title: Anatomical organization of descending cortical projections orchestrating the patterns of cortically induced rhythmical jaw muscle activity in guinea pigs.
abstract: Repetitive electrical microstimulation to the cortical masticatory area (CMA) evokes distinct patterns of rhythmical jaw muscle activities (RJMAs) in animals. This study aimed to investigate the characteristics of the descending projections from the CMA, associated with distinct patterns of RJMAs, to the thalamus, midbrain, pons and medulla in guinea pigs. RJMAs with continuous masseter and digastric bursts (CB-RJMAs) and stimulus-locked digastric sub-bursts (SLB-RJMAs) were induced from the anterior and posterior areas of the rostral region of the lateral agranular cortex, and chewing-like RJMAs from the rostral region of the granular cortex. Anterograde tracer, biotinylated dextran amine, was injected into the three cortical areas. The cortical area inducing CB-RJMAs had strong ipsilateral projections to the motor thalamus, red nucleus, midbrain reticular formation, superior colliculus, parabrachial nucleus, and supratrigeminal region, and contralateral projections mainly to the lateral reticular formation around the trigeminal motor nucleus (Vmo). The cortical area inducing SLB-RJMAs had moderate projections to the motor thalamus and lateral reticular formation around the Vmo, but few projections to the midbrain nuclei. The cortical area inducing chewing-like RJMAs had strong projections to the ipsilateral sensory thalamus and contralateral trigeminal sensory nuclei, and moderate projections to the lateral reticular formation. The three cortical areas consistently had few projections to the ventromedial reticular formation. The present study demonstrates that multiple direct and indirect descending projections from the CMA onto the premotor systems connecting the trigeminal motoneurons represent the neuroanatomical repertoires for generating RJMAs during the distinct phases of natural ingestive behavior.
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, Suita, Osaka 565-0871, Japan. Electronic address: takafumi@dent.osaka-u.ac.jp.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kato
authors.affiliation: Department of Oral and Maxillofacial Anatomy, Institute of Health Biosciences, University of Tokushima, Tokushima, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Seki
authors.affiliation: Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Suita, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Higashiyama
authors.affiliation: Department of Oral and Maxillofacial Biology, Graduate School of Oral, Medicine, Matsumoto Dental University, Shiojiri, Nagano, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Masuda
authors.affiliation: Department of Oral and Maxillofacial Anatomy, Institute of Health Biosciences, University of Tokushima, Tokushima, Japan.
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Kitamura
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yoshida
mesh_terms: D000818:Animals; D001933:Brain Stem / Q000033:anatomy & histology / Q000502:physiology; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000502:physiology*; D006168:Guinea Pigs; D007568:Jaw / Q000033:anatomy & histology / Q000502:physiology*; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D008409:Mastication / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology; D009068:Movement / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology*; D012154:Reticular Formation / Q000033:anatomy & histology / Q000502:physiology*; D014278:Trigeminal Nuclei / Q000033:anatomy & histology / Q000502:physiology
keywords: Cortical masticatory area; Descending projection; Mastication; Rhythmical jaw movement; Trigeminal system