Evelina Fedorenko

Broad domain generality in focal regions of frontal and parietal cortex

Significance One of the oldest debates in cognitive neuroscience concerns the degree of functional specialization present in the human brain. Prior work has discovered several highly specialized components dedicated to particular mental functions, like face recognition or motion perception. However, our cognitive versatility suggests the additional existence of more general-purpose machinery. Building on prior neuroimaging evidence, along with neurophysiological evidence from non-human primates, we searched for such domain-general brain regions in humans. Seven diverse demanding cognitive tasks produced overlapping activation at the individual-subject level in a number of frontal and parietal brain regions. Thus, human cognition arises from hardware that includes not only specialized components, but also very general-purpose ones that plausibly enable us to solve novel problems. Unlike brain regions that respond selectively to specific kinds of information content, a number of frontal and parietal regions are thought to be domain- and process-general: that is, active during a wide variety of demanding cognitive tasks. However, most previous evidence for this functional generality in humans comes from methods that overestimate activation overlap across tasks. Here we present functional MRI evidence from single-subject analyses for broad functional generality of a specific set of brain regions: the same sets of voxels are engaged across tasks ranging from arithmetic to storing information in working memory, to inhibiting irrelevant information. These regions have a specific topography, often lying directly adjacent to domain-specific regions. Thus, in addition to domain-specific brain regions tailored to solve particular problems of longstanding importance to our species, the human brain also contains a set of functionally general regions that plausibly endow us with the cognitive flexibility necessary to solve novel problems.

Functional specificity for high-level linguistic processing in the human brain.

Neuroscientists have debated for centuries whether some regions of the human brain are selectively engaged in specific high-level mental functions or whether, instead, cognition is implemented in multifunctional brain regions. For the critical case of language, conflicting answers arise from the neuropsychological literature, which features striking dissociations between deficits in linguistic and nonlinguistic abilities, vs. the neuroimaging literature, which has argued for overlap between activations for linguistic and nonlinguistic processes, including arithmetic, domain general abilities like cognitive control, and music. Here, we use functional MRI to define classic language regions functionally in each subject individually and then examine the response of these regions to the nonlinguistic functions most commonly argued to engage these regions: arithmetic, working memory, cognitive control, and music. We find little or no response in language regions to these nonlinguistic functions. These data support a clear distinction between language and other cognitive processes, resolving the prior conflict between the neuropsychological and neuroimaging literatures.

New Method for fMRI Investigations of Language: Defining ROIs Functionally in Individual Subjects

Previous neuroimaging research has identified a number of brain regions sensitive to different aspects of linguistic processing, but precise functional characterization of these regions has proven challenging. We hypothesize that clearer functional specificity may emerge if candidate language-sensitive regions are identified functionally within each subject individually, a method that has revealed striking functional specificity in visual cortex but that has rarely been applied to neuroimaging studies of language. This method enables pooling of data from corresponding functional regions across subjects rather than from corresponding locations in stereotaxic space (which may differ functionally because of the anatomical variability across subjects). However, it is far from obvious a priori that this method will work as it requires that multiple stringent conditions be met. Specifically, candidate language-sensitive brain regions must be identifiable functionally within individual subjects in a short scan, must be replicable within subjects and have clear correspondence across subjects, and must manifest key signatures of language processing (e.g., a higher response to sentences than nonword strings, whether visual or auditory). We show here that this method does indeed work: we identify 13 candidate language-sensitive regions that meet these criteria, each present in >or=80% of subjects individually. The selectivity of these regions is stronger using our method than when standard group analyses are conducted on the same data, suggesting that the future application of this method may reveal clearer functional specificity than has been evident in prior neuroimaging research on language.

Language processing in the occipital cortex of congenitally blind adults

Humans are thought to have evolved brain regions in the left frontal and temporal cortex that are uniquely capable of language processing. However, congenitally blind individuals also activate the visual cortex in some verbal tasks. We provide evidence that this visual cortex activity in fact reflects language processing. We find that in congenitally blind individuals, the left visual cortex behaves similarly to classic language regions: (i) BOLD signal is higher during sentence comprehension than during linguistically degraded control conditions that are more difficult; (ii) BOLD signal is modulated by phonological information, lexical semantic information, and sentence-level combinatorial structure; and (iii) functional connectivity with language regions in the left prefrontal cortex and thalamus are increased relative to sighted individuals. We conclude that brain regions that are thought to have evolved for vision can take on language processing as a result of early experience. Innate microcircuit properties are not necessary for a brain region to become involved in language processing.

Structural integration in language and music: Evidence for a shared system

In this study, we investigate whether language and music share cognitive resources for structural processing. We report an experiment that used sung materials and manipulated linguistic complexity (subject-extracted relative clauses, object-extracted relative clauses) and musical complexity (in-key critical note, out-of-key critical note, auditory anomaly on the critical note involving a loudness increase). The auditory-anomaly manipulation was included in order to test whether the difference between in-key and out-of-key conditions might be due to any salient, unexpected acoustic event. The critical dependent measure involved comprehension accuracies to questions about the propositional content of the sentences asked at the end of each trial. The results revealed an interaction between linguistic and musical complexity such that the difference between the subject- and object-extracted relative clause conditions was larger in the out-of-key condition than in the in-key and auditory-anomaly conditions. These results provide evidence for an overlap in structural processing between language and music.

