Electrophysiological Correlates of Visual Object Category Formation in a Prototype-Distortion Task

In perceptual learning studies, participants engage in extensive training in the discrimination of visual stimuli in order to modulate perceptual performance. Much of the literature in perceptual learning has looked at the induction of the reorganization of low-level representations in V1. However, much remains to be understood about the mechanisms behind how the adult brain (an expert in visual object categorization) extracts high-level visual objects from the environment and categorically represents them in the cortical visual hierarchy. Here, I used event-related potentials (ERPs) to investigate the neural mechanisms involved in object representation formation during a hybrid visual search and prototype distortion category learning task. EEG was continuously recorded while participants performed the hybrid task, in which a peripheral array of four dot patterns was briefly flashed on a computer screen. In half of the trials, one of the four dot patterns of the array contained the target, a distorted prototype pattern. The remaining trials contained only randomly generated patterns. After hundreds of trials, participants learned to discriminate the target pattern through corrective feedback. A multilevel modeling approach was used to examine the predictive relationship between behavioral performance over time and two ERP components, the N1 and the N250. The N1 is an early sensory component related to changes in visual attention and discrimination (Hopf et al., 2002; Vogel & Luck, 2000). The N250 is a component related to category learning and expertise (Krigolson et al., 2009; Scott et al., 2008; Tanaka et al., 2006). Results indicated that while N1 amplitudes did not change with improved performance, increasingly negative N250 amplitudes did develop over time and were predictive of improvements in pattern detection accuracy

Dynamic reorganization of the middle fusiform gyrus: long-term bird expertise predicts decreased face selectivity

What is the functional relationship between face-selective and expertise-predicated object-selective regions in the human middle fusiform gyrus? In two separate fMRI experiments, superior behaviorally-measured bird expertise predicts both higher middle fusiform gyrus selectivity for birds and, concomitantly, lower selectivity for faces. This finding suggests a long-term dynamic reorganization of the neural mechanisms underlying the visual recognition of faces and non-face

DEVELOPMENTAL FMRI STUDY: FACE AND OBJECT RECOGNITION

Visual processing, though seemingly automatic, is complex. Typical humansprocess objects and faces routinely. Yet, when a disease or disorder disrupts face andobject recognition, the effects are profound. Because of its importance and complexity,visual processing has been the subject of many adult functional imaging studies.However, relatively little is known about the development of the neural organization andunderlying cognitive mechanisms of face and object recognition. The current projectused functional magnetic resonance imaging (fMRI) to identify maturational changes inthe neural substrates of face and object recognition in 5-8 year olds, 9-11 year olds, andadults. A passive face and object viewing task revealed cortical shifts in the faceresponsiveloci of the ventral processing stream (VPS), an inferior occipito-temporalregion known to function in higher visual processing. Older children and adults recruitedmore anterior regions of the ventral processing stream than younger children. Toinvestigate the potential cognitive basis for these developmental changes, researchersimplemented a shape-matching task with parametric variations of shape overlap,structural similarity (SS), in stimulus pairs. VPS regions sensitive to high SS emerged inolder children and adults. Younger children recruited no structurally-sensitive regions inthe VPS. Two right hemisphere VPS regions were sensitive to maturational changes inSS. A comparison of face-responsive regions from the passive viewing task and the VPSSS regions did not reveal overlap. Though SS drives organization of the VPS, it did notexplain the cortical shifts in the neural substrates for face processing. In addition to VPSregions, results indicated additional maturational SS changes in frontal, parietal, andcerebellar regions. Based on these findings, further analyses were conducted to quantifyand qualify maturational changes in face and object processing throughout the brain.Results indicated developmental changes in activation extent, signal magnitude, andlateralization of face and object recognition networks. Collectively, this project supportsa developmental change in visual processing between 5-8 years and 9-11 years of age.Chapters Four through Six provide an in-depth discussion of the implications of thesefindings

