Structural and effective connectivity reveals potential network-based influences on category-sensitive visual areas

Visual category perception is thought to depend on brain areas that respond specifically when certain categories are viewed. These category-sensitive areas are often assumed to be modules (with some degree of processing autonomy) and to act predominantly on feedforward visual input. This modular view can be complemented by a view that treats brain areas as elements within more complex networks and as influenced by network properties. This network-oriented viewpoint is emerging from studies using either diffusion tensor imaging to map structural connections or effective connectivity analyses to measure how their functional responses influence each other. This literature motivates several hypotheses that predict category-sensitive activity based on network properties. Large, long-range fiber bundles such as inferior fronto-occipital, arcuate and inferior longitudinal fasciculi are associated with behavioural recognition and could play crucial roles in conveying backward influences on visual cortex from anterior temporal and frontal areas. Such backward influences could support top-down functions such as visual search and emotion-based visual modulation. Within visual cortex itself, areas sensitive to different categories appear well-connected (e.g., face areas connect to object- and motion sensitive areas) and their responses can be predicted by backward modulation. Evidence supporting these propositions remains incomplete and underscores the need for better integration of DTI and functional imaging

Content-specific activity in frontoparietal and default-mode networks during prior-guided visual perception

How prior knowledge shapes perceptual processing across the human brain, particularly in the frontoparietal (FPN) and default-mode (DMN) networks, remains unknown. Using ultra-high-field (7T) functional magnetic resonance imaging (fMRI), we elucidated the effects that the acquisition of prior knowledge has on perceptual processing across the brain. We observed that prior knowledge significantly impacted neural representations in the FPN and DMN, rendering responses to individual visual images more distinct from each other, and more similar to the image-specific prior. In addition, neural representations were structured in a hierarchy that remained stable across perceptual conditions, with early visual areas and DMN anchored at the two extremes. Two large-scale cortical gradients occur along this hierarchy: first, dimensionality of the neural representational space increased along the hierarchy; second, prior’s impact on neural representations was greater in higher-order areas. These results reveal extensive and graded influences of prior knowledge on perceptual processing across the brain

How and When? Metacognition and Solution Timing Characterize an “Aha” Experience of Object Recognition in Hidden Figures

The metacognitive feelings of an “aha!” experience are key to comprehending human subjective experience. However, behavioral characteristics of this introspective cognition are not well known. An aha experience sometimes occurs when one gains a solution abruptly in problem solving, a subjective experience that subserves the conscious perception of an insight. We experimentally induced an aha experience in a hidden object recognition task, and analyzed whether this aha experience was associated with metacognitive judgments and behavioral features. We used an adaptation of Mooney images, i.e., morphing between a grayscale image and its binarised image in 100 steps, to investigate the phenomenology associated with insight: aha experience, confidence, suddenness, and pleasure. Here we show that insight solutions are more accurate than non-insight solutions. As metacognitive judgments, participants’ confidence in the correctness of their solution is higher in insight than non-insight problem solving. Intensities of the aha feeling are positively correlated with subjective rating scores of both suddenness and pleasure, features that show marked signs of unexpected positive emotions. The strength of the aha experience is also positively correlated with response times from the onset of presentation until finding the solution, or with task difficulty only if the solution confidence is high enough. Our findings provide metacognitive and temporal conditions for an aha experience, characterizing features distinct from those supporting non-aha experience

Towards Implicit Visual Memory-Based Authentication

International audienceSelecting and remembering secure passwords puts a high cognitive burdenon the user, which has adverse effects on usability and security.Authentication schemes based on implicit memory can relieve the user ofthe burden of actively remembering a secure password. In this paper, wepropose a new authentication scheme (MooneyAuth) that relies onimplicitly remembering the content of previously seen Mooney images.These images are thresholded two-tone images derived from imagescontaining single objects. Our scheme has two phases: In the enrollmentphase, a user is presented with Mooney images, their correspondingoriginal images, and labels. This creates an implicit link between theMooney image and the object in the user's memory that serves as theauthentication secret. In the authentication phase, the user has tolabel a set of Mooney images, a task that gets performed withsubstantially fewer mistakes if the images have been seen in theenrollment phase. We applied an information-theoretical approach tocompute the eligibility of the user, based on which images were labeledcorrectly. This new dynamic scoring is substantially better thanpreviously proposed static scoring by considering the surprisal of theobserved events. We built a prototype and performed three experimentswith 230 and 70 participants over the course of 264 and 21 days,respectively. We show that MooneyAuth outperforms current implicitmemory-based schemes, and demonstrates a promising new approach forfallback authentication procedures on the Web

How a mind works. Parts I, II and III

This paper presents the simplest known theory of processes involved in a person’s unconscious and conscious achievements such as intending, perceiving, reacting and thinking. The basic principle is that an individual has mental states which possess quantitative causal powers and are susceptible to influences from other mental states. Mental performance discriminates the present level of a situational feature from its level in an individually acquired, multiple featured norm (exemplar, template, standard). The effect on output of a moderate disparity between input and norm is scaled in a universal unit of discrimination (Weber’s fraction), with the norm’s level being zero. When one process converts separate sources of input into an output, their discriminative distances from norm are summated. Distinct processes converging on an output combine their discriminations from norm orthogonally. An output may be influenced by other outputs as well as by inputs. Descriptive performance is the influence of one category of input on a verbal output. Reasoning is minimally the effect of one verbal process on another. In deeper mental processing, the influence on a response comes from a concept modulating a description: this process gives the meaning to an emotion or a motive. Descriptive modulation of stimulation corresponds to a bodily sensation or other conceptualized percept. When an output is explained solely by sources of input, that response to the stimulation may be mediated unconsciously. Development of a person within physical and communal environments embodies such mental causation within material causation and acculturates that mind to social causation

Theoretical and methodological approaches to studying recurrent processing in the human brain using transcranial magnetic stimulation

The experiments presented in thesis aimed to investigate how communication takes between and within different brain regions. A particular focus was on predictive coding frameworks, which may explain how information is fed forward and backward within the human brain (Rao & Ballard, 1999; Friston, 2005; Lamme & Roelfsema, 2000). Early visual cortex (EVC) and dorsolateral prefrontal cortex (DLPFC) were subjected to transcranial magnetic stimulation (TMS) in order to reveal when, and under what cognitive contexts, these two sites accomplish fundamental visual processes. Behavioural paradigms that manipulate and measure constituent cognitive functions were developed in order to test the critical premises of predictive coding. Since the main experiments were publicly pre-registered, a new approach for simulating data for a priori planning of statistical analyses in TMS studies was also developed. Results indicate that the temporal positions of EVC-and DLPFC-TMS induced effects occur at the same time. Results also indicate that the familiarity (or frequency) at which a target appears could be a determined of the duration of processing within EVC. The results also reveal a series of methodological considerations that should be taken into account when relying on a probabilistic experimental manipulation to probe the existence of predictive coding