Imaging Language and Communication

Modern Imaging Techniques Reveal the Complexity of Language  

The classic brain areas associated with language – Broca’s and Wernicke’s area – have been identified from patients with brain lesions (see page 8). It is plausible that other regions, such as the auditory cortex for hearing and the visual cortex for reading, also play a role in communication. However, in recent years, imaging has contributed a great deal to a more network-like understanding of the representation of language and communication in the brain and demonstrated its complexity.

via Wikimedia Commons

Different Imaging Modalities 

Imaging studies with combined functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) have shown that the arcuate fascicle directly connects Broca’s with Wernicke’s area [1]. This fiber bundle is thought to represent the dorsal pathway of language. It connects auditory cortices to parietal and frontal lobe networks, and seems to mediate between hearing sounds and articulation of words [2]. Furthermore, a second pathway exists and is represented by the extreme capsule [1]. This ventral stream projects from auditory cortices to the temporal lobe. It is thought to be the connection between hearing sound and understanding the meaning of spoken words [2].

Resting-state fMRI studies demonstrate that the language network is even more extended. MRI signals in Broca’s and Wernicke’s areas have a positive correlation with signals in neighbouring prefrontal, temporal, and parietal regions, but also with subcortical structures like the basal ganglia [3].

Studies on communication and language have also been performed using near-infrared spectroscopy (NIRS). This technique allows subjects to communicate in a natural environment. NIRS has proven useful in examining the brain activity of infants to get an insight into how we learn to speak [4].

It seems that with every fMRI, PET or NIRS study conducted on the subject, it is proven further that the language network is more extended and complex than previously thought.

Clinical Applications 

This more detailed knowledge of the extent of the language network also has direct clinical applications. Brain surgeries on tumor or epilepsy patients need to avoid areas that can affect the ability of the patients to speak. The Wada test, which “switches off” one cerebral hemisphere with barbiturates, was formally the gold standard to determine the dominant hemisphere for language production. Modern imaging methods, like fMRI or navigated transcranial magnetic stimulation (nTMS) can map the individual brain areas involved in language much more precisely and in much more detail. Therefore, these methods are increasingly being used for preoperative planning [5,6] and are considered an adequate replacement for the Wada test [7].
Furthermore, imaging studies are a great tool to help us understand how functional recovery takes place after stroke or surgery, and to what extend other structures can take over functions essential for communication [1]. This further adds to understanding of the language network.

Social Aspects of Communication 
Not only have the structural components of the language network been analyzed with imaging, the social aspects of communication have also taken center stage in recent years.
A study conducted with simultaneous MRI scanning of close female friends showed that neuronal coupling happens during live verbal communication about autobiographical events. The time course of neural activity in language areas was coupled with the time course of neural activity in the friends’ auditory cortex, representing very basic reciprocal mechanisms of social interaction [8]. So-called hyperscanning – the parallel scanning of two subjects who can interact during the session – is a great way to study brain activation during live social interaction.
However, in a social context it is not only the literal meaning of words and sentences that have to be processed, but also the intended meaning of the speaker. This is especially true for metaphors and sarcasm. Differences in brain activations during communication with metaphors and sarcasm have been investigated with fMRI. Interestingly, brain activation related to metaphors was found in the head of the caudate. Sarcasm elicited activation in the left amygdala, which probably represents the processing of the speaker's emotional status [9].
All in all, imaging has given us much insight into the complexity of the language network and its use in social context. To know how the brains of healthy participants function during communication is important to understand conditions such as autism or schizophrenia and has great clinical implications in rehabilitation and surgical planning.

[1] Saur and Hartwigsen, Arch Phys Med Rehab, 2012   

[2] Friederici and Gierhan, Curr Opin Neurobiol, 2013

[3] Tomasi and Volkow, Mol Psychiatry, 2012

[4] Rossi et al, Brain & Language, 2012

[5] Mahvash et al, Clin Neurol Neurosurg, 2014

[6] Picht et al, Neurosurgery, 2013

[7] Papanicolaou et al, Epilepsia, 2014

[8] Spiegelhalder et al, Behav Brain Res, 2014
[9] Uchiyama et al, Cortex, 2012

by Ann-Christin Ostwaldt, PhD Student, AG Fiebach
this article originally appeared 2014 in CNS Volume 7, Issue 4, Communication and Social Media