Lateral prefrontal cortex: architectonic and functional organization

1. Lateral prefrontal cortex:architectonicand functional organization Michael Petrides

2. 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……

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

4. Cytoarchitectonic maps of the lateral surface ofthe humancerebral cortex a) By Brodmann b) BySarkissov et al

5. Dorsal Rostral Caudal Ventral Cytoarchitectonic map of the lateral surface of the prefrontal cortexby Petrides & Pandya a) Of human brain b) Of macaque monkey brain

7. FUNCTIONAL ORGANIZATION OFTHE 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

8. The rostral–caudal axis of frontal cortex organization • Lesion of the mid-dorsolateral prefrontal cortex-MDL (area 46 & rostral 9/46 • 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. Yield a severe deficit on tasks designed to measure the monitoring of information in working memory

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

10. 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

11. Thank you …