Source: brainnews (ID: brainnews)
Humans can visually distinguish thousands of different colors and shapes. How does the brain process these visual information?Scientists used to think that the visual system first encodes colors and shapes separately through different neurons, and then combines them later.
But a new study published by the Salk Institute on June 27, 2019 in Science shows thatSome neurons can produce selective responses to specific combinations of color shapes.This poses a challenge to existing ideas.
Similar to digital camera sensors, light-sensitive cells (photoreceptors) in the eye detect wavelength information of light in a specific range and location, and then transmit to the cortical visual center through the optic nerve to translate and unlock the content of the image.
Previously, researchers thought that color and shape information were extracted separately and only in the highest level of the brain.And the new results of the Salk Institute show that this combination appears earlier.
From left to right, Dr. Lee, Professor Edward Callaway, Dr. Anupam Garg from Salk Institute
Professor Edward Callaway of the System Neurobiology Laboratory at the Salk Institute mentioned: “The new genetic sensors and imaging technologies allow us to more intuitively test the connection between the visual pathways of color and shape. These test results are in the brain. The question of how the visual pathways are connected and combined provides valuable clues. ”
The first author of the study, Dr. Anupam Garg of the University of California, San Diego, said that their research aims to better understand how the visual system handles the color and shape of visual stimuli and wants to solve these long-standing problems with new imaging techniques. Visual processing problems.
Visual response of single neurons in primate primary visual cortex
Researchers combine imaging technology with sensors for gene expressionThe function of thousands of individual neurons involved in processing color and shape information in the primary visual cortex center was studied. During the long recording process, approximately 500 possible combinations of color shapes were tested to find the stimulus that best activates each visual response neuron.
The team found that visual neurons respond selectively to color and shape, some neurons are only activated by specific colors or shapes, while others react to specific colors and shapes at the same time.This discovery is contrary to the long-standing concept of visual information processing..
The researchers used stable GCaMP6f expression and two-photon calcium imaging to detect large spatial and color visual stimulation spaces and map thousands of neuronal single-cell resolution functional microstructures.
Compared with achromatic stimuli, primary visual cortical neurons are more sensitive to iso-optic color stimuli and have directional selectivity at the same time.This indicates that there is overlap between the direction and color pathways in the primary visual cortex..
A single neuron can accurately and clearly encode shapes and colors.Behind this is the complex systemic relationship between color tuning, directional selection, and cytochrome oxidase histology.
Dr. Lee, the first author of the Callaway Lab, believes that the human brain efficiently encodes visual information through precisely designed pathways. Not in the classroom, color and shape information are separated from the early stages of the visual cortex and then passed through unknown mechanisms. Integration, but a combination of a systematic path to coding.
For the past 20 years, Professor Callaway has been working to understand how the visual system handles color information. The research is a great encouragement. He said: “This finding lays the foundation for understanding how the neural circuit calculates color vision, and we expect to determine how neurons in the visual cortex work together to extract color and shape information.”
Anupam K, Garg, Peichao Li, etal. Color and orientation are jointly coded and spatially organized in primate primary visual cortex [J]. Science, 2019, 364 (6447): 1275-1279.author informationCompiled: Juno (brainnews creative team)
School review: Simon (brainnews editorial department)