Reservoir-computing based associative memory and itinerancy for complex dynamical attractors.

Traditional neural network models of associative memories were used to store and retrieve static patterns. We develop reservoir-computing based memories for complex dynamical attractors, under two common recalling scenarios in neuropsychology: location-addressable with an index channel and content-addressable without such a channel. We demonstrate that, for location-addressable retrieval, a single reservoir computing machine can memorize a large number of periodic and chaotic attractors, each retrievable with a specific index value. We articulate control strategies to achieve successful switching among the attractors, unveil the mechanism behind failed switching, and uncover various scaling behaviors between the number of stored attractors and the reservoir network size. For content-addressable retrieval, we exploit multistability with cue signals, where the stored attractors coexist in the high-dimensional phase space of the reservoir network. As the length of the cue signal increases through a critical value, a high success rate can be achieved. The work provides foundational insights into developing long-term memories and itinerancy for complex dynamical patterns.

Noradrenaline tracks emotional modulation of attention in human amygdala.

The noradrenaline (NA) system is one of the brain's major neuromodulatory systems; it originates in a small midbrain nucleus, the locus coeruleus (LC), and projects widely throughout the brain.1,2 The LC-NA system is believed to regulate arousal and attention3,4 and is a pharmacological target in multiple clinical conditions.5,6,7 Yet our understanding of its role in health and disease has been impeded by a lack of direct recordings in humans. Here, we address this problem by showing that electrochemical estimates of sub-second NA dynamics can be obtained using clinical depth electrodes implanted for epilepsy monitoring. We made these recordings in the amygdala, an evolutionarily ancient structure that supports emotional processing8,9 and receives dense LC-NA projections,10 while patients (n = 3) performed a visual affective oddball task. The task was designed to induce different cognitive states, with the oddball stimuli involving emotionally evocative images,11 which varied in terms of arousal (low versus high) and valence (negative versus positive). Consistent with theory, the NA estimates tracked the emotional modulation of attention, with a stronger oddball response in a high-arousal state. Parallel estimates of pupil dilation, a common behavioral proxy for LC-NA activity,12 supported a hypothesis that pupil-NA coupling changes with cognitive state,13,14 with the pupil and NA estimates being positively correlated for oddball stimuli in a high-arousal but not a low-arousal state. Our study provides proof of concept that neuromodulator monitoring is now possible using depth electrodes in standard clinical use.

Task sequencing does not systematically affect the factor structure of cognitive abilities.

Latent variable analyses of cognitive abilities are among the major means by which cognitive psychologists test theories regarding the structure of human cognition. Models are fit to observed variance-covariance structures, and the fit of those models are compared to assess the merits of competing theories. However, an often unconsidered and potentially important methodological issue is the precise sequence in which tasks are delivered to participants. Here we empirically tested whether differences in task sequences systematically affect the observed factor structure. A large sample (N = 587) completed a battery of 12 cognitive tasks measuring four constructs: working memory, long-term memory, attention control, and fluid intelligence. Participants were assigned to complete the assessment in one of three sequences: fixed and grouped by construct vs. fixed and interleaved across constructs vs. random by participant. We generated and tested two hypotheses: grouping task sequences by construct (i.e., administering clusters of tasks measuring a cognitive construct consecutively) would (1) systematically increase factor loadings and (2) systematically decrease interfactor correlations. Neither hypothesis was supported. The measurement models were largely invariant across the three conditions, suggesting that latent variable analyses are robust to such subtle methodological differences as task sequencing.

Testing locus coeruleus-norepinephrine accounts of working memory, attention control, and fluid intelligence.

