Dec 17, 2022 12:23 AM
(This post was last modified: Dec 17, 2022 12:47 AM by C C.)
How the brain distinguishes memories from perceptions
https://www.quantamagazine.org/how-the-b...-20221214/
EXCERPTS: Memory and perception seem like entirely distinct experiences, and neuroscientists used to be confident that the brain produced them differently, too. But in the 1990s neuroimaging studies revealed that parts of the brain that were thought to be active only during sensory perception are also active during the recall of memories.
“It started to raise the question of whether a memory representation is actually different from a perceptual representation at all,” said Sam Ling, an associate professor of neuroscience and director of the Visual Neuroscience Lab at Boston University. Could our memory of a beautiful forest glade, for example, be just a re-creation of the neural activity that previously enabled us to see it?
“The argument has swung from being this debate over whether there’s even any involvement of sensory cortices to saying ‘Oh, wait a minute, is there any difference?’” said Christopher Baker, an investigator at the National Institute of Mental Health who runs the learning and plasticity unit. “The pendulum has swung from one side to the other, but it’s swung too far.”
Even if there is a very strong neurological similarity between memories and experiences, we know that they can’t be exactly the same. “People don’t get confused between them,” said Serra Favila, a postdoctoral scientist at Columbia University and the lead author of a recent Nature Communications study. Her team’s work has identified at least one of the ways in which memories and perceptions of images are assembled differently at the neurological level.
[...] As participants recalled the images, the receptive fields in the highest level of visual processing were the same size they had been during perception — but the receptive fields stayed that size down through all the other levels painting the mental image. The remembered image was a large, blurry blob at every stage.
This suggests that when the memory of the image was stored, only the highest-level representation of it was kept. When the memory was experienced again, all the areas of the visual cortex were activated — but their activity was based on the less precise version as an input.
[...] Perception and memory “are different; our experience of them is different, and pinning down exactly the ways in which they’re different will be important to understanding how memory is expressed,” Favila said. The differences were “lurking in the data the whole time.” (MORE - details)
Some claim culture affects our basic visual perception. A UCLA study takes a fresh look
https://newsroom.ucla.edu/releases/cultu...perception
RELEASE: Research claims made over recent years that people of East Asian and European descent perform differently on a well-known visual perception test as a result of fundamental cultural differences may be overstated, according to UCLA psychologists.
In new experiments conducted by the UCLA researchers, white, Asian American and recent Asian immigrant college students in the U.S. performed similarly on the test, known as the rod-and-frame task, which measures the influence of surrounding contextual visual information on perception.
The findings, published in PLOS One suggest that the basics of visual perception, such as object orientation, are largely independent of cultural variation and apply broadly across human populations.
What is the rod-and-frame task and what is the debate? The rod-and-frame task asks participants to view a single line within a square frame and to orient that line straight up and down vertically. The difficulty comes when the surrounding frame is tilted in various ways, which can influence viewers' perception of the vertical orientation of the line.
Historically, much of this type of research had been conducted in Western countries with college students as participants, raising questions about how accurate the data is for people in other cultures and parts of the world.
In some previous, highly publicized work produced since 2000, researchers exploring that question found that East Asians and Europeans performed differently on the rod-and-frame task; East Asians, the researchers said, tended to focus on the square frame first or give equal attention to the frame and the line, while Europeans placed more emphasis on the line.
These researchers hypothesized that cultural influences could be at the root of the differences, with participants from East Asian cultures, which social scientists say emphasize the embeddedness of individuals within collective groups, perceiving more holistically and taking context into consideration. Similarly, participants from Western cultures, which social scientists say tend to elevate individuals over groups, may perceive more analytically and independently of context. The claims bucked against a fundamental assumption in visual neuroscience research that basic visual functions are the same for humans everywhere, as well as for non-human primates.
