Posts tagged temporal cortex
Articles and news from the latest research reports.
A novel look at how stories may change the brain
Many people can recall reading at least one cherished story that they say changed their life. Now researchers at Emory University have detected what may be biological traces related to this feeling: Actual changes in the brain that linger, at least for a few days, after reading a novel.
Their findings, that reading a novel may cause changes in resting-state connectivity of the brain that persist, were published by the journal Brain Connectivity.
“Stories shape our lives and in some cases help define a person,” says neuroscientist Gregory Berns, lead author of the study and the director of Emory’s Center for Neuropolicy. “We want to understand how stories get into your brain, and what they do to it.”
His co-authors included Kristina Blaine and Brandon Pye from the Center for Neuropolicy, and Michael Prietula, professor of information systems and operations management at Emory’s Goizueta Business School.
Neurobiological research using functional magnetic resonance imaging (fMRI) has begun to identify brain networks associated with reading stories. Most previous studies have focused on the cognitive processes involved in short stories, while subjects are actually reading them as they are in the fMRI scanner.
The Emory study focused on the lingering neural effects of reading a narrative. Twenty-one Emory undergraduates participated in the experiment, which was conducted over 19 consecutive days.
All of the study subjects read the same novel, “Pompeii,” a 2003 thriller by Robert Harris that is based on the real-life eruption of Mount Vesuvius in ancient Italy. “The story follows a protagonist, who is outside the city of Pompeii and notices steam and strange things happening around the volcano,” Berns says. “He tries to get back to Pompeii in time to save the woman he loves. Meanwhile, the volcano continues to bubble and nobody in the city recognizes the signs.”
The researchers chose the book due to its page-turning plot. “It depicts true events in a fictional and dramatic way,” Berns says. “It was important to us that the book had a strong narrative line.”
For the first five days, the participants came in each morning for a base-line fMRI scan of their brains in a resting state. Then they were given nine sections of the novel, about 30 pages each, over a nine-day period. They were asked to read the assigned section in the evening, and come in the following morning. After taking a quiz to ensure they had finished the assigned reading, the participants underwent an fMRI scan of their brain in a non-reading, resting state. After completing all nine sections of the novel, the participants returned for five more mornings to undergo additional scans in a resting state.
The results showed heightened connectivity in the left temporal cortex, an area of the brain associated with receptivity for language, on the mornings following the reading assignments. “Even though the participants were not actually reading the novel while they were in the scanner, they retained this heightened connectivity,” Berns says. “We call that a ‘shadow activity,’ almost like a muscle memory.”
Heightened connectivity was also seen in the central sulcus of the brain, the primary sensory motor region of the brain. Neurons of this region have been associated with making representations of sensation for the body, a phenomenon known as grounded cognition. Just thinking about running, for instance, can activate the neurons associated with the physical act of running.
“The neural changes that we found associated with physical sensation and movement systems suggest that reading a novel can transport you into the body of the protagonist,” Berns says. “We already knew that good stories can put you in someone else’s shoes in a figurative sense. Now we’re seeing that something may also be happening biologically.”
The neural changes were not just immediate reactions, Berns says, since they persisted the morning after the readings, and for the five days after the participants completed the novel.
“It remains an open question how long these neural changes might last,” Berns says. “But the fact that we’re detecting them over a few days for a randomly assigned novel suggests that your favorite novels could certainly have a bigger and longer-lasting effect on the biology of your brain.”
The brain processes complex stimuli more cumulatively than we thought
A new study reveals that the representation of complex features in the brain may begin earlier—and play out in a more cumulative manner—than previously thought.
The finding represents a new view of how the brain creates internal representations of the visual world. “We are excited to see if this novel view will dominate the wider consensus” said senior author Dr. Miyashita, who is also Professor of Physiology at the University of Tokyo’s School of Medicine, “and also about the potential impact of our new computational principle on a wide range of views on human cognitive abilities.”
