scholarly journals Downregulation of early visual cortex excitability mediates oscillopsia suppression

Neurology ◽  
2017 ◽  
Vol 89 (11) ◽  
pp. 1179-1185 ◽  
Author(s):  
Hena Ahmad ◽  
R. Edward Roberts ◽  
Mitesh Patel ◽  
Rhannon Lobo ◽  
Barry Seemungal ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Motion ◽  
Cortical Excitability ◽  
Critical Role ◽  
Adaptive Mechanism ◽  
Motion Adaptation ◽  
Adaptive Mechanisms ◽  
Symptom Load ◽  
Early Visual Cortex ◽  
Adaptation Condition

Objective:To identify in an observational study the neurophysiologic mechanisms that mediate adaptation to oscillopsia in patients with bilateral vestibular failure (BVF).Methods:We directly probe the hypothesis that adaptive changes that mediate oscillopsia suppression implicate the early visual-cortex (V1/V2). Accordingly, we investigated V1/V2 excitability using transcranial magnetic stimulation (TMS) in 12 avestibular patients and 12 healthy controls. Specifically, we assessed TMS-induced phosphene thresholds at baseline and cortical excitability changes while performing a visual motion adaptation paradigm during the following conditions: baseline measures (i.e., static), during visual motion (i.e., motion before adaptation), and during visual motion after 5 minutes of unidirectional visual motion adaptation (i.e., motion adapted).Results:Patients had significantly higher baseline phosphene thresholds, reflecting an underlying adaptive mechanism. Individual thresholds were correlated with oscillopsia symptom load. During the visual motion adaptation condition, no differences in excitability at baseline were observed, but during both the motion before adaptation and motion adapted conditions, we observed significantly attenuated cortical excitability in patients. Again, this attenuation in excitability was stronger in less symptomatic patients.Conclusions:Our findings provide neurophysiologic evidence that cortically mediated adaptive mechanisms in V1/V2 play a critical role in suppressing oscillopsia in patients with BVF.

scholarly journals Differential effect of visual motion adaption upon visual cortical excitability

2017 ◽  
Vol 117 (3) ◽  
pp. 903-909 ◽  
Author(s):  
Astrid J. A. Lubeck ◽  
Angelique Van Ombergen ◽  
Hena Ahmad ◽  
Jelte E. Bos ◽  
Floris L. Wuyts ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Motion ◽  
Cortical Excitability ◽  
Roll Motion ◽  
Subjective Visual Vertical ◽  
Motion Adaptation ◽  
Visual Vertical ◽  
Early Visual Cortex ◽  
Phosphene Threshold ◽  
Visual Cortical

The objectives of this study were 1) to probe the effects of visual motion adaptation on early visual and V5/MT cortical excitability and 2) to investigate whether changes in cortical excitability following visual motion adaptation are related to the degree of visual dependency, i.e., an overreliance on visual cues compared with vestibular or proprioceptive cues. Participants were exposed to a roll motion visual stimulus before, during, and after visual motion adaptation. At these stages, 20 transcranial magnetic stimulation (TMS) pulses at phosphene threshold values were applied over early visual and V5/MT cortical areas from which the probability of eliciting a phosphene was calculated. Before and after adaptation, participants aligned the subjective visual vertical in front of the roll motion stimulus as a marker of visual dependency. During adaptation, early visual cortex excitability decreased whereas V5/MT excitability increased. After adaptation, both early visual and V5/MT excitability were increased. The roll motion-induced tilt of the subjective visual vertical (visual dependence) was not influenced by visual motion adaptation and did not correlate with phosphene threshold or visual cortex excitability. We conclude that early visual and V5/MT cortical excitability is differentially affected by visual motion adaptation. Furthermore, excitability in the early or late visual cortex is not associated with an increase in visual reliance during spatial orientation. Our findings complement earlier studies that have probed visual cortical excitability following motion adaptation and highlight the differential role of the early visual cortex and V5/MT in visual motion processing. NEW & NOTEWORTHY We examined the influence of visual motion adaptation on visual cortex excitability and found a differential effect in V1/V2 compared with V5/MT. Changes in visual excitability following motion adaptation were not related to the degree of an individual's visual dependency.

scholarly journals Cortical excitability controls the strength of mental imagery

2016 ◽  
Author(s):  
Rebecca Keogh ◽  
Johanna Bergmann ◽  
Joel Pearson
Keyword(s):  
Visual Cortex ◽  
Mental Imagery ◽  
Visual Imagery ◽  
Cortical Excitability ◽  
Mental Health Research ◽  
Causative Role ◽  
Mental Images ◽  
Neurophysiological Mechanism ◽  
Early Visual Cortex ◽  
Sensory Imagery

AbstractMental imagery provides an essential simulation tool for remembering the past and planning the future, with its strength affecting both cognition and mental health. Research suggests that neural activity spanning prefrontal, parietal, temporal, and visual areas supports the generation of mental images. Exactly how this network controls the strength of visual imagery remains unknown. Here, brain imaging and transcranial magnetic phosphene data show that lower resting activity and excitability levels in early visual cortex (V1-V3) predict stronger sensory imagery. Electrically decreasing visual cortex excitability using tDCS increases imagery strength, demonstrating a causative role of visual cortex excitability in controlling visual imagery. These data suggest a neurophysiological mechanism of cortical excitability involved in controlling the strength of mental images.

