No Effect of Anodal Transcranial Direct Current Stimulation (tDCS) Over hMT+ on Motion Perception Learning

Background: Human visual cortical area hMT+, like its homolog MT in the macaque monkey, has been shown to be particularly selective to visual motion. After damage to the primary visual cortex (V1), patients often exhibit preserved ability to detect moving stimuli, which is associated with neural activity in area hMT+. As an anatomical substrate that underlies residual function in the absence of V1, promoting functional plasticity within hMT+ could potentially boost visual performance despite primary visual cortical damage.Objective: To establish in healthy participants whether it is possible to use transcranial direct current stimulation (tDCS) over hMT+ to potentiate learning of visual motion direction discrimination.Methods: Twenty-one participants were trained daily for 5 days on a visual motion direction discrimination task. Task difficulty was increased as performance improved, by decreasing the proportion of coherently moving dots, such that participants were always performing at psychophysical threshold. tDCS, either anodal or sham, was applied daily during 20 min of training. Task performance was assessed at baseline and at the end of the training period. Performance was also compared with a third group of 10 participants from an earlier study who had undergone the same procedures but without tDCS.Results: All participants showed improved task performance both during and after training. Contrary to our hypothesis, anodal tDCS did not further improve performance compared to sham stimulation or no stimulation. Bayesian statistics indicated weak evidence in favor of the null hypothesis.Conclusion: This study found no evidence for a robust effect of anodal tDCS over hMT+ on visual motion direction discrimination learning in the young healthy visual system, although more subtle effects may have been missed in the relatively small sample size

Baseline Psychological Traits Contribute to Lake Louise Acute Mountain Sickness Score at High Altitude

Talks, Benjamin James, Catherine Campbell, Stephanie J. Larcombe, Lucy Marlow, Sarah L. Finnegan, Christopher T. Lewis, Samuel J.E. Lucas, Olivia K. Harrison, and Kyle T.S. Pattinson. Baseline psychological traits contribute to Lake Louise Acute Mountain Sickness score at high altitude. High Alt Med Biol. 23:69-77, 2022. Background: Interoception refers to an individual's ability to sense their internal bodily sensations. Acute mountain sickness (AMS) is a common feature of ascent to high altitude that is only partially explained by measures of peripheral physiology. We hypothesized that interoceptive ability may explain the disconnect between measures of physiology and symptom experience in AMS. Methods: Two groups of 18 participants were recruited to complete a respiratory interoceptive task three times at 2-week intervals. The control group remained in Birmingham (140 m altitude) for all three tests. The altitude group completed test 1 in Birmingham, test 2 the day after arrival at 2,624 m, and test 3 at 2,728 m after an 11-day trek at high altitude (up to 4,800 m). Results: By measuring changes to metacognitive performance, we showed that acute ascent to altitude neither presented an interoceptive challenge, nor acted as interoceptive training. However, AMS symptom burden throughout the trek was found to relate to sea level measures of anxiety, agoraphobia, and neuroticism. Conclusions: This suggests that the Lake Louise AMS score is not solely a reflection of physiological changes on ascent to high altitude, despite often being used as such by researchers and commercial trekking companies alike. Keywords: acute mountain sickness; altitude; breathlessness; exercise; filter detection task; interoceptio

Investigation of motion perception learning in healthy subjects, for application as a rehabilitative therapy for visual field defects following primary visual cortex damage

Perceptual learning is the ability to improve performance of a perceptual task, with repeated practice. The concept of perceptual learning in the adult visual system has been established for many years, however, the neural mechanisms which mediate it have proved complex to unravel. Improved understanding could be used to guide novel rehabilitative strategies for those with damage to the brain which a↵ects the primary visual cortex (V1) in the occipital lobe. Motion perception learning is thought to involve the brain area hMT+, which is located in the parieto-temporo- occipital cortex, distal from V1. It is possible that motion perception training may improve the vision or subjective quality of life for individuals with damage to V1. This project initially looked at the e↵ect of motion perception training in healthy individuals, in order to establish and quantify the potential behavioural and neural impact of behavioural training. A five-day motion perception training paradigm applied in these experiments produced robust improvement of motion perception in healthy participants. This learning was found to be partially transferable to untrained regions of the visual field. If the training timecourse was reduced to a single day, the location specificity of learning e↵ects was increased significantly. Functional MRI analysis indicated that the motion perception training paradigm applied here altered activity at extrastriate visual areas and frontotemporal decision areas. When motion perception training was combined with brain stimulation, it was shown that 20 minutes of anodal transcranial direct current stimulation (tDCS) over hMT+ had no impact on learning magnitude or timecourse. Finally, the motion perception training paradigm was applied as a case study in a patient with damage to V1. The results were promising but inconclusive with such a minimal dataset. Motion perception training produces robust improvements in perception in healthy individuals, which are likely mediated by visual extrastriate and decision-making areas of the brain. As such, motion perception training shows promise, with further development, as an avenue for rehabilitation of the visual system and visual perception following damage to the primary visual cortex.</p

