Secondary Working Memory Task Research Articles

The influence of pupil responses on subjective brightness perception.

When the pupil dilates, the amount of light that falls onto the retina increases. However, in daily life, this does not make the world look brighter. Here we asked whether pupil size (resulting from active pupil movement) influences subjective brightness in the absence of indirect cues that, in daily life, support brightness constancy. We measured the subjective brightness of a tester stimulus relative to a referent as a function of pupil size during tester presentation. In Experiment 1, we manipulated pupil size through a secondary working-memory task (larger pupils with higher load and after errors). We found some evidence that the tester was perceived as darker, rather than brighter, when pupils were larger. In Experiment 2, we presented a red or blue display (larger pupils following red displays). We again found that the tester was perceived as darker when pupils were larger. We speculate that the visual system takes pupil size into account when making brightness judgments. Finally, we highlight the challenges associated with manipulating pupil size. In summary, the current study (as well as a recent pharmacological study on the same topic by another team) is intriguing first steps towards understanding the role of pupil size in brightness perception.

Effects of auditory training on low-pass filtered speech perception and listening-related cognitive load.

Studies supporting learning-induced reductions in listening-related cognitive load have lacked procedural learning controls, making it difficult to determine the extent to which effects arise from perceptual or procedural learning. Here, listeners were trained in the coordinate response measure (CRM) task under unfiltered (UT) or degraded low-pass filtered (FT) conditions. Improvements in low-pass filtered CRM performance were larger for FT. Both conditions showed training-related reductions in cognitive load as indexed by a secondary working memory task. However, only the FT condition showed a correlation between CRM improvement and secondary task performance, suggesting that effects can be driven by perceptual and procedural learning.

Adaptive Value Normalization in the Prefrontal Cortex Is Reduced by Memory Load.

Adaptation facilitates neural representation of a wide range of diverse inputs, including reward values. Adaptive value coding typically relies on contextual information either obtained from the environment or retrieved from and maintained in memory. However, it is unknown whether having to retrieve and maintain context information modulates the brain’s capacity for value adaptation. To address this issue, we measured hemodynamic responses of the prefrontal cortex (PFC) in two studies on risky decision-making. In each trial, healthy human subjects chose between a risky and a safe alternative; half of the participants had to remember the risky alternatives, whereas for the other half they were presented visually. The value of safe alternatives varied across trials. PFC responses adapted to contextual risk information, with steeper coding of safe alternative value in lower-risk contexts. Importantly, this adaptation depended on working memory load, such that response functions relating PFC activity to safe values were steeper with presented versus remembered risk. An independent second study replicated the findings of the first study and showed that similar slope reductions also arose when memory maintenance demands were increased with a secondary working memory task. Formal model comparison showed that a divisive normalization model fitted effects of both risk context and working memory demands on PFC activity better than alternative models of value adaptation, and revealed that reduced suppression of background activity was the critical parameter impairing normalization with increased memory maintenance demand. Our findings suggest that mnemonic processes can constrain normalization of neural value representations.

The role of working memory in the temporal control of discrete and continuous movements.

Music performance requires precise control of limb movements in order to achieve temporal precision of performed tone onsets. Previous findings suggest that processes recruited for the temporal control of rhythmic body movements, such as those required in music performance, depend on the movement type (discrete vs. continuous) and the rate of the produced interonset intervals (sub-second vs. supra-second). Using a dual-task paradigm, the current study addressed these factors in the temporal control of cellists’ bowing movements. Cellists performed melodies in a synchronization-continuation timing task at a specified fast (intertone interval = 700 ms) or slow (intertone interval = 1,100 ms) tempo with either discrete (staccato) or continuous (legato) bowing movements. A secondary working memory task involved a concurrent digit-switch counting task. Analyses of the produced tone durations showed that the working memory load significantly impaired temporal regularity when the melodies were performed with discrete bowing movements at the slower tempo. In addition, discrete movements led to more errors on the working memory task. These findings suggest that continuous body movements provide temporal control information to performers under high cognitive load conditions.

Effects of a secondary task and working memory load on multisensory hand position

Information about where our hands are arises from different sensory modalities; chiefly proprioception and vision. These inputs differ in variability from situation to situation (or task to task). According to the idea of ‘optimal integration’, the information provided by different sources is combined in proportion to their relative reliabilities, thus maximizing the reliability of the combined estimate. It is uncertain whether optimal multisensory integration of multisensory contributions to limb position requires executive resources. If so, then it should be possible to observe effects of secondary task performance and/or working memory load (WML) on the relative weighting of the senses under conditions of crossmodal sensory conflict. Alternatively, an integrated signal may be affected by upstream influences of WML or a secondary task on the reliabilities of the individual sensory inputs. We examine these possibilities in two experiments which examine effects of WML on reaching tasks in which bisensory visual-proprioceptive (Exp. 1), and unisensory proprioceptive (Exp. 2) cues to hand position are provided. WML increased visual capture under conditions of visual-proprioceptive conflict, regardless of the direction of visual-proprioceptive conflict, and the degree of load imposed. This indicates that task-switching (rather than WML load) leads to an increased reliance on visual information regardless of its task-specific reliability (Exp. 1). This could not be explained due to an increase in the variability of proprioception under secondary working memory task conditions (Exp. 2). We conclude that executive resources are involved in the relative weighting of visual and proprioceptive cues to hand position.

On the flexibility of grammatical advance planning during sentence production: Effects of cognitive load on multiple lexical access.

Three picture-word interference experiments addressed the question of whether the scope of grammatical advance planning in sentence production corresponds to some fixed unit or rather is flexible. Subjects produced sentences of different formats under varying amounts of cognitive load. When speakers described 2-object displays with simple sentences of the form "the frog is next to the mug," the 2 nouns were found to be lexically-semantically activated to similar degrees at speech onset, as indexed by similarly sized interference effects from semantic distractors related to either the first or the second noun. When speakers used more complex sentences (including prenominal color adjectives; e.g., "the blue frog is next to the blue mug") much larger interference effects were observed for the first than the second noun, suggesting that the second noun was lexically-semantically activated before speech onset on only a subset of trials. With increased cognitive load, introduced by an additional conceptual decision task and variable utterance formats, the interference effect for the first noun was increased and the interference effect for second noun disappeared, suggesting that the scope of advance planning had been narrowed. By contrast, if cognitive load was induced by a secondary working memory task to be performed during speech planning, the interference effect for both nouns was increased, suggesting that the scope of advance planning had not been affected. In all, the data suggest that the scope of advance planning during grammatical encoding in sentence production is flexible, rather than structurally fixed.