention.

Decisions about where to move the eyes depend on neurons in frontal eye field (FEF). Movement neurons in FEF accumulate salience evidence derived from FEF visual neurons to select the location of a saccade target among distractors. How visual neurons achieve this salience representation is unknown. We present a neuro-computational model of target selection called salience by competitive and recurrent interactions (SCRI), based on the competitive interaction model of attentional selection and decision-making (Smith & Sewell, 2013). SCRI selects targets by synthesizing localization and identification information to yield a dynamically evolving representation of salience across the visual field. SCRI accounts for neural spiking of individual FEF visual neurons, explaining idiosyncratic differences in neural dynamics with specific parameters. Many visual neurons resolve the competition between search items through feedforward inhibition between signals representing different search items, some also require lateral inhibition, and many act as recurrent gates to modulate the incoming flow of information about stimulus identity. SCRI was tested further by using simulated spiking representations of visual salience as input to the gated accumulator model of FEF movement neurons (Purcell et al., 2010, 2012). Predicted saccade response times fit those observed for search arrays of different set sizes and different target-distractor similarities, and accumulator trajectories replicated movement neuron discharge rates. These findings offer new insights into visual decision-making through converging neuro-computational constraints and provide a novel computational account of the diversity of FEF visual neurons. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

D2-Like Receptor Expression in the Hippocampus and Amygdala Informs Performance on the Stop-Signal Task in Parkinson's Disease.

The stop-signal task is a well-established assessment of response inhibition, and in humans, proficiency is linked to dorsal striatum D2 receptor availability. Parkinson's disease (PD) is characterized by changes to efficiency of response inhibition. Here, we studied 17 PD patients (6 female and 11 male) using the stop-signal paradigm in a single-blinded d-amphetamine (dAMPH) study. Participants completed [18F]fallypride positron emission topography (PET) imaging in both placebo and dAMPH conditions. A voxel-wise analysis of the relationship between binding potential (BPND) and stop-signal reaction time (SSRT) revealed that faster SSRT is associated with greater D2-like BPND in the amygdala and hippocampus (right cluster qFDR-corr = 0.026, left cluster qFDR-corr = 0.002). A region of interest (ROI) examination confirmed this association in both the amygdala (coefficient = -48.26, p = 0.005) and hippocampus (coefficient = -104.94, p = 0.007). As healthy dopaminergic systems in the dorsal striatum appear to regulate response inhibition, we interpret our findings in PD to indicate either nigrostriatal damage unmasking a mesolimbic contribution to response inhibition, or a compensatory adaptation from the limbic and mesial temporal dopamine systems. These novel results expand the conceptualization of action-control networks, whereby limbic and motor loops may be functionally connected.SIGNIFICANCE STATEMENT While Parkinson's disease (PD) is characteristically recognized for its motor symptoms, some patients develop impulsive and compulsive behaviors (ICBs), manifested as repetitive and excessive participation in reward-driven activities, including sex, gambling, shopping, eating, and hobbyism. Such cognitive alterations compel a consideration of response inhibition in PD. To investigate inhibitory control and assess the brain regions that may participate, we assessed PD patients using a single-blinded d-amphetamine (dAMPH) study, with [18F]fallypride positron emission topography (PET) imaging, and stop-signal task performance. We find a negative relationship between D2-like binding in the mesial temporal region and top-signal reaction time (SSRT), with greater BPND associated with a faster SSRT. These discoveries indicate a novel role for mesolimbic dopamine in response inhibition, and advocate for limbic regulation of action control in this clinical population.

Previously retrieved items contribute to memory for serial order.

