200,052 research outputs found
Control of goal-directed and stimulus-driven attention in the brain
No full textWe review evidence for partially segregated networks of brain areas that carry out different attentional functions. One system, which includes parts of the intraparietal cortex and superior frontal cortex, is involved in preparing and applying goal-directed (top-down) selection for stimuli and responses. This system is also modulated by the detection of stimuli. The other system, which includes the temporoparietal cortex and inferior frontal cortex, and is largely lateralized to the right hemisphere, is not involved in top-down selection. Instead, this system is specialized for the detection of behaviourally relevant stimuli, particularly when they are salient or unexpected. This ventral frontoparietal network works as a 'circuit breaker' for the dorsal system, directing attention to salient events. Both attentional systems interact during normal vision, and both are disrupted in unilateral spatial neglect
Semantics of multimodal adjoint type theory
No full textWe show that contrary to appearances, Multimodal Type Theory (MTT) over a
2-category M can be interpreted in any M-shaped diagram of categories having,
and functors preserving, M-sized limits, without the need for extra left
adjoints. This is achieved by a construction called "co-dextrification" that
co-freely adds left adjoints to any such diagram, which can then be used to
interpret the "context lock" functors of MTT. Furthermore, if any of the
functors in the diagram have right adjoints, these can also be internalized in
type theory as negative modalities in the style of FitchTT. We introduce the
name Multimodal Adjoint Type Theory (MATT) for the resulting combined general
modal type theory. In particular, we can interpret MATT in any finite diagram
of toposes and geometric morphisms, with positive modalities for inverse image
functors and negative modalities for direct image functors.Comment: 19 pages. v2: Improved notation; extended pre-proceedings version for
MFPS 2023. v3: correct some mis-wordings, final. v4: condensed version for
conference postproceeding
Attention to memory and the environment: functional specialization and dynamic competition in human posterior parietal cortex
No full textPosterior parietal cortex has been traditionally associated with perceptual attention and sensory-motor processing, but recent studies also indicate a potential role in episodic memory retrieval. Here, we developed a new paradigm to isolate top-down attention-related activity directed to either memory or perceptual information. We demonstrated a robust topographic separation in human posterior parietal cortex associated with searching for task-relevant information in episodic memory or in the environment. Control analyses confirmed that this difference was not dependent on differences in sensory stimulation or eye movements across tasks. Notably, we observed in memory-and perception-related regions a mechanism of reciprocal dynamic competition that was related to behavioral performance. These results provide the first evidence for a double dissociation between parietal networks involved in top-down attention to memory and the environment and support the idea of neural competition between perception and memory
Visuospatial reorienting signals in the human temporo-parietal junction are independent of response selection
No full textThis study contrasts visuospatial reorienting and response selection signals in the right temporo-parietal junction (TPJ) with functional magnetic resonance imaging. The overall goal was to investigate whether spatial orienting signals and motor signals interacted or were independent in TPJ. The right TPJ showed a greater response to targets at invalidly rather than validly cued locations, but no significant modulation from the effector used to respond. We suggest that TPJ may work as a modality-independent 'circuit breaker' for the dorsal fronto-parietal attention system, directing attention to salient events and enabling a variety of responses to those events
Domain-general Signals in the Cingulo-opercular Network for Visuospatial Attention and Episodic Memory
No full textWe investigated the functional properties of a previously described cingulo-opercular network (CON) putatively involved in cognitive control. Analyses of common fMRI task-evoked activity during perceptual and episodic memory search tasks that differently recruited the dorsal attention (DAN) and default mode network (DMN) established the generality of this network. Regions within the CON (anterior insula/frontal operculum and anterior cingulate/presupplementary cortex) displayed sustained signals during extended periods in which participants searched for behaviorally relevant information in a dynamically changing environment or from episodic memory in the absence of sensory stimulation. The CON was activated during all phases of both tasks, which involved trial initiation, target detection, decision, and response, indicating its consistent involvement in a broad range of cognitive processes. Functional connectivity analyses showed that the CON flexibly linked with the DAN or DMN regions during perceptual or memory search, respectively. Aside from the CON, only a limited number of regions, including the lateral pFC, showed evidence of domain-general sustained activity, although in some cases the common activations may have reflected the functional-anatomical variability of domain-specific regions rather than a true domain generality. These additional regions also showed task-dependent functional connectivity with the DMN and DAN, suggesting that this feature is not a specific marker of cognitive control. Finally, multivariate clustering analyses separated the CON from other frontoparietal regions previously associated with cognitive control, indicating a unique fingerprint. We conclude that the CON's functional properties and interactions with other brain regions support a broad role in cognition, consistent with its characterization as a task control network
Is the Posner Reaction Time Test More Accurate Than Clinical Tests in Detecting Left Neglect in Acute and Chronic Stroke?
No full textRengachary J, d' Avossa G, Sapir A, Shulman GL, Corbetta M. Is the Posner Reaction Time Test more accurate than clinical tests in detecting left neglect in acute and chronic stroke? Arch Phys Med Rehabil 2009;90:2081-8. Objective: To compare the accuracy of common clinical tests for left neglect with that of a computerized reaction time Posner test in a stroke population. Design: Neglect measures were collected longitudinally in patients with stroke at the acute (approximate to 2wk) and chronic (approximate to 9mo) stages. Identical measures were collected in a healthy control group. Setting: Inpatient and outpatient rehabilitation. Participants: Patients with acute stroke (n=59) with left neglect, 30 of whom were tested longitudinally; healthy agematched controls (n=30). Interventions: Not applicable. Main Outcome Measures: A receiver operating characteristic analysis ranking the measures' sensitivity and specificity using a single summary statistic. Results: Most clinical tests were adequately accurate at the acute stage, but many were near chance at the chronic stage. The Posner test was the most sensitive test at both stages. The most sensitive variable was the reaction time difference for detecting targets appearing on the left compared with the right side. Conclusions: Computerized reaction time tests can be used to screen for subtle but potentially clinically relevant left neglect, which may not be detectable by conventional clinical tests, especially at the chronic stage. Such tests may be useful to assess the severity of the patients' deficits and provide more accurate measures of the degree of recovery in clinical trials than established clinical measures
Brain signals for spatial attention predict performance in a motion discrimination task
No full textThe reliability of visual perception is thought to reflect the quality of the sensory information. However, we show that subjects' performance can be predicted, trial-by-trial, by neural activity that precedes the onset of a sensory stimulus. Using functional MRI (fMRI), we studied how neural mechanisms that mediate spatial attention affect the accuracy of a motion discrimination judgment. The amplitude of blood oxygen level-dependent (BOLD) signals after a cue directing spatial attention predicted subjects' accuracy on 60-75% of the trials. Widespread predictive signals, which included dorsal parietal, visual extra-striate, prefrontal and sensory-motor cortex, depended on whether the cue correctly specified the stimulus location. Therefore, these signals indicate the degree of utilization of the cued information and play a role in the control of spatial attention. We conclude that variability in perceptual performance can be partly explained by the variability in endogenous, preparatory processes and that BOLD signals can be used to forecast human behavior
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
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