Semantic memory underpins our understanding of objects, people, places, and ideas. Anomia, a disruption of semantic memory access, is the most common residual language disturbance and is seen in dementia and following injury to temporal cortex. While such anomia has been well characterized by lesion symptom mapping studies, its pathophysiology is not well understood. We hypothesize that inputs to the semantic memory system engage a specific heteromodal network hub that integrates lexical retrieval with the appropriate semantic content. Such a network hub has been proposed by others, but has thus far eluded precise spatiotemporal delineation. This limitation in our understanding of semantic memory has impeded progress in the treatment of anomia. We evaluated the cortical structure and dynamics of the lexical semantic network in driving speech production in a large cohort of patients with epilepsy using electrocorticography (n = 64), functional MRI (n = 36), and direct cortical stimulation (n = 30) during two generative language processes that rely on semantic knowledge: visual picture naming and auditory naming to definition. Each task also featured a non-semantic control condition: scrambled pictures and reversed speech, respectively. These large-scale data of the left, language-dominant hemisphere uniquely enable convergent, high-resolution analyses of neural mechanisms characterized by rapid, transient dynamics with strong interactions between distributed cortical substrates. We observed three stages of activity during both visual picture naming and auditory naming to definition that were serially organized: sensory processing, lexical semantic processing, and articulation. Critically, the second stage was absent in both the visual and auditory control conditions. Group activity maps from both electrocorticography and functional MRI identified heteromodal responses in middle fusiform gyrus, intraparietal sulcus, and inferior frontal gyrus; furthermore, the spectrotemporal profiles of these three regions revealed coincident activity preceding articulation. Only in the middle fusiform gyrus did direct cortical stimulation disrupt both naming tasks while still preserving the ability to repeat sentences. These convergent data strongly support a model in which a distinct neuroanatomical substrate in middle fusiform gyrus provides access to object semantic information. This under-appreciated locus of semantic processing is at risk in resections for temporal lobe epilepsy as well as in trauma and strokes that affect the inferior temporal cortex-it may explain the range of anomic states seen in these conditions. Further characterization of brain network behaviour engaging this region in both healthy and diseased states will expand our understanding of semantic memory and further development of therapies directed at anomia.

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Spoken language, both perception and production, is thought to be facilitated by an ensemble of predictive mechanisms. We obtain intracranial recordings in 37 patients using depth probes implanted along the anteroposterior extent of the supratemporal plane during rhythm listening, speech perception, and speech production. These reveal two predictive mechanisms in early auditory cortex with distinct anatomical and functional characteristics. The first, localized to bilateral Heschl’s gyri and indexed by low-frequency phase, predicts the timing of acoustic events. The second, localized to planum temporale only in language-dominant cortex and indexed by high-gamma power, shows a transient response to acoustic stimuli that is uniquely suppressed during speech production. Chronometric stimulation of Heschl’s gyrus selectively disrupts speech perception, while stimulation of planum temporale selectively disrupts speech production. This work illuminates the fundamental acoustic infrastructure—both architecture and function—for spoken language, grounding cognitive models of speech perception and production in human neurobiology.

1Reading is a rapid, distributed process that engages multiple components of the 2 ventral visual stream. However, the neural constituents and their interactions that allow 3 us to identify written words are not well understood. Using direct intracranial recordings 4 in a large cohort of humans, we comprehensively isolated the spatiotemporal 5 dynamics of visual word recognition across the entire left ventral occipitotemporal 6 cortex. The mid-fusiform cortex is the first region that is sensitive to word identity and 7 to both sub-lexical and lexical frequencies. Its activation, response latency and 8 amplitude, are highly dependent on the statistics of natural language. Information 9 about lexicality and word frequency propagates posteriorly from this region to 10 traditional visual word form regions and to earlier visual cortex. This unique sensitivity 11 of mid-fusiform cortex to the lexical characteristics of written words points to its central 12 role as an orthographic lexicon, which accesses the long-term memory 13representations of visual word forms. 14 Woodhead et al., 2014) to enable rapid orthographic-lexical-semantic transformations. 36While most of our knowledge of the cortical architecture of reading arises from 37 functional MRI, the rapid speed of reading demands that we use methods with very 38 high spatiotemporal resolution to study these processes. To this end, we used 39 recordings in 35 individuals with 784 intracranial electrodes, to comprehensively 40 characterize the spatial organization and functional roles of orthographic and lexical 41 regions across the ventral visual pathway during sub-lexical and lexical processes. 42Given their construction, these two tasks, performed in the same cohort, tap into 43 varying levels of attentional modulation of orthographic processing. Specifically, we 44 isolated functionally distinct regions across the vOTC that are highly sensitive to the 45 structure and statistics of natural language at multiple stages of orthographic 46 processing. 47