"If culture influences even the most basic visual functions, then all studies must take into consideration the cultures of the participants and the fact that findings might not apply to other cultures," said Zili Liu, a UCLA psychology professor and the current study's corresponding author. "Perhaps more importantly, vision research with animals will have limited utility."
If these previous findings were true, Liu noted, it would stand to reason that people who have been immersed in another's culture for enough time will start to perform similarly to people raised in that culture on the rod-and-frame task.
"I thought UCLA was a good place to test this because we have many Asian American students, as well as more recent Asian immigrants to the U.S., and they should serve as supportive evidence that the longer people have lived here, the less the data would look like Asian nations," Liu said.
Reassessing the influence of culture on the rod-and-frame task. Chéla R Willey, a UCLA doctoral student at the time of the study who is now an assistant professor at Loyola Marymount University, recruited a diverse group of 342 UCLA students to perform the rod-and-frame task using virtual reality goggles. All participating students answered a questionnaire about their ethnicity and country of citizenship. In this first experiment, participants used a computer mouse to rotate the center line to make it vertical.
In a second experiment, 216 of the 342 students judged whether the line was clockwise or counter-clockwise with respect to the vertical.
Among the 84 East Asian participants who completed both experiments, 40 were second-generation Americans (born in the U.S. with at least one immigrant parent) or beyond and 44 were first generation or non-citizens. Among the white dual-experiment participants, nearly all -- 51 out of 57 -- were second-generation Americans or beyond, while six were first generation or non-citizens.
The results of the first experiment revealed that a participant's cultural background had little, if anything, to do with how they judged the line's vertical orientation inside both tilted and non-tilted frames. In the second experiment, the researchers once again found no significant difference between ethnicity or generation. They did, however, observe a well-known gender difference in which frame tilt affects the perception of women more than men.
"The gender finding replicates what has been found in many other studies, indicating that our data are of reasonable quality," Liu said. "Our failure to replicate the cultural effect therefore suggests that culture might not influence orientation perception that much."
The work lends support to research showing that some basic mechanisms of visual perception are universal and that for these kinds of studies, it might not matter much which population the researchers use.
https://www.quantamagazine.org/how-the-b...-20221214/
EXCERPTS: Memory and perception seem like entirely distinct experiences, and neuroscientists used to be confident that the brain produced them differently, too. But in the 1990s neuroimaging studies revealed that parts of the brain that were thought to be active only during sensory perception are also active during the recall of memories.
“It started to raise the question of whether a memory representation is actually different from a perceptual representation at all,” said Sam Ling, an associate professor of neuroscience and director of the Visual Neuroscience Lab at Boston University. Could our memory of a beautiful forest glade, for example, be just a re-creation of the neural activity that previously enabled us to see it?
“The argument has swung from being this debate over whether there’s even any involvement of sensory cortices to saying ‘Oh, wait a minute, is there any difference?’” said Christopher Baker, an investigator at the National Institute of Mental Health who runs the learning and plasticity unit. “The pendulum has swung from one side to the other, but it’s swung too far.”
Even if there is a very strong neurological similarity between memories and experiences, we know that they can’t be exactly the same. “People don’t get confused between them,” said Serra Favila, a postdoctoral scientist at Columbia University and the lead author of a recent Nature Communications study. Her team’s work has identified at least one of the ways in which memories and perceptions of images are assembled differently at the neurological level.
[...] As participants recalled the images, the receptive fields in the highest level of visual processing were the same size they had been during perception — but the receptive fields stayed that size down through all the other levels painting the mental image. The remembered image was a large, blurry blob at every stage.
This suggests that when the memory of the image was stored, only the highest-level representation of it was kept. When the memory was experienced again, all the areas of the visual cortex were activated — but their activity was based on the less precise version as an input.
