Given the important amount of visual and auditory linguistic information that pilots have to process, operating an aircraft generates a high working-memoryload (WML). In this context, the ability to focus attention on relevant information and to remain responsive to concurrent stimuli might be altered. Consequently, understanding the effects of WML on the processing of both linguistic targets and distractors is of particular interest in the study of pilot performance. In the present work, participants performed a simplified p iloting t ask i n w hich t hey h ad t o f ollow o ne o f t hree colored aircraft, according to specific w ritten i nstructions ( i.e., t he w ritten w ord f or t he color corresponding to the color of one of the aircraft) and to ignore either congruent or incongruent concurrent auditory distractors (i.e., a spoken name of color). The WML was manipulated with an n-back sub-task. Participants were instructed to apply the current written instruction in the low WML condition, and the 2-back written instruction in the high WML condition. Results revealed a major effect of WML at behavioral (i.e., decline of piloting performance), electrophysiological, and autonomic levels (i.e., greater pupil diameter). Increased WML consumed resources that could not be allocated to the processing of the linguistic stimuli, as indexed by lower P300/P600 amplitudes. Also, significantly, lower P600 responses were measured in incongruent vs. congruent trials in the low WML condition, showing a higher difficulty reorienting attention toward the written instruction, but this effect was canceled in the high WML condition. This suppression of interference in the high load condition is in line with the engagement/distraction trade-off model. We propose that P300/P600 components could be reliable indicators of WML and that they allow an estimation of its impact on the processing of linguistic stimuli.
Workingmemoryload affects chronotype- and time-of-day dependent cerebral activity modulations
Christina Schmidt, Philippe Peigneux, Yves Leclercq, Virginie Sterpenich, Gilles Vandewalle, Christophe Phillips, Gilberte Tinguely, Annabelle, Steffen Gais, Manuel Schabus, Martin Desseilles, Thanh Dang-Vu, Eric Salmon, Evelyne Balteau, André Luxen, Christian Cajochen, Pierre Maquet, Fabienne Collette
made at p<0.05, corrected for multiple comparisons over small volumes of interest. Here, only the comparison between the 3-back and the 0-back condition will be considered.
Although a repeated-measures ANOVA on accuracy performance including the three variables of interest (workingmemoryload*chronotype*time of day) did not reach significance (F(1,19) = 2.19; p = .16) Figure 1 indicates that, for the 3-back condition, morning and evening types differed in their performance levels according to time of day. When we performed an ANOVA on the 3-back condition separately, there was a trend toward an interaction between chronotype and time of day (F(1,19) = 4,1986, p = .054), with evening types’ performance improving from the morning to the evening hours (LSD Fisher post hoc; p < .05). We also observed a trend toward higher performance levels during the evening hours for evening types than for morning types (LSD Fisher post hoc; p = .078). From a functional neuroimaging point of view, our preliminary findings indicate that activity in a thalamic region (x = -6; y = -6; z = 4; z-score = 3.26) predominantly projecting to the prefrontal cortex (thalamic connectivity atlas: http://www.fmrib.ox.ac.uk/cgi-bin/thalamus.pl) is simultaneously modulated by all three variables [(morning/evening session)*(morning/evening type)*(0-back/3-back)]. This triple interaction effect indicates that the chronotype-dependent time-of-day modulation in performance acts differentially depending on the workingmemoryload (see Figure 1). Globally, higher thalamic activity was observed in the high–workingmemoryload condition (3- back) than in the control condition (0-back; no memoryload). Interestingly, parameter estimates shown in Figure 1 indicate that evening types present increased thalamic activity differences between the 3- and 0- back condition from the morning to the evening session, whereas morning types show the reverse profile. BOLD activity in frontal brain areas such as the left middle (x = -24; y = 48; z = 12; z- score = 4.39) and right superior (x = -8; y = 10; z = 62; z-score = 3.41) frontal gyrus behave similarly.
