Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

The cognitive neuroscience of visual working memory

Visual working memory allows us to temporarily maintain and manipulate visual information in order to solve a task. The study of the brain mechanisms underlying this function began more than half a century ago, with Scoville and Milner’s (1957) seminal discoveries with amnesic patients. This timely collection of papers brings together diverse perspectives on the cognitive neuroscience of visual working memory from multiple fields that have traditionally been fairly disjointed: human neuroimaging, electrophysiological, behavioural and animal lesion studies, investigating both the developing and the adult brain

Shades Of Meaning: Capturing Meaningful Context-Based Variations In Neural Patterns

When cognitive psychologists and psycholinguists consider the variability that arises during the retrieval of conceptual information, this variability it is often understood to arise from the dynamic interactions between concepts and contexts. �When cognitive neuroscientists and neurolinguists think about this variability, it is typically treated as noise and discarded from the analyses. In this dissertation, we bridge these two traditions by asking: can the variability in neural patterns evoked by word meanings reflect the contextual variation that occurs during conceptual processing? We employ functional magnetic resonance imaging (fMRI) to measure, quantify, and predict brain activity during context-dependent retrieval of word meanings. Across three experiments, we test the ways in which word-evoked neural variability is influenced by the sentence context in which the word appears (Chapter 2); the current set of task demands (Chapter 3); or even undirected thoughts about other concepts (Chapter 4). Our findings indicate that not only do the neural patterns evoked by the same stimulus word vary over time, but we can predict the degree to which these patterns vary using meaningful, theoretically motivated variables. These results demonstrate that cross-context, within-concept variations in neural responses are not exclusively due to statistical noise or measurement error. Rather, the degree of a concept’s neural variability varies in a manner that accords with a context-dependent view of semantic representation. In addition, we present preliminary evidence that prefrontally-mediated cognitive control processes are involved in expression of context-appropriate neural patterns. In sum, these studies provide a novel perspective on the flexibility of word meanings and the variable brain activity patterns associated with them

Attention Restraint, Working Memory Capacity, and Mind Wandering: Do Emotional Valence or Intentionality Matter?

Attention restraint appears to mediate the relationship between working memory capacity (WMC) and mind wandering (Kane et al., 2016). Prior work has identifed two dimensions of mind wandering—emotional valence and intentionality. However, less is known about how WMC and attention restraint correlate with these dimensions. Te current study examined the relationship between WMC, attention restraint, and mind wandering by emotional valence and intentionality. A confrmatory factor analysis demonstrated that WMC and attention restraint were strongly correlated, but only attention restraint was related to overall mind wandering, consistent with prior fndings. However, when examining the emotional valence of mind wandering, attention restraint and WMC were related to negatively and positively valenced, but not neutral, mind wandering. Attention restraint was also related to intentional but not unintentional mind wandering. Tese results suggest that WMC and attention restraint predict some, but not all, types of mind wandering

Activity in area V3A predicts positions of moving objects

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Building Mental Experiences: From Scenes to Events

Mental events are central to everyday cognition, be it our continuous perception of the world, recalling autobiographical memories, or imagining the future. Little is known about the fine-grained temporal dynamics of these processes. Given the apparent predominance of scene imagery across cognition, in this thesis I used magnetoencephalography to investigate whether and how activity in the hippocampus and ventromedial prefrontal cortex (vmPFC) supports the mental construction of scenes and the events to which they give rise. In the first experiment, participants gradually imagined scenes and also closely matched non-scene arrays; this allowed me to assess whether any brain regions showed preferential responses to scene imagery. The anterior hippocampus and vmPFC were particularly engaged by the construction of scene imagery, with the vmPFC driving hippocampal activity. In the second experiment, I found that certain objects – those that were space-defining – preferentially engaged the vmPFC and superior temporal gyrus during scene construction, providing insight into how objects affect the creation of scene representations. The third experiment involved boundary extension during scene perception, permitting me to examine how single scenes might be prepared for inclusion into events. I observed changes in evoked responses just 12.5-58 ms after scene onset over fronto-temporal sensors, with again the vmPFC exerting a driving influence on other brain regions, including the hippocampus. In the final experiment, participants watched brief movies of events built from a series of scenes or non-scene patterns. A difference in evoked responses between the two event types emerged during the first frame of the movies, the primary source of which was shown to be the hippocampus. The enduring theme of the results across experiments was scene-specific engagement of the hippocampus and vmPFC, with the latter being the driving influence. Overall, this thesis provides insights into the neural dynamics of how scenes are built, made ready for inclusion into unfolding mental episodes, and then linked to produce our seamless experience of the world

Tracking the temporal dynamics of cultural perceptual diversity in visual information processing

Human perception and cognition processing are not universal. Culture and experience markedly modulate visual information sampling in humans. Cross-cultural studies comparing between Western Caucasians (WCs) and East Asians (EAs) have shown cultural differences in behaviour and neural activities in regarding to perception and cognition. Particularly, a number of studies suggest a local perceptual bias for Westerners (WCs) and a global bias for Easterners (EAs): WCs perceive most efficiently the salient information in the focal object; as a contrast EAs are biased toward the information in the background. Such visual processing bias has been observed in a wide range of tasks and stimuli. However, the underlying neural mechanisms of such perceptual tunings, especially the temporal dynamic of different information coding, have yet to be clarified. Here, in the first two experiments I focus on the perceptual function of the diverse eye movement strategies between WCs and EAs. Human observers engage in different eye movement strategies to gather facial information: WCs preferentially fixate on the eyes and mouth, whereas EAs allocate their gaze relatively more on the center of the face. By employing a fixational eye movement paradigm in Study 1 and electroencephalographic (EEG) recording in study 2, the results confirm the cultural differences in spatial-frequency information tuning and suggest the different perceptual functions of preferred eye movement pattern as a function of culture. The third study makes use of EEG adaptation and hierarchical visual stimulus to access the cultural tuning in global/local processing. Culture diversity driven by selective attention is revealed in the early sensory stage. The results here together showed the temporal dynamic of cultural perceptual diversity. Cultural distinctions in the early time course are driven by selective attention to global information in EAs, whereas late effects are modulated by detail processing of local information in WC observers