The Fast Lane Hypothesis: Von Economo Neurons Implement a Biological Speed-Accuracy Tradeoff

Von Economo neurons (VENs) are large bipolar projection neurons found exclusively in the anteriorcingulate cortex (ACC) and frontal insula of species with complex social cognition, including humans, great apes,and cetaceans. Their selective depletion in frontotemporal dementia (FTD) and altered development in autismimplicate them in rapid social decision-making, yet no computational model of VEN function has previously existed.We introduce the Fast Lane Hypothesis: VENs implement a biological speed-accuracy tradeoff (SAT) by providing asparse, fast projection pathway that enables rapid social decisions at the cost of deliberate processing accuracy. Wemodel VENs as fast leaky integrate-and-fire (LIF) neurons with membrane time constant 5ms and sparse dendriticfan-in of eight afferents, compared to 20ms and eighty afferents for standard pyramidal neurons, within a spikingcortical circuit of Npyr = 2,000 neurons trained on a social discrimination task. Networks are evaluated under threeclinically motivated conditions across 10 independent random seeds: typical (2% VENs), autism-like (0.4% VENs),and FTD-like (post-training VEN ablation). All configurations achieve equivalent asymptotic classification accuracy(∼99.4%), consistent with the prediction that VENs modulate decision speed rather than representational capacity.Temporal analysis confirms that VENs produce median first-spike latencies 4ms earlier than pyramidal neurons,providing direct evidence of a fast signalling pathway. At a fixed decision threshold of θ = 3, the typical condition issignificantly faster than FTD-like (t = −23.31, p < 0.0001), while the autism-like condition is intermediate (meanRT =26.91±9.01ms vs. typical 20.70 ±2.02ms; p = 0.078). A preliminary evolutionary analysis shows qualitativecorrespondence between model-optimal VEN fraction and the primate phylogenetic gradient. To our knowledge,this is the first computational model that asks what a Von Economo neuron actually computes