1,721,007 research outputs found
Dynamic visual noise: No interference with visual short-term memory or the construction of visual images
No full textThe effects of dynamic visual noise (DVN) and static visual noise (SVN) were assessed on a visual short-term memory (STM) task, in which a matrix pattern was briefly presented and followed by a recognition test, and a new, cumulative imagery task, in which the elements of a pattern were presented one at a time, and participants were asked to imagine the pattern formed by displaying all the elements together. When presented during the retention interval neither DVN nor SVN affected visual STM performance. The cumulative imagery task was not affected by visual noise presented either during the retention interval or concurrently while the elements of the pattern were shown. Increasing the spatial demands of the task decreased performance, but did not interact with type of visual noise. The results (1) show that DVN in relatively short bursts does not interfere with visual STM, (2) argue against the view that DVN impairs the localisation of pattern elements, and (3) provide no support for the view that concurrent DVN mandatorily disrupts the formation of visual images. The implications for studies of visual imagery and visual STM are discussed
Choice-predictive activity in parietal cortex during source memory decisions
No full textNeurobiological research has classically focused on perceptual decision-making, although many real-life decisions are based on information that is not currently available but stored in long-term memory. Previous studies have suggested that the lateral parietal cortex encodes decision-related signals during item recognition judgments. In the present fMRI study, we employed a parametric manipulation of evidence for source memory judgments and tested several hypotheses concerning memory decision signals in parietal cortex. As expected, the mean BOLD signal in several parietal regions was modulated by decision evidence. An analysis of the locally distributed pattern of activity, moreover, identified a parietal cluster showing significant choice-predictive activity even at the lowest level of decision evidence, with decoding accuracy that increased as a function of evidence. Decoding patterns were consistent across subjects as shown by a leave-one-subject-out classification analysis. Finally, we found that the pattern of choice-predictive activity in parietal lobe was temporally correlated with that observed in medial temporal regions traditionally associated with long-term memory functions. The present findings are consistent with a general role of lateral parietal regions located around the intraparietal sulcus in representing a decision variable for memory-based decisions
Searching for Linearity: Reconstructive Processes Reverse Temporal Scrambling in Memory for Movie Scenes
No full textMeaning-making and temporal memory are closely intertwined, yet we still do not know how the overall understanding of complex events affects retrospective temporal judgments. The present study investigated the effect of a manipulation of the temporal linearity of a narrative on the subsequent memory-for-time performance. Participants indicated the time of occurrence of short video clips extracted from a previously encoded movie on a horizontal timeline representing the movie duration. Importantly, a group of participants (N = 20) watched the original movie, which depicts events occurring in chronological order, whereas another group (N = 30) watched a scrambled version of the same movie in which the temporal linearity was lost. This procedure allowed us to measure the quantity and direction of the temporal memory bias. The scrambled presentation produced a mild and general impairment of recognition memory compared to the linear presentation. More importantly, it biased temporal judgments as a function of the direction and amount of discrepancy between the story and the viewing time, in accordance with an automatic reshaping of temporal memory caused by a chronological representation of the storyline. This effect could be distinguished from a tendency to move judgments toward the center of the timeline, independently from the specific scrambling arrangement, consistent with the idea that the non-linearity of the story also generally increased the degree of temporal uncertainty. Taken together, our results provide further evidence that temporal memories are automatically reconstructed according to the general meaning of the events
Long-term memory for movie details: selective decay for verbal information at one week
No full textMnemonic representations of complex events are multidimensional, incorporating information about objects and characters, their interactions and their spatial-temporal context. The present study investigated the degree to which detailed verbal information (i.e., dialogues), as well as semantic and spatiotemporal (i.e., "what", "where", and "when") elements of episodic memories for movies, are forgotten over the course of a week. Moreover, we tested whether the amount of dimension-specific forgetting differed as a function of the participant's age. In a mixed design, younger and middle-aged participants were asked to watch a & SIM;90 min movie and provide yes/no answers to detailed questions about different dimensions of the presented material after 1, 3 days, and 1 week. The results indicate that memory decay mainly affects the verbal dimension, both in terms of response accuracy and confidence. Instead, detailed information about objects/characters' features and spatiotemporal context seems to be relatively preserved, despite a general decrease in response confidence. Furthermore, younger adults were in general more accurate and confident than middle-aged participants, although, again, the verbal dimension exhibited a significant age-related difference. We propose that this selective forgetting depends on the progressive advantage of visual compared to auditory/verbal information in memory for complex events
