Lateral prefrontal cortex: architectonic and functional organization Michael Petrides

In Brief.. Subdivision of the cerebral cortex according to.. differences in the arrangement of the cellular elements into layers, such as, differences in: cell packing density across layers, cell size or type in one or more layers, the relative thickness of the layers, or even in overall cortical thickness Led to the brain mapping of the primates…… 1786Vick d’Azyr Regional differences in the structure of the cerebral cortex such as white stripe in the visual cortex of primates 1840Baillarger Outer and inner stripes of Baillarger (white stripes) Meynert / Betz / Lewis & Clarke Cerebral cortex is not a homogeneous sheet of grey matter, but it consists of several different areas 1905Campbell The first complete cytoarchitectonic map of the human brain based on 8 hemispheres 1905Brodmann Published his architectonic map of the monkey cerebral cortex 1907Elliot Smith Other major maps of the human cerebral cortex 1908Brodmann Architectonic map of the human cerebral cortex 1925 Economo & Koskinas Architectonic map of the human cerebral cortex 1951 Bailey & Bonin Two more atlases of the human cerebral cortex 1955 Sarkissov et al Other maps based on Brodmann’s

monkey Cytoarchitectonic maps of the lateral and orbital prefrontal cortex of the monkey a) By Brodmann b) By Walker

b) By Sarkissov et al human Cytoarchitectonic maps of the lateral surface of the human cerebral cortex a) By Brodmann

of the lateral surface of the prefrontal cortexby Petrides & Pandya Cytoarchitectonic map of the lateral surface of the prefrontal cortex by Petrides & Pandya a) Of human brain b) Of macaque monkey brain RostralCaudal Dorsal Ventral

BASIC DIFFERENCES Monkey BrainHuman Brain Classic cytoarchitectonic maps (Brodmann, Sarkissov et al) Area 10  part of orbital an ventrolateral frontal region Area 12  frontopolar region No area 46, 45 Granular frontal area 9 Area 46 adjacent to area 9, No common border with area 8 Area 10  frontopolar region Walker et al Area 46  large granular, adjacent to area 8, not homogeneous Area 12  ventrolateral part of the prfrontal Area 45  might correspond to Brodmann’s area 45 of the human cortex Area 10  frontopolar region No human brain maps Petrides & Pandya Dorsolateral Prefrontal Cortex Area 9  lying on the supirior frontal gyrus, a poorly developed layer IV and large pyramidal cells in the deeper part of layer III Area 46 Area 9/46 Ventrolateral Prefrontal Cortex Area 44 Area 45 Area 47/12

FUNCTIONAL ORGANIZATION OF THE PREFRONTAL CORTEX major role in high-order control processes that exercise a top-down regulation of cognition and behaviour In particular, there is.. a rostral - caudal axis of functional organization within the lateral frontal cortex  cognitive control and a dorso - ventral axis in the mid-lateral part of the prefrontal  executive control

The rostral–caudal axis of frontal cortex organization I.Lesion of caudal dorsolateral region- PA (periarcuate) lesions (area 8 & rostral 6 ) Problem on tasks that require the selection between alternative competing responses based on conditional operations. II.Lesion of the mid- dorsolateral prefrontal cortex-MDL (area 46 & rostral 9/46 Yield a severe deficit on tasks designed to measure the monitoring of information in working memory

A dorsal–ventral axis of organization a)An example of a pair of abstract designs b)At familiarity/novelty decision condition relative to the control condition  Increased activity in the right mid-ventrolateral prefrontal cortex (area 47/12) c)an additional increase of activity in the right mid-dorsolateral prefrontal cortex (areas 46 and 9/46) in the monitoring condition minus control condition comparison d)only the mid-dorsolateral prefrontal cortex (areas 46 and 9/46) showed increased activity at the familiarity/novelty decision condition relative to monitoring condition

To summarize.. The lateral frontal cortex is functionally organized both along a rostral–caudal axis and a dorsal– ventral axis Caudally, The most caudal frontal region, the motor region on the precentral gyrus, is involved in fine motor control and direct sensorimotor mappings The caudal lateral frontal region is involved in higher order control processes  conditional operations Rostrally, the mid-lateral prefrontal region  cognitive control is itself organized along a dorsal–ventral axis of organization the mid-dorsolateral prefrontal cortex  monitoring of information in working memory the mid-ventrolateral prefrontal region  in active judgments on information held in posterior cortical association regions that are necessary for active retrieval and encoding of information

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