The current set of studies examined the relationship among working memory capacity, attention control, fluid intelligence, and pupillary correlates of tonic arousal regulation and phasic responsiveness in a combined sample of more than 1,000 participants in two different age ranges (young adults and adolescents). Each study was designed to test predictions made by two recent theories regarding the role of the locus coeruleus-norepinephrine (LC-NE) system in determining individual differences in cognitive ability. The first theory, proposed by Unsworth and Robison (2017a), posits two important individual differences: the moment-to-moment regulation of tonic arousal, and the phasic responsiveness of the system to goal-relevant stimuli. The second theory, proposed by Tsukahara and Engle (2021a), argues that people with higher cognitive abilities have greater functional connectivity between the LC-NE system and cortical networks at rest. These two theories are not mutually exclusive, but they make different predictions. Overall, we found no evidence consistent with a resting-state theory. However, phasic responsiveness was consistently correlated with working memory capacity, attention control, and fluid intelligence, supporting a prediction made by Unsworth and Robison (2017a). Tonic arousal regulation was not correlated with working memory or fluid intelligence and was inconsistently correlated with attention control, which offers only partial support for Unsworth and Robison's (2017a) second prediction.

An assessment of learning rates in habitual prospective memory.

Most laboratory research in the field of prospective memory has focused on newly formed (episodic) intentions that are carried out in the experimental context once or only a small number of times. However, many naturalistic prospective memories are carried out many times and these types of (habitual) intentions have been studied much less in the laboratory. In the current study, our aim was to extend prior work examining habitual intentions in laboratory prospective memory paradigms. Participants formed a typical prospective memory intention and then completed an ongoing task in which the intention could be executed up to 63 times. We examined changes in performance across trials in three traditionally important prospective memory metrics: cue detection, task interference, and cue interference. Across repeated performance of the prospective memory task, we observed an increase in cue detection, elimination of task interference, and elimination of cue interference. These results provide key insights into the operation of learning mechanisms in prospective memory paradigms and promote theory development by showing that many of the resource-demanding processes that are theorized to be necessary for successful prospective memory play much less of a role when intentions are repeatedly completed.

Midbrain-Hippocampus Structural Connectivity Selectively Predicts Motivated Memory Encoding.

Motivation is a powerful driver of learning and memory. Functional MRI studies show that interactions among the dopaminergic midbrain substantia nigra/ventral tegmental area (SN/VTA), hippocampus, and nucleus accumbens (NAc) are critical for motivated memory encoding. However, it is not known whether these effects are transient and purely functional, or whether individual differences in the structure of this circuit underlie motivated memory encoding. To quantify individual differences in structure, diffusion-weighted MRI and probabilistic tractography were used to quantify SN/VTA-striatum and SN/VTA-hippocampus pathways associated with motivated memory encoding in humans. Male and female participants completed a motivated source memory paradigm. During encoding, words were randomly assigned to one of three conditions, reward ($1.00), control ($0.00), or punishment (-$1.00). During retrieval, participants were asked to retrieve item and source information of the previously studied words and were rewarded or penalized according to their performance. Source memory for words assigned to both reward and punishment conditions was greater than those for control words, but there were no differences in item memory based on value. Anatomically, probabilistic tractography results revealed a heterogeneous, topological arrangement of the SN/VTA. Tract density measures of SN/VTA-hippocampus pathways were positively correlated with individual differences in reward-and-punishment-modulated memory performance, whereas density of SN/VTA-striatum pathways showed no association. This novel finding suggests that pathways emerging from the human SV/VTA are anatomically separable and functionally heterogeneous. Individual differences in structural connectivity of the dopaminergic hippocampus-VTA loop are selectively associated with motivated memory encoding.SIGNIFICANCE STATEMENT Functional MRI studies show that interactions among the SN/VTA, hippocampus, and NAc are critical for motivated memory encoding. This has led to competing theories that posit either SN/VTA-NAc reward prediction errors or SN/VTA-hippocampus signals underlie motivated memory encoding. Additionally, it is not known whether these effects are transient and purely functional or whether individual differences in the structure of these circuits underlie motivated memory encoding. Using diffusion-weighted MRI and probabilistic tractography, we show that tract density measures of SN/VTA-hippocampus pathways are positively correlated with motivated memory performance, whereas density of SN/VTA-striatum pathways show no association. This finding suggests that anatomic individual differences of the dopaminergic hippocampus-VTA loop are selectively associated with motivated memory encoding.

Individual differences in working memory capacity, attention control, fluid intelligence, and pupillary measures of arousal.

