Visual cortex location testing is a popular way to identify brain regions involved in visual perception and can be useful when comparing two different visual stimuli or when detecting an effect on one of the subjects visual field.
But the way in which it is used can be problematic when it comes to how the brain responds to different visual information.
To test this, scientists at the University of California, Berkeley used the visual field to record neural activity from the eyes of a rat and compared the activity with visual cortex locations.
As expected, visual cortex areas involved in seeing color were activated by color and a more pronounced effect of light was observed in areas involved with visual encoding.
The findings were published in the journal Neuron.
However, the researchers note that their work doesn’t necessarily mean that visual cortex activity is localized in specific areas.
Rather, the results suggest that the activity might be linked to a region called the visual system, which is also responsible for some of the cognitive processes in humans and other animals.
“We are not suggesting that visual cortical activity in visual regions is specific to visual processing, but rather that visual processing may be an important part of visual cortex function,” the researchers wrote in their paper.
“There is a lot of speculation about the nature of visual cortical regions, but we show that visual cognition may be closely related to visual cortex.”
The researchers note the fact that visual areas in the rat brain are involved in encoding and processing visual information and that this is a process that has been associated with changes in visual function in other animals as well.
“The finding of a neural signature of visual encoding may provide an opportunity to probe the neural substrates underlying these processes in different species,” they wrote.
“In this regard, we hypothesize that visual encoding is a function of the neural circuitry in the visual areas involved.”
Brain scans also showed that some of these areas in particular, the dorsolateral prefrontal cortex, were more active in response to color when the rat was presented with a series of different colors.
“As this is not a typical situation for visual encoding, we cannot rule out that the specific activation patterns seen in the brain of color-blind rats might reflect a different neural signature than those seen in humans, such as the color-sensitive visual cortex,” the scientists wrote.
For their work, the team used an image-recognition task.
The researchers recorded the rat’s eye movements while the rat watched a series in a sequence, including three color images presented in sequence.
The visual cortex of the rats was stimulated by each of the three colors as it was being viewed.
When the rat moved its eyes to a different location, the neural activity of these regions was also recorded.
After the rat viewed the color images for a brief time, the brain activity was recorded again, as if the rat had just viewed the same color as before.
This process was repeated until the rat could no longer move its eyes without seeing a new color.
To check if the neural signal was related to any visual processing the researchers used functional magnetic resonance imaging (fMRI).
They then measured the activity of the visual cortices in the rats brains, which were also stimulated by the same sequence of color images.
The activity of areas that encode colors was correlated with the activity in areas that process visual information, indicating that the neural responses to color in the dorsomedial prefrontal cortex are associated with visual processing.
“Our results suggest the existence of a visual cortex-related signal in humans that may serve as a marker for visual processing,” the authors wrote.
When asked about their results, the authors noted that this was a preliminary finding and further research would be necessary to establish the relationship between the activity seen in specific regions and visual cortex functioning.
However this research is promising and opens the door to future studies that will allow researchers to map specific areas of the brain to identify and map brain activity related to different tasks.
“Visual cortex regions are involved with many cognitive processes that are related to spatial processing,” they concluded.
“These regions may be associated with spatial processing and visual memory.
Future work will investigate whether visual cortex regions contribute to these processes.”