scholarly journals Primary visual cortex excitability is not atypical in acquired synaesthesia

2019 ◽  
Author(s):  
Laura Lungu ◽  
Ryan Stewart ◽  
David P. Luke ◽  
Devin B. Terhune
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Primary Visual Cortex ◽  
Magnetic Stimulation ◽  
Neural Mechanisms ◽  
Cortical Hyperexcitability ◽  
Psychedelic Drugs ◽  
Phosphene Threshold ◽  
Threshold Range

AbstractA wealth of data suggests that psychedelic drugs elicit spontaneous perceptual states that resemble synaesthesia although it is unclear whether these different forms of synaesthesia share overlapping neural mechanisms. Multiple studies have shown that developmental and trained synaesthesia is characterized by selective hyperexcitability in primary visual cortex and it has been proposed that cortical hyperexcitability may contribute to induced and acquired synaesthesia. This study tested the prediction that a case of acquired synaesthesia (LW) would display selectively elevated primary visual cortex excitability, as reflected in lower transcranial magnetic stimulation (TMS) phosphene thresholds, but no difference in motor thresholds, relative to controls. In contrast to this prediction, LW’s phