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SummaryVisual acuity was tested and the anterior portion of the eye inspected among the Gidra in Lowland Papua New Guinea, who depend on hunting for their animal food. The visual acuity of the youths and adults was as high as that of hunters and gatherers; 88% of the males and 81% of the females had an acuity of 1·2 or better. The elders had far lower acuity, correlated with the advance of cataract. The senescent (...) class='Hi'>visual acuity is discussed in relation to little practice and low productivity of the elders' hunting, and to the Gidra traditional age-grade system. (shrink)

After a discourse about the literature on visual acuity before Hume, I discuss how the "size" of visual objects is defined and determined. I shall then present circumstantial, but commanding, evidence for the influence of James Jurin's Essay upon Distinct and Indistinct Vision on Hume's thought. This work contains well-supported findings incompatible with claims made in T 1.2, "Of the ideas of space and time," and elsewhere. Specifically, the prominent principle of the Treatise, "[w]hat consists of parts (...) is distinguishable into them, and what is distinguishable is separable" (T 1.2.1.3; SBN 27) is shown to be false. A powerful principle, it is a premise to the most important arguments of the Treatise, but is shunned in the Enquiry and later writings because, I believe, Hume had read Jurin. (shrink)

Angry faces have been shown to be detected more efficiently in a crowd of distractors compared to happy faces, known as the anger superiority effect (ASE). The present study investigated whether the ASE could be modified by top-down manipulation of working memory (WM), in central and peripheral visual fields. In central vision, participants held a colour in WM for a final memory test while simultaneously performing a visual search task that required them to determine whether a face (...) showed a different expression from other coloured faces. The colour held in WM matched either the colour of the target face (target-matching), the colour of a distractor face (distractor-matching), or neither (non-matching). Results showed that the ASE was observed when the probability of target-matching trials was low. However, when the top-down WM effect was strengthened by raising the probability of target-matching trials, the ASE in the target-matching condition was completely eliminated. Intriguingly, when the visual search task was substituted by a peripheral crowding task, similar results to central vision were found in the target-matching condition. Taken together, our findings indicate that the ASE is subject to the top-down WM effect, regardless of the visual field. (shrink)

Neurofibromatosis type 1 is associated with peripheral and central nervous system tumors. It is noteworthy that the regions in which these tumors frequently arise are the optic pathways and the brainstem. Thus, we decided to trace the procedure of diffusion Magnetic Resonance Imaging alterations along with Short-Wavelength Automated Perimetry examinations of the OPs after surgery and chemotherapy over 1 year, which enabled us to evaluate chemotherapy's efficacy in an NF1 patient with an OP tumor. In this study, a 25-year-old (...) woman with NF1 and left optic radiation glioma underwent surgery to remove the glioma. Immunohistochemistry revealed a Pilocytic Astrocytoma WHO grade I. Post-operation chemotherapy done using nine treatment cycles of administering Temozolomide for 5 days every 4 weeks. Applying the region of interest differential tractography method and SWAP four times every 3 months allowed us to follow the patient's visual acuity alterations longitudinally. The differential deterministic tractography method and statistical analyses enabled us to discover the white matter tracts anisotropy alterations over time. Furthermore, statistical analyses on the SWAP results along time illustrated possible alterations in visual acuity. Then, we could compare and associate the findings with the SWAP examinations and patient symptoms longitudinally. Statistical analyses of SWAP tests revealed a significant improvement in visual fields, and longitudinal differential tractography showed myelination and dense axonal packing in the left OR after 1 year of treatment. In this study, we examined an old hypothesis suggesting that chemotherapy is more effective than radiotherapy for NF1 patients with OP gliomas because of the radiation side effects on the visual field, cognition, and cerebrovascular complications. Our longitudinal clinical case study involving dMRI and SWAP on a single NF1-OPG patient showed that chemotherapy did not suppress the OP myelination over time. However, it should be noted that this is a clinical case study, and, therefore, the generalization of results is limited. Future investigations might focus on genetic-based imaging, particularly in more cases. Further, meta-analyses are recommended for giving a proper Field Of View to researchers as a subtle clue regarding precision medicine. (shrink)

Sensory substitution devices (SSDs) aim to compensate for the loss of a sensory modality, typically vision, by converting information from the lost modality into stimuli in a remaining modality. “The vOICe” is a visual-to-auditory SSD which encodes images taken by a camera worn by the user into “soundscapes” such that experienced users can extract information about their surroundings. Here we investigated how much detail was resolvable during the early induction stages by testing the acuity of blindfolded sighted, naïve (...) vOICe users. Initial performance was well above chance. Participants who took the test twice as a form of minimal training showed a marked improvement on the second test. Acuity was slightly but not significantly impaired when participants wore a camera and judged letter orientations “live”. A positive correlation was found between participants' musical training and their acuity. The relationship between auditory expertise via musical training and the lack of a relationship with visual imagery, suggests that early use of a SSD draws primarily on the mechanisms of the sensory modality being used rather than the one being substituted. If vision is lost, audition represents the sensory channel of highest bandwidth of those remaining. The level of acuity found here, and the fact it was achieved with very little experience in sensory substitution by naïve users is promising. (shrink)

Proprioceptive acuity is of great significance in basic research exploring a possible neural mechanism of fine motor control and in neurorehabilitation practice promoting motor function recovery of limb-disabled people. Moreover, body representation relies on the integration of multiple somatic sensations, including proprioception that is mainly generated in muscles and tendons of human joints. This study aimed to examine two hypotheses: First, different extension positions of wrist joint have different proprioceptive acuities, which might indicate different body representations of wrist joint (...) in the brain. Second, repetitive peripheral magnetic stimulation applied peripherally to the forearm radial nerve and extensors could change proprioceptive acuity at the wrist joint. Thirty-five healthy participants were recruited then randomly divided into the real stimulation group and the sham stimulation group. The participants’ non-dominant side wrist joint position sense was tested at six extension positions within the physiological joint motion range both before stimulation and after stimulation. Results showed that proprioceptive bias among six extension positions could be divided into lower-extension position and higher-extension position. One session rPMS could influence proprioceptive bias in lower-extension position but not in higher-extension position. However, proprioceptive precision was not influenced. To conclude, proprioceptive bias may vary between different wrist extension positions due to different hand postures being related to changes in body representation, and different functions relating to proprioceptive bias and proprioceptive precision may underlie two aspects of body representation. (shrink)