Acoustic correlates of information structure

This paper reports three studies aimed at addressing three questions about the acoustic correlates of information structure in English: (1) do speakers mark information structure prosodically, and, to the extent they do; (2) what are the acoustic features associated with different aspects of information structure; and (3) how well can listeners retrieve this information from the signal? The information structure of subject–verb–object sentences was manipulated via the questions preceding those sentences: elements in the target sentences were either focused (i.e., the answer to a wh-question) or given (i.e., mentioned in prior discourse); furthermore, focused elements had either an implicit or an explicit contrast set in the discourse; finally, either only the object was focused (narrow object focus) or the entire event was focused (wide focus). The results across all three experiments demonstrated that people reliably mark (1) focus location (subject, verb, or object) using greater intensity, longer duration, and higher mean and maximum F0, and (2) focus breadth, such that narrow object focus is marked with greater intensity, longer duration, and higher mean and maximum F0 on the object than wide focus. Furthermore, when participants are made aware of prosodic ambiguity present across different information structures, they reliably mark focus type, so that contrastively focused elements are produced with greater intensity, longer duration, and lower mean and maximum F0 than noncontrastively focused elements. In addition to having important theoretical consequences for accounts of semantics and prosody, these experiments demonstrate that linear residualisation successfully removes individual differences in peoples productions thereby revealing cross-speaker generalisations. Furthermore, discriminant modelling allows us to objectively determine the acoustic features that underlie meaning differences.

An algorithmic method for functionally defining regions of interest in the ventral visual pathway

In a widely used functional magnetic resonance imaging (fMRI) data analysis method, functional regions of interest (fROIs) are handpicked in each participant using macroanatomic landmarks as guides, and the response of these regions to new conditions is then measured. A key limitation of this standard handpicked fROI method is the subjectivity of decisions about which clusters of activated voxels should be treated as the particular fROI in question in each subject. Here we apply the Group-Constrained Subject-Specific (GSS) method for defining fROIs, recently developed for identifying language fROIs (Fedorenko et al., 2010), to algorithmically identify fourteen well-studied category-selective regions of the ventral visual pathway (Kanwisher, 2010). We show that this method retains the benefit of defining fROIs in individual subjects without the subjectivity inherent in the traditional handpicked fROI approach. The tools necessary for using this method are available on our website (http://web.mit.edu/bcs/nklab/GSS.shtml).

The role of domain-general cognitive control in language comprehension

What role does domain-general cognitive control play in understanding linguistic input? Although much evidence has suggested that domain-general cognitive control and working memory resources are sometimes recruited during language comprehension, many aspects of this relationship remain elusive. For example, how frequently do cognitive control mechanisms get engaged when we understand language? And is this engagement necessary for successful comprehension? I here (a) review recent brain imaging evidence for the neural separability of the brain regions that support high-level linguistic processing vs. those that support domain-general cognitive control abilities; (b) define the space of possibilities for the relationship between these sets of brain regions; and (c) review the available evidence that constrains these possibilities to some extent. I argue that we should stop asking whether domain-general cognitive control mechanisms play a role in language comprehension, and instead focus on characterizing the division of labor between the cognitive control brain regions and the more functionally specialized language regions.

The Syntactic Complexity of Russian Relative Clauses

Although syntactic complexity has been investigated across dozens of studies, the available data still greatly underdetermine relevant theories of processing difficulty. Memory-based and expectation-based theories make opposite predictions regarding fine-grained time course of processing difficulty in syntactically constrained contexts, and each class of theory receives support from results on some constructions in some languages. Here we report four self-paced reading experiments on the online comprehension of Russian relative clauses together with related corpus studies, taking advantage of Russian’s flexible word order to disentangle predictions of competing theories. We find support for key predictions of memory-based theories in reading times at RC verbs, and for key predictions of expectation-based theories in processing difficulty at RC-initial accusative noun phrase (NP) objects, which corpus data suggest should be highly unexpected. These results suggest that a complete theory of syntactic complexity must integrate insights from both expectation-based and memory-based theories.

Info/Information Theory: Speakers Choose Shorter Words in Predictive Contexts.

A major open question in natural language research is the role of communicative efficiency in the origin and on-line processing of language structures. Here, we use word pairs like chimp/chimpanzee, which differ in length but have nearly identical meanings, to investigate the communicative properties of lexical systems and the communicative pressures on language users.If language is designed to be information-theoretically optimal, then shorter words should convey less information than their longer counterparts, when controlling for meaning. Consistent with this prediction, a corpus analysis revealed that the short form of our meaning-matched pairs occurs in more predictive contexts than the longer form. Second, a behavioral study showed that language users choose the short form more often in predictive contexts, suggesting that tendencies to be information-theoretically efficient manifest in explicit behavioral choices. Our findings, which demonstrate the prominent role of communicative efficiency in the structure of the lexicon, complement and extend the results of Piantadosi, Tily, and Gibson (2011), who showed that word length is better correlated with Shannon information content than with frequency. Crucially, we show that this effect arises at least in part from active speaker choice.