An international team of scientists has shown that the use of non-instrumental verbs in speech requires additional activation of brain regions that are affected in patients with aphasia. The research results are presented in the Journal of Neurolinguistics.
Aphasia is a systemic speech disorder due to trauma, such as stroke. In general, the speech of such patients is characterized by poor vocabulary, in particular, they can use instrumental ("fish" - fish, "cut" - with a knife) verbs, but have difficulty using abstract ("swim", "walk"). Given the relatively well-known neural correlate, the reasons for this specificity are still unclear.
To fill the gap, scientists from the Higher School of Economics (Russia), Ludwig Maximilian University of Munich and other institutions conducted an experiment involving 16 healthy (German-speaking) people aged 26–39 years. They performed two tasks. The first was that the volunteers were shown verb plus two nouns ("cook", "soup", "hill"), which they had to associate in meaning.
The second task was control and was of a non-linguistic nature. The subjects were shown bundles of characters in the Wingdings font, within which they had to find an identical pair. During the tasks, the authors recorded the brain activity of the participants using magnetic resonance imaging (MRI). Based on the data obtained, for each volunteer, a profile of the brain activity characteristic of certain verbs was compiled.
The results showed that instrumental verbs activate the lateral frontal and temporal regions of the brain, especially the inferior frontal and middle temporal gyrus, as well as the occipital and parietal regions. Non-instrumental verbs used more sites: for example, extensive activation, among other things, was observed in the frontal and parietal cortex. In other words, non-instrumental verbs also activated areas that are characteristic of operating with symbols.
According to the authors, it is these areas that are affected in aphasia, which clarifies the difficulties that patients experience when using abstract verbs. Their brains are incapable of activating additional areas that are required to recognize and form such words. The researchers note that their findings contradict most of the previous studies that explained the phenomenon of fundamentally different physiological basic processing of verbs.