Infratemporal Cortex Calibrates for Contrast in the Perception of Novel Visual Information

Article: A new theory for what’s happening in the brain when something looks familiar
Source: University of Pennsylvania, via ScienceDaily  and NEI
Published: April 27, 2021

Visual information starts with the detection of incoming light at the retina's photoreceptors. The complex process is simplified here as then being relayed via the optic nerve to the visual cortex. The present research investigated the role of the intratemporal (IT) cortex in interpreting the complex patterns of visual information, specifically teasing apart the difference between the perception of novel and familiar patterns. According to an earlier theory known as repetition suppression, greater activation of the IT cortex meant that a person was viewing something new, while less activity in the IT cortex indicated familiarity. The researchers, however, note that different images produce different amounts of activity even when they are all novel, possibly influenced by factors such as brightness, contrast, and even memory. They instead propose a new theory called sensory reference suppression that suggests that the brain calibrates for the level of activation expected, correcting for these other factors and leaving behind the signal of familiarity. In particular, to explore the difference between memory and contrast, the researchers presented sequences of grayscale images to two adult rhesus monkeys and recorded the neural activity of their IT cortex, using a unique method that measures the spikes of hundreds of individual neurons. Using mathematical analysis, they found that both familiarity and contrast change the overall firing rate of neurons, and that the brain can tease apart one from the other. The researchers state that understanding how the brain builds memory in the presence of changes in sensory input could have implications for artificial intelligence and memory-impairing disorders such as Alzheimer's.

My rating of this study: ⭐⭐

Mehrpour V, Meyer T, Simoncelli EP, et al. "Pinpointing the neural signatures of single-exposure visual recognition memory." PNAS.  118(18):e2021660118. 4 May 2021. https://doi.org/10.1073/pnas.2021660118