Our brains tend to ignore even the most obvious things in our environment if they are irrelevant to our immediate goals. Hungarian researchers, in collaboration with their American colleagues, have published a study in the journal Nature Communications on how the brain filters out distracting stimuli and switches based on what it perceives as distracting or useful.
The 'invisible gorilla' experiment became famous back in the 1990s. Participants were shown a video and asked to count the number of passes made by people wearing white T-shirts. In the middle of the video, a man in a gorilla suit suddenly appears and walks through the group. Although the gorilla is quite conspicuous, most viewers did not notice him, nor did they see anyone pass through.
This phenomenon is known as inattentional blindness, which arises because the nervous system must select relevant features from a multitude of stimuli while filtering out distracting ones. It is akin to having a desk to work on, where we only place items that are relevant to us. Our brains create a similar 'workspace' when observing our environment. However, what is considered relevant can change from task to task. For example, what would happen if participants were instructed to observe the number of gorillas passing through the room in the aforementioned video? How does the nervous system manage changes in relevance? This is what Gergő Orbán's research group at the HUN-REN Wigner Research Centre for Physics investigated through mouse experiments, in close collaboration with Peyman Golshani's laboratory at the University of California, Los Angeles. The results of the experiment were published in Nature Communications, with Márton Hajnal as the lead author.
The research revealed that while information about relevant and irrelevant features is accessible 'intact' within the visual system, a network of neurons in a higher-level area responsible for selecting behavioural strategies, known as the anterior cingulate cortex (ACC), can suppress a stimulus depending on its relevance to the given situation.
HUN-REN researchers, in collaboration with their partners from California, analysed the neural activity of mice. The animals performed a task that required them to make decisions based on either auditory or visual information, meaning that the relevance of the incoming information changed throughout the experiment.
The analysis revealed that within the network of neurons, the 'workspace' represents a subspace where different modalities of information (auditory or visual) are represented by the same cells but independently of each other. This solution, known as multiplexing, creates a unique 'workspace': looking at it from one direction allows us to identify visual information from the environment, while from another perspective, auditory information becomes apparent.
At the same time, by training an artificial neural network, it was demonstrated that when the brain needs to find the correct solution among data of changing relevance, it can filter out unnecessary information and obscure distracting visuals—essentially suppressing irrelevant inputs. This specific function was identified in the ACC, a specialised region of the brain, providing insights that extend beyond the decision-making processes of mice. Due to the similarities between human and rodent brains, this also enhances our understanding of how we filter out truly important information amidst numerous distractions.
The ACC thus appears to function as a 'workspace,' and it doesn’t matter if a gorilla is occasionally doing yoga there; if our focus is solely on the unpaid bills lying around, the monkey has no chance of receiving attention, remaining unnoticed despite its best efforts.