The present study examined individual differences in 3 cognitive abilities: attention control (AC), working memory capacity (WMC), and fluid intelligence (gF) as they relate the tendency to experience task-unrelated thoughts (TUTs) and the regulation of arousal. Cognitive abilities were measured with a battery of 9 laboratory tasks, TUTs were measured via thought probes inserted into 2 tasks, and arousal regulation was measured via pupillometry. Recent theorizing (Unsworth & Robison, 2017b) suggests that 1 reason why some people experience relatively frequent TUTs and relatively poor cognitive performance-especially AC and WMC-is that they exhibit dysregulated arousal. Here, we examined how arousal regulation might predict both AC and WMC, but also higher-order cognitive abilities like gF. Further, we examine direct and indirect associations with these abilities via a mediating influence of TUT. Participants who reported more TUTs also tended to exhibit poorer AC, lower WMC, and lower gF. Arousal dysregulation correlated with more TUTs and lower AC. However, there was no direct correlation between arousal regulation and WMC, nor between arousal regulation and gF. The association between arousal regulation and gF was indirect via TUT. We discuss the implications of the results in light of the arousal regulation theory of individual differences and directions for future research. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The impact of divided attention on automatic postural responses: A systematic review and meta-analysis.

Quick responses to a loss of balance or "automatic postural responses" (APRs) are critical for fall prevention. The addition of a distracting task- dual-tasking (DT), typically worsens performance on mobility tasks. However, the effect of DT on APRs is unclear. We conducted a systematic review and meta-analyses to examine the effects of DT on spatial, temporal, and neuromuscular components of APRs and the effect of DT on cognitive performance. A Meta-analysis of 19 cohorts (n = 329) showed significant worsening in spatial kinematic features of APRs under DT conditions (P = 0.01), and a meta-analysis of 9 cohorts (n = 123) demonstrated later muscle onset during DT (P = 0.003). No significant DT effect was observed for temporal kinematic outcomes in 18 cohorts (n = 328; P = 0.47). Finally, significant declines in cognitive performance were evident in 20 cohorts (n = 400; P = 0.002). These results indicate that, despite the somewhat reactive nature of APRs, the addition of a secondary task negatively impacts some aspects of the response. These findings underscore the importance of cortical structures in APR generation. Given the importance of APRs for falls, identifying aspects of APRs that are altered under DT may inform fall-prevention treatment approaches.

Individual differences in memory and attention processes in prospective remembering.

Successful prospective memory (PM) involves not only detecting that an environmental cue requires action (i.e., prospective component), but also retrieval of what is supposed to be done at the appropriate moment (i.e., retrospective component). The current study examined the role of attention and memory during PM tasks that placed distinct demands on detection and retrieval processes. Using a large-scale individual differences design, participants completed three PM tasks that placed high demands on detection (but low demands on retrieval) and three tasks that placed high demands on retrieval (but low demands on detection). Additionally, participants completed three attention control, retrospective memory, and working memory tasks. Latent variable structural equation modeling showed that the prospective and retrospective components of PM were jointly influenced by multiple cognitive abilities. Critically, attention and retrospective memory fully mediated the relation between working memory and prospective memory. Furthermore, only attention uniquely predicted PM detection, whereas only retrospective memory uniquely predicted PM retrieval. These findings highlight the value of independently assessing different PM components and suggest that both attention and memory abilities must be considered to fully understand the dynamic processes underlying prospective remembering.

The effect of binaural beat stimulation on sustained attention.

