# Functional Magnetic Resonance Imaging in Research on Dog Cognition: A Systematic Review
## 1 Introduction  
Functional magnetic resonance imaging (fMRI) is a technique that identifies neural activity in the brain by detecting changes in blood flow, referred to as the hemodynamic response. This process utilizes the blood oxygenation level-dependent (BOLD) effect, based on the principle that heightened neural activity in the brain region triggers increased metabolic activity. As a result, the oxygen supply rises beyond the increased demand, leading to a higher ratio of oxygenated to deoxygenated hemoglobin. This activity-dependent elevated oxygen saturation produces a stronger signal in the regions where neural activity occurs during specific magnetic resonance imaging (MRI) sequences [1, 2].  
The fMRI is a cognitive neuroscience tool widely used in humans to understand brain functions [3]. Dogs' neurocognitive patterns are the subject of scientific interest in the context of their presumed co-evolution with humans impacting the development of specific neural pathways [4]. Additionally, there is significant social interest in the topic--dogsare treated as family members and form social bonds with humans, making it particularly interesting to explore the similarities and differences in neurological mechanisms of cognition [5]. Furthermore, dogs are considered a comparative model for social neuroscience [6]. Finally, the studies illustrate the promise of using fMRI not only to understand canine brain function, but also to enhance the selection of and training processes for working dogs. Neurocognitive research is being conducted to predict the suitability of dogs for assistance work [7].  
Conducting fMRI studies on dogs presents challenges, mainly because it requires subjects to remain still during the scanning session. It is possible to conduct some fMRI studies yielding informative data on anesthetized dogs. Nevertheless, this makes it impossible to detect pathways for conscious processing [8]. Therefore, conducting studies on non-anesthetized, unrestrained dogs is necessary, and it requires long-term preparation and training. Detailed protocols have been described for preparing dogs for awake studies [9]. Most studies require the use of stimuli, except for resting state network studies, which by definition describe no task condition. For this analysis, the research has been divided into the following groups based on the types of activated pathways: those utilizing visual stimuli, auditory stimuli, olfactory stimuli, somatosensory stimuli, and multi-stimuli.  
This systematic review summarizes the recent knowledge on canine brain areas activated in response to various stimuli. As the first such review, this study integrates previous fMRI studies in dogs and provides valuable insights for veterinary, comparative, and translational research. The review highlights both the achievements and gaps in existing canine fMRI studies and outlines future research directions. By introducing elements of scientific innovation, this work has the potential to advance canine neurocognitive research significantly. Following the PICOT (Population, Intervention, Comparison, Outcome, Time) format, the research question is formulated as follows: \"In dogs (P), what brain areas (I) against the resting state network (C) have been activated in response to various stimuli (O) in existing fMRI studies on dog cognition (T)?\"