Autonomous Encoding of Irrelevant Goals and Outcomes by Prefrontal Cortex Neurons

Abstract

Two rhesus monkeys performed a distance discrimination task in which they reported whether a red square or a blue circle had appeared farther from a fixed reference point. Because a new pair of distances was chosen randomly on each trial, and because the monkeys had no opportunity to correct errors, no information from the previous trial was relevant to a current one. Nevertheless, many prefrontal cortex neurons encoded the outcome of the previous trial on current trials. A smaller, intermingled population of cells encoded the spatial goal on the previous trial or the features of the chosen stimuli, such as color or shape. The coding of previous outcomes and goals began at various times during a current trial, and it was selective in that prefrontal cells did not encode other information from the previous trial. The monitoring of previous goals and outcomes often contributes to problem solving, and it can support exploratory behavior. The present results show that such monitoring occurs autonomously and selectively, even when irrelevant to the task at hand.

Cortical neural responses to previous trial outcome during learning of a directional choice task

“…However, we found that only a small number of recorded units (6.3%, 12 out of all 192 neurons; 7.8%, 8 out of 103 AGl neurons; 4.5%, 4 out of 89 AGm neurons) were modulated by the previous choice factor. In the Genovesio et al (2014) study, the percentage of primate PFC neurons showing a significant effect of the previous choice decreased to a chance level soon after trial start. However, they observed much higher percentage of neurons with effect of the previous outcome factor.…”

“…Significant evidence from primate and rodent studies indicated a widespread neural modulation in response to previous outcome during learning. Trial outcome as a transient event was shown clearly encoded in single unit activity in PFC (Narayanan and Laubach 2008;Histed et al 2009;Genovesio et al 2014), anterior cingulate cortex (Seo and Lee 2007;Quilodran et al 2008), striatum (Histed et al 2009), andhippocampus (Wirth et al 2009). The signal was sustained in the intertrial interval and carried over to the next trial, which may have contributed to linking past outcomes with future actions (Donahue et al 2013).…”

“…Recent studies (Narayanan and Laubach 2008;Histed et al 2009;Genovesio et al 2014) reported persistent firing rate modulation by previous trial outcome even into a new trial. While their observations were in prefrontal areas, published results reviewed above also point to AGm and AGl as candidates for encoding the outcome of previous trials and suggest that this information plays a role in improving performance during learning.…”

Neuronal Reward and Decision Signals: From Theories to Data

“…Reward responses are found also in premotor, prefrontal, cingulate, insular, and perirhinal cortex (8,246,369,569). Some prefrontal neurons code the reward of the preceding trial (30,179).…”

The influence of recent decisions on future goal selection

“…More recently, we studied [76] previous goal representation in the PFd and periarcuate cortex (PA) in a distance discrimination task (figure 4a), in which the task of the monkey did not require previous trial monitoring and the monkeys were not trained in other tasks that required it. In this task, the monkeys were instructed to determine which of two stimuli, presented sequentially at different distances from the screen centre, was the farthest away.…”