Trimodal assessment in agoraphobia research: Further observations on heart rate and synchrony/ desynchrony

This paper reports new observations on heart rate and synchrony/desynchrony in the context of 22 chronic agoraphobic patients' trimodal assessment pre and post exposure treatment. The results corroborated previous reports showing weak and/or inconsistent improvement in heart rate, in contrast to significant improvement in behavioral and subjective response systems. Moreover, the results did not support recent suggestions that heartrate reactivity at pretreatment or global categories of synchrony/dysynchrony at posttreatment have important implications for treatment outcome. However, subtypes of dysynchrony based on the direction of divergence between variables had different implications for the clinical response, indicating that simply dichotomizing patients into synchronizers/desynchronizers may be misleading in addition to being uninformative.This work was supported by Grants MH34177 and MH40141 from the National Institute of Mental Health. Mary Sue Hamann, M.S., assisted in the statistical analyses.     

Connectionism and the Philosophical Foundations of Cognitive Science

This is an overview of recent philosophical discussion about connectionism and the foundations of cognitive science. Connectionist modeling in cognitive science is described. Three broad conceptions of the mind are characterized, and their comparative strengths and weaknesses are discussed: (1) the classical computation conception in cognitive science; (2) a popular foundational interpretation of connectionism that John Tienson and I call "non-sentential computationalism"; and (3) an alternative interpretation of connectionism we call "dynamical cognition." Also discussed are two recent philosophical attempts to enlist connectionism in defense of eliminativism about folk psychology.     

A Poetics of Psychological Explanation

Intentional, 'commonsense,' or 'folk' psychology is, as Jerry Fodor has remarked, ubiquitous. Explanations of what we say and do in terms of our reasons for acting are the stock in trade of intentional psychology. But there is a question whether explanations in terms of reasons are properly explanatory. Donald Davidson and Daniel Dennett, to name two, have defended intentional psychology and its reason-explanations. Still, many philosophers – including Fodor, Davidson and Dennett – fail to pay due attention to the narrative basis of such agent-centered accounts of action. In this paper, I argue that psychological explanation is an agent-centered, narrative-based interpretive practice. To make my case, I present a poetics of psychological explanation: seven elements which collectively describe what makes psychological explanations work. Narrative form allows us to represent the temporal arc of agents' actions – as well as the temporal arc of their reasoning about their actions, both prospective and retrospective. It allows us to negotiate between the canonical and the exceptional in human experience, and thus to account for actions that strike us as puzzling or unusual – whether the puzzle originates in our suboptimal understanding or the agent's suboptimal reasoning. And it allows us to juxtapose different perspectives on any action. Such juxtapositioning gives us a mechanism for coming to see how an action that strikes us as misguided might have been construed by the agent as reasonable given her understanding of her circumstances. After establishing the seven elements of the poetics, I address the objection that narrative-based accounts of intentional action are not properly explanatory.     

On the Poverty of Scientism, or: The Ineluctable Roughness of Rationality

If there is one rationality there must be a plurality of them. This conclusion follows, I argue, partly from the extreme and ineradicable vagueness of the fundamental concepts that every would-be rational explanation must presuppose. Logicistic/scientistic assaults on this vagueness are doomed to fail partly because they are unable to acknowledge the imaginative dimension of rational thought. Being limited to the play of "outward appearances," scientific investigations are also dependent on "inward imaginings" on their speculative side. The upshot is that schools of philosophy should be characterized by the kind of imaginary they adopt rather than by their logics. In which case, every attempt to get and tell something right about the world is bound to incorporate mythopoeic elements in its explanations.     

