Biology subjects

Kean, H.

Publications and source records attributed to Kean, H..

9 recordsLinked to original sources

bioRxiv2026

The cerebellum specializes for language even in the absence of contralateral neocortical inputs

Long considered a structure dedicated primarily to motor control, the cerebellum is now known to contain regions that respond selectively to language. However, how cerebellar language specialization emerges during development remains unknown. The prevailing proposal is that cerebellar functional specialization critically depends on inputs from the contralateral neocortex, received through well-established reciprocal cortico-cerebellar connections. Here, we test this proposal in two individuals with atypical brain development: EG, a right-handed woman who lacks most of her left temporal lobe (presumably from birth) and whose neocortical language network resides in her right hemisphere, and C1, an individual missing the entire left cerebral hemisphere from birth. Using precision functional MRI in EG and a cohort of 74 typically-developing adults, we find that EG's cerebellar language network shows a strong left-hemispheric bias, mirroring the atypical lateralization of language in her cerebral cortex, while preserving canonical topography and response profiles of the language-dominant cerebellar regions. Critically, however, EG's right cerebellar hemisphere also responds to language and even contains a language-selective region despite the absence of language regions in the neocortical left hemisphere. We replicate these cerebellar findings in C1, a more extreme case who is missing the entire left hemisphere. These results show that the cerebellum develops language sensitivity despite the absence of contralateral inputs in the face of early injury. Together, these findings challenge the view that cerebellar specialization critically requires contralateral neocortical inputs, and point instead to some degree of intrinsic neocortex-independent cerebellar organization.

neuroscience↗

bioRxiv2025

A distinct set of brain areas process prosody--the melody of speech

Human speech carries information beyond the words themselves: pitch, loudness, duration, and pauses--jointly referred to as prosody--emphasize critical words, help group words into phrases, and convey emotional and other socially-relevant information. Using a novel fMRI paradigm, we identify a set of prosody-responsive brain areas and then richly characterize them across 8 experiments (25 experimental conditions; n=51 participants). These areas--located on the lateral temporal surface bilaterally and in the frontal lobe--respond to the presence of prosody in both meaningful and meaningless speech, and are distinct from nearby temporal pitch- and speech-perception areas and from frontal areas sensitive to general cognitive and attentional demands. They are also dissociable from--but show partial overlap with--the language areas and with the area that processes dynamic facial expressions. Thus, prosodic information is processed by a distinct set of brain areas, which may help integrate linguistic meanings with non-verbal communicative signals.

neuroscience↗

bioRxiv2025

Evidence from Formal Logical Reasoning Reveals that the Language of Thought is not Natural Language

Humans are endowed with a powerful capacity for inductive and deductive logical thought: we easily form generalizations based on a few examples and draw conclusions from known premises. Humans also arguably have the most sophisticated communication system in the animal kingdom: natural language allows us to express complex and structured meanings. Some have therefore argued for a tight relationship between complex thought and language, postulating that reasoning, including logical reasoning, relies on linguistic representations. We systematically investigated the relationship between logical reasoning and language using two complementary approaches. First, we used non-invasive brain imaging (fMRI) to examine neural activity as healthy adults engaged in logical reasoning tasks. And second, we behaviorally evaluated logical abilities in individuals with extensive lesions to the language brain areas and consequent severe linguistic impairment. Our findings reveal that the language brain network is not engaged during logical reasoning, and patients with severe aphasia exhibit intact performance on logic tasks. Instead, inductive reasoning recruits the domain-general multiple demand network implicated broadly in goal-directed behaviors, whereas deductive reasoning draws on brain regions that are distinct from both the language and the multiple demand networks. Together, these results indicate that linguistic representations are neither utilized nor required for inductive or deductive logical reasoning. SignificanceWhich cognitive mechanisms allow humans to reason logically, to understand whether a conclusion follows from the premises? Are they the same ones that allow the assembly of words into structured representations? Scholars have debated for millennia whether logical reasoning is inextricably tied to natural language, or instead relies on a distinct "language of thought" (LOT). Using fMRI in healthy adults and evaluating logical ability in individuals with severe aphasia, we find that distinct neural systems support language processing vs. logical (inductive and deductive) reasoning. These results suggest that, at least in mature brains, language processing does not underpin logical inference, perhaps due to the distinct representational format of the logical LOT.

neuroscience↗

bioRxiv2023

Preserved functional organization of human auditory cortex in individuals missing one temporal lobe from infancy

Human cortical responses to natural sounds, measured with fMRI, can be approximated as the weighted sum of a small number of canonical response patterns (components), each having interpretable functional and anatomical properties. Here, we asked whether this organization is preserved in cases where only one temporal lobe is available due to early brain damage by investigating a unique family: one sibling born without a left temporal lobe, another without a right temporal lobe, and a third anatomically neurotypical. We analyzed fMRI responses to diverse natural sounds within the intact hemispheres of these individuals and compared them to 12 neurotypical participants. All siblings manifested the neurotypical auditory responses in their intact hemispheres. These results suggest that the development of the auditory cortex in each hemisphere does not depend on the existence of the other hemisphere, highlighting the redundancy and equipotentiality of the bilateral auditory system.

neuroscience↗

bioRxiv2022

LanA (Language Atlas): A probabilistic atlas for the language network based on fMRI data from >800 individuals

