Although in conventional models of visual information processing, object identity and spatial information are processed separately and independently in ventral and dorsal cortical visual pathways respectively, some recent studies have shown that information about both object’s identity (of shape) and space are present in both visual pathways. However, it is still unclear whether the presence of identity and spatial information in both pathways have functional roles or not. In a recent study (Han & Sereno, in press), we have tried to answer this question through computational modeling. Our simulation results suggested that two separate cortical visual pathways for identity and space (1) actively retain information about both identity and space; (2) retain information about identity and space differently; (3) that this differently retained information about identity and space in the two pathways may be necessary to accurately and optimally recognize and localize objects. However, in these simulations, there was only one object in each image. In reality, there may be more than one object in an image. In this master’s thesis, I have tried to run visual recognition simulations with two objects in each image. My two object simulations suggest that (1) the two separate cortical visual pathways for identity and space (orientation) still retain information about both identity and space (orientation) when there are two objects in each image; (2) the retained information about identity and space (orientation) in the two pathways may be necessary to accurately and optimally recognize objects’ identity and orientation. These results agree with our one object simulation results.

The Lateral Prefrontal Cortex (LPFC) and the Dorsal Premotor cortex (PMd) are two cortical structures that are involved in cognitive processes such as motor planning and decision-making. The LPFC is extensively connected to sensory, somatosensory, and motor cortices that help it control several cognitive functions [for review, see: (Tanji & Hoshi, 2008)]. Similarly, the PMd can integrate information from the prefrontal and motor cortex, acting as a link, in action planning and decision making [for review, see: (Hoshi & Tanji, 2007)]. Therefore, it is important to study the cortical pathways between these areas because of their common role in processing and selecting relevant information in tasks requiring decision-making. Using neural tract-tracing, immunolabeling and microscopy in rhesus monkeys (M. mulatta), we assessed the distribution and layer-specific organization of projection neurons from LPFC area 46 and PMd area 6 directed to the LPFC area 9. Our study revealed that projection neurons to area 9 were found originating from upper (L2-3) and deep (L5-6) layers of both areas, but with a slight upper layer bias. We found that the LPFC area 46 had a higher density of projection neurons directed to LPFC area 9 compared to the PMd area 6. Additionally, our data also revealed laminar differences in the perisomatic parvalbumin (PV) inhibitory inputs onto area 9 projection neurons, which were dependent on area of origin. Within ventral LPFC area 46, perisomatic PV+ inhibitory inputs onto upper layer projection neurons to area 9 was greater than those onto deep layer projection neurons. The opposite pattern was found for PMd area 6DR, where perisomatic PV+ inhibition onto deep layer projection neurons to area 9 was greater than those onto upper layer neurons. These findings provide additional insights into the layer-specific organization of prefrontal and premotor pathways that play an important role in action planning and decision-making.