[...] Perception and memory “are different; our experience of them is different, and pinning down exactly the ways in which they’re different will be important to understanding how memory is expressed,” Favila said. The differences were “lurking in the data the whole time.” (MORE - details)
Some claim culture affects our basic visual perception. A UCLA study takes a fresh look
https://newsroom.ucla.edu/releases/cultu...perception
RELEASE: Research claims made over recent years that people of East Asian and European descent perform differently on a well-known visual perception test as a result of fundamental cultural differences may be overstated, according to UCLA psychologists.
In new experiments conducted by the UCLA researchers, white, Asian American and recent Asian immigrant college students in the U.S. performed similarly on the test, known as the rod-and-frame task, which measures the influence of surrounding contextual visual information on perception.
The findings, published in PLOS One suggest that the basics of visual perception, such as object orientation, are largely independent of cultural variation and apply broadly across human populations.
What is the rod-and-frame task and what is the debate? The rod-and-frame task asks participants to view a single line within a square frame and to orient that line straight up and down vertically. The difficulty comes when the surrounding frame is tilted in various ways, which can influence viewers' perception of the vertical orientation of the line.
Historically, much of this type of research had been conducted in Western countries with college students as participants, raising questions about how accurate the data is for people in other cultures and parts of the world.
In some previous, highly publicized work produced since 2000, researchers exploring that question found that East Asians and Europeans performed differently on the rod-and-frame task; East Asians, the researchers said, tended to focus on the square frame first or give equal attention to the frame and the line, while Europeans placed more emphasis on the line.
These researchers hypothesized that cultural influences could be at the root of the differences, with participants from East Asian cultures, which social scientists say emphasize the embeddedness of individuals within collective groups, perceiving more holistically and taking context into consideration. Similarly, participants from Western cultures, which social scientists say tend to elevate individuals over groups, may perceive more analytically and independently of context. The claims bucked against a fundamental assumption in visual neuroscience research that basic visual functions are the same for humans everywhere, as well as for non-human primates.
"If culture influences even the most basic visual functions, then all studies must take into consideration the cultures of the participants and the fact that findings might not apply to other cultures," said Zili Liu, a UCLA psychology professor and the current study's corresponding author. "Perhaps more importantly, vision research with animals will have limited utility."
If these previous findings were true, Liu noted, it would stand to reason that people who have been immersed in another's culture for enough time will start to perform similarly to people raised in that culture on the rod-and-frame task.
"I thought UCLA was a good place to test this because we have many Asian American students, as well as more recent Asian immigrants to the U.S., and they should serve as supportive evidence that the longer people have lived here, the less the data would look like Asian nations," Liu said.
Reassessing the influence of culture on the rod-and-frame task. Chéla R Willey, a UCLA doctoral student at the time of the study who is now an assistant professor at Loyola Marymount University, recruited a diverse group of 342 UCLA students to perform the rod-and-frame task using virtual reality goggles. All participating students answered a questionnaire about their ethnicity and country of citizenship. In this first experiment, participants used a computer mouse to rotate the center line to make it vertical.
In a second experiment, 216 of the 342 students judged whether the line was clockwise or counter-clockwise with respect to the vertical.
Among the 84 East Asian participants who completed both experiments, 40 were second-generation Americans (born in the U.S. with at least one immigrant parent) or beyond and 44 were first generation or non-citizens. Among the white dual-experiment participants, nearly all -- 51 out of 57 -- were second-generation Americans or beyond, while six were first generation or non-citizens.
The results of the first experiment revealed that a participant's cultural background had little, if anything, to do with how they judged the line's vertical orientation inside both tilted and non-tilted frames. In the second experiment, the researchers once again found no significant difference between ethnicity or generation. They did, however, observe a well-known gender difference in which frame tilt affects the perception of women more than men.
"The gender finding replicates what has been found in many other studies, indicating that our data are of reasonable quality," Liu said. "Our failure to replicate the cultural effect therefore suggests that culture might not influence orientation perception that much."
The work lends support to research showing that some basic mechanisms of visual perception are universal and that for these kinds of studies, it might not matter much which population the researchers use.