Control of rodent and human spatial navigation by room and apparatus cues

A growing body of literature indicates that rats prefer to navigate in the direction of a goal in the environment (directional responding) rather than to the precise location of the goal (place navigation). This paper provides a brief review of this literature with an emphasis on recent findings in the Morris water task. Four experiments designed to extend this work to humans in a computerized, virtual Morris water task are also described. Special emphasis is devoted to how directional responding and place navigation are influenced by room and apparatus cues, and how these cues control distinct components of navigation to a goal. Experiments 1 and 2 demonstrate that humans, like rats, perform directional responses when cues from the apparatus are present, while Experiment 3 demonstrates that place navigation predominates when apparatus cues are eliminated. In Experiment 4, an eyetracking system measured gaze location in the virtual environment dynamically as participants navigated from a start point to the goal. Participants primarily looked at room cues during the early segment of each trial, but primarily focused on the apparatus as the trial progressed, suggesting distinct, sequential stimulus functions. Implications for computational modeling of navigation in the Morris water task and related tasks are discussed.     

The POL area of the honey bee's eye: behavioural evidence

ABSTRACT. The uppermost dorsal part of the honey bee's compound eye contains a group of c. 150 specialized ommatidia. The photoreceptors of these ommatidia are characterized by a number of anatomical and physiological peculiarities which suggest that they have functional significance for the detection of polarized skylight. Here, we show by painting out different parts of the eye and recording the bee's behavioural responses that the specialized photoreceptors at the dorsal margin of the eye are indeed necessary for detecting polarized skylight and deriving compass information from celestial e-vector patterns. Hence, this group of specialized ommatidia can be called the POL area of the bee's compound eye.     

A Standardized Obstacle Course for Assessment of Visual Function in Ultra Low Vision and Artificial Vision

We describe an indoor, portable, standardized course that can be used to evaluate obstacle avoidance in persons who have ultralow vision. Six sighted controls and 36 completely blind but otherwise healthy adult male (n=29) and female (n=13) subjects (age range 19-85 years), were enrolled in one of three studies involving testing of the BrainPort sensory substitution device. Subjects were asked to navigate the course prior to, and after, BrainPort training. They completed a total of 837 course runs in two different locations. Means and standard deviations were calculated across control types, courses, lights, and visits. We used a linear mixed effects model to compare different categories in the PPWS (percent preferred walking speed) and error percent data to show that the course iterations were properly designed. The course is relatively inexpensive, simple to administer, and has been shown to be a feasible way to test mobility function. Data analysis demonstrates that for the outcome of percent error as well as for percentage preferred walking speed, that each of the three courses is different, and that within each level, each of the three iterations are equal. This allows for randomization of the courses during administration.Abbreviations: preferred walking speed (PWS) course speed (CS) percentage preferred walking speed (PPWS)     

Practical Methodology of Cognitive Tasks Within a Navigational Assessment

This paper describes an approach for measuring navigation accuracy relative to cognitive skills. The methodology behind the assessment will thus be clearly outlined in a step-by-step manner. Navigational skills are important when trying to find symbols within a speech-generating device (SGD) that has a dynamic screen and taxonomical organization. The following skills have been found to impact children’s ability to find symbols when navigating within the levels of an SGD: sustained attention, categorization, cognitive flexibility, and fluid reasoning^1,2. According to past studies, working memory was not correlated with navigation^1,2.The materials needed for this method include a computerized tablet, an augmentative and alternative communication application, a booklet of symbols, and the Leiter International Performance Scale-Revised (Leiter-R)³. This method has been used in two previous studies. Robillard, Mayer-Crittenden, Roy-Charland, Minor-Corriveau and Bélanger¹ assessed typically developing children, while Rondeau, Robillard and Roy-Charland² assessed children and adolescents with a diagnosis of Autism Spectrum Disorder. The direct observation of this method will facilitate the replication of this study for researchers. It will also help clinicians that work with children who have complex communication needs to determine the children’s ability to navigate an SGD with taxonomical categorization.     

Successful ablation of frequent atrial premature beats from non-coronary aortic cusp with remote magnetic navigation

A 59-year-old female with structurally normal heart was admitted to our hospital for treatment of highly symptomatic, drug refractory atrial premature beats (APB). ECG revealed atrial parasystolic trigeminy. The arrhythmogenic focus was mapped and ablated using magnetic remote navigation and 3D electroanatomical mapping system. To our knowledge, this is the first report on successful ablation of frequent APBs in the non-coronary aortic cusp.