Classification And Function Of The Awake Monkey V1 Neurons Integrate Field Research

The integration field (IF) is a broad area outside the classical receptive field (CRF) of cortical neurons, which can have a modulatory effect on responses to stimuli presented within the classical receptive field. The structure and functional significance of the IFs of area 17 and area 18 neurons have already been investigated in the anesthetized cat (Li et al,1994). The current study was designed to investigate the organization and functional properties of IFs in the awake primate. Unit cell recordings were made from V1 and V2 of four monkeys (Macaca mullata), and the nature of the end and side regions of the IFs were determined with reference to the shape of the length and width summation curves. The results indicated: (1) Extensive IFs existed beyond the CRFs of visual cortical (V1 and V2) neurons of macaque monkey. The extend of the IFs was 3-12 times the size of the related CRFs. The extend of V2 neurons'IFs was larger than V1 neurons'while the extend of V1 neurons'IFs in awake monkey was larger than in anaesthetized monkey. (2) Stimulated by gratings, together with CRFs , the IFs had facilitatory(+), inhibitory(-), and disinhibitory effects on the responsiveness of the CRFs. (3) Four categories of IF structures were found: Type a, in which both the side and end regions showed facilitation; Type b, in which both regions showed an inhibitory effect; Type c, in which the end regions were facilitatory, but the side regions were inhibitory; and Type d, in which the IF had inhibitory end regions and facilitatory side regions. Of the 159 cells recorded, the majority (73.6%) of the IFs of V1 neurons were found to be Type b, while most (46.2%) of the IFs of V2 neurons were found to belong to Type c. The differences in IF structure between awake and anesthetized animals are discussed.