Neuronal Activity in Area 7

Abstract

In the 1960’s the posterior parietal cortex was considered as a somatic associative area. This opinion was based on what was known of anatomical connections, ablation studies and recordings from area 5. However, when cellular recordings from area 7 of behaving monkeys were first started in Helsinki in 1970, we found to our surprise that many neurones were activated by visual stimuli. The preliminary findings were described by Hyvärinen and Poranen (1974) as follows: “Cutaneous activation from the contralateral side of the face was an effective stimulus for some area 7 cells, but they sometimes discharged action potentials before their peripheral receptive fields had been touched. This ‘anticipatory activation’ was not due to weak air streams set in motion by the approaching stimuli as shown by the fact that the ‘anticipatory activation’ was abolished when the animal was prevented from seeing the approaching stimulus. As long as vision was blocked only tactile stimuli to the cutaneous receptive field discharged such cortical cells. Thus we concluded that visual activation was capable of driving the cells in area 7. Light stimuli flashing on or off at a distance did not discharge these cells, nor did contoured stimuli approaching from the other side of the face (contralateral to the cutaneous receptive field). It therefore seemed that the visual stimulus had to emerge in a location close to the cutaneous receptive field of the cell.”