Biology subjects

Naotsugu Tsuchiya

Publications and source records attributed to Naotsugu Tsuchiya.

6 recordsLinked to original sources

bioRxiv2016

Optokinetic nystagmus reflects perceptual directions in the onset binocular rivalry in Parkinson′s disease

Optokinetic nystagmus (OKN), the reflexive eye movements evoked by a moving field, has recently gained interest among researchers as a useful tool to assess conscious perception. When conscious perception and stimulus are dissociated, such as in binocular rivalry --when dissimilar images are simultaneously presented to each eye and perception alternates between the two images over time -- OKN correlates with perception rather than with the physical direction of the moving field. While this relationship is well established in healthy subjects it is yet unclear whether it also generalizes to clinical populations, for example, patients with Parkinsons disease. Parkinsons disease is a motor disorder, causing tremor, slow movements and rigidity. It may also be associated with oculomotor deficits, such as impaired saccades and smooth pursuit eye movements. Here, we employed short-duration, onset binocular rivalry (2 s trial of stimulus presentation followed by 1 s inter-trial interval) with moving grating stimuli to assess OKN in Parkinsons disease patients (N=39) and controls (N=29) of a similar age. Each trial was either non-rivalrous (same stimuli presented to both eyes) or rivalrous, as in binocular rivalry. We analyzed OKN to discriminate direction of stimulus and perception on a trial-by-trial basis. OKN reflected conscious perceptions in both groups. Treatment with anti-Parkinson drugs and deep brain stimulation improved motor ability of patients assessed by a standard scale of Parkinsons disease, but did not impact on OKN. Furthermore, OKN-based measures were robust and their latencies were shorter than manual button-based measures in all subjects, regardless of stimulus condition. Our findings suggest that OKN can be used as an indicator of conscious perception in binocular rivalry even in Parkinsons disease patients in whom impaired manual dexterity may render button-press reports less reliable.

Neuroscience↗

bioRxiv2016

Learning improves conscious access at the bottom, but not the top: Reverse hierarchical effects in perceptual learning and metacognition

Experience with visual stimuli can improve their perceptual performance, a phenomenon termed visual perceptual learning (VPL), but how does VPL shape our conscious experience of learned stimuli? VPL has been found to improve measures of metacognition, suggesting increased conscious stimulus accessibility. Such studies however, have largely failed to control objective task accuracy, which typically correlates with metacognition. Here, using a staircase method to control this confound, we investigated whether VPL improves the metacognitive accuracy of perceptual judgements. Across three consecutive days, subjects learned to discriminate faces based on either their identity or contrast. Holding objective accuracy constant, perceptual thresholds improved in both tasks, while metacognitive accuracy diverged, with face contrast VPL improving metacognition, and face identity VPL failing to. Our findings can be interpreted in a reverse hierarchy theory-like model of VPL, which counterintuitively predicts that the VPL of low- but not high-level stimulus properties should improve conscious stimulus accessibility.

Neuroscience↗

bioRxiv2016

Simulated forward and backward self motion, based on realistic parameters, causes strong motion induced blindness

Motion Induced Blindness (MIB) is a well-established visual phenomenon whereby highly salient targets disappear when viewed against a moving background mask. No research has yet explored whether contracting and expanding optic flow can also trigger target disappearance. We explored MIB using mask speeds corresponding to driving at 35, 50, 65 and 80 km/h in simulated forward (expansion) and backward (contraction) motion as well as 2-D radial movement, random, and static mask motion types. Participants (n = 18) viewed MIB targets against masks with different movement types, speed, and target locations. To understand the relationship between saccades, pupil response and perceptual disappearance, we ran two additional eye-tracking experiments (n = 19). Target disappearance increased significantly with faster mask speeds and upper visual field target presentation. Simulated optic flow and 2-D radial movement caused comparable disappearance, and all moving masks caused significantly more disappearance than a static mask. Saccades could not entirely account for differences between conditions, suggesting that self-motion optic flow does cause MIB in an artificial setting. Pupil analyses implied that MIB disappearance induced by optic flow is not subjectively salient, potentially explaining why MIB is not noticed during driving. Potential implications of MIB for driving safety and Head-Up-Display (HUD) technologies are discussed.

Neuroscience↗

bioRxiv2016

Local versus global effects of isoflurane anesthesia on visual processing in the fly brain

Introduction Introduction Results Discussion Methods References Volatile general anesthetics such as isoflurane abolish behavioral responsiveness in all animals, but the neural underpinnings of this phenomenon remain unclear (van Swinderen and Kottler, 2014). Although the cellular and molecular mechanisms through which general anesthetics work have been quite well characterized (Franks, 2008, Garcia et al., 2010, Brown et al., 2011), it is unclear what aspect of neural activity is at the core of the profound disconnection from the environment that is induced by all general anesthetics. To some extent, our understanding of the mechanisms of general anesthesia has paralleled our understanding of how the brain works, from neurons and action potentials, to receptor ...

Neuroscience↗

bioRxiv2016

Contents of Consciousness Investigated as Integrated Information in Direct Human Brain Recordings

Integrated information theory postulates that the particular way stimuli appear when we consciously experience them arises from integrated information relationships across neural populations. We investigated if such equivalence holds by testing if similar/different percepts map onto similar/different information structures. We computed integrated information structure from intracranial EEGs recorded in 6 neurosurgical patients who had electrodes implanted over posterior cortices. During recording, we dissociated subjective percepts from physical inputs in three distinct stimulus paradigms (passive viewing, continuous flash suppression, and backward masking). Unsupervised classification showed that integrated information within stimulus-selective cortical regions classified visual experiences with significant accuracy (peaking on average around 64% classification accuracy). Classification by other relevant information theoretic measures such as mutual information and entropy was consistently poorer (56% and 54% accuracy). The findings argue that concepts from integrated information theory are empirically testable, promising a potential link between conscious experience and informational structures.

Neuroscience↗

bioRxiv2016

Intracranial Markers of Conscious Face Perception in Humans

The comparison between perceived and unperceived trials at perceptual threshold isolates not only the core neuronal substrate of a particular conscious perception, but also aspects of brain activity that facilitate, hinder or tend to follow conscious perception. We take a step towards the resolution of these confounds by combining an analysis of ECoG neuronal responses observed during the presentation of faces partially masked by Continuous Flash Suppression, and those responses observed during the unmasked presentation of faces and other images in the same subjects. Neuronal activity in both the fusiform gyrus and the superior temporal sulcus discriminated seen vs. unseen faces in the masked paradigm and upright faces vs. other categories in the unmasked paradigm. However, only the former discriminated upright vs. inverted faces in the unmasked paradigm. Our results suggest a prominent role for the fusiform gyrus in the configural perception of faces.

Neuroscience↗