I. Concept Formation and Categorization in Dynamic Cognitive Tasks
What are the cognitive processes that determine successful problem solving during goal-directed behavior? How do people determine and selectively employ only the relevant aspects of their knowledge about common objects in the world when they attempt to accomplish an everyday task?

People can entertain multiple identities for the same object (typical or atypical) depending on their current circumstances (Malt & Sloman, 2007). In fact, category membership for artifacts may be defined by the user’s goal at any given time and this membership status changes constantly within the flexible and dynamic nature of human cognition and under the influence of social and cultural factors, as well as specific situational constraints (see Barsalou, 1982, 1983, 1991). The presence of a goal (e.g., inserting a nail into the wall) requires the retrieval of goal-relevant information within semantic memory that will facilitate the achievement of that goal (e.g., using a hammer). Importantly, this activation of semantic knowledge is modulated by the availability of ideal means in the environment toward goal achievement (e.g., inserting a nail into the wall when a hammer is unavailable).

In past work I examined a novel and intriguing hypothesis, namely that one’s tendency to organize knowledge about the world in concepts and categories (e.g., birds, animals, furniture) in a particular way can predict problem-solving performance. Although concept formation and problem solving are areas not typically examined in conjunction with each other, I have presented a new theoretical model of goal oriented action that is anchored in categorization processes (Chrysikou, 2008). In particular, I asserted that success in problem solving depends on the solvers’ ability to construct goal-derived categories, namely categories that are formed ad hoc to serve specific goals (e.g., things-that-float). I further provided for the first time experimental evidence suggesting that goal-derived categorization is implicated considerably in problem solving: In a series of behavioral experiments I have shown that training individuals to categorize common objects in alternative ways (e.g., using a shoe as a hammer) significantly increases participants’ solution rates in unrelated insight problem solving tasks which require participants to think broadly about a problem by re-categorizing its elements (Chrysikou, 2006; see Figure 1).














What are the cognitive and neural mechanisms underlying these effects? Importantly, what is their duration and generalizability to other tasks? Ongoing research in my lab suggests that the effects of this kind of categorization training may be associated with changes in participants’ attentional states (or mindsets) and can generalize to other domains by affecting performance on a broad range of cognitive tasks (Chrysikou et al., in preparation). Within this line of work, the questions I aim to pursue in the future focus on the characterization of flexible cognitive control in dynamic everyday tasks. An additional line of inquiry refers to the cognitive processes that underlie the activation of specific properties of an object and determine its function: What is the influence of typical or atypical contexts in determining the function of an object? How does the presence of a goal affect the relative dominance of certain aspects of the object’s representation? Finally, I am interested in identifying factors or strategies that either enhance or impede one’s efforts to reach an intended goal. For example, in my earlier research I have examined the conditions under which the presence of examples leads participants to ‘fixate’ on an incorrect solution during problem solving and explored effective ways to counteract these effects (Chrysikou & Weisberg, 2005). Current work in my lab explores whether the modality of the stimulus input (verbal or pictorial) influences the speed and efficiency in determining aspects of an object that are relevant for a specific task. Among the future research aims of the lab is to explore the educational implications and possible applications of these findings for children and young adults.

II. Prefrontal Cortex Involvement in Purposeful Behavior
Work in neuroscience has revealed the critical role of the frontal lobes in higher-order cognitive tasks, such as paying attention while one is engaged in everyday activities (e.g., writing a letter, cooking, playing cards), organizing and planning future actions (e.g., a vacation), or avoiding distraction from unwanted information. Yet, previous studies have not provided a detailed account of the involvement and function of the frontal lobes in goal-oriented tasks. In our current work, we employ neuroimaging (fMRI), transcranial Direct Current Stimulation (tDCS), and behavioral techniques to explore the neural mechanisms that underlie the flexibility of cognitive control of semantic knowledge during everyday action. The goal of this line of our research is to reveal different patterns of prefrontal brain activity that are associated with different components of purposeful behavior, in tasks tied to participants’ everyday experiences.

















