The dorsomedial frontal cortex (DMFC): a cortical area involved in attentive fixation.

The activity of dorsomedial frontal cortex has been studied in two macaca monkeys. The animals were trained for saccade and fixation task. We recorded many cells that discharged after saccades and continued for the entire period of fixation. These are fixation and not position units since the neurons are silent during relaxed scanning for the same positions. Each of these cells were tested by classic visual stimuli and by complex and motivational stimuli. None of the cells presented a visual receptive field. These neurons presented different fixation field prevalently contralateral, non only excitatory but also inhibitory. The electrical stimulation of the fixation cells evoked eye movements directed toward the fixation field. We propose that these fields are attentional motor fields because they are not expression of a motor code and the visual afferences are not directly involved. This hypothesis is corroborated by studies of cortical lesions: humans with a frontal lesion cannot avoid making saccades to a stimulus when il appears.