scholarly journals Opposite Dependencies on Visual Motion Coherence in Human Area MT+ and Early Visual Cortex

2006 ◽  
Vol 17 (7) ◽  
pp. 1542-1549 ◽  
Author(s):  
B. Handel ◽  
W. Lutzenberger ◽  
P. Thier ◽  
T. Haarmeier
Keyword(s):  
Visual Cortex ◽  
Visual Motion ◽  
Area Mt ◽  
Motion Coherence ◽  
Early Visual Cortex

scholarly journals Topographic organization of areas V3 and V4 and its relation to supra-areal organization of the primate visual system

2015 ◽  
Vol 32 ◽  
Author(s):  
M.J. ARCARO ◽  
S. KASTNER
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Large Scale ◽  
Critical Role ◽  
Visual Space ◽  
Anatomical Location ◽  
Visual Areas ◽  
Connectivity Patterns ◽  
Early Visual Cortex ◽  
Functional Areas

AbstractAreas V3 and V4 are commonly thought of as individual entities in the primate visual system, based on definition criteria such as their representation of visual space, connectivity, functional response properties, and relative anatomical location in cortex. Yet, large-scale functional and anatomical organization patterns not only emphasize distinctions within each area, but also links across visual cortex. Specifically, the visuotopic organization of V3 and V4 appears to be part of a larger, supra-areal organization, clustering these areas with early visual areas V1 and V2. In addition, connectivity patterns across visual cortex appear to vary within these areas as a function of their supra-areal eccentricity organization. This complicates the traditional view of these regions as individual functional “areas.” Here, we will review the criteria for defining areas V3 and V4 and will discuss functional and anatomical studies in humans and monkeys that emphasize the integration of individual visual areas into broad, supra-areal clusters that work in concert for a common computational goal. Specifically, we propose that the visuotopic organization of V3 and V4, which provides the criteria for differentiating these areas, also unifies these areas into the supra-areal organization of early visual cortex. We propose that V3 and V4 play a critical role in this supra-areal organization by filtering information about the visual environment along parallel pathways across higher-order cortex.

scholarly journals USING TRANSCRANIAL MAGNETIC STIMULATION (TMS) TO PROBE EFFECTS OF VISUAL MOTION ADAPTATION ON PRIMARY VISUAL CORTEX (V1) EXCITABILITY IN BILATERAL VESTIBULAR FAILURE (BVF) PATIENTS

2015 ◽  
Vol 86 (11) ◽  
pp. e4.70-e4
Author(s):  
Hena Ahmad ◽  
Richard Roberts ◽  
Qadeer Arshad Arshad ◽  
Mitesh Patel ◽  
Adolfo Bronstein
Keyword(s):  
Visual Motion ◽  
Cortical Plasticity ◽  
Cortical Excitability ◽  
Motion Processing ◽  
Motion Adaptation ◽  
Visual Motion Perception ◽  
Ocular Reflex ◽  
Visual Motion Processing ◽  
Vestibulo Ocular Reflex ◽  
Visual Cortical

Background and aimPatients with BVF report oscillopsia due to a defective vestibulo-ocular reflex causing retinal slip. No previous studies have probed visual cortical excitability using TMS and visual motion processing in these patients. We investigated the effects of visual motion adaptation on V1 cortical excitability in BVF patients and correlated this with psychophysical parameters.Methods12 BVF patients (7 males) aged 29–65 (mean=54.5) and 12 controls (6 males) aged 42–73 (mean=55) were recruited. Biphasic TMS pulses were applied at V1 and phosphene threshold (PT) was estimated. 3 measurement phases were (1) Stationary (2) Motion with optokinetic stimulation (OKS) Adaptation: OKS rightwards for 5 minutes 3) Post adaptation during viewing motion. All subjects completed questionnaires prior to the experiment. Results were analysed offline by calculating the probability of phosphene perception.ResultsBaseline phosphene thresholds were significantly higher in BVF patients (p=0.024) reflecting reduced visual cortical excitability. Lower oscillopsia scores correlated with reduced baseline V1 excitability (p=0.009).ConclusionsThis novel finding acts as a neurophysiological correlate for clinical observations of adaptive visual motion perception and is also correlated with psychophysical parameters. These results provide evidence for adaptive mechanisms leading to cortical plasticity following BVF.

scholarly journals Cortical excitability controls the strength of mental imagery

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Rebecca Keogh ◽  
Johanna Bergmann ◽  
Joel Pearson
Keyword(s):  
Visual Cortex ◽  
Mental Imagery ◽  
Visual Imagery ◽  
Cortical Excitability ◽  
Mental Health Research ◽  
Causative Role ◽  
Mental Images ◽  
Neurophysiological Mechanism ◽  
Early Visual Cortex ◽  
Sensory Imagery

Mental imagery provides an essential simulation tool for remembering the past and planning the future, with its strength affecting both cognition and mental health. Research suggests that neural activity spanning prefrontal, parietal, temporal, and visual areas supports the generation of mental images. Exactly how this network controls the strength of visual imagery remains unknown. Here, brain imaging and transcranial magnetic phosphene data show that lower resting activity and excitability levels in early visual cortex (V1-V3) predict stronger sensory imagery. Further, electrically decreasing visual cortex excitability using tDCS increases imagery strength, demonstrating a causative role of visual cortex excitability in controlling visual imagery. Together, these data suggest a neurophysiological mechanism of cortical excitability involved in controlling the strength of mental images.

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