The Neuroscience of Mathematical Cognition and Learning

The synergistic potential of cognitive neuroscience and education for efficient learning has attracted considerable interest from the general public, teachers, parents, academics and policymakers alike. This review is aimed at providing 1) an accessible and general overview of the research progress made in cognitive neuroscience research in understanding mathematical learning and cognition, and 2) understanding whether there is sufficient evidence to suggest that neuroscience can inform mathematics education at this point. We also highlight outstanding questions with implications for education that remain to be explored in cognitive neuroscience. The field of cognitive neuroscience is growing rapidly. The findings that we are describing in this review should be evaluated critically to guide research communities, governments and funding bodies to optimise resources and address questions that will provide practical directions for short- and long-term impact on the education of future generations

Normal Acquisition of Expertise with Greebles in Two Cases of Acquired Prosopagnosia

Face recognition is generally thought to rely on different neurocognitive mechanisms than most types of objects, but the specificity of these mechanisms is debated. One account suggests the mechanisms are specific to upright faces, whereas the expertise view proposes the mechanisms operate on objects of high within-class similarity with which an observer has become proficient at rapid individuation. Much of the evidence cited in support of the expertise view comes from laboratory-based training experiments involving computer-generated objects called greebles that are designed to place face-like demands on recognition mechanisms. A fundamental prediction of the expertise hypothesis is that recognition deficits with faces will be accompanied by deficits with objects of expertise. Here we present two cases of acquired prosopagnosia, Herschel and Florence, who violate this prediction: Both show normal performance in a standard greeble training procedure, along with severe deficits on a matched face training procedure. Herschel and Florence also meet several response time criteria that advocates of the expertise view suggest signal successful acquisition of greeble expertise. Furthermore, Herschel’s results show that greeble learning can occur without normal functioning of the right fusiform face area, an area proposed to mediate greeble expertise. The marked dissociation between face and greeble expertise undermines greeble-based claims challenging face-specificity and indicates face recognition mechanisms are not necessary for object recognition after laboratory-based training

Connecting Art and the Brain: An Artist's Perspective on Visual Indeterminacy

In this article I will discuss the intersection between art and neuroscience from the perspective of a practicing artist. I have collaborated on several scientific studies into the effects of art on the brain and behavior, looking in particular at the phenomenon of “visual indeterminacy.” This is a perceptual state in which subjects fail to recognize objects from visual cues. I will look at the background to this phenomenon, and show how various artists have exploited its effect through the history of art. My own attempts to create indeterminate images will be discussed, including some of the technical problems I faced in trying to manipulate the viewer's perceptual state through paintings. Visual indeterminacy is not widely studied in neuroscience, although references to it can be found in the literature on visual agnosia and object recognition. I will briefly review some of this work and show how my attempts to understand the science behind visual indeterminacy led me to collaborate with psychophysicists and neuroscientists. After reviewing this work, I will discuss the conclusions I have drawn from its findings and consider the problem of how best to integrate neuroscientific methods with artistic knowledge to create truly interdisciplinary approach

Neural correlates of cognitive intervention in persons at risk of developing Alzheimer's disease.

Cognitive training is an emergent approach that has begun to receive increased attention in recent years as a non-pharmacological, cost-effective intervention for Alzheimer's disease (AD). There has been increasing behavioral evidence regarding training-related improvement in cognitive performance in early stages of AD. Although these studies provide important insight about the efficacy of cognitive training, neuroimaging studies are crucial to pinpoint changes in brain structure and function associated with training and to examine their overlap with pathology in AD. In this study, we reviewed the existing neuroimaging studies on cognitive training in persons at risk of developing AD to provide an overview of the overlap between neural networks rehabilitated by the current training methods and those affected in AD. The data suggest a consistent training-related increase in brain activity in medial temporal, prefrontal, and posterior default mode networks, as well as increase in gray matter structure in frontoparietal and entorhinal regions. This pattern differs from the observed pattern in healthy older adults that shows a combination of increased and decreased activity in response to training. Detailed investigation of the data suggests that training in persons at risk of developing AD mainly improves compensatory mechanisms and partly restores the affected functions. While current neuroimaging studies are quite helpful in identifying the mechanisms underlying cognitive training, the data calls for future multi-modal neuroimaging studies with focus on multi-domain cognitive training, network level connectivity, and individual differences in response to training

