Listening in on the language centers

In a new EU-funded project, LMU neurobiologist Anton Sirota plans to unlock the potential of brain signals emerging from the functional neural networks involved in speech perception and comprehension. His results could point to new ways of alleviating language disorders.

Every year, more than 5 million people worldwide experience localized brain damage that results in one of the several forms of aphasias. Aphasias are clinical disorders that affect the production and comprehension of natural language, due to neurodegeneration or traumatic nerve-cell loss in specific regions of the cerebral cortex. Patients who suffer from these conditions display cognitive deficits in comprehending spoken language and/or expressing themselves fluently. The use of digital interfaces that are capable of decoding electrical signals relayed by electrodes implanted in specific areas of the brain could provide a promising approach to the rehabilitation of these patients. A new international project called BrainCom, funded by the EU, will establish and apply the brain interface technology aimed to record the activity from the cortical language network in the brain in unprecedented detail, with a view to developing innovative computer-based interfaces to help aphasic patients. Neurobiologist Professor Anton Sirota and his colleagues at LMU will make a vital contribution to the project by establishing the link between such detailed brain signals and coding elements emerging from the cortical neural circuitry, such as the one involved in the encoding of natural language in the brain. These data will provide vital input for the development of computer-based systems that can convert patterned nerve impulses into spoken words or written messages.

The perception and processing of natural language in the brain involves highly complex cognitive processes. BrainCom will exploit the unique mechanical and electrical properties of innovative nanomaterials for the production of flexible electrodes capable of detecting and stimulating neuronal activity with unprecedented spatial and temporal resolution over large areas of the cerebral cortex. “With current technologies only relatively simple signals in the motor cortex – the region of the cerebral cortex responsible for the control of voluntary movements – can be decoded and used to alter the position of a cursor on a monitor,” Sirota says. “Language perception and comprehension is immensely more complex and requires far more sophisticated and physiologically-grounded brain-computer interfaces”

The electrical impulses that can be detected by means of electrodes implanted on the surface of the cerebral cortex reflect the collective activity of large sets of neuronal ensembles located deeper in the brain. As yet, however, these impulses cannot be decomposed into the contributions of individual neural networks and their potential for decoding motor patterns is limited. Sirota and his team will use an animal model to establish strategies to extract patterns of dynamics in specific layers and networks using densely recorded potentials at the surface of the cerebral cortex. “The goal is to analyze how the cell networks in the deeper areas contribute to the integrated impulses that can be recorded on the surface,” Sirota explains. “Our ultimate aim, however, is to define the contributions of individual cell types by studying how the surface signals are altered by targeted modulation of activity of particular cell types with methods of optogenetic – light-mediated control of neural activity.“ Thus, Sirota‘s investigations will provide the basis for the design of decoding and processing strategies for use in digital speech prosthesis devices.

The BrainCom project has been selected for funding by the EU Commission in the context of its Future & Emerging Technologies Program, and will receive grant support amounting to 8.35 million euros over the coming 5 years. The venture will be coordinated by the Fundació Institut Català de Nanociència i Nanotecnologia in Barcelona. The interdisciplinary collaboration involves researchers from 10 institutions based in Germany, Spain, France, Switzerland, the UK and Luxembourg.