Role of Lateral Inhibition on Visual Number Sense

Lateral inhibition is a basic principle of information processing and widely exists in the human and animal nervous systems. Lateral inhibition is also involved in processing visual information because it travels through the retina, primary visual cortex, and visual nervous system. This finding suggests that lateral inhibition is associated with visual number sense in humans and animals. Here, we show a number-sensing neural network model based on lateral inhibition. The model can reproduce the size and distance effects of the output response of human and animal number-sensing neurons when the network connection weights are set randomly without adjustment. The number sense of the model disappears when lateral inhibition is removed. Our study shows that the first effect of lateral inhibition is to strengthen the linear correlation between the total response intensity of the input layer and the number of objects. The second one is to allow the output cells to prefer different numbers. Results indicate that lateral inhibition plays an indispensable role in untrained spontaneous number sense.

Increasing entropy reduces perceived numerosity throughout the lifespan

Illusions that arise from systematic bias in perceiving numerosity serve as a powerful window into the mechanisms supporting our visual number sense. Recent research has shown that similarly oriented elements appear more numerous than randomly oriented elements in an array. However, this coherence illusion is not predicted by dominant models of numerosity perception. Here we examine whether the orientation coherence illusion is a more general byproduct of the effect of entropy on numerical information processing. Participants engaged in an ordinal numerical comparison task where the color entropy of arrays was manipulated. We found that homogenously colored arrays were perceived as more numerous than entropic colored arrays (Experiments 1 and 2), suggesting that the coherence illusion on numerosity perception is not specific to a particular visual property (e.g., orientation) but instead that the entropy of visual arrays more generally affects numerical processing. In Experiment 3, we explored the developmental trajectory of the color entropy effect in children aged 5 to 17 and found that the strength of the coherence illusion increases into adulthood, raising intriguing questions as to how perceptual experiences influence the progression of this numerosity illusion. We consider a recently proposed resource-rational model as a framework for understanding the entropy effect on numerosity perception under an information-theoretic perspective.

Visual number sense in untrained deep neural networks

Number sense, the ability to estimate numerosity, is observed in naïve animals, but how this cognitive function emerges in the brain remains unclear. Here, using an artificial deep neural network that models the ventral visual stream of the brain, we show that number-selective neurons can arise spontaneously, even in the complete absence of learning. We also show that the responses of these neurons can induce the abstract number sense, the ability to discriminate numerosity independent of low-level visual cues. We found number tuning in a randomly initialized network originating from a combination of monotonically decreasing and increasing neuronal activities, which emerges spontaneously from the statistical properties of bottom-up projections. We confirmed that the responses of these number-selective neurons show the single- and multineuron characteristics observed in the brain and enable the network to perform number comparison tasks. These findings provide insight into the origin of innate cognitive functions.

Influence of Alcohol and Cognitive Capacity on Visual Number Judgements

We used an enumeration task to address the question of whether acute alcohol intoxication reduces cognitive or perceptual capacity. To control for individual differences in cognitive resources, we took a sober record of each participant’s working memory capacity (WMC). Alcohol was expected to impair enumeration performance, either for the automatic parallel counting of small stimulus sets indicating a perceptual impairment, or the controlled counting or estimating of larger sets indicating a cognitive impairment. Enumeration showed an overall decline in accuracy following a vodka beverage and the deficit was negligible for small sets, which is inconsistent with a loss of perceptual capacity. Having a higher WMC facilitated the enumeration of larger sets and the correlation between WMC and accuracy was stronger in the alcohol condition suggesting that low-WMC participants were more impaired by the beverage. Our findings therefore suggest that alcohol diminished cognitive rather than perceptual capacity.

Tactile to visual number priming in the left intraparietal cortex of sighted Braille readers

Numbers can be presented in different notations and sensory modalities. It is currently debated to what extent these formats overlap onto a single representation. We asked whether such an overlap exists between symbolic numbers represented in two sensory modalities: Arabic digits and Braille numbers. A unique group of sighted Braille readers underwent extensive Braille reading training and was tested in an fMRI repetition-suppression paradigm with tactile Braille digit primes and visual Arabic digit targets. Our results reveal cross-modal priming: compared to repetition of two different quantities (e.g., Braille “5” and Arabic “2”), repetition of the same quantity presented in two modalities (e.g., Braille “5” and Arabic “5”) led to a reduction of activation in several sub-regions of the Intraparietal Sulcus (IPS), a key cortical region for magnitude processing. Thus, in sighted Braille readers, the representations of numbers read by sight and by touch overlap to a degree sufficient to cause repetition suppression. This effect was modulated by the numerical prime-probe distance. Altogether this indicates that the left parietal cortex hosts neural assemblies that are sensitive to numerical information from different notations (number words or Arabic digits) and modalities (tactile and visual).