Binaural beats have been used as a way of modifying cognition via auditory stimulation. A recent meta-analysis suggests that binaural beat stimulation can have a positive effect on attention (Garcia-Argibay et al., Psychologische Forschung 83:1124-1136, 2019a, Psychological Research Psychologische Forschung 83:357-372, 2019b), with the sample-weighted average effect size being about .58. This is an intriguing and potentially useful finding, both theoretically and practically. In this study, we focus on sustained attention. We delivered beta-frequency (16 Hz) binaural beat stimulation during a sustained attention task. In "Experiment 1", reaction times were faster under beat stimulation than control stimulation in a between-subjects design. However, the effect was modest in magnitude, and model comparisons using Bayes Factors were indiscriminate between including and excluding the effect from the model. We followed this initial experiment with two concurrently administered follow-up experiments. In "Experiment 2", we added thought probes to measure any changes in task engagement associated with binaural beat stimulation. "Experiment 2" revealed a different effect from "Experiment 1": participants in the binaural beat condition exhibited a shallower vigilance decrement. However, the beat stimulation did not affect the thought probes responses. Combining data across the two experiments indicated rather strong evidence against the hypothesis that beta-frequency binaural beats can augment sustained attention, either via a general speeding of responding or a mitigation of the vigilance decrement. Finally, in "Experiment 3", we investigated whether pupillary measures of arousal and/or task engagement would be affected by binaural beat stimulation. There was no evidence for such effects. Overall, we did not observe any consistent evidence that binaural beat stimulation can augment sustained attention or its subjective and physiological correlates.

Individual Differences in Disqualifying Monitoring Underlie False Recognition of Associative and Conjunction Lures.

The current study leveraged experimental and individual differences methodology to examine whether false memories across different list-learning tasks arise from a common cause. Participants completed multiple false memory (associative and conjunction lure), working memory (operation and reading span), and source monitoring (verbal and picture) tasks. Memory discriminability in the associative and conjunction tasks loaded onto a single (general) factor and were unaffected by warnings provided at encoding. Consistent with previous research, source-monitoring ability fully mediated the relation between working memory and false memories. Moreover, individuals with higher source monitoring-ability were better able to recall contextual information from encoding to correctly reject lures. These results suggest that there are stable individual differences in false remembering across tasks. The commonality across tasks may be due, at least in part, to the ability to effectively use disqualifying monitoring processes.

Examining the effects of goal-setting, feedback, and incentives on sustained attention.

Across four experiments we examined the effects of goal-setting, feedback, and incentivizing manipulations on sustained attention. In addition to measuring task performance, we measured subjective attentional states and momentary feelings of motivation and alertness. Experiment 1 compared two specific goal conditions-one difficult and one easy-with a standard set of instructions. The specific goal conditions both reduced RTs and attenuated the vigilance decrement but did not impact task engagement (motivation or task-unrelated thoughts). Experiment 2 manipulated both goal-setting and feedback across conditions. The combination of a specific goal and feedback had strong effects on both task performance and task engagement. Additionally, feedback increased task engagement (higher motivation and fewer task-unrelated thoughts) regardless of whether or not it was paired with a specific goal. Experiment 3 examined the effect of pairing goals with a reward. Participants in one reward condition (time-based incentive) reported higher motivation but did not show better task performance. Offering a cash incentive to meet a goal did not have an effect on any dependent variables. Finally, in an effort to examine whether more moderately-difficult goals might lead to optimal performance, Experiment 4 examined a broader range of goals. However, we did not see an effect of a moderately-difficult goal on any of the dependent variables. Although some of the experimental manipulations were effective in mitigating the vigilance decrement, none eliminated it. We discuss the theoretical implications of the results with regard to goal-setting theory and theories of vigilance. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Acute pain impairs sustained attention.

Pain affects the lives of many individuals by creating physical, psychological, and economic burdens. A critical psychological factor negatively affected by pain is one's ability to sustain attention. In order to better understand the effect of pain on sustained attention we conducted three experiments utilizing the psychomotor vigilance task, thought probes, and pupillometry. In Experiment 1, participants in acute pain exhibited overall poorer task performance. However, this effect was localized to the relative frequency and duration of the participants' slowest responses with their faster responses being equivalent to a no-pain control group. In Experiment 2, we replicated the procedure and included periodic thought probes to overtly measure subjective experiences during the task. Participants in pain reported fewer "on-task" thoughts and more thoughts directed toward the source of their pain. In Experiment 3, we replicated the procedure while simultaneously tracking pupillary dynamics using an eye-tracker. Participants in pain had smaller task-evoked pupillary responses, which is thought to be an indicator of task engagement. However, the behavioral effects of pain from Experiments 1 and 2 were not replicated in Experiment 3. Taken together, pain led to poorer performance in the form of an increase in the relative frequency and extremeness of slow responses, increases in off-task thoughts, and reductions in a physiological indicator of task engagement. These data speak to theories of how pain competes with task goals for attention and negatively impacts behavior. The broader implications of this work are the identification of a low-level mechanism by which pain can interfere with normal cognitive functioning. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The Cognitive Underpinnings of Multiply-Constrained Problem Solving.

