Summary: When one sense is absent from birth, the brain adapts in unexpected ways. New research shows that in people born deaf, the auditory cortex represents visual information not by increasing activity, but by selectively decreasing it. These systematic deactivations map to visual space and suggest that inhibitory signals play a central role in cross-modal neuroplasticity.
Instead of simply “turning on” auditory areas for vision, the deaf brain appears to “dim” parts of the auditory cortex in response to particular visual locations. This selective suppression likely helps filter irrelevant inputs and sharpen visual attention.
Key Facts
- Organized deactivation: In congenitally deaf individuals, the auditory cortex shows consistent selective deactivation patterns that correspond to the location of visual stimuli, rather than increased activation.
- Spatial mapping: These deactivations follow a structured pattern—responding primarily to stimuli in the contralateral visual field and concentrating on central vision—indicating an organized representation of visual space within auditory regions.
- A new view of plasticity: The findings expand the concept of neuroplasticity by demonstrating that inhibitory processes can reorganize deprived sensory cortex, potentially to optimize visual attention and suppress neural noise.
- Scientific implications: Models of brain reorganization should include deactivation-driven mechanisms as a core mode of sensory compensation in addition to increased activations.
Source: BIAL Foundation
Reorganizing without sound: how the deaf brain represents vision
Neuroplasticity enables the brain to rewire its structure and function across the lifespan. When a sensory modality is absent from birth, areas normally devoted to that sense can be recruited for other modalities—a process known as cross-modal plasticity. Research on congenital blindness and deafness has repeatedly shown this capacity, with deprived cortical regions supporting tasks from other senses.
Previous studies established that the visual system can recruit auditory regions in congenital deafness, with reorganized auditory cortex responding to visual motion, rhythm and location—often linked with behavioral advantages in visual tasks. What remained unclear was how low-level spatial features of vision are represented in these repurposed auditory areas.
To investigate, Alessio Fracasso and collaborators, supported by the BIAL Foundation, compared brain responses in young congenitally deaf and hearing participants during simple visual stimulation. Using classic stimuli that swept across the visual field, the team recorded functional magnetic resonance imaging (fMRI) responses across visual and auditory regions.
As expected, hearing participants showed visual-cortex activation tied to stimulus position and little modulation in auditory cortex. Deaf participants, however, exhibited a surprising pattern: portions of the auditory cortex showed systematic negative blood-oxygen-level-dependent (BOLD) signals—deactivations—when visual stimuli appeared.
These negative responses were consistent and stimulus-dependent, indicating they were not random noise. Further exploratory analyses using population receptive field–style approaches revealed that auditory deactivations were organized contralaterally (responding to the opposite side of space), emphasized central visual field locations, and covered broad spatial areas. In other words, the deprived auditory cortex encodes where visual stimuli appear by selectively decreasing its activity in a structured way.
Published in Human Brain Mapping, the study—“The Neural Organization of Visual Information in the Auditory Cortex of the Congenitally Deaf”—is the result of an international collaboration including researchers affiliated with the University of Coimbra (Portugal), University of Glasgow (UK), University of Padua (Italy), and Peking University (China).
According to Alessio Fracasso, these results “offer a new perspective on brain plasticity: the brain does not simply replace one sense with another by boosting activity; it can repurpose deprived regions through selective deactivation, possibly as a mechanism to filter irrelevant signals or enhance visual attention.” Incorporating deactivation mechanisms into models of sensory reorganization may provide a fuller account of cross-modal plasticity and its functional consequences.
Key Questions Answered
A: Selective deactivation likely improves efficiency. By suppressing parts of the auditory cortex that would otherwise generate irrelevant activity, the brain can reduce neural noise and better focus on spatial visual information—similar to dimming background lights to see a stage more clearly.
A: No. In the hearing control group, visual stimulation produced the expected activations in visual cortex, and the auditory cortex showed no such organized deactivation. This pattern appears to be a specific adaptation to congenital deafness.
A: It refers to contralateral organization: stimuli presented in the left visual field primarily engage the right hemisphere, and vice versa. The fact that auditory deactivations follow this contralateral mapping shows the reorganized auditory cortex has adopted an orderly visual representation.
Editorial Notes
- This article was edited by a Neuroscience News editor.
- The full journal paper was reviewed.
- Additional explanatory context was added by editorial staff.
About this auditory neuroscience research news
Author: Sandra Pinto
Source: BIAL Foundation
Contact: Sandra Pinto – BIAL Foundation
Image: Image credited to Neuroscience News
Original Research: Open access. “The Neural Organization of Visual Information in the Auditory Cortex of the Congenitally Deaf” by Zohar Tal, Joana Sayal, Fang Fang, Yanchao Bi, Jorge Almeida, and Alessio Fracasso. Human Brain Mapping. DOI: 10.1002/hbm.70444
Abstract
The Neural Organization of Visual Information in the Auditory Cortex of the Congenitally Deaf
Neuroplasticity enables the brain to reorganize its functional architecture over time. In congenital deafness, the auditory cortex—deprived of sound—can be recruited to process information from other senses, a phenomenon called cross-modal plasticity. While prior work has shown visual recruitment of auditory regions in deaf individuals, it was unclear whether these cross-modal responses encode low-level visual spatial features or form an organized map of the visual field.
Using two fMRI experiments and conventional visual stimuli, the study compared cross-modal processing in the auditory cortex of deaf and hearing participants during passive viewing. At the group level, deaf participants showed predominant negative BOLD signals in early and associative auditory areas, suggesting that visual information may be represented via organized deactivations rather than increased activation. Complementary exploratory analyses further supported a structured, contralateral representation of visual space through deactivation signals. These results provide new insight into the neural mechanisms underlying sensory reorganization.