title: Deficits in action selection based on numerical information after inactivation of the posterior parietal cortex in monkeys.
abstract: A previous study identified neuronal activity in area 5 of the monkey posterior parietal cortex that reflects the numerosity of a series of self-performed actions. It is not known, however, whether area 5 is crucially involved in the selection of an action based on numerical information or, instead, merely reflects numerosity-related signals that originate in other brain regions. We transiently and focally inactivated area 5 to test its functional contributions to numerosity-based action selection. Two monkeys were trained to either push or turn a handle in response to a visual trigger signal. The selection of the action was solely based on numerical information from a series of actions performed by the monkey: select A five times, select B five times, and then return to A in a cyclical fashion. When muscimol was applied to a portion of area 5 in which the activity in the numerosity-selective cells was recorded, the error rate in the selection task increased significantly. This transient neural inactivation also caused omission errors that were not observed before the muscimol injection. A control task showed that the errors were not caused by motor deficits or impaired ability to select between two possible actions. Our results indicate that area 5 is crucial for selecting actions on the basis of numerical information about a series of actions performed by the tested individual.
authors.affiliation: Department of Physiology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Sawamura
authors.forename: Keisetsu
authors.initials: K
authors.lastname: Shima
authors.forename: Jun
authors.initials: J
authors.lastname: Tanji
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000704:Analysis of Variance; D000818:Animals; D001931:Brain Mapping; D002755:Choice Behavior / Q000187:drug effects / Q000502:physiology*; D003072:Cognition Disorders / Q000139:chemically induced / Q000503:physiopathology*; D056344:Executive Function / Q000187:drug effects / Q000502:physiology*; D007839:Functional Laterality; D058785:GABA-A Receptor Agonists / Q000494:pharmacology; D008252:Macaca fascicularis; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D010296:Parietal Lobe / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
chemical_list: D058785:GABA-A Receptor Agonists; D009118:Muscimol