The brain recalls the patterns and objects we observe by developing distinct neuronal representations that go along with them (this is the same way it recalls memories). Scientists have long hypothesized that these neuronal representations emerge in a hierarchical process limited to the same cortical region in which the representations are first processed.
Because the brain perceives and recognizes the external world through these internal images, any new information about the process by which this takes place has the power to inform our understanding of related functions, including knowledge acquisition and memory.
However, studies attempting to uncover the functional hierarchy involved in the cortical process of visual stimuli have tried to characterize this hierarchy by analyzing the activity of single nerve cells, which are not necessarily correlated with neurons nearby, thus leaving these analyses lacking.
In a new study appearing in the 12 July issue of the journal Science, lead author Toshiyuki Hirabayashi and colleagues focus not on single neurons but instead on the relationship between neuron pairs, testing the possibility that the representation of an object in a single brain region emerges in a hierarchically lower brain area.
"I became interested in this work," said Dr. Hirabayashi, "because I was impressed by the elaborate neuronal circuitry in the early visual system, which is well-studied, and I wanted to explore the circuitry underlying higher-order visual processing, which is not yet fully understood."
Hirabayashi and colleagues analyzed nerve cell pairs in cortical areas TE and 36, the latter of which is hierarchically higher, in two adult macaques. After these animals looked at six sets of paired stimuli for several months to learn to associate related objects (a process that can lead to pair-coding neurons in the brain), the researchers recorded neuron responses in areas TE and 36 of both animals as they again performed this task.
The neurons exhibited pair association, but not where the researchers would have thought. “The most surprising result,” said senior author Dr. Yasushi Miyashita “was that the neuronal circuit that generated pair-association was found only in area TE, not in area 36.” Indeed, based on previous studies, which indicated that the number of pair-coding neurons in area TE is much smaller, the researchers would have expected the opposite.
During their study, Miyashita and other team members observed that in region TE of the macaque cortex, unit 1 neurons (or source neurons) provided input to unit 2 neurons (or target neurons), which—unlike unit 1 neurons—responded to both members of a stimulus pair.
"The representations generated in area TE did not reflect a mere random fluctuation of response patterns," explained Dr. Miyashita, "but rather, they emerged as a result of circuit processing inherent to that area of the brain."
In area 36, meanwhile, members of neuron pairs behaved differently; on average, unit 1 as well as unit 2 neurons responded to both members of a stimulus pair. Neurons in area 36 received input from area TE, but only from its unit 2 neurons.
Taken together, these findings lead the authors to hypothesize the existence of a hierarchical relationship between regions TE and 36, in which paired associations first established in the former region are propagated to the latter one. Here, area 36 represents the next level of a so-called feed forward hierarchy.
The work by Hirabayashi and colleagues suggests that the detailed representations of objects commonly observed in the brain are attained not by buildup of representations in a single area, but by emergence of these representations in a hierarchically prior area and their subsequent transfer to the brain region that follows. There, they become sufficiently prevalent for the brain to register. The work also reveals that the brain activity involved in recreating visual stimuli emerges in a hierarchically lower brain area than previously thought.
Moving forward, the Japanese research team has plans to expand upon this research, thus continuing to contribute to studies worldwide that aim to give scientists the best possible tools with which to obtain a dynamic picture of the brain. As a next step, the team hopes to further elucidate interactions between the various cortical microcircuits that operate in memory encoding. Dr. Miyashita has conjectured that these microcircuits are manipulated by a global brain network. Using the results of this latest study, he and colleagues are poised to further evaluate this assumption.
"It will also be important to weave the neuronal circuit mechanisms into a unified framework," said Dr. Hirabayashi," and to examine the effects of learning on these circuit organizations."
Equipped with their new view of cortical processing, the team also hopes to trace the causal chain of memory retrieval across different areas of the cortex. “I am excited by the recent development of genetic tools that will allow us to do this,” said Dr. Miyashita. A better understanding of object representations from one area of the brain to the next will shed even greater light on elusive aspects of this hierarchical organ.
(Source: eurekalert.org)