Multivariate pattern analysis of input and output representations of speech

Repeating a word or nonword requires a speaker to map auditory representations of incoming sounds onto learned speech items, maintain those items in short-term memory, interface that representation with the motor output system, and articulate the target sounds. This dissertation seeks to clarify the nature and neuroanatomical localization of speech sound representations in perception and production through multivariate analysis of neuroimaging data. The major portion of this dissertation describes two experiments using functional magnetic resonance imaging (fMRI) to measure responses to the perception and overt production of syllables and multivariate pattern analysis to localize brain areas containing associated phonological/phonetic information. The first experiment used a delayed repetition task to permit response estimation for auditory syllable presentation (input) and overt production (output) in individual trials. In input responses, clusters sensitive to vowel identity were found in left inferior frontal sulcus (IFs), while clusters responsive to syllable identity were found in left ventral premotor cortex and left mid superior temporal sulcus (STs). Output-linked responses revealed clusters of vowel information bilaterally in mid/posterior STs. The second experiment was designed to dissociate the phonological content of the auditory stimulus and vocal target. Subjects were visually presented with two (non)word syllables simultaneously, then aurally presented with one of the syllables. A visual cue informed subjects either to repeat the heard syllable (repeat trials) or produce the unheard, visually presented syllable (change trials). Results suggest both IFs and STs represent heard syllables; on change trials, representations in frontal areas, but not STs, are updated to reflect the vocal target. Vowel identity covaries with formant frequencies, inviting the question of whether lower-level, auditory representations can support vowel classification in fMRI. The final portion of this work describes a simulation study, in which artificial fMRI datasets were constructed to mimic the overall design of Experiment 1 with voxels assumed to contain either discrete (categorical) or analog (frequency-based) vowel representations. The accuracy of classification models was characterized by type of representation and the density and strength of responsive voxels. It was shown that classification is more sensitive to sparse, discrete representations than dense analog representations

History as science:the fifteenth-century debate in Arabic and Persian

In the fifteenth century, scholars writing in Arabic and Persian debated the nature of historical inquiry and its place among the sciences. While the motivations and perspectives of the various scholars differed, the terms and parameters of the debate remained remarkably fixed and focused, even as it unfolded across a vast geographic space between Herat, Cairo, and Constantinople. This article examines the contours of this debate and the relationships between five historians working on these issues. Although the scholars who considered these questions frequently arrived at different conclusions, they all firmly agreed, in contrast to previous doubt regarding the status of history, that historical inquiry did indeed constitute a distinct science requiring its own particular method. Accordingly, the debate and its conclusions helped cement the place of history within the broader pantheon of the sciences as conceived by scholars in the Ottoman Empire from the sixteenth century onwards

On type II_0 E_0-semigroups induced by boundary weight doubles

Powers has shown that each spatial E_0-semigroup can be obtained from the boundary weight map of a CP-flow acting on B(K \otimes L^2(0, \infty)) for some separable Hilbert space K. In this paper, we define boundary weight maps through boundary weight doubles (\phi, \nu), where \phi: M_n(\C) \to M_n(\C) is a q-positive map and \nu is a boundary weight over L^2(0, \infty). These doubles induce CP-flows over K for 1<dim(K)<\infty which then minimally dilate to E_0-semigroups by a theorem of Bhat. Through this construction, we obtain uncountably many mutually non-cocycle conjugate E_0-semigroups for each n>1, n \in \mathbb{N}.Comment: 38 pages; numbering format changed; various typos corrected; journal reference adde