Representing Where along with What Information in a Model of a Cortical Patch

Behaving in the real world requires flexibly combining and maintaining information about both continuous and discrete variables. In the visual domain, several lines of evidence show that neurons in some cortical networks can simultaneously represent information about the position and identity of objects, and maintain this combined representation when the object is no longer present. The underlying network mechanism for this combined representation is, however, unknown. In this paper, we approach this issue through a theoretical analysis of recurrent networks. We present a model of a cortical network that can retrieve information about the identity of objects from incomplete transient cues, while simultaneously representing their spatial position. Our results show that two factors are important in making this possible: A) a metric organisation of the recurrent connections, and B) a spatially localised change in the linear gain of neurons. Metric connectivity enables a localised retrieval of information about object identity, while gain modulation ensures localisation in the correct position. Importantly, we find that the amount of information that the network can retrieve and retain about identity is strongly affected by the amount of information it maintains about position. This balance can be controlled by global signals that change the neuronal gain. These results show that anatomical and physiological properties, which have long been known to characterise cortical networks, naturally endow them with the ability to maintain a conjunctive representation of the identity and location of objects

Treatment responsive executive and behavioral dysfunction associated with Vitamin B12 deficiency

Vitamin B12 deficiency can manifest with various neuropsychiatric symptoms. We report a case of an individual with vitamin B12 deficiency presenting with personality, emotional and behavioral changes. Neuropsychological tests revealed disproportionate disturbance of executive functions. Single photon emission tomography (Tc99m HMPAO) showed right fronto-temporo-parietal hypoperfusion. After vitamin B12 injections, the patient's executive and behavioral dysfunction disappeared and performance on neuropsychological tests was once again in the normal range

Efficacy of epley maneuver on quality of life of elderly patients with subjective BPPV

OBJECTIVES: This study aimed to evaluate the efficacy of the repositioning maneuver on quality of life in elderly patients with dizziness and/or vertigo. MATERIALS and METHODS: This controlled, prospective randomized clinical trial was conducted in elderly patients aged 65 years and above with a positive history of benign paroxysmal positional vertigo (BPPV), presence of vertigo, and no observable nystagmus during the Dix-Hallpike test, so-called Subjective BPPV (S-BPPV). Individuals were evaluated by visual analog scale (VAS) and dizziness handicap inventory (DHI). Groups were defined as treatment (treated with Epley maneuver bilaterally) or no treatment control (no treatment modality or canalith repositioning maneu-ver). Ten days after the first assessment, all patients were reassessed using VAS and DHI. RESULTS: A total of 50 patients were randomized into two groups: 25 to the treatment group, and 25 to the control group. No significant differences were observed for baseline VAS and total DHI scores between the groups (p=0.636, p=0.846, respectively). On the other hand, after the reassessment, VAS and total DHI scores were both significantly reduced in the treatment group (p<0.001, p<0.001, respectively), but no reduction in either score was found in the control group (p=0.216, p=0.731, respectively). CONCLUSION: This study showed that elderly patients with S-BPPV benefit from the Epley maneuver, in particular global and disease-specific quality of life. © 2019, AVES. All rights reserved