27th May 2021
Repeated rewarding objects are processed in the visual cortex with greater weight.
By Fred Schwaller
There is a concept in psychology called the Baader-Meinhof phenomenon, also known as the frequency illusion, where once you purchase a new car you start seeing it everywhere. The idea is that there is an attentional ‘awakening’ to the object that now holds value to you.
A new study suggests that this attentional awakening occurs early in the visual processing stream in the primary visual cortex (V1), an area of the brain that receives sensory input from the optic nerve via the thalamus. The study, published in Current Biology in April 2020, found that neuronal representation of a repeated visual stimulus is enhanced in V1, but only when it is associated with a reward.
The idea behind the study came from research showing that when sensory information comes into the brain, it is not a simple real-time representation of the sensory environment. Instead, information is modified by previous experiences so that important visual stimuli are prioritized in the visual cortex to become more salient.
The authors began by investigating how repeatedly showing the same visual stimulus to a mouse affected its neuronal representation in V1. To do this, they presented mice with the same stimulus over consecutive days in a virtual reality environment using the Phenosys Virtual Reality system, and trained the mice to link the stimulus with a water reward.
Over time, they found that the neuronal representation of the repeated stimulus was enhanced in V1, as measured by in vivo two-photon Ca2+ imaging of V1 neurons in awake mice. Importantly, this increased neuronal representation only occurred when the stimulus was paired with a water reward. If there was no reward associated with a stimulus, repeated exposure to the stimulus did not change its representation in V1.
In a second set of experiments, the authors showed that when a second visual stimulus was paired with a water reward, this also had enhanced representation in V1 but in a separate population of neurons from those that represented the first stimulus.
“The first time I saw these robust reward signals in V1, I was really surprised,” co-lead author Janelle Pakan said. “but this shows the fundamental principle of integration across multiple brain regions. Interestingly this is happening in the visual processing stream earlier than we thought.”
Overall, these findings show that visual stimuli are continuously processed in relation to their behavioral relevance, where more rewarding stimuli are represented with greater weight in the visual cortex. This supports the view that visual stimuli are continuously and dynamically regulated in the visual cortex, where newly rewarding stimuli can be rapidly prioritized in a matter of days.
So unfortunately you didn’t set a new trend by buying that car; more likely it became a salient image in your brain where once it was part of the noise.