Materiality and human cognition

In this paper, we examine the role of materiality in human cognition. We address issues such as the ways in which brain functions may change in response to interactions with material forms, the attributes of material forms that may cause change in brain functions, and the spans of time required for brain functions to reorganize when interacting with material forms. We then contrast thinking through materiality with thinking about it. We discuss these in terms of their evolutionary significance and history as attested by stone tools and writing, material forms whose interaction endowed our lineage with conceptual thought and meta-awareness of conceptual domains

Semantic Memory for Food and Brain Correlates

Semantic memory stores knowledge about different types of objects: plants, animals, vehicles, utensils, conspecifics and food, among the others. Our ability to quickly recognize and categorize an object when we encounter it depends upon having experienced that object before and on semantic knowledge integrity. Semantic memory is one the most resilient cognitive abilities, it is less prone to interference than episodic memory and more declines slowly. The interest in how semantic memory is organized traces way back, however a great impulse was provided by the first systematic neuropsychological observations of patients with category specific recognition deficits. However, this debate is far from being resolved. In my dissertation, I will show how the study of food as a semantic category is extremely suitable to shed light on the organization of semantic knowledge. The thesis is organized as follow. In Chapter 1, I will first define semantic memory, focusing on its characteristics, such as its relationship with experience, its resilience to cognitive decline and its neural correlates, and on how it has been studied by neuropsychologists. In addition, I will review the studies on the food category, focusing on some intrinsic dimensions such as the level of transformation. Chapter 2 includes Study 1, in which I have investigated the organization of semantic memory by using food (natural and transformed) and non-food (living and on-living things) in a group of patients suffering from temporal lobe atrophy (Alzheimer\u2019s disease, PPA and FTD) and healthy controls, using Voxel Based Morphometry and DTI. Results have shown that food breaks down in natural and transformed, and that this parsing mirrors that of living and non-living things, thus strongly supporting the Sensory-functional model of semantic knowledge. Chapter 3 contains Study 2, in which I have explored the relationship between semantic memory and experience. I collected information about life-long eating habits as a proxy of long-term experience with specific foods as well as information about semantic memory of food in participants of different ages (36 \u2013 108 years old). Results support the hypothesis that semantic memory is modulated by experience. In Chapter 4, the focus of Study 3 is on episodic memory. Here I investigated whether the difference between semantic memory for natural and transformed food highlighted in Study 2 extends also to episodic memory, and whether the animacy effect - a facilitation to remember living exemplars - holds for food as well. Specifically, I administered a recognition memory task to the same participants of Study 2, to a group of young participants and to patients with Alzheimer\u2019s disease, PPA and FTD. I found that young adults had better recognition memory for transformed foods compared to natural foods. This difference disappeared in centenarians, consistently with Study 2, and in patients. The natural/transformed distinction appears susceptible to decay only in the presence of a high degree of episodic memory impairment. Finally, with Study 4, described in Chapter 5, my aim was more translational, that is, to test whether a deficit in semantic memory for food could lead to specific eating disorders. This study empirically establishes the behavioural and neural correlates of abnormal changes in eating habits in dementia and their relationship with semantic memory. In this thesis, I have shown that natural and transformed food do have different neural correlates, and that they are differently represented in semantic memory. By drawing together evidence from my studies and from studies of others I was allowed to propose a comprehensive model of semantic knowledge. Additionally, in my thesis I showed how food can be employed to study the organization of semantic knowledge, the way in which semantic knowledge is shaped by learning and experience, and its effect on behaviour