Isolated oculomotor nerve palsy secondary to acute sinusitis.

Sinusitis is a common condition, but only very rarely accompanied by isolated cranial nerve palsies. We describe a case of a 64-year-old male with a two-day history of left-sided ptosis associated with one week of nasal congestion and frontal sinus pain. Examination revealed ptosis with left pupil mydriasis. Uncontrasted computed tomography and angiography of the head demonstrated neither intracranial vascular abnormalities nor acute lesions; however, it did show mucosal thickening in the left frontal sinus, ethmoid air cells and left maxillary sinus, indicating potential obstruction of the left ostiomeatal complex. The sinusitis was treated with intranasal steroids, xylomethazoline and nasal douching. The patient reported resolution of all symptoms, including left ptosis, within one week of therapy. This rare case of sinusitis causing ptosis is presented due to its infrequent nature, such that awareness of the differential diagnosis of cranial nerve palsy and complications of sinusitis may be improved

Reviewing the Recent Developments in Idiopathic Intracranial Hypertension.

There is increasing evidence and appreciation of idiopathic intracranial hypertension (IIH) in medicine. The pathological processes underlying raised intracranial pressure are being studied, with new insights found in both hormonal dysregulation and the metabolic neuroendocrine axis. These will potentially lead to novel therapeutic targets for IIH. The first consensus guidelines have been published on the investigation and management of adult IIH, and the International Headache Society criteria for headache attributable to IIH have been modified to reflect our evolving understanding of IIH. Randomized clinical trials have been published, and a number of studies in this disease area are ongoing

Data supporting "Learning to optimize perceptual decisions through suppressive interactions in the human brain"

Behavioural data. Resting state fMRI data. GABA measurements. For further information, see the associated Data Description file. Raw data can be provided upon request to the first and/or corresponding author

Learning to optimize perceptual decisions through suppressive interactions in the human brain.

Translating noisy sensory signals to perceptual decisions is critical for successful interactions in complex environments. Learning is known to improve perceptual judgments by filtering external noise and task-irrelevant information. Yet, little is known about the brain mechanisms that mediate learning-dependent suppression. Here, we employ ultra-high field magnetic resonance spectroscopy of GABA to test whether suppressive processing in decision-related and visual areas facilitates perceptual judgments during training. We demonstrate that parietal GABA relates to suppression of task-irrelevant information, while learning-dependent changes in visual GABA relate to enhanced performance in target detection and feature discrimination tasks. Combining GABA measurements with functional brain connectivity demonstrates that training on a target detection task involves local connectivity and disinhibition of visual cortex, while training on a feature discrimination task involves inter-cortical interactions that relate to suppressive visual processing. Our findings provide evidence that learning optimizes perceptual decisions through suppressive interactions in decision-related networks.This work was supported by 717 funding to ZK from the Alan Turing Institute, the Biotechnology and Biological Sciences 718 Research Council (Grants: H012508, P021255), the European Community’s Seventh 719 Framework Programme (Grant FP7/ 2007–2013 under agreement PITN-GA 2011-290011), 720 and the Wellcome Trust (Grant 205067). CJS holds a Sir Henry Dale Fellowship, funded by 721 the Wellcome Trust and the Royal Society (102584/Z/13/Z). ELH is supported by the NIHR 722 Oxford Health Biomedical Research Centre. The Wellcome Centre for Integrative 723 Neuroimaging is supported by core funding from the Wellcome Trust (203139/Z/16/Z)