Neuronal networks in the prefrontal cortex related to working memory processes for multiple bits of information.

点击翻译按钮获取中文摘要

Working memory has been considered as a temporary storage mechanism of information. Since working memory is a basic mechanism for higher cognitive functions such as thinking, it can be considered as not only a storage mechanism but also a dynamic system for processing information. To understand neuronal mechanisms for higher cognitive functions, we need to know the mechanisms for processing and integrating information. We have been analyzed singleneuron activity in the prefrontal cortex while monkeys performed working memory tasks, and found that many neurons exhibited delay-period activity. Since this activity lasted tonically during the delay period and showed preferences depending upon stored spatial information, we concluded that neurons having this activity have spatial memory fields (MF) in the visual field. To understand how to integrate multiple spatial positions in these neurons, we tested an effect on delay-period activity by visual cues presented outside the neuron's MF.We first determined the neuron's MF using a conventional oculomotor delayd-response (ODR) task, then analyzed delay-period activity using a s-ODR task, in which two visual cues were presented sequentially at different positions, one of which was always within the neuron's MF.Locations of MF were determined in 39 neurons. In 11, delay-period activity was observed whenever visual cues were presented within MF.However, in 28, delay-period activity was enhanced or diminished if either the first or the second cue was presented outside MF.These results indicate that delay-period activity is affected by visual cues presented outside MF immediately before or after the cue presentation within MF,suggesting that a prefrontal neuron with MF receives excitatory or inhibitory input from neurons that have MF adjacent to it.