Systems/Circuits Signal Multiplexing and Single-Neuron Computations in Lateral Intraparietal Area During Decision-Making

Previouswork has revealed a remarkably direct neural correlate of decisions in the lateral intraparietal area (LIP). Specifically, firing rate has been observed to ramp up or down in a manner resembling the accumulation of evidence for a perceptual decision reported by making a saccade into (or away from) the neuron’s response field (RF). However, this link between LIP response and decision formation emerged from studies where a saccadic target was always stimulating the RF during decisions, and where the neural correlate was the averaged activity of a restricted sample of neurons. Because LIP cells are (1) highly responsive to the presence of a visual stimulus in the RF, (2) heterogeneous, and (3) not clearly anatomically segregated from large numbers of neurons that fail selection criteria, the under-lying neuronal computations are potentially obscured. To address this, we recorded single neuron spiking activity in LIP during a well-studiedmoving-dotdirection–discrimination taskandmanipulatedwhether a saccade targetwaspresent in theRFduringdecision-making.Wealso recorded fromabroad sample of LIPneurons, including ones conventionally excluded inprior studies. Our results show that cells multiplex decision signals with decision-irrelevant visual signals. We also observed disparate, repeating response “motifs” across neurons that, when averaged together, resemble traditional ramping decision signals. In sum, neural responses in LIP simulta-neously carry decision signals and decision-irrelevant sensory signals while exhibiting diverse dynamics that reveal a broader range of neural computations than previously entertained