Although earlier studies in monkeys had suggested that such a decision-making hub exists, its location in the human brain was not previously known.
The researchers took advantage of the fact that it takes the brain longer to figure out what it's looking at when an image is very blurred or obscured like trying to recognize people standing on a street corner in a downpour versus on a clear day. Hard to discern images evoke a relatively slower and reduced response in the decision-making area, as it mulls the strength of competing signals from specialized visual processing areas, where neurons fire only to the extent that they see certain objects or features, the monkey studies showed. While their brain activity was monitored with functional magnetic resonance imaging (fMRI), twelve healthy subjects pressed buttons to indicate whether they saw a face or a house, as images flashed on a computer monitor. Some of the images were so noisy that they were barely discernable, reducing accuracy from 95 percent to 82 percent.
The researchers looked for a site in the brain's frontal cortex showing the telltale reduced activity during hard trials that coincided with activity in temporal lobe visual processing circuits that they had determined are specialized for responding to faces and houses, respectively. An area in the left front of the brain (dorsolateral prefrontal cortex) responded with more activity when images were easier to identify than when they were hard to discern. These respon
Contact: Jules Asher
NIH/National Institute of Mental Health