Neurophysiology and neuroanatomy of smooth pursuit in humans

Smooth pursuit eye movements enable us to focus our eyes on moving objects by utilizing well-established mechanisms of visual motion processing, sensorimotor transformation and cognition. Novel smooth pursuit tasks and quantitative measurement techniques can help unravel the different smooth pursuit components and complex neural systems involved in its control. The maintenance of smooth pursuit is driven by a combination of the prediction of target velocity and visual feedback about performance quality, thus a combination of retinal and extraretinal information that has to be integrated in various networks. Different models of smooth pursuit with specific in- and output parameters have been developed for a better understanding of the underlying neurophysiological mechanisms and to make quantitative predictions that can be tested in experiments. Functional brain imaging and neurophysiological studies have defined motion sensitive visual area V5, frontal (FEF) and supplementary (SEF) eye fields as core cortical smooth pursuit regions. In addition, a dense neural network is involved in the adjustment of an optimal smooth pursuit response by integrating also extraretinal information. These networks facilitate interaction of the smooth pursuit system with multiple other visual and non-visual sensorimotor systems on the cortical and subcortical level. Future studies with fMRI advanced techniques (e.g., event-related fMRI) promise to provide an insight into how smooth pursuit eye movements are linked to specific brain activation. Applying this approach to neurological and also mental illness can reveal distinct disturbances within neural networks being present in these disorders and also the impact of medication on this circuitry.     

Lexical categories at the edge of the word

Language acquisition may be one of the most difficult tasks that children face during development. They have to segment words from fluent speech, figure out the meanings of these words, and discover the syntactic constraints for joining them together into meaningful sentences. Over the past couple of decades, computational modeling has emerged as a new paradigm for gaining insights into the mechanisms by which children may accomplish these feats. Unfortunately, many of these models assume a computational complexity and linguistic knowledge likely to be beyond the abilities of developing young children. This article shows that, using simple statistical procedures, significant correlations exist between the beginnings and endings of a word and its lexical category in English, Dutch, French, and Japanese. Therefore, phonetic information can contribute to individuating higher level structural properties of these languages. This article also presents a simple 2-layer connectionist model that, once trained with an initial small sample of words labeled for lexical category, can infer the lexical category of a large proportion of novel words using only word-edge phonological information, namely the first and last phoneme of a word. The results suggest that simple procedures combined with phonetic information perceptually available to children provide solid scaffolding for emerging lexical categories in language development.     

A neural model of how the brain computes heading from optic flow in realistic scenes

Visually-based navigation is a key competence during spatial cognition. Animals avoid obstacles and approach goals in novel cluttered environments using optic flow to compute heading with respect to the environment. Most navigation models try either explain data, or to demonstrate navigational competence in real-world environments without regard to behavioral and neural substrates. The current article develops a model that does both. The ViSTARS neural model describes interactions among neurons in the primate magnocellular pathway, including V1, MT⁺, and MSTd. Model outputs are quantitatively similar to human heading data in response to complex natural scenes. The model estimates heading to within 1.5° in random dot or photo-realistically rendered scenes, and within 3° in video streams from driving in real-world environments. Simulated rotations of less than 1°/s do not affect heading estimates, but faster simulated rotation rates do, as in humans. The model is part of a larger navigational system that identifies and tracks objects while navigating in cluttered environments.     

Age-related differences in the involvement of the prefrontal cortex in attentional control

We investigated the relative involvement of cortical regions supporting attentional control in older and younger adults during performance on a modified version of the Stroop task. Participants were exposed to two different types of incongruent trials. One of these, an incongruent-ineligible condition, produces conflict at the non-response level, while the second, an incongruent-eligible condition, produces conflict at both non-response and response levels of information processing. Greater attentional control is needed to perform the incongruent-eligible condition compared to other conditions. We examined the cortical recruitment associated with this task in an event-related functional magnetic resonance imaging paradigm in 25 older and 25 younger adults. Our results indicated that while younger adults demonstrated an increase in the activation of cortical regions responsible for maintaining attentional control in response to increased levels of conflict, such sensitivity and flexibility of the cortical regions to increased attentional control demands was absent in older adults. These results suggest a limitation in older adults’ capabilities for flexibly recruiting the attentional network in response to increasing attentional demands.