Summary: New research reveals the brain’s role in semantic integration during reading, providing insights into the challenges faced by individuals with aphasia. The study found that the posterior temporal cortex is involved in early semantic processing, while the inferior frontal cortex has a broader role in understanding meaning. By studying how the brain deduces meaning from context, researchers gained a better understanding of the difficulties experienced by people with aphasia when making semantic inferences.
Key Facts:
- The posterior temporal cortex is responsible for initial semantic processing, while the inferior frontal cortex is involved in broader comprehension.
- The study utilized intracranial recordings in epilepsy patients to observe how the brain derives meaning from phrases.
- This study provides deeper insights into semantic deficits in aphasia, particularly after frontal strokes.
Source: UT Houston
Two different regions of the brain play a critical role in integrating semantic information while reading, shedding light on why individuals with aphasia struggle with semantics, according to a new study from UTHealth Houston.
The study, led by Elliot Murphy, PhD, a postdoctoral research fellow, and Nitin Tandon, MD, a professor and chair in the Vivian L. Smith Department of Neurosurgery with McGovern Medical School at UTHealth Houston, was published in Nature Communications.
Language heavily relies on integrating vocabulary across multiple words to derive semantic concepts. However, the process of integrating semantic information during reading remains unknown.
“We wanted to know how patients made inferences about meaning. For example, one of the definitions in our study was ‘a round red fruit’ – the word ‘apple’ did not appear in the sentence. We were able to reveal how the human brain integrates semantic information and identify the different areas involved at different stages,” said Murphy.
The researchers analyzed intracranial recordings from 58 epilepsy patients who read word definitions. They discovered that different areas of the brain showed sensitivity to meaning during a small window of activity. Specifically, they identified complementary cortical mosaics for semantic integration in the posterior temporal cortex and the inferior frontal cortex.
The posterior temporal cortex is activated early in the process of semantic integration, while the inferior frontal cortex is particularly sensitive to all aspects of meaning, especially in deep sulcal sites.
These findings provide insights into the inner workings of aphasia, a disorder that affects language expression and comprehension. Individuals with aphasia often struggle with semantic integration, meaning they have difficulty making additional inferences beyond individual words.
“Both the frontal and posterior temporal cortex disrupt semantic integration, which we observe in individuals with various types of aphasia. We believe that this complex mosaic structure helps explain the different semantic deficits people experience after frontal strokes,” Murphy explained.
Co-authors from UTHealth Houston who contributed to the study include Kathryn M. Snyder, MD/PhD student, and Patrick S. Rollo, research associate and third-year medical student from the Vivian L. Smith Department of Neurosurgery and the Texas Institute for Restorative Neurotechnologies (TIRN) at McGovern Medical School.
About this information processing and language research news
Author: Jeannette Sanchez
Source: UT Houston
Contact: Jeannette Sanchez – UT Houston
Image: The image is credited to Neuroscience News
Original Research: Open access.
“The spatiotemporal dynamics of semantic integration in the human brain” by Elliot Murphy et al. Nature Communications
Abstract
The spatiotemporal dynamics of semantic integration in the human brain
Language relies on integrating lexical information across multiple words to derive semantic concepts. Previous limitations in spatiotemporal resolution have hindered the identification of processes involved in semantic integration.
In this study, intracranial recordings were conducted on epilepsy patients (n = 58) who read written word definitions. The descriptions were either referential or non-referential to a common object. Semantically referential sentences elicited high-frequency broadband gamma activation in the inferior frontal sulcus (IFS), medial parietal cortex, orbitofrontal cortex (OFC), and medial temporal lobe in the left, language-dominant hemisphere.
Activity in the IFS, OFC, and posterior middle temporal gyrus was influenced by the semantic coherence of non-referential sentences, indicating semantic effects independent of task-based referential status.
Components of this network, along with the posterior superior temporal sulcus, were engaged in referential sentences that did not clearly narrow down the search space for lexical information by the final word.
These findings suggest the existence of complementary cortical mosaics for semantic integration in the posterior temporal and inferior frontal cortex.