Task and Regions Specific Top-Down Modulation of Alpha Rhythms in Parietal Cortex
Full text linkAlpha (8-12 Hz) power desynchronization is strongly associated to visual perception but has been observed in a large variety of tasks, indicating a general role in task anticipation. We previously reported in human observers that interference by repetitive transcranial magnetic stimulation (rTMS) of core regions of the dorsal attention network (DAN) disrupts both anticipatory alpha desynchronization and performance during a visuospatial attention (VSA) task. Here, we test the hypothesis that alpha desynchronization is task specific, and can be selectively modulated by interfering with activity in different higher-order parietal regions. We contrast the effects of rTMS on alpha rhythms and behavior on 2 different tasks: a VSA and a semantic decision task, by targeting the posterior intraparietal sulcus (pIPS), a core region of the DAN, or the angular gyrus (AG), a core region of the default mode network (DMN). We found that both performance and anticipatory alpha desynchronization were affected by stimulation of IPS only during VSA, and of AG only during semantic decisions. These findings indicate the existence of multiple dedicated parietal channels for the modulation of anticipatory alpha rhythms, which in turn reflect task-specific modulation of excitability in human parieto-occipital cortex
Neuroimaging evidence supporting a dual-network architecture for the control of visuospatial attention in the human brain: a mini review
Full text linkNeuroimaging studies conducted in the last three decades have distinguished two frontoparietal networks responsible for the control of visuospatial attention. The present review summarizes recent findings on the neurophysiological mechanisms implemented in both networks and describes the evolution from a model centered on the distinction between top-down and bottom-up attention to a model that emphasizes the dynamic interplay between the two networks based on attentional demands. The role of the dorsal attention network (DAN) in attentional orienting, by boosting behavioral performance, has been investigated with multiple experimental approaches. This research effort allowed us to trace a distinction between DAN regions involved in shifting vs. maintenance of attention, gather evidence for the modulatory influence exerted by the DAN over sensory cortices, and identify the electrophysiological correlates of the orienting function. Simultaneously, other studies have contributed to reframing our understanding of the functions of the ventral attention network (VAN) and its relevance for behavior. The VAN is not simply involved in bottom-up attentional capture but interacts with the DAN during reorienting to behaviorally relevant targets, exhibiting a general resetting function. Further studies have confirmed the selective rightward asymmetry of the VAN, proposed a functional dissociation along the anteroposterior axis, and suggested hypotheses about its emergence during the evolution of the primate brain. Finally, novel models of network interactions explain the expression of complex attentional functions and the emergence and restorations of symptoms characterizing unilateral spatial neglect. These latter studies emphasize the importance of considering patterns of network interactions for understanding the consequences of brain lesions
The contribution of the human posterior parietal cortex to episodic memory
Full text linkThe posterior parietal cortex (PPC) is traditionally associated with attention, perceptual decision making and sensorimotor transformations, but more recent human neuroimaging studies support an additional role in episodic memory retrieval. In this Opinion article, we present a functional-anatomical model of the involvement of the PPC in memory retrieval. Parietal regions involved in perceptual attention and episodic memory are largely segregated and often show a push-pull relationship, potentially mediated by prefrontal regions. Moreover, different PPC regions carry out specific functions during retrieval - for example, representing retrieved information, recoding this information based on task demands, or accumulating evidence for memory decisions
Preferential coding of eye/hand motor actions in the human ventral occipito-temporal cortex
No full textRecent evidence showed that pupil dilation (PD) reflects modulations in the magnitude of the Simon interference effect due to correspondence sequence. In the present study we used this measure to assess whether these modulations, thought to result from cognitive control mechanisms, are influenced by prior practice with an incompatible stimulus-response (S-R) mapping. To this end, PD and reaction times (RTs) were recorded while participants performed a Simon task before and after executing a spatially incompatible practice. The sequential analysis revealed that PD mirrored the conflict-adaptation pattern observed in RTs. Crucially, sequential modulations were not affected by prior practice. These findings support the view that the modulations of the Simon effect due to prior practice and those due to correspondence sequence result from two different mechanisms, and suggest that PD can help to better understand the mechanisms underlying response selection and cognitive control in the Simon task
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