Individuals encounter problems daily wherein varying numbers of constraints require delimitation of memory to target goal-satisfying information. Multiply-constrained problems, such as the compound remote associates, are commonly used to study this type of problem solving. Since their development, multiply-constrained problems have been theoretically and empirically related to creative thinking, analytical problem solving, insight problem solving, and a multitude of other cognitive abilities. In the present study, we empirically evaluated the range of cognitive abilities previously associated with multiply-constrained problem solving to assess common versus unique predictive variance (i.e., working memory, attention control, episodic and semantic memory, and fluid and crystallized intelligence). Additionally, we sought to determine whether problem-solving ability and self-reported strategy adoption (analytical or insightful) were task specific or task general through the use of novel multiply-constrained problem-solving tasks (TriBond and Location Bond). Performance across these tasks was shown to be domain general, solutions derived through insightful strategies were more often correct than those derived through analytical strategies, and crystallized intelligence was the sole cognitive ability that provided unique predictive value after accounting for all other abilities.

Wait a second . . . Boundary conditions on delayed responding theories of prospective memory.

Research suggests that forcing participants to withhold responding for as brief as 600 ms eliminates one of the most reliable findings in prospective memory (PM): the cue focality effect. This result undermines the conventional view that controlled attentional monitoring processes support PM, and instead suggests that cue detection results from increased response thresholds that allow more time for PM information to accumulate. Given the significance of such findings, it is critical to examine the generalizability of the delay mechanism. Experiments 1-4 examined boundary conditions of the delay theory of PM, whereas Experiment 5 more directly tested contrasting theoretical predictions from monitoring theory (e.g., multiprocess framework) and delay theory. Using the same (Experiment 1) or conceptually similar (Experiment 2) delay procedure and identical cues (nonfocal "tor" intention) from the original study failed to show any influence of delay on performance. Using a different nonfocal intention (first letter "S") similarly did not influence performance (Experiment 3), and the difference between focal and nonfocal cue detection was never completely eliminated even with delays as long as 2,500 ms (Experiment 4). Experiment 5 did find the anticipated reduction in the focality effect with increased delays with a larger sample (n = 249). However, the focality effect was not moderated by attention control ability despite the fact that participants with impoverished attention control should benefit most from the delay procedure. These results suggest that any theory of PM that considers only a delay mechanism may not fully capture the dynamic attention processes that support cue detection. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Reliability and Convergence of Conflict Effects.

Recent work in attentional control has suggested that conflict effects measured across different tasks are not reliable and by extension unrelated. The lack of correlation between these conflict effects is in juxtaposition not only to theoretical predictions of a domain-general attentional control mechanism but also to a large body of individual differences research that has used these tasks to show evidence for an attentional control construct and its relatedness to other psychological constructs. In an effort to address this, we fit hierarchical models to each task that modeled trial-to-trial variability in response times to assess the extent to which the parameter estimates for the conflict effect correlated across tasks. We compared this method of assessing shared variance to more traditional summed difference score estimates of the conflict effect by analyzing data from a large-scale individual differences experiment, in which N = 582 subjects completed a Stroop, Flanker, and Simon task. Across tasks, we found that while the reliability of the conflict was sufficiently high and the between-task conflict effect significantly correlated, the magnitude of the between-task correlation was low. We discuss the implications of these results as providing more support for a domain-specific than domain-general attentional control mechanism.

Individual differences in working memory capacity and the regulation of arousal.

