Language areas of the brain

Wernicke-Lichtheim-Geschwind model

The classical Wernicke-Lichtheim-Geschwind model is the first model proposed for language processing in the brain. Despite its simplicity, this model is still used, even though the language network in the dominant hemisphere is much more extended than initially assumed. In this model, Wernicke’s area is responsible for language comprehension and Broca’s area only for production. The arcuate fasciculus is crucial for the information exchange between these areas, particularly in tasks such as reading aloud.

Non-invasive functional brain imaging has greatly helped in understanding the neurobiology of language. Especially fMRI, permits the in vivo investigation of the anatomy and physiology of the human brain and the network connectivity of the brain that is related with language production and comprehension.

1. The Wernicke-Lichtheim-Geschwind model treats language as a serial pathway. Repeating a heard word, or reading one aloud, traces this route:
2. Auditory input reaches Heschl's gyrus, the primary auditory cortex (BA 41).
3. Wernicke's area (BA 22) decodes the phonological pattern, producing comprehension.
4. The arcuate fasciculus carries the phonological information forward to Broca's area.
5. Broca's area (BA 44 and 45) plans the motor program for speech. The premotor and primary motor cortex drive the articulatory movements, with the insular cortex helping coordinate them.

Dual-stream model

A most recent model is the dual-stream model of language processing. This model distinguishes 2 different streams with different functions. The dorsal stream includes the arcuate and the superior longitudinal fascicles, responsible for connecting the temporal cortex with the Broca’s area and the premotor cortex, and enables speech production and phonological mapping. The ventral stream includes the extreme capsule linking anterior Broca’s regions to the superior temporal gyrus and the uncinate fasciculus connecting ventral frontal areas to anterior temporal regions. The ventral stream enables semantic interpretation and comprehension.

Memory, Unification, and Control (MUC) model

Another model is the Memory, Unification, and Control (MUC) model which emphasizes distributed brain networks rather than single regions. The Memory component, primarily in the temporal cortex and angular gyrus, stores linguistic knowledge such as phonological word forms, morphology, meanings, and syntactic templates acquired through experience. The unification component, centered in the left lateral inferior frontal cortex (Broca’s area), integrates this knowledge into larger unified structures at 3 different levels: semantics, syntax, and phonology. The Control component, involving dorsolateral prefrontal cortex, anterior cingulate, and parietal attention systems, regulates language in social and cognitive context by guiding selection of the appropriate target language, managing turn-taking in conversation, and coordinating joint action in communication. This model emphasizes that language arises from dynamic networks of interacting brain areas, where contributions of specific regions depend on their connectivity and integration with others.

Language comprehension and production are supported by a network of interconnected brain regions, and the different neurobiological models highlight the complexity of these processes from multiple perspectives. Classic models, such as the Wernicke–Lichtheim–Geschwind model, emphasize distinct cortical areas for comprehension and production, while more contemporary approaches, like the dual-stream model, underscore the dynamic interaction between dorsal and ventral pathways. Neurocognitive and connectionist models further extend this view by integrating the role of distributed neural networks, plasticity, and real-time processing demands. To sum up, no single area of the brain operates in isolation, but language emerges from the coordinated activity of specialized and interactive neural systems.