Cross-species studies of orbitofrontal cortex and value-based decision-making

Abstract

Recent work has emphasized the role that orbitofrontal cortex (OFC) has in value-based decision-making. However, it is also clear that a number of discrepancies have arisen when comparing the findings from animal models to those from humans. Here, we examine several possibilities that might explain these discrepancies, including anatomical difference between species, the behavioral tasks used to probe decision-making and the methodologies used to assess neural function. Understanding how these differences affect the interpretation of experimental results will help us to better integrate future results from animal models. This will enable us to fully realize the benefits of using multiple approaches to understand OFC function.

Figure 1

Architectonic maps of the medial (top) and orbital (bottom) surfaces of the frontal lobe in A) humans and B) monkeys . C) Medial (top) and lateral (bottom) frontal cortex in rats . Agranular cortex lacks layer IV. Dysgranular cortex contains a rudimentary layer IV. Granular cortex has a well-developed layer IV. Layer IV neurons are described as granular because their cell bodies are small and round and changes in this layer are clearly visible as one transitions from agranular to granular cortex. Abbreviations: AON, anterior olfactory nucleus; Fr2, second frontal area; I, insula; LO, lateral orbital area; M1, primary motor area; Par, parietal cortex; Pir, Piriform cortex; AC, anterior cingulate area; cc, corpus callosum; IL, infralimbic cortex; MO, medial orbital area; PL, prelimbic cortex; VO, ventral orbital area; l, lateral; m, medial; o, orbital; r, rostral; c, caudal; i, inferior; p, posterior; s, sulcal; v, ventral. Numbers indicate cortical fields, except that after certain areas, such as Fr2 and AC1, they indicate subdivisions of cortical fields. a has two meanings: in Ia, it means agranular; in 13a, it distinguishes that area from area 13b. Figures reproduced with permission .

Figure 2

The medial (top) and orbital (bottom) surfaces of the macaque frontal lobe, color-coded according to the areas with which they interconnect . Areas in pink connect strongly with pink and purple areas, but weakly or not at all with blue areas. Areas in blue connect strongly with blue and purple areas, but weakly or not at all with pink areas. Abbreviations as in Figure 1.

Figure 3

a) Architectonic parcellation of the human and macaque monkey orbital and ventromedial surface . b) Mean density of layer IV and layer Va between comparable architectonic areas in the monkey (dark blue) and the human (light blue) brains. Error bars indicate standard deviation. Figures reproduced with permission .

Figure 4

Photomicrographs of cortical architecture in dysgranular and granular regions of OFC. Cortical layers are identified by Roman numerals. Layer IV consists of granule cells, neurons with small, round cell bodies. Figures reproduced with permission .