It has long been understood that associations can form between items that are paired (Ebbinghaus, 1885), but it is commonly assumed that previously retrieved items are not used when remembering items in serial order. We present a series of experiments that test this assumption, using a serial learning procedure inspired by Ebenholtz (1963). In this procedure, participants practiced recalling ordered lists of letters, and the order of the letters was manipulated. Half of the lists were scrambled such that the serial positions and relative positions of the letters were inconsistent over practice. The other half of the lists were spun (e.g., ABCDEF → FABCDE), making the serial positions inconsistent but preserving the relative positions of the letters over practice. In Experiment 1, participants learned to recall spun lists more accurately than the scrambled lists with practice. In Experiments 2 and 3, participants recalled new lists more accurately when they shared the relative order of previously learned spun lists. In Experiments 4 and 5, the influences of motor and perceptual representations were removed and shown to have little impact on the advantage for spun lists. Experiment 6 extended our findings to the more traditional Hebb (1961) learning procedure. The results of our experiments indicate that the commonly held assumption is incorrect-previously retrieved items can contribute to memory for serial order. Previously retrieved items best serve serial memory when there is ample opportunity to strengthen item-to-item associations. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Serial memory: Putting chains and position codes in context.

From the beginning of research on serial memory, chaining theories and position coding theories have been pitted against each other. The central question is whether items are associated with each other or with a set of position codes that are independent of the items. Around the turn of this century, the debate focused on serial recall tasks and patterns of error data that chaining models could not accommodate. Consequently, theories based on other ideas flourished and position coding models became prominent. We present an analysis of a retrieved context model that integrates chains and position codes. Under some parameter values, it produces classic chains. Under most parameter values, it produces context representations that contain information sufficient to specify the position codes in position coding theories. We suggest three ways to extract position codes from context representations and show the codes they produce are mathematically equivalent to the codes in position coding models. The extracted position codes can be substituted for the position codes in position coding models and run through their machinery to mimic their predictions exactly. We suggest that chains, position codes, and retrieved contexts may reflect different strategies for extracting desired information from a common set of memory representations, and we emphasize the value of considering item-dependent context representations that are made from fading traces of past items encoded or retrieved. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

An integrated theory of deciding and acting.

This article presents a theory in which motor execution in perceptual decision-making tasks is determined by the same evolving decision variable that drives response time. The theory builds upon recent insights from the neuroscience of decision-making and motor control. It is formalized as an extension of Ratcliff's diffusion model, and assumes that two thresholds operate on the evidence accumulation decision variable. The first threshold, referred to as electromyographic (EMG) threshold, marks the onset of electrical activity in the response-relevant muscle and the beginning of force production. The second threshold corresponds to the response. The theory makes several benchmark predictions. Notably, the mean duration of motor execution, as quantified by the mean latency between EMG onset and the response, should depend on the rate of evidence accumulation, and should thus increase as the perceptual difficulty of the task increases. We tested these predictions in a paradigmatic perceptual decision-making task, the random dot motion task, and recorded the EMG activity of response-relevant muscles. The behavioral and EMG data provide very strong evidence for each prediction. A final quantitative evaluation of the model showed good fits to these data. The theory resolves conflicting findings in the fields of mathematical psychology, motor control, and decision neurosciences. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The episodic flanker effect: Memory retrieval as attention turned inward.

This article tests the conjecture that memory retrieval is attention turned inward by developing an episodic flanker task that is analogous to the well-known perceptual flanker task and by developing models of the spotlight of attention focused on a memory list. Participants were presented with a list to remember (ABCDEF) followed by a probe in which one letter was cued (# # C # # #). The task was to indicate whether the cued letter matched the letter in the cued position in the memory list. The data showed classic results from the perceptual flanker task. Response time and accuracy were affected by the distance between the cued letter in the probe and the memory list (# # D # # # was worse than # # E # # #) and by the compatibility of the uncued letters in the probe and the memory list (ABCDEF was better than STCRVX). There were six experiments. The first four established distance and compatibility effects. The fifth generalized the results to sequential presentation of memory lists, and the sixth tested the boundary conditions of distance and flanker effects with an item recognition task. The data were fitted with three families of models that apply space-based, object-based, and template-based theories of attention to the problem of focusing attention on the cued item in memory. The models accounted for the distance and compatibility effects, providing measures of the sharpness of the focus of attention on memory and the ability to ignore distraction from uncued items. Together, the data and theory support the conjecture that memory retrieval is attention turned inward and motivate further research on the topic. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Severe violations of independence in response inhibition tasks.

