The goal of this project is to test critical aspects of the neural mechanisms thought to underlie perceptually- guided choices, with reference to the lateral intraparietal area (LIP) and its putative role in perceptual decision- making. A perceptual judgment is typically conceptualized as a covert process whereby sensory evidence is weighted for or against potential choice alternatives, governing the execution of an overt motor response. This dynamic process underlies all perceptually-guided behavior and involves a high level of coordination between sensory, motor, and cognitive (e.g. attentional, memory, and reward) systems. The neural basis of perceptually-guided behavior is typically studied using psychophysical tasks that afford the subject ample time to complete the formation of a perceptual judgment before reporting the outcome with a motor action. However, it is difficult, if not impossible to make accurate inferences about the dynamics of the decision- making process based on behavioral measurements taken only after the judgment has already concluded its development in time. To overcome this problem, the proposed study employs an ?urgent? decision-making paradigm, which allows for the temporal dynamics of a perceptual judgment to be inferred based on behavioral measures gathered throughout its evolution in time. The experiments are designed such that neuronal activity will be recorded from area LIP of non-human primates performing various urgent saccadic eye-movement tasks, in order to address two specific aims.
The first aim i s to elucidate the behavioral correlates of perceptual decision formation during performance of an urgent, dot-motion direction-discrimination task, as well as the corresponding neural correlates in area LIP. Preliminary results indicate that monkeys can accurately discriminate the direction of dot-motion within ~200 ms of stimulus onset, considerably sooner than previously thought. Do direction-sensitive signals in LIP develop early enough to inform such rapid, accurate choices? Thus far, the data show that they do not; i.e., under urgent conditions, motion-based signals in LIP develop too late to inform the subject's accurate behavioral discriminations.
The second aim i s to elucidate whether and how attentional context (i.e. top-down, bottom-up) influences the relationship between LIP activity and rapid visually-guided choice behavior. Overall, the findings tentatively suggest that, rather than a direct representation of sensory evidence integration (a widely held view), the activity in LIP may be better understood as an attentional signal that often correlates with, but is not a pre-requisite to accurate, visually- guided behavior. This investigation will help define the behavioral correlates and neural bases of rapid perceptual decision-making ? necessary steps toward improving the diagnosis, treatment, and understanding of many neurological conditions of contemporary societal concern (e.g., sensory neglect, ADHD, impulsivity).
Every voluntary movement we make represents the outcome of a decision about where to move next, and such decisions involve not only perceptual and motor systems, but also mechanisms of attention, memory, and reward. The neural mechanisms that give rise to a decision are extremely difficult to determine empirically, due to the natural rapidity by which simple decisions commonly unfold (voluntary saccadic eye movements are made, on average, 2-3 times per second). The proposed experiments will help define the behavioral correlates and neurophysiological bases of rapid perceptual decision formation ? necessary steps toward improving the diagnosis, treatment, and understanding of numerous neurological conditions of contemporary societal concern (e.g., sensory neglect, ADHD, impulsivity).
| Seideman, Joshua A; Stanford, Terrence R; Salinas, Emilio (2018) Saccade metrics reflect decision-making dynamics during urgent choices. Nat Commun 9:2907 |
