In the study, subjects were briefly shown two subsequent images of a grating, each image oriented at a different angle. They were then given a cue telling them which one to remember. To ensure that the memory was maintained, subjects were shown a third grating several seconds later and prompted to indicate how it was rotated compared with the remembered one. Throughout the whole process, an fMRI scanner monitored activity in four different early visual areas of the brain.
By analyzing the activity in those areas during the 11-second remembering period, the experimenters were able to determine, with more than 80 percent accuracy, which grating orientation the subject had in mind. To do so, they used a sophisticated analytical tool called a pattern classifier, calibrated for each individual subject by a number of training trials. Rather than simply measuring the overall level of activity, the pattern classifier could probe for patterns in how that activity was distributed across the brain.
The researchers also found that the brain-activity patterns linked to looking at a grating and remembering it bear a striking resemblance to each other. It still remains to be seen how the activity patterns detected by fMRI, which essentially measures blood flow in the brain, translate into actual neural signals, says Haynes. Because it measures information in chunks of three cubic millimeters, fMRI can't gather information about what individual neurons are doing.
The ability to reconstruct from scratch a complex memory or imagined scenario is a long way off.
Stephenie Harrison,Frank Tong
Vanderbilt University Research
By analyzing the activity in those areas during the 11-second remembering period, the experimenters were able to determine, with more than 80 percent accuracy, which grating orientation the subject had in mind. To do so, they used a sophisticated analytical tool called a pattern classifier, calibrated for each individual subject by a number of training trials. Rather than simply measuring the overall level of activity, the pattern classifier could probe for patterns in how that activity was distributed across the brain.
The researchers also found that the brain-activity patterns linked to looking at a grating and remembering it bear a striking resemblance to each other. It still remains to be seen how the activity patterns detected by fMRI, which essentially measures blood flow in the brain, translate into actual neural signals, says Haynes. Because it measures information in chunks of three cubic millimeters, fMRI can't gather information about what individual neurons are doing.
The ability to reconstruct from scratch a complex memory or imagined scenario is a long way off.
Stephenie Harrison,Frank Tong
Vanderbilt University Research
Comments
Post a Comment