For example, the classic effects of ventrolateral prefrontal and premotor lesions on expressive speech (ie, “Broca’s aphasia”) may be more readily appreciated as breakdowns in the regulation of sequentially organized actions in regions that are somatotopically
mapped to the motor control of the articulatory apparatus (mouth, tongue, larynx, and pharynx), Inhibitors,research,lifescience,medical and this system better explains how some (more posterior frontal) lesions have greater effect on articulator)’ agility and buccolingual praxis, while other (more anterior) lesions leave the motor regulation of speech intact but nevertheless yield alogia or other higher-order speech impairments. Goldberg provides many examples, and also an elegant explanation of how agnosias emerge as a cardinal consequence of lesions in the
secondary divisions of posterior cortical regions, and how analogous disruptions in the classification of behavioral programs may result from premotor cortex dysfunction.42 Some Inhibitors,research,lifescience,medical difficulties for these theories include: (i) the observation that the secondary divisions of the cortex (ie, premotor cortex) are actually phylogenetically older and less differentiated than either tertiary prefrontal cortex or primary motor cortex, which appear to have evolved more recently (see refs 50,51); (ii) a lack of specification Inhibitors,research,lifescience,medical about the nature of regulatory influence expressed by the frontal cortex in its Inhibitors,research,lifescience,medical connections to posterior
cortical regions; and (iii) while the hierarchical theories account well for diverse motor and planning phenomena, they often pay less attention to the importance of frontal systems as regulators of the limbic, diencephalic, and brain stem systems, and thereby offer less insight into how frontal Inhibitors,research,lifescience,medical systems regulate visceral and autonomic function. The Pribram-McGuiness hypothesis and other autoregulatory control theories In his classic paper “The riddle of frontal lobe function in man,” Hans-Lukas Teuber31 highlighted dilemmas faced by the field in its attempts to identify a unitary theory of frontal lobe functions, and he focused on taking a “180-degree” Thalidomide shift in thinking by examining the impact of frontal systems on the rest of the brain including sensory cortices. Teuber’s emphasis on “corollary www.selleckchem.com/products/CAL-101.html discharge” anticipated interpretations that focused on the role of frontal projections in biasing the processing of other cortical systems to “prepare” for engagement in task-relevant activity, thereby providing representation of “expectation” and “context based on prior memory.” 52 These ideas are similar to later theoretical contributions that attribute to frontal systems a unique role in guiding behavior via context.
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