Performance dissociation during verbal and spatial working memory tasks

Past research has inconsistently distinguished the neural substrates of various types of working memory. Task design and individual performance differences are known to alter patterns of brain response during working-memory tasks. These task and individual differences may have produced discrepancies in imaging findings. This study of 50 healthy adults (M(age) = 19.6 yr., SD = .8) examined performance during various parametric manipulations of a verbal and spatial n-back working-memory task. Performance systematically dissociated on the basis of working-memory load, working memory type, and stimulus difficulty, with participants having greater accuracy but slower response time during conditions requiring verbal versus spatial working memory. These findings hold implications for cognitive and neuroimaging studies of verbal and spatial working memory and highlight the importance of considering both task design and individual behavior.     

Moderating effects of sensitivity to punishment and sensitivity to reward on associations between marijuana effect expectancies and use.

The study examined associations between sensitivity to reward (SR), sensitivity to punishment (SP), positive and negative expectancies, and marijuana use in a college sample (N = 809). Marijuana users (n = 227) reported lower SP and greater SR than nonusers. SR attenuated the association between SP and the probability of marijuana use. SP attenuated the association between positive expectancies and the probability of marijuana use as well as the frequency of use among users. SP potentiated the association between negative expectancies and use. The results indicate that SP and SR have interactive effects and that SP moderates the strength of positive and negative cues for risk behavior.     

Mapping Cognition to the Brain Through Neural Interactions

Brain imaging methods, such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), provide a unique opportunity to study the neurobiology of human memory. As these methods can measure most of the brain, it is possible to examine the operations of large-scale neural systems and their relation to cognition. Two neuroimaging studies, one concerning working memory and the other episodic memory retrieval, serve as examples of application of two analytic methods that are optimised for the quantification of neural systems, structural equation modelling, and partial least squares. Structural equation modelling was used to explore shifting prefrontal and limbic interactions from the right to the left hemisphere in a delayed match-to-sample task for faces. A feature of the functional network for short delays was strong right hemisphere interactions between hippocampus, inferior prefrontal, and anterior cingulate cortices. At longer delays, these same three areas were strongly linked, but in the left hemisphere, which was interpreted as reflecting change in task strategy from perceptual to elaborate encoding with increasing delay. The primary manipulation in the memory retrieval study was different levels of retrieval success. The partial least squares method was used to determine whether the image-wide pattern of covariances of Brodmann areas 10 and 45/47 in right prefrontal cortex (RPFC) and the left hippocampus (LGH) could be mapped on to retrieval levels. Area 10 and LGH showed an opposite pattern of functional connectivity with a large expanse of bilateral limbic cortices that was equivalent for all levels of retrieval as well as the baseline task. However, only during high retrieval was area 45/47 included in this pattern. The results suggest that activity in portions of the RPFC can reflect either memory retrieval mode or retrieval success depending on other brain regions to which it is functionally linked, and imply that regional activity must be evaluated within the neural context in which it occurs. The general hypothesis that learning and memory are emergent properties of large-scale neural network interactions is discussed, emphasising that a region can play a different role across many functions and that role is governed by its interactions with anatomically related regions.     

Mapping cognition to the brain through neural interactions

Brain imaging methods, such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), provide a unique opportunity to study the neurobiology of human memory. As these methods can measure most of the brain, it is possible to examine the operations of large-scale neural systems and their relation to cognition. Two neuroimaging studies, one concerning working memory and the other episodic memory retrieval, serve as examples of application of two analytic methods that are optimised for the quantification of neural systems, structural equation modelling, and partial least squares. Structural equation modelling was used to explore shifting prefrontal and limbic interactions from the right to the left hemisphere in a delayed match-to-sample task for faces. A feature of the functional network for short delays was strong right hemisphere interactions between hippocampus, inferior prefrontal, and anterior cingulate cortices. At longer delays, these same three areas were strongly linked, but in the left hemisphere, which was interpreted as reflecting change in task strategy from perceptual to elaborate encoding with increasing delay. The primary manipulation in the memory retrieval study was different levels of retrieval success. The partial least squares method was used to determine whether the image-wide pattern of covariances of Brodmann areas 10 and 45/47 in right prefrontal cortex (RPFC) and the left hippocampus (LGH) could be mapped on to retrieval levels. Area 10 and LGH showed an opposite pattern of functional connectivity with a large expanse of bilateral limbic cortices that was equivalent for all levels of retrieval as well as the baseline task. However, only during high retrieval was area 45/47 included in this pattern. The results suggest that activity in portions of the RPFC can reflect either memory retrieval mode or retrieval success depending on other brain regions to which it is functionally linked, and imply that regional activity must be evaluated within the neural context in which it occurs. The general hypothesis that learning and memory are emergent properties of large-scale neural network interactions is discussed, emphasising that a region can play a different role across many functions and that role is governed by its interactions with anatomically related regions.     

