Neuronal codes for the inhibitory control of impulsive actions in the rat infralimbic cortex.
Poor impulse control is a debilitating condition observed in various psychiatric disorders and could be a risk factor for drug addiction, criminal involvement, and suicide. The rat infralimbic cortex (IL), located in the ventral portion of the medial prefrontal cortex, has been implicated in impulse control. To elucidate the neurophysiological basis of impulse control, we recorded single unit activity in the IL of a rat performing a 3-choiceserial reaction time task (3-CSRTT) and 2-choice task (2-CT), which are animal models for impulsivity. The inactivation of IL neuronal activity with an injection of muscimol (0.1 μg /side) disrupted impulse control in the 3-CSRTT. More than 60% (38/56) of isolated IL units were linked to impulse control, while approximately 30% of all units were linked to attentional function in the 3-CSRTT. To avoid confounding motor-related units with the impulse control-related units, we further conducted the 2-CT in which the animals' motor activities were restricted during recording window. More than 30% (14/44) of recorded IL units were linked to impulse control in the 2-CT. Several types of impulse control-related units were identified. Only 16% of all units were compatible with the results of the muscimol experiment, which showed a transient decline in the firing rate immediately before the release of behavioral inhibition. This is the first study to elucidate the neurophysiological basis of impulse control in the IL and to propose that IL neurons control impulsive actions in a more complex manner than previously considered.
Department of Neuropharmacology, Hokkaido University Graduate School of Medicine, Sapporo, Japan; Department of Neuropsychiatry, Keio University, School of Medicine, Tokyo, Japan; Research Fellow of Japan Society for thePromotion of Science, Japan.
Iku
I
Tsutsui-Kimura
Department of Neuropharmacology, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
Yu
Y
Ohmura
Department of Neuropharmacology, Hokkaido University Graduate School of Medicine, Sapporo, Japan. Electronic address: psyizumi@med.hokudai.ac.jp.
Takeshi
T
Izumi
Department of Biology, Faculty of Science, Hokkaido University, Sapporo, Japan.
Toshiya
T
Matsushima
Graduate School of Life Science, Hokkaido University, Sapporo, Japan; Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, USA.
Hidetoshi
H
Amita
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Nagasaki International University, Sasebo, Japan.
Taku
T
Yamaguchi
Department of Neuropharmacology, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
Takayuki
T
Yoshida
Department of Neuropharmacology, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
Mitsuhiro
M
Yoshioka
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D002755:Choice Behavior / Q000187:drug effects / Q000502:physiology; D056344:Executive Function / Q000187:drug effects / Q000502:physiology*; D058785:GABA-A Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D007175:Impulsive Behavior / Q000187:drug effects / Q000502:physiology*; D007266:Inhibition, Psychological; D008297:Male; D009118:Muscimol / Q000008:administration & dosage / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D017397:Prefrontal Cortex / Q000187:drug effects / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar
D058785:GABA-A Receptor Agonists; D009118:Muscimol
Five-choice serial reaction time task; Impulsivity; Response inhibition; Single-cell recording; Ventromedial prefrontal cortex