The stop-signal paradigm, a primary experimental paradigm for understanding cognitive control and response inhibition, rests upon the theoretical foundation of race models, which assume that a go process races independently against a stop process that occurs after a stop-signal delay (SSD). We show that severe violations of this independence assumption at short SSDs occur systematically across a wide range of conditions, including fast and slow reaction times, auditory and visual stop signals, manual and saccadic responses, and especially in selective stopping. We also reanalyze existing data and show that conclusions can change when short SSDs are excluded. Last, we suggest experimental and analysis techniques to address this violation, and propose adjustments to extant models to accommodate this finding.

Serial order in perception, memory, and action.

This article asks whether serial order phenomena in perception, memory, and action are manifestations of a single underlying serial order process. The question is addressed empirically in two experiments that compare performance in whole report tasks that tap perception, serial recall tasks that tap memory, and copy typing tasks that tap action, using the same materials and participants. The data show similar effects across tasks that differ in magnitude, which is consistent with a single process operating under different constraints. The question is addressed theoretically by developing a Context Retrieval and Updating (CRU) theory of serial order, fitting it to the data from the two experiments, and generating predictions for 7 different summary measures of performance: list accuracy, serial position effects, transposition gradients, contiguity effects, error magnitudes, error types, and error ratios. Versions of the model that allowed sensitivity in perception and memory to decrease with serial position fit the data best and produced reasonably accurate predictions for everything but error ratios. Together, the theoretical and empirical results suggest a positive answer to the question: Serial order in perception, memory, and action may be governed by the same underlying mechanism. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Sequential sampling models without random between-trial variability: the racing diffusion model of speeded decision making.

Most current sequential sampling models have random between-trial variability in their parameters. These sources of variability make the models more complex in order to fit response time data, do not provide any further explanation to how the data were generated, and have recently been criticised for allowing infinite flexibility in the models. To explore and test the need of between-trial variability parameters we develop a simple sequential sampling model of N-choice speeded decision making: the racing diffusion model. The model makes speeded decisions from a race of evidence accumulators that integrate information in a noisy fashion within a trial. The racing diffusion does not assume that any evidence accumulation process varies between trial, and so, the model provides alternative explanations of key response time phenomena, such as fast and slow error response times relative to correct response times. Overall, our paper gives good reason to rethink including between-trial variability parameters in sequential sampling models.

Countermanding Perceptual Decision-Making.

We investigated whether a task requiring concurrent perceptual decision-making and response control can be performed concurrently, whether evidence accumulation and response control are accomplished by the same neurons, and whether perceptual decision-making and countermanding can be unified computationally. Based on neural recordings in a prefrontal area of macaque monkeys, we present behavioral, neural, and computational results demonstrating that perceptual decision-making of varying difficulty can be countermanded efficiently, that single prefrontal neurons instantiate both evidence accumulation and response control, and that an interactive race between stochastic GO evidence accumulators for each alternative and a distinct STOP accumulator fits countermanding choice behavior and replicates neural trajectories. Thus, perceptual decision-making and response control, previously regarded as distinct mechanisms, are actually aspects of a common neuro-computational mechanism supporting flexible behavior.

Dynamics of attentional focusing in the Eriksen flanker task.

Eriksen and Eriksen (Perception & Psychophysics, 16, 143-149, 1974) explained the flanker compatibility effect in terms of response competition. A simplified version of the original flanker task, featuring a 1-to-1 mapping of stimuli onto responses, has become prominent in the literature. Compatible flanker trials present identical items (HHHHH), whereas incompatible trials present different items (HHSHH). The 1-to-1 mapping is potentially problematic because it invites a strategy that people could use to perform the task. Subjects could first determine whether all the items are the same and focus attention on the central target only if they are not. Response times (RTs) would be longer for incompatible trials partly because they require the extra step of focusing attention. We tested this conditional focusing hypothesis by combining a 1-to-1 flanker task with a digit probe detection procedure. In half of the trials, the digit '7' appeared immediately after the response to the flanker display, at the target or a flanker location. Three experiments showed a V-shaped function of RTs to digits across locations that was not modulated by flanker compatibility. These results demonstrate that subjects focused attention on the central target regardless of the same/different configuration of the display, refuting the conditional focusing hypothesis. Our findings support Eriksen and Eriksen's original interpretation of the flanker task.