4.1. Group differences in striatal reactivity
In MDD patients, behavioral and neuroimaging studies evidenced (i) higher difficulty to evaluate potential gains ( Eshel and Roiser, 2010 ; Fig. 4. Illustration of the fourfold interaction effect (group × stress × reward x load) in the bilateral putamen. (A) Post-hoc comparisons evidenced a significant stress-induced reduction in the bilateral putamen activation in response to no-reward cues in the unpredictable threat-of-shock compared to no-shock conditions in healthy control (HCon) adults without increased familial risk for major depression, but exclusively in the low cognitive load condition. (B) In healthy adults with increased familial risk for major depression (HVul, healthy vulnerable), threat-of-shock potentiated the bilateral putamen reactivity in response to reward compared to no-reward cues, in particular when the task was more demanding (i.e., high workingmemoryload). In turn, threat-of-shock resulted in a deactivation in response to both reward and no-reward cues in the low cognitive load condition, with stronger deactivation in response to no-reward compared to reward cues. Parameter estimates (βeta weights) mean with standard errors and ROI's masks from which parameter estimates were extracted are presented at the top of the figure. Statistical parametric map corresponding to the fourfold interaction effect (group × stress × reward × load) is presented below These whole-brain activations are corrected for multiple comparisons, but thresholded here at 0.05 for visualization purpose. ★ p ≤ 0.05, ★★ p ≤ 0.01, ★★★ p ≤ 0.001.
Workingmemory (WM) plays an important role in pilots since they have to continuously inte- grate and dynamically update information within a rapidly changing environment. WM is essen- tial for overcoming response conflict and for optimal selective attention performance. Yet, WM is a capacity-limited system and increasing the demands on WM reduces the ability to ignore irrel- evant stimuli and can led decreased performance in dual –tasking. In the present study we used an experimental approach aiming at providing evidence for the sensitivity of the functional near infrared spectroscopy (fNIRS) in providing measures of brain activity within the prefrontal cortex (PFC), with regard to WM-specific task demands combined to an additional different secondary task.
Our analysis revealed an association between CPLX2 polymorphisms and workingmemoryload-dependent neural activity in a frontoparietal brain network in schizophrenia patients but not in healthy controls. Results were strengthened by subsequent analyses including potentially confounding variables such as lifetime anti- psychotic exposure and workingmemory performance. Our findings are in line with the results from Cplx2 -/- rodent models and consistent with the ‘second-hit’ hypothesis of schizophrenia, i.e., CPLX2 risk variants increase neural inefficiency if the individual has experi- enced an additional risk factor. Second-hit risk factors such as prenatal infections, perinatal complications, early insults to the brain, stressful life events, or drug abuse are more prevalent in people affected by schizophrenia than demo- graphically similar control samples (for a review, see Vi- lain et al. [ 45 ]).
• Campoy, G., Castellà, J., Provencio, V., Hitch, G. J., & Baddeley, A. D. (2015). Automatic semantic encoding in verbal short-term memory: Evidence from the concreteness effect. The Quarterly Journal of Experimental Psychology, 68(4), 759–778.
• Kowialiewski, B., & Majerus, S. (2018). The non-strategic nature of linguistic long-term memory effects in verbal short-term memory. Journal of Memory and Language, 101, 64–83.
• Workingmemory is dedicated to the simultaneous storage and manipulation of cognitive representations in order to complete complex activities like, for example, mental calculation. There are strong relationships between workingmemory and executive functioning (i.e. the cognitive system that ensures the adaptation to new situations).
experimental paradigms, such as the delayed alternation task (requiring monkeys to alternate lever presses; Kubota and Niki, 1971 ) or oculomotor versions of the delayed-response task (requiring monkeys to make a saccade to a spatial location held in workingmemory; Funahashi et al., 1989 ).