How and when does the lateral prefrontal cortex mediate behavior in language comprehension and goal-directed actions? In past work I examined the effects of neurodegenerative diseases and, in particular, fronto-temporal dementia and Alzheimer’s disease on semantic knowledge for tools and goal-directed action (Chrysikou et al., in press; Giovannetti et al., 2006). Our ongoing studies explore the relationship between prefrontal cortex functioning, semantic memory, and goal-oriented behavior in healthy young adults. Using fMRI, tDCS, and behavioral measures we are currently investigating the extent to which the lateral prefrontal cortex exerts cognitive control over one’s semantic knowledge for everyday objects depending on task demands. Specifically, the results of our recent experiments suggest a tradeoff between regions involved in rule-based processing (i.e., prefrontal cortex) and regions involved in object processing (i.e., lateral occipital complex, see Figure 2). In particular, the prefrontal cortex (PFC) appears to be involved in determining the well-established aspects of object use (e.g., use a baseball bat to hit a baseball); however, its involvement is moderated under circumstances of impromptu goal achievement (e.g., use a baseball bat as a rolling pin; Chrysikou & Thompson-Schill, 2011). In our ongoing research we use a combination of behavioral, fMRI, tDCS, and neuropsychological paradigms to identify the conditions under which lower levels of prefrontal-cortex-mediated cognitive control might be beneficial for certain aspects of goal oriented behavior, yet detrimental for others (see Chrysikou & Thompson-Schill, 2011; Chrysikou et al., 2013; Chrysikou et al., 2011; Thompson-Schill, Ramscar, & Chrysikou, 2009).

Evaluating the role of the prefrontal cortex in the organization of purposeful behavior has the potential to be of interest not only within the field of cognitive neuroscience but also to other disciplines related to scientific education and educational technology. Accordingly, we are interested in how our findings can influence education in science and technology by guiding the design of training tasks on the modulation of PFC functioning that may promote creative problem solving and higher-order reasoning.

III. Effects of Psychopathology on Goal-Oriented Behavior
Understanding the contributions of prefrontal brain systems in controlling behavior during goal-oriented tasks has direct applications to the characterization and treatment of certain psychiatric disorders. Current research has revealed a selective hypometabolic activity of certain regions in the anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (DLPFC), or orbitofrontal cortex (OFC) in depression, as evident in a number of positron emission tomography (PET), functional neuroimaging (fMRI), and single photonemission computerized tomography (SPECT) studies. However, the exact implication of frontostriatal circuits in symptom manifestation in the disorder remains unknown. Among the current research aims of the lab, facilitated by a recently awarded Frontiers pilot grant, is to establish a translational research program that explores the relations between the deficient cognitive profile in depression—particularly during purposeful behavior (i.e., disruptions in normal cognitive and motor inhibition, attentional disturbances, impulsivity)—and a physiological profile characterized by PFC-limbic system abnormalities. We are currently exploring these relationships in a study employing transcranial direct current stimulation (tDCS) as well as functional magnetic resonance imaging (fMRI). The long-term objective of the lab is to identify how an understanding of these relationships can have functional implications for the diagnosis and treatment of depression, as well as other psychiatric syndromes characterized by prefrontal cortex hypofunction such as attention-deficit-hyperactivity- disorder (ADHD) and obsessive-compulsive disorder (OCD). Specifically, our goal is to employ a new combination of methodologies, including behavioral, functional and perfusion MRI, tDCS, as well as neuropsychological/clinical studies, in order to establish more detailed neurocognitive assessments of hypofrontal functioning in depression that will allow for better characterization of different patient subgroups. The complementarity of these approaches has the potential to improve our understanding of basic behavioral processes and PFC involvement in cognitive tasks, as well as patients’ functional abilities in depression beyond the insights provided by traditional psychometric or structural imaging measures. Our aim is to apply knowledge from basic neuroscience toward the development of a comprehensive set of neurocognitive assessment procedures; such procedures will allow for a better characterization of different populations of patients diagnosed with depression and other disorders based on lateral PFC hypo-functioning and will permit specific predictions on the effectiveness and outcome of different treatment plans.

Drexel  University

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