An event-related brain potential substrate of disturbed response monitoring in paranoid schizophrenic patients.

Response monitoring in schizophrenic patients and healthy controls was assessed by measuring performance and event-related brain potentials in the flanker priming task. Three visual-context conditions were construed: Flankers and targets pointed either into the same direction or into different directions. Stimuli without any response assignment were used as flankers in the neutral context condition. The schizophrenic patients were further subdivided into paranoid (n = 19) and nonparanoid (n = 10) patients and compared with healthy controls (n = 18). Performance scores revealed that the flankers induced a similar degree of distraction by visual context in all 3 groups. Although the schizophrenic patients showed normal error correction performance, the error negativity (NE) was significantly reduced in paranoid schizophrenic patients. The attenuation of the NE possibly reflects disturbed response monitoring in these patients.     

Incremental Validity of Coping-oriented Marijuana Use Motives in the Prediction of Affect-based Psychological Vulnerability

The present investigation examined whether coping-oriented motives to use marijuana, as measured by the Marijuana Motives Measure (MMM; Simons et al. in J. Couns. Psychol. 45:265–273, 1998), were uniquely related to affect-based psychological vulnerability factors among marijuana users. Participants were 131 adult current marijuana users (72 women, M _age = 20.14, SD = 3.37 years). As hypothesized, after controlling for gender, cigarettes smoked per day, past 30-day marijuana use, total years of marijuana use, and alcohol consumption, coping motives were significantly and incrementally related to negative affect-based psychological vulnerability factors. No other marijuana use motives demonstrated a similar type of relationship to the dependent variables, providing a high degree of explanatory specificity. These data suggest that coping-oriented motives to use marijuana may be an important explanatory construct in better understanding marijuana and psychological vulnerability relations.     

Working memory components and imagery instructions in the elaboration of a spatial mental model

The paper investigates the involvement of verbal and visuo-spatial working memory during the processing of spatial texts via a dual-task paradigm. Subjects were presented with three texts describing locations from a route perspective, and had either to imagine themselves moving along a route in surroundings or to rehearse verbal information. Concurrently they had to perform a spatial tapping task, an articulatory task, or no secondary task. Performance on a verification test used to assess the product of comprehension showed that the concurrent tapping task impaired performance in the imagery instructions group but not in the repetition instructions group, and caused the beneficial effect of imagery instructions to vanish. This result was not observed with the articulatory task, where interference effects were similar in both instructions groups. Performance on the concurrent tasks confirmed the pattern obtained with the verification test. In addition, results seem partly dependent on the capacity of spatial working memory as measured by the Corsi Blocks Test. We argue that these results clarify the processes of the construction of a spatial mental model, and confirm that the visuo-spatial working memory is involved in mental imagery.     

Parallel working memory for spatial location and food-related object cues in foraging pigeons: binocular and lateralized monocular performance

During foraging, animals can increase their success by both remembering feeding sites and remembering food-related object cues. Because earlier studies have tested either the site or object memory in isolation, the aim of the present study was to evaluate how efficiently birds can utilize both memories simultaneously. Furthermore, the idea was tested that lateralization might be the principle of brain organization that allows for efficient parallel processing. Pigeons learned to search for food in a complex maze with 16 baited sites. To obtain the maximum reward they had to perform two tasks in parallel, a spatial working memory task and an object-specific working memory task. Birds performed well on this dual task but, compared with spatial working memory alone, they were impaired during the first choices of a trial (Experiment 1). When the left and the right brain hemispheres were tested separately by means of monocular occlusion (Experiment 2), object discrimination was better when birds used their right eye/left hemisphere. This was most pronounced during the first choices of a trial. On the spatial component of the task, performance on binocular trials was better than on monocular trials, but monocularly both hemispheres performed at the same level. Results show that on this dual task, discrimination of food-related object cues predominantly involved the left brain hemisphere whereas both hemispheres contributed equally to spatial performance.     

The effect of memory load on cortical activity in the spatial working memory circuit

Accumulating evidence from electrophysiology and neuroimaging studies suggests that spatial working memory is subserved by a network of frontal and parietal regions. In the present study, we parametrically varied the memory set size (one to four spatial locations) of a delayed-response task and applied time-resolved fMRI to study the influence of memory load upon the spatial working memory circuit. Our behavioral results showed that performance deteriorates (lower accuracy and longer reaction time) as memory load increases. Memory load influenced cortical activity during the cue, delay, and response phases of the delayed-response task. Although delay-related activity in many regions increased with increasing memory load, it also was significantly reduced in the middle frontal gyrus and frontal eye fields and leveled off in the parietal areas when memory load increased further. Delayrelated activity in the left posterior parietal cortex was also lower during the error trials, in comparison with the correct trials. Our findings indicate that the delay period activity in the spatial working memory circuit is load sensitive and that the attenuation of this signal is the neural manifestation of performance limitation in the face of excessive memory load.     

