Cholinergic neurotransmission has been shown to play an important role in modulating attentional processing of visual stimuli. However, it is not yet clear whether the neurochemical acetylcholine (ACh) is necessary exclusively for visual attention, or if it also contributes to attentional functions through some modality-independent (supramodal) mechanism. To answer this question, we examined the effects of reduced cortical cholinergic afferentation on both a traditional visual and a novel olfactory five-choice serial reaction time task (5-CSRTT), the benchmark rodent test of sustained attention in rats. Following the successful acquisition of both modalities of the task, the rats underwent either a cholinergic immunotoxic-or sham-lesion surgery of the nucleus basalis magnocellularis (NBM), the basal forebrain nuclei that provide the majority of neocortical ACh. Reduced cholinergic afferentation to the neocortex was induced by bilaterally infusing the cholinergic immunotoxin 192 IgG-saporin into the NBM. After surgery, ACh-NBM-lesioned rats performed comparably to sham-lesioned rats under the conditions of low attentional demand, but displayed behavioral decrements relative to the sham-lesioned rats when the attentional demands of the task were increased. Moreover, this decrement in attentional functioning correlated significantly with the number of choline acetyltransferase-immunoreactive cells in the NBM. Importantly, the nature of this behavioral decrement was identical in the visual and olfactory 5-CSRTTs. Together, these data suggest the presence of a supramodal attentional modulatory cortical network whose activity is dependent on cholinergic innervation from the NBM.

A critical function of attention is to support a state of readiness to enhance stimulus detection, independent of stimulus modality. The nucleus basalis magnocellularis (NBM) is the major source of the neurochemical acetylcholine (ACh) for frontoparietal cortical networks thought to support attention. We examined a potential supramodal role of ACh in a frontoparietal cortical attentional network supporting target detection. We recorded local field potentials (LFPs) in the prelimbic frontal cortex (PFC) and the posterior parietal cortex (PPC) to assess whether ACh contributed to a state of readiness to alert rats to an impending presentation of visual or olfactory targets in one of five locations. Twenty male Long-Evans rats underwent training and then lesions of the NBM using the selective cholinergic immunotoxin 192 IgG-saporin (0.3 μg/μl; ACh-NBM-lesion) to reduce cholinergic afferentation of the cortical mantle. Postsurgery, ACh-NBM-lesioned rats had less correct responses and more omissions than sham-lesioned rats, which changed parametrically as we increased the attentional demands of the task with decreased target duration. This parametric deficit was found equally for both sensory targets. Accurate detection of visual and olfactory targets was associated specifically with increased LFP coherence, in the beta range, between the PFC and PPC, and with increased beta power in the PPC before the target's appearance in sham-lesioned rats. Readiness-associated changes in brain activity and visual and olfactory target detection were attenuated in the ACh-NBM-lesioned group. Accordingly, ACh may support supramodal attention via modulating activity in a frontoparietal cortical network, orchestrating a state of readiness to enhance target detection. We examined whether the neurochemical acetylcholine (ACh) contributes to a state of readiness for target detection, by engaging frontoparietal cortical attentional networks independent of modality. We show that ACh supported alerting attention to an impending presentation of either visual or olfactory targets. Using local field potentials, enhanced stimulus detection was associated with an anticipatory increase in power in the beta oscillation range before the target's appearance within the posterior parietal cortex (PPC) as well as increased synchrony, also in beta, between the prefrontal cortex and PPC. These readiness-associated changes in brain activity and behavior were attenuated in rats with reduced cortical ACh. Thus, ACh may act, in a supramodal manner, to prepare frontoparietal cortical attentional networks for target detection.

Background: With the increasing awareness and action amongst stakeholders in addressing the concerning rise of unmatched Canadian Medical Graduates (CMGs), little is known from those who go unmatched. We use our unmatched experience to contribute to this dialogue. Methods: We present an issues-based examination of the matching process by reflecting on the pre- and post-match period, providing suggestions related to the Canadian context from the unmatched perspective.  Results: The challenge in the pre-match period was handling uncertainty in elective scheduling. This uncertainty was largely manifested from not knowing elective availability at the time of elective application submission, as well as not knowing what “strategy” we should follow in how to structure our elective schedule. For the post-matched period, we were challenged by making decisions during a time-sensitive period, deciding on career issues like scheduling post-match electives, handling our finances, and trying to improve our future residency applications without feedback. Conclusion: Providing a real-time document of elective availability, providing focused feedback from our residency applications, and implementing and expanding upon extended curriculums for all medical schools to continue CMG training for their unmatched students for upcoming match cycles would greatly improve the unmatched experience.

Highlights Gallbladder volvulus is a challenging radiological diagnosis. Hepatobiliary iminodiacetic acid (HIDA) scans demonstrate no filling of the gallbladder in gallbladder volvulus. Persisting cholecystitis symptoms in the absence of gallstones can be indicative of gallbladder volvulus.