Two analytic traditions characterize fMRI language research. One relies on averaging activations voxel-wise across individuals. This approach has limitations: because of inter-individual variability in the locations of language areas, a location in a common brain space cannot be meaningfully linked to function. An alternative approach relies on identifying language areas in each individual using a functional localizer. Because of its greater sensitivity, functional resolution, and interpretability, functional localization is gaining popularity, but it is not always feasible, and cannot be applied retroactively to past studies. We provide a solution for bridging these currently disjoint approaches in the form of a probabilistic functional atlas created from fMRI data for an extensively validated language localizer in 806 individuals. This atlas enables estimating the probability that any given location in a common brain space belongs to the language network, and thus can help interpret group-level peaks and meta-analyses of such peaks, and lesion locations in patient investigations. More meaningful comparisons of findings across studies should increase robustness and replicability in language research.

neuroscience↗

bioRxiv2021

'Constituent length' effects in fMRI do not provide evidence for abstract syntactic processing

Human language has a remarkable capacity to encode complex ideas. This capacity arises because language is compositional: the form and arrangement of words in sentences (structure) determine the conceptual relations that hold between the words referents (meaning). A foundational question in human cognition is whether the brain regions that support language are similarly factored into structure-selective and meaning-selective areas. In an influential study, Pallier et al. (2011, PNAS) used fMRI to investigate the brain response to sequences of real words and pseudowords and reported a sharp dissociation between structure-selective and meaning-selective brain regions. In the present study, we argue that no such dissociation emerges when individual differences in brain anatomy are considered. We report three experiments (including a close conceptual replication of Pallier et al.s original study) that use precision fMRI methods to capture separation or overlap of function in the brains of individual participants. Our results replicate Pallier et al.s finding that the brains response is modulated by the sequential structure of language but paint a different picture with respect to the structure-meaning relationship. Instead of distinct structure-selective and meaning-selective brain areas, we find distributed sensitivity to both linguistic structure and meaning throughout a broad frontotemporal brain network. Our results join a growing body of evidence for an integrated network for language in the human brain within which internal specialization is primarily a matter of degree rather than kind, in contrast with influential proposals that advocate distinct specialization of different brain areas for different types of linguistic functions. Significance StatementUsing fMRI, we show that a broad network of frontal and temporal areas in the left hemisphere of the human brain is sensitive to both the structure of language and the meaning that it encodes. This finding challenges many current theories of the neurobiology of language, which propose a sharp separation between areas that encode structure and areas that encode meaning. Instead, results support a broad distribution of word- and sentence-level processing across an integrated brain network for language. This PDF file includes: Main Text Figures 1 to 3 Tables 1 to 1

neuroscience↗

bioRxiv2021

The language network supports both lexical access and sentence generation during language production

A fronto-temporal brain network has long been implicated in language comprehension. However, this networks role in language production remains debated. In particular, it remains unclear whether all or only some language regions contribute to production, and which aspects of production these regions support. Across three fMRI experiments that rely on robust individual-subject analyses, we characterize the language networks response to high-level production demands. We report three novel results. First, sentence production, spoken or typed, elicits a strong response throughout the language network. Second, the language network responds to both phrase-structure building and lexical access demands, although the response to phrase-structure building is stronger and more spatially extensive, present in every language region. Finally, contra some proposals, we find no evidence of brain regions--within or outside the language network--that selectively support phrase-structure building in production relative to comprehension. Instead, all language regions respond more strongly during production than comprehension, suggesting that production incurs a greater cost for the language network. Together, these results align with the idea that language comprehension and production draw on the same knowledge representations, which are stored in a distributed manner within the language-selective network and are used to both interpret and generate linguistic utterances.

neuroscience↗

bioRxiv2021

The human language system does not support music processing

Language and music are two human-unique capacities whose relationship remains debated. Some have argued for overlap in processing mechanisms, especially for structure processing. Such claims often concern the inferior frontal component of the language system located within Brocas area. However, others have failed to find overlap. Using a robust individual-subject fMRI approach, we examined the responses of language brain regions to music stimuli, and probed the musical abilities of individuals with severe aphasia. Across four experiments, we obtained a clear answer: music perception does not engage the language system, and judgments about music structure are possible even in the presence of severe damage to the language network. In particular, the language regions responses to music are generally low, often below the fixation baseline, and never exceed responses elicited by non-music auditory conditions, like animal sounds. Further, the language regions are not sensitive to music structure: they show low responses to intact and structure-scrambled music, and to melodies with vs. without structural violations. Finally, in line with past patient investigations, individuals with aphasia who cannot judge sentence grammaticality perform well on melody well-formedness judgments. Thus the mechanisms that process structure in language do not appear to process music, including music syntax.

neuroscience↗

bioRxiv2021

Frontal language areas do not emerge in the absence of temporal language areas: A case study of an individual born without a left temporal lobe

Language relies on a left-lateralized fronto-temporal brain network. How this network emerges ontogenetically remains debated. We asked whether frontal language areas emerge in the absence of temporal language areas through a deep-data investigation of an individual (EG) born without her left temporal lobe. Using fMRI methods that have been validated to elicit reliable individual-level responses, we find that--as expected for early left hemisphere damage--EG has a fully functional language network in her right hemisphere (comparable to that in n=145 controls) and performs normally on language assessments. However, we detect no response to language in EGs left frontal lobe (replicated across two sessions, 3 years apart). Another network--the multiple demand network--is robustly present in frontal lobes bilaterally, suggesting that EGs left frontal cortex can support non-linguistic cognition. The existence of temporal language areas therefore appears to be a prerequisite for the emergence of the frontal language areas.

neuroscience↗