Whole brain dynamics during optogenetic self-stimulation of the medial prefrontal cortex in mice.

Intracranial self-stimulation, in which an animal performs an operant response to receive regional brain electrical stimulation, is a widely used procedure to study motivated behavior. While local neuronal activity has long been measured immediately before or after the operant, imaging the whole brain in real-time remains a challenge. Herein we report a method that permits functional MRI (fMRI) of brain dynamics while mice are cued to perform an operant task: licking a spout to receive optogenetic stimulation to the medial prefrontal cortex (MPFC) during a cue ON, but not cue OFF. Licking during cue ON results in activation of a widely distributed network consistent with underlying MPFC projections, while licking during cue OFF (without optogenetic stimulation) leads to negative fMRI signal in brain regions involved in acute extinction. Noninvasive whole brain readout combined with circuit-specific neuromodulation opens an avenue for investigating adaptive behavior in both healthy and disease models.

Supramammillary neurons projecting to the septum regulate dopamine and motivation for environmental interaction in mice.

The supramammillary region (SuM) is a posterior hypothalamic structure, known to regulate hippocampal theta oscillations and arousal. However, recent studies reported that the stimulation of SuM neurons with neuroactive chemicals, including substances of abuse, is reinforcing. We conducted experiments to elucidate how SuM neurons mediate such effects. Using optogenetics, we found that the excitation of SuM glutamatergic (GLU) neurons was reinforcing in mice; this effect was relayed by their projections to septal GLU neurons. SuM neurons were active during exploration and approach behavior and diminished activity during sucrose consumption. Consistently, inhibition of SuM neurons disrupted approach responses, but not sucrose consumption. Such functions are similar to those of mesolimbic dopamine neurons. Indeed, the stimulation of SuM-to-septum GLU neurons and septum-to-ventral tegmental area (VTA) GLU neurons activated mesolimbic dopamine neurons. We propose that the supramammillo-septo-VTA pathway regulates arousal that reinforces and energizes behavioral interaction with the environment.

A Novel, Adaptable Laryngeal Mask to Facilitate a Percutaneous Dilatational Tracheostomy: Proof-of-Concept Prototype Demonstration on a Mannequin Model and Cadaver.

BACKGROUND: Most percutaneous dilatational tracheostomy (PDT) mortalities result from airway-related complications. Improved airway pressure management and gas delivery are targets for innovation. This study describes an adaptable laryngeal mask (ALM) designed to remove the bronchoscope from the endotracheal tube (ETT) and place it in a separate lumen. Airflow and device efficacy were evaluated during PDTs with an ALM on mannequins and cadavers, respectively. METHODS: Procedures were completed by a single physician using an 8.0 mm ETT and the Ciaglia Blue Rhino method on simulation mannequins (TruCorp AirSim Traci) and fresh-frozen cadavers. Mannequin simulation tested the respiratory capabilities of an ALM utilizing a BioPac spirometer and a Maquet Servo ventilator. Qualitative analysis on device efficacy was performed on 2 fresh-frozen cadavers (1 male, 1 female). RESULTS: Preliminary ventilation testing on a PDT-able mannequin using the ALM showed an increase in airflow reaching the lungs compared with a deflated ETT. During mannequin and cadaver testing, the ALM was placed over the in situ ETT effectively, thereby removing the bronchoscope from the ETT while maintaining a continuous visual of the incision site. Both mannequin and cadaveric testing using an ALM enabled a single physician to safely perform the PDT procedure with minimal assistance. CONCLUSIONS: Initial testing using an ALM during PDT on mannequins and cadavers showed an improvement in airflow and the removal of the bronchoscope from the ETT, respectively. Further studies using the ALM in a patient population compared with standard techniques would be useful.