Neural and Functional States of Working Memory

Working memory is akin to holding onto a phone-number until it’s dialled. But,not all digits have the same functional role here while each digit is individuallydialled whereas others are just retained. Our research investigated how theshifting functional roles of memories influence our brain states, by using aunique method to study low or non-activity brain states. In Chapter 2, weprobed memory when only one of the two memorized colours would bereported. Surprisingly, both colours, including the unnecessary one, weredetectable in brain signals. Crucially, the brain states of these two coloursdiffered, reflecting functional differences. With a similar set-up in Chapter 3 westudied memory for orientations. Importantly we asked participants to rotatethe cued orientation and use only rotation-product to judge a new probe.Astonishingly, brain signals represented both the cued and the rotatedmemory, but not the non-rotated one. These results suggest that memoriescan persist in low/non-active brain states even after they lose their functionalrole. In Chapter 4, pre-learned orientations were used to judge the tilt of aprobe. Orientations were either visually shown or were cued by an auditorytone. In both cases the brain states were similar, although neural-connectivitydiffered, as evidence indicated connections between visual and auditoryregions when a tone was presented. Overall results show that brain stateschange when functional roles change but the states vary more than just‘actively guiding behaviour’ and ‘idly retained’. Different response strategiesof the participants may also contribute to this

Neural and Functional States of Working Memory

Working memory is akin to holding onto a phone-number until it’s dialled. But,not all digits have the same functional role here while each digit is individuallydialled whereas others are just retained. Our research investigated how theshifting functional roles of memories influence our brain states, by using aunique method to study low or non-activity brain states. In Chapter 2, weprobed memory when only one of the two memorized colours would bereported. Surprisingly, both colours, including the unnecessary one, weredetectable in brain signals. Crucially, the brain states of these two coloursdiffered, reflecting functional differences. With a similar set-up in Chapter 3 westudied memory for orientations. Importantly we asked participants to rotatethe cued orientation and use only rotation-product to judge a new probe.Astonishingly, brain signals represented both the cued and the rotatedmemory, but not the non-rotated one. These results suggest that memoriescan persist in low/non-active brain states even after they lose their functionalrole. In Chapter 4, pre-learned orientations were used to judge the tilt of aprobe. Orientations were either visually shown or were cued by an auditorytone. In both cases the brain states were similar, although neural-connectivitydiffered, as evidence indicated connections between visual and auditoryregions when a tone was presented. Overall results show that brain stateschange when functional roles change but the states vary more than just‘actively guiding behaviour’ and ‘idly retained’. Different response strategiesof the participants may also contribute to this

Neural and Functional States of Working Memory

Working memory is akin to holding onto a phone-number until it’s dialled. But,not all digits have the same functional role here while each digit is individuallydialled whereas others are just retained. Our research investigated how theshifting functional roles of memories influence our brain states, by using aunique method to study low or non-activity brain states. In Chapter 2, weprobed memory when only one of the two memorized colours would bereported. Surprisingly, both colours, including the unnecessary one, weredetectable in brain signals. Crucially, the brain states of these two coloursdiffered, reflecting functional differences. With a similar set-up in Chapter 3 westudied memory for orientations. Importantly we asked participants to rotatethe cued orientation and use only rotation-product to judge a new probe.Astonishingly, brain signals represented both the cued and the rotatedmemory, but not the non-rotated one. These results suggest that memoriescan persist in low/non-active brain states even after they lose their functionalrole. In Chapter 4, pre-learned orientations were used to judge the tilt of aprobe. Orientations were either visually shown or were cued by an auditorytone. In both cases the brain states were similar, although neural-connectivitydiffered, as evidence indicated connections between visual and auditoryregions when a tone was presented. Overall results show that brain stateschange when functional roles change but the states vary more than just‘actively guiding behaviour’ and ‘idly retained’. Different response strategiesof the participants may also contribute to this

Neural and Functional States of Working Memory

Working memory is akin to holding onto a phone-number until it’s dialled. But,not all digits have the same functional role here while each digit is individuallydialled whereas others are just retained. Our research investigated how theshifting functional roles of memories influence our brain states, by using aunique method to study low or non-activity brain states. In Chapter 2, weprobed memory when only one of the two memorized colours would bereported. Surprisingly, both colours, including the unnecessary one, weredetectable in brain signals. Crucially, the brain states of these two coloursdiffered, reflecting functional differences. With a similar set-up in Chapter 3 westudied memory for orientations. Importantly we asked participants to rotatethe cued orientation and use only rotation-product to judge a new probe.Astonishingly, brain signals represented both the cued and the rotatedmemory, but not the non-rotated one. These results suggest that memoriescan persist in low/non-active brain states even after they lose their functionalrole. In Chapter 4, pre-learned orientations were used to judge the tilt of aprobe. Orientations were either visually shown or were cued by an auditorytone. In both cases the brain states were similar, although neural-connectivitydiffered, as evidence indicated connections between visual and auditoryregions when a tone was presented. Overall results show that brain stateschange when functional roles change but the states vary more than just‘actively guiding behaviour’ and ‘idly retained’. Different response strategiesof the participants may also contribute to this

Neural and Functional States of Working Memory

Working memory is akin to holding onto a phone-number until it’s dialled. But,not all digits have the same functional role here while each digit is individuallydialled whereas others are just retained. Our research investigated how theshifting functional roles of memories influence our brain states, by using aunique method to study low or non-activity brain states. In Chapter 2, weprobed memory when only one of the two memorized colours would bereported. Surprisingly, both colours, including the unnecessary one, weredetectable in brain signals. Crucially, the brain states of these two coloursdiffered, reflecting functional differences. With a similar set-up in Chapter 3 westudied memory for orientations. Importantly we asked participants to rotatethe cued orientation and use only rotation-product to judge a new probe.Astonishingly, brain signals represented both the cued and the rotatedmemory, but not the non-rotated one. These results suggest that memoriescan persist in low/non-active brain states even after they lose their functionalrole. In Chapter 4, pre-learned orientations were used to judge the tilt of aprobe. Orientations were either visually shown or were cued by an auditorytone. In both cases the brain states were similar, although neural-connectivitydiffered, as evidence indicated connections between visual and auditoryregions when a tone was presented. Overall results show that brain stateschange when functional roles change but the states vary more than just‘actively guiding behaviour’ and ‘idly retained’. Different response strategiesof the participants may also contribute to this

Unimodal and Bimodal Access to Sensory Working Memories by Auditory and Visual Impulses

It is unclear to what extent sensory processing areas are involved in the maintenance of sensory information in working memory (WM). Previous studies have thus far relied on finding neural activity in the corresponding sensory cortices, neglecting potential activity-silent mechanisms, such as connectivity-dependent encoding. It has recently been found that visual stimulation during visual WM maintenance reveals WM-dependent changes through a bottom-up neural response. Here, we test whether this impulse response is uniquely visual and sensory-specific. Human participants (both sexes) completed visual and auditory WM tasks while electroencephalography was recorded. During the maintenance period, the WM network was perturbed serially with fixed and task-neutral auditory and visual stimuli. We show that a neutral auditory impulse-stimulus presented during the maintenance of a pure tone resulted in a WM-dependent neural response, providing evidence for the auditory counterpart to the visual WM findings reported previously. Interestingly, visual stimulation also resulted in an auditory WM-dependent impulse response, implicating the visual cortex in the maintenance of auditory information, either directly or indirectly, as a pathway to the neural auditory WM representations elsewhere. In contrast, during visual WM maintenance, only the impulse response to visual stimulation was content-specific, suggesting that visual information is maintained in a sensory-specific neural network, separated from auditory processing areas

Object-based visual working memory:an object benefit for equidistant memory items presented within simple contours

Previous research has shown that more information can be stored in visual working memory (VWM) when multiple items belong to the same object. Here, in four experiments, we investigated the object effect on memory for spatially equidistant features by manipulating simple, task-irrelevant contours that combined these features. In Experiments 1, 3, and, 4, three grating orientations, and in Experiment 2, one color and two orientations, were presented simultaneously to be memorized. Mixture modeling was applied to estimate both the precision and the guess rates of recall errors. Overall results showed that two target features were remembered more accurately when both were part of the same object. Further analysis showed that the probability of recall increased in particular when both features were extracted from the same object. In Experiment 2, we found that the object effect was greater for features from orthogonal dimensions, but this came at the cost of lower memory precision. In Experiment 3, when we kept the locations of the features perfectly consistent over trials so that the participants could attend to these locations rather than the contour, we still found object benefits. Finally, in Experiment 4 when we manipulated the temporal order of the object and the memory features presentations, it was confirmed that the object benefit is unlikely to stem from the strategical usage of object information. These results suggested that the object benefit arises automatically, likely at an early perceptual level.</p

Impulse perturbation reveals cross-modal access to sensory working memory through learned associations

Using MVPA of EEG data to investigate visual memories encoded after visual presentation and after retrieval from long-term memory via auditory cues