Previously it has been theorized that differential functioning of the locus coeruleus-norepinephrine (LC-NE) system affects people's ability to regulate arousal, which has impacts on cognitive abilities. In the present study, we investigated three potential mechanisms by which the LC-NE system can fail to regulate arousal appropriately: hypoarousal, hyperarousal, and dysregulation of arousal. Each of these three could potentially account for why arousal affects cognition. To test the contributions of these three mechanisms, the present study examined individual differences in working memory capacity (WMC) and the regulation of arousal using pupillometry. Participants completed multiple complex span and visual arrays change-detection measures of WMC. An eye-tracker recorded pupil diameter as participants completed the visual arrays tasks. We found rather mixed evidence for the three mechanisms. Arousal dysregulation correlated with lower visual arrays performance and more self-reported attentional lapses. However, arousal regulation did not correlate with complex span performance. There was also some evidence for hypoarousal as an explanatory mechanism, as arousal correlated with attentional lapses. We discuss the implications of the results for theories regarding the role of arousal regulation in cognitive performance and individual differences in cognitive abilities.

Individual differences in value-directed remembering.

Capacity limits in cognition require that valuable information be prioritized for encoding and retrieval. Individual differences in prioritized value-directed encoding may derive from differences in the general ability to encode memories, or from differences in how strategies are altered for different stimuli to modulate maintenance in working memory. We collected multiple cognitive ability measures to test whether variation in episodic memory, working memory capacity, or both predict differences in value-directed remembering among a large sample of participants (n = 205). Confirmatory factor analysis and structural equation modeling was used to assess the contributions of episodic and working memory to value sensitivity in value-directed remembering tasks. Episodic memory ability, but not working memory capacity, was predictive of value-directed remembering. These results suggest that the ability to prioritize memory derives principally from episodic memory ability overall, so that greater capacity also permits greater flexibility.

The role of working memory capacity in analytic and multiply-constrained problem-solving in demanding situations.

Working memory processes are important for analytic problem-solving; however, their role in multiply-constrained problem-solving is currently debated. This study explored individual differences in working memory and successful completion of analytic and multiply-constrained problem-solving by having participants solve algebra and compound remote associate (CRAT) problems of varying difficulty under low and high memory demand conditions. Working memory was predictive of both algebra and multiply-constrained problem-solving. Specifically, participants with high working memory solved more problems than those with low working. Memory load did not differentially affect performance for low and high working memory participants. However, for multiply-constrained problem-solving the effect of item difficulty was more detrimental for high-span participants than low-span participants. Together, these findings suggest that working memory processes are important for both types of problem-solving and that participants with low working memory capacity may need to offload internal memory demands onto the environment to efficiently solve problems.

Neural correlates underlying the effect of reward value on recognition memory.

The prioritized encoding and retrieval of valuable information is an essential aspect of human memory. We used electroencephalography (EEG) to determine which of two hypothesized processes underlies the influence of reward value on episodic memory. One hypothesis is that value engages prefrontal executive control processes, so that valuable stimuli engage an elaborative rehearsal strategy that benefits memory. A second hypothesis is that value acts through the reward-related midbrain dopamine system to modulate synaptic plasticity in hippocampal and cortical efferents, thereby benefiting memory encoding. We used a value-directed recognition memory (VDR) paradigm in which participants encoded words assigned different point values and aimed to maximize the point value of subsequently recognized words. Subjective states of recollection (i.e., "remember") and familiarity (i.e., "know") were assessed at retrieval. Words assigned higher values at study were recognized more effectively than words assigned lower values, due to increased "remember" responses but no difference in "know" responses. Greater value was also associated with larger amplitudes of an EEG component at retrieval that indexes recollection (parietal old/new component), but had no relationship with a component that indexes familiarity (FN400 component). During encoding, we assessed a late frontal positivity (frontal slow wave, FSW) that has been related to elaborative rehearsal strategies and an early parietal component (P3) thought to index dopamine driven attention allocation. Our findings indicate that the effect of value on recognition memory is primarily driven by the dopamine-driven reward valuation system (P3) with no discernible effect on rehearsal processes (FSW).