前頭前野における行動のゴール表現とゴール変換

Representation and transformation of behavioral goals in the monkey prefrontal cortex

背外側前頭前野が，ゴール指向的な行動調節にどのように関わるかを明らかにする目的で，筆者らは，サルが，ゴールに到達するのにマルチステップのカーソルの動きが必要になる課題で，前頭前野から細胞活動を記録した。ほとんどの前頭前野細胞は，運動直前にも関わらず手の運動を反映するものはなく，最終ゴールや第一手のカーソル移動の即時ゴールを表現していた。さらに，最終ゴールと即時のゴールの同時に表現する細胞も見出された。したがって，前頭前野は，感覚情報から運動情報への変換過程に関わるというよりも，ゴールからサブゴールの情報生成に関わることが明らかになった。

We examined neuronal activity in the lateral prefrontal cortex of monkeys performing a path-planning task in a maze that required the planning of actions in multiple steps. The animals received an instruction that prompted them to prepare to move a cursor in the maze stepwise from a starting position to a goal position by operating manipulanda with either arm. During a delay period in which the animal prepared to start the first of three cursor movements to approach the pre-instructed goal, we identified two types of neuronal activity：the first type reflected the position within the maze to which the animal intended to move the cursor as an initial step（an immediate goal）, and the second type reflected the position within the maze that was to be captured as a final goal. None of goal-related PFC neurons tested revealed apparent relation to eye positions or movements and that final goal-selective activity coded the location of the goal in a spatial reference frame defined in the maze, rather than in a retinocentric reference frame. Neither type of neuronal activity reflected motor responses. We propose that these two types of neuronal activity are neuronal correlates that represent immediate and final behavioral goals. This finding implicates the prefrontal cortex in representation of behavioral goals and goal-subgoal transformation rather than sensorimotor transformation.