How did these early studies interpret this sustained neural activity? It might surprise you that these authors (in particular the ones of the first two papers) actually did not equate the persistent firing with the storage of representations in workingmemory (as is typically assumed to be the case today). They instead suggested that it reflected the animals’ sustained attention towards the internally stored representations of the to-be-remembered information, thus corroborating the contemporary views on prefrontal cortex function we talked about before. Subsequent investigations, however, were able to provide increasingly convincing evidence in favor of the role of persistent neural activity as a genuine neural correlate of the workingmemory engram ( Goldman-Rakic, 1995 ): They, for instance, ruled out possible alternative explanations for the sustained neural firing observed in the original studies (e.g., preparation of upcoming motor response) and, crucially, demonstrated that it was in particular those neurons that were selective for the current content of workingmemory that exhibited this kind of persistent delay-period activity ( Funahashi et al., 1989 ; Miller et al., 1996 ). Since then, sustained working-memory related activity has been observed in many brain imaging studies in humans ( Courtney et al., 1997, 1998a, 1998b ; Jansma et al., 2000 ; Sakai et al., 2002 ; Figure 1.8B ) and stimulus-selective sustained neural firing has very recently even been reported in single neurons of the human medial temporal lobe ( Kamiński et al., 2017 ; Kornblith et al., 2017 ; Figure 1.8C ) as well as populations of neurons in the prefrontal cortex ( Haller et al., 2018 ) . In their totality, these findings thus support an extraordinarily appealing view of the nature and neural substrates of workingmemory: In order for us to keep a stable thought in mind, neurons coding for the respective information will have to remain active until that information is no longer needed. What could possibly be more beautiful than that?
In conjunction with prior evidence ( King et al., 2016 ; Salti et al., 2015 ), our findings therefore indicate that there may be two successive mechanisms for the short-term maintenance of conscious and non-conscious stimuli: an initial, transient period of ~1 s, during which the representation is encoded by active firing with a slowly decaying amplitude, and an ensuing activity-silent mainte- nance via short-term changes in synaptic weights, during which activity either intermittently resurfa- ces (conscious case) or vanishes (non-conscious case). Such activity-silent retention need not necessarily be specific to workingmemory. Recent investigations have, for instance, demonstrated the existence of recognition memory for invisible cues ( Chong et al., 2014 ; Rosenthal et al., 2016 ). As delay periods ranged in the order of minutes rather than seconds, persistent neural activity seems to be an unlikely candidate mechanism of maintenance. Activity-silent codes might have been at play, though they probably depended on mechanisms with longer time constants than the relatively rapidly decaying patterns of synaptic weights discussed in the context of the present experiments. Nevertheless, activity-silent representations may constitute a general mechanism for maintenance across the whole spectrum of temporal delays (from seconds over minutes/hours to days/weeks/dec- ades), thus forming a generic property of memory.
Attout, L., Kaa, M.-A. V. der, George, M., & Majerus, S. (2012). Dissociating short-term memory and language impairment: The importance of item and serial order information. Aphasiology , 26 (3-4), 355-382. Collette, F., Péters, F., Hogge, M., & Majerus, S. (2007). Mémoire de travail et vieillissement normal. Neuropsychologie de la mémoire de travail .
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✓ If there is a reduction of verbal WM abilities in healthy aging, it is
WorkingMemory Assessment: Construct Validity of the
The Brown-Peterson task was originally created by Brown (1958) and elaborated by Peterson and Peterson (1959) to examine the hypothesis that memory trace decay is a cause of forgetting. Specifically, the Brown-Peterson technique was designed to measure the effects of both interference and delay on short-term memory performance. Over time, various versions of the task have been developed (e.g., Belleville, Chatelois, Fontaine, & Peretz, 2002; Mertens, Gagnon, Coulombe, & Messier, 2006; Ryan & Butters, 1980; for a recent adaptation in children, see Rai & Harris, 2013). However, the basic principle of the Brown-Peterson paradigm always remains the same. Typically, participants are instructed to recall a few items (usually, three consonants) after variable delays (usually, from 0 to approximately 30 seconds) during which an interference task must be performed (e.g., mental addition, repetition of numbers, counting backward).