Rehearsal in Spatial Working Memory: Evidence From Neuroimaging

A variety of biological evidence has identified a frontal-parietal circuit underlying spatial working memory for visual stimuli. But the question remains, how do these neural regions accomplish the goal of maintaining location information on-line? We tested the hypothesis that the active rehearsal of spatial information in working memory is accomplished by means of focal shifts of spatial selective attention to memorized locations. Spatial selective attention has been shown to cause changes in the early visual processing of stimuli that appear in attended locations. Thus, the hypothesis of attention-based rehearsal predicts similar modulations of visual processing at memorized locations. We used functional magnetic resonance imaging to observe posterior visual activations during the performance of a spatial working memory task. In line with the hypothesis, spatial rehearsal led to enhanced activation in the early visual areas contralateral to the memorized locations.     

A transcranial Doppler sonography study of shoot/don’t-shoot responding

The purpose of this study was to examine the relationship between changes in cerebral blood-flow velocity and performance on a speeded shoot/don’t-shoot task. Brain activity as indicated by cerebral blood-flow velocity (hemovelocity) was recorded using the transcranial Doppler ultrasonography. A shoot/don’t-shoot decisionmaking task presented participants with threat/nonthreat stimuli in the form of bull’s-eye images of various colors. Participants were required to shoot threat targets using a laser-modified handgun. Results support a vigilance decrement in both the performance measures and hemovelocity. Performance, as measured by reaction time, number of hits, and marksmanship, decreased across the length of the vigil. Hemovelocity slowed across the left and right hemispheres as the task progressed, and hemovelocity was slower in the right hemisphere than in the left hemisphere.     

Does the letter number sequencing task measure anything more than digit span?

A total of 102 undergraduate students performed the Letter Number Sequencing (LNS) task in addition to a series of other measures of reading, working memory, motor execution, visuo-spatial memory, and executive functions. Performance on the LNS was uniquely contributed to by reading level, digit span forward and backward, arithmetic, visual spatial learning, and by performance on the Symbol Search subtest of the WAIS-III. The results indicate that while much of the variance on the LNS task is explained by performance on the traditional measures of digit span, additional unique contributions to prediction of LNS performance are provided by measures of processing speed and visual spatial working memory.     

A male advantage for spatial and object but not verbal working memory using the n-back task

Sex-related differences have been reported for performance and neural substrates on some working memory measures that carry a high cognitive load, including the popular n-back neuroimaging paradigm. Despite some evidence of a sex effect on the task, the influence of sex on performance represents a potential confound in neuroimaging research. The present study investigated sex-related differences in verbal, spatial, and common object versions of the high cognitive load "n-back" working memory task. Eighteen male and 18 female undergraduates completed all 3 versions of the task. A mixed ANOVA, with Sex (male and female) as the between-subjects factor and Condition (verbal, spatial, and object) as the within-subjects repeated measure revealed that males were significantly more accurate than females on the spatial and object versions of the n-back task and performed equivalently to females on the verbal version of the task. Although the expected female advantage for verbal working memory was not found using this effortful n-back task, these results support a male advantage for high cognitive load spatial and object working memory. Future research should take into account the influence of sex on performance of the n-back task, and examine sex-related differences in working memory using other paradigms.     

Études des caractéristiques de l'utilisateur,de la tâche et de l'interface en réalité virtuelle

The increase of virtual reality application and its use into new fields (training, entertainment and health) point up the difficulty for users to be efficient with this new technology. In order to understand these inter-individual differences, we have studied the impact of the task, the interface and the users' characteristics on this performance. For the task, we have focused on manipulation and travel tasks. For the interface, we have studied the impact of the screen size on the performance and finally with regard to the user, we have focused on the impact of working memory and spatial capacities on performance. Our results show a performance gain on large screen whatever the task. They show that the users' spatial capacities predicted the performance, particularly for the tasks realized on a small screen. We conclude that a large screen is a cognitive aid that permits a high level of performance.     

Reasoning strategies: the role of working memory and verbal-spatial ability

Evidence increasingly suggests individual differences in strategies adopted on reasoning tasks and that these are either verbal-propositional or visuospatial in nature. However, the cognitive foundations of these strategies remain uncertain. Experiment 1 examined the relationship between the use of working memory resources and strategy selection for syllogistic reasoning. Verbal and spatial strategy users did not differ on working memory capacity, but confirmatory factor analysis indicated that while verbal reasoners draw primarily on verbal working memory, spatial reasoners use both this and spatial resources. Experiment 2 investigated the relationship between strategies and verbal and spatial abilities. Although strategy groups were similar in overall ability, regression analysis showed that performance on a spatial ability measure (Vandenberg mental rotation task) predicted syllogistic reasoning performance, but only for spatial strategy users. The findings provide converging evidence that verbal and spatial strategies are underpinned by related differences in fundamental cognitive factors, drawing differentially on the subcomponents of working memory and on spatial ability.     

The structure of working memory abilities across the adult life span

The present study addresses three questions regarding age differences in working memory: (1) whether performance on complex span tasks decreases as a function of age at a faster rate than performance on simple span tasks; (2) whether spatial working memory decreases at a faster rate than verbal working memory; and (3) whether the structure of working memory abilities is different for different age groups. Adults, ages 20-89 (n = 388), performed three simple and three complex verbal span tasks and three simple and three complex spatial memory tasks. Performance on the spatial tasks decreased at faster rates as a function of age than performance on the verbal tasks, but within each domain, performance on complex and simple span tasks decreased at the same rates. Confirmatory factor analyses revealed that domain-differentiated models yielded better fits than models involving domain-general constructs, providing further evidence of the need to distinguish verbal and spatial working memory abilities. Regardless of which domain-differentiated model was examined, and despite the faster rates of decrease in the spatial domain, age group comparisons revealed that the factor structure of working memory abilities was highly similar in younger and older adults and showed no evidence of age-related dedifferentiation.     

Oculomotor delayed response abnormalities in young offspring and siblings at risk for schizophrenia

Individuals with schizophrenia are know to demonstrate cognitive and behavioral difficulties, particularly alterations in executive functions, including working memory. It is unclear whether these deficits reflect trait-related vulnerability to schizophrenia indicators and can be assessed by studying nonpsychotic relatives of patients with schizophrenia. In this study, we used an oculomotor delayed response (ODR) paradigm to examine spatial working memory in 37 "high-risk" child and adolescent offspring and siblings (age range=6-25 years) of patients with schizophrenia or schizoaffective disorder. Compared with 37 age- and sex-matched healthy controls (age range=6-23 years), high-risk subjects showed nonsignificantly greater errors in the ODR task at longer delay intervals. Statistical analyses suggested that performance improved with age in healthy control subjects, whereas it worsened with age in high-risk subjects. In both groups, the ODR errors were generally associated with poorer sustained attention (Continuous Performance Test: visuospatial d prime), somewhat poorer executive function (Wisconsin Card Sorting Test), and elevated Heinrichs-Buchanan neurological soft signs scores. These findings indicate the presence of spatial working memory abnormalities in individuals at risk for schizophrenia. Furthermore, these abnormalities may be progressive in nature. The ODR task is a valuable indicator of prefrontal cortical function and spatial working memory and may be a potentially valuable marker for familial risk of schizophrenia.     

Nonword repetition and identification skills in Kannada speaking school-aged children who do and do not stutter

PurposeThe present study employed nonword repetition and nonword identification tasks to explore the phonological working memory (PWM) abilities and its interaction with speech motor control in school-aged children who do and do not stutter.MethodParticipants were 17 children who stutter (CWS) (Age range = 7–12) and 17 age and gender-matched children who do not stutter (CWNS). For the nonword repetition task, the participants repeated sets of 2-, 3-, and 4-syllable nonwords (n = 12 per set). The participants silently identified a target nonword from a subsequent set of three nonwords (n = 12 per 2-, 3- and 4-syllable length) for the nonword identification task. The performance of CWS on the nonword repetition task was compared with the CWNS for the mean number of accurate repetitions, number of trials taken, number of accurate repetitions on initial trial, and number of fluent repetitions across the three-syllable conditions for the tasks. For the nonword identification task, the number of nonwords identified accurately by the two groups were subjected to analysis.ResultsCWS were significantly less accurate on the initial production of nonwords and required significantly more number of attempts to repeat the nonword accurately. Further for the nonword identification task, CWS were significantly less accurate than CWNS in correctly identifying the target nonword.ConclusionsThe present findings suggest that, in addition to limitations in PWM capacity, an unstable speech motor control system in CWS may lead to dysfluent speech.     

Implicit task sets in task switching?

In 2 experiments, the authors compare stimulus-based versus task-rule-based task performance. Participants practiced 8 stimulus-response mappings either with or without knowledge about 2 underlying task sets. After practice, 2 transfer blocks with 8 new stimuli were presented. Results show that rule knowledge leads to significant switch and transfer costs, whereas without rule knowledge neither switch nor transfer costs occur. However, significant Task Type x Response Type interactions occurred in both conditions. In a second experiment including only the no rule condition, half of the stimulus-response mappings in the transfer blocks were incongruent to the underlying task rule. Slower response times for these incongruent stimuli as compared with congruent stimuli and the absence of switch costs suggest that participants acquired (presumably implicit) knowledge about 4 different stimulus-response categories.