Cortical Neuroprosthesis Merges Visible and Invisible Light Without Impairing Native Sensory Function

Area of Science:

• Neuroscience
• Biomedical Engineering
• Sensory Prosthetics

Background:

• Sensory prostheses can transduce infrared (IR) signals into electrical signals for brain stimulation.
• Previous studies delivered these signals to the somatosensory cortex (S1), requiring significant learning time.
• The potential for utilizing other primary sensory cortices, like the visual cortex (V1), remains largely unexplored.

Purpose of the Study:

• To investigate the impact of projecting infrared (IR) signals to the primary visual cortex (V1) versus the somatosensory cortex (S1) in rats.
• To determine if prior visual training influences the learning rate of IR discrimination tasks in V1.
• To assess the capacity for integrating novel sensory information with existing processing streams and evaluate potential impacts on native sensory functions.

Main Methods:

• Adult rats were implanted with sensory prostheses to convert infrared (IR) signals into electrical stimulation.
• Stimulation was delivered to either the primary visual cortex (V1) or the somatosensory cortex (S1).
• Rats performed IR discrimination tasks, with some groups pre-trained on visual discrimination tasks, and a visual-IR integration task was also employed. Tactile discrimination tasks using whiskers were assessed in S1-implanted rats.

Main Results:

• Rats with IR prostheses in V1, pre-trained on visual tasks, learned IR discrimination on day one, significantly faster than S1-implanted rats (approx. 4 days).
• Without prior visual training, learning rates for V1 and S1 implantation were comparable, indicating no intrinsic difference in learning capacity between areas.
• Rats successfully integrated IR signals into ongoing visual processing in V1 and showed no loss, and in some cases enhanced, whisker-based tactile discrimination abilities when prostheses were in S1.

Conclusions:

• Cortical sensory prostheses can rapidly enhance the representational scope of primary sensory areas.
• Novel sensory information can be integrated into existing neural processing streams with minimal disruption to native functions.
• The primary visual cortex (V1) is a viable target for sensory prostheses, capable of rapid learning and integration of new sensory modalities.