The first neuroimaging study which explored dual-task coordination was that of D’Esposito et al. . Participants were administered two tasks predominantly involving posterior brain regions and requiring no storage in workingmemory: a semantic judgement task (to identify exemplars of a target category in series of orally presented words) and a spatial-rotation task (to indicate which of two squares had a dot in the same location, relative to a double line, as a spatially rotated target square). In order to determine the cerebral area involved in dual-task coordination, changes in the metabolic activity when participants have to perform the tasks in isolation were compared to cerebral activity when the two tasks are performed simultaneously. Comparison of the single task versus resting baseline conditions showed activation in the bilateral parieto-occipital regions for the dot-location task and in the left temporal region for the semantic judgement task. The comparison of the dual-task condition to the single-task conditions showed significantly increased activity bilaterally in the dorsolateral prefrontal cortex (BA 9 and 46) and the anterior cingulate region. Such a pattern of activity cannot be attributed to task difficulty since increasing difficulty in the single task at the level of the dual task (as attested by the accuracy of performance) resulted in increased activation in posterior brain regions although no additional prefrontal activation was observed. These data support the hypothesis that the dorsolateral prefrontal cortex is involved in the allocation and coordination of attentional resources. Activity of the anterior cingulate was attributed to response selection among competing, complex contingencies.
At the theoretical level, the concept of WM has made a long journey since the proposal of the workingmemory model by Baddeley and Hitch (1974) . The initial workingmemory model contained a phonological loop system for storing verbal information, with a subdivision into in a buﬀer system, the phonological store, and a refreshing mechanism, the subvocal articulatory rehearsal process. This model also contained a visuo-spatial sketchpad for storing visuo-spatial information, as a well as an attentional supervisory system. This model captured well the observation of patients with apparent isolated verbal WM de ﬁcits, as WM was considered to be a separate function from the language system and hence could be impaired in isolation ( Vallar & Baddeley, 1984 ). However, this model did not capture the complex interactions that exist between verbal WM and language processing. These interactions are of particular importance for an accurate understanding of verbal WM de ﬁcits in patients with aphasia, as these deﬁcits can be the cause or the consequence of underlying language impairment. For example, patients with reduced semantic processing abilities will show impaired storage abilities for stimuli with a semantic content such as words, but not for nonwords ( Majerus, Patterson, & Norris, 2007 ). Even in patients with so-called isolated verbal WM impairment, a review of published cases showed that the vast majority of these patients initially presented with aphasia, and the severity of their verbal storage deﬁcit correlated with their residual language processing abilities ( Majerus, 2009 ). Progressively, WM models started to acknowledge more explicitly the interactions that link WM and language processing. Some models took a strong position by considering that short-term storage of verbal information is a processing property of the language system and reﬂects the decay rate of activated language representations (N. Martin & Saﬀran, 1992 ). Other models
It is possible that the sequence [word1 word2] has been mostly uttered as a single AP with the default /LHi LH*/ pattern in both clash and no-clash conditions (Fig. 4). Specifically, speakers of the C group and speakers of the MS group with high workingmemory could have consistently placed an initial Hi on word1 since in both conditions there is no violation of AVOID HHH. Given the ‘loose’ association of Hi with the left edge of the AP, its phonetic could have variably realized on IA and FA. This could explain the high values of maxf0 in FA in both clash and no-clash conditions, as well as the lack of differences for ratioPitch_IA/FA in the CL-condition. Moreover, the lack of durational results can be explained by the fact that the syllable carrying the initial rise is not marked by lengthening.
The ability to maintain the serial order of events is recognized as a major function of workingmemory. Although general models of workingmemory postulate a close link between workingmemory and attention, such a link has so far not been proposed specifically for serial-order workingmemory. The present study provided the first empirical demonstration of a direct link between serial order in verbal workingmemory and spatial selective attention. We show that the retrieval of later items of a sequence stored in workingmemory—compared with that of earlier items— produces covert attentional shifts toward the right. This observation suggests the conceptually surprising notion that serial-order workingmemory, even for nonspatially defined verbal items, draws on spatial attention.
Linguistics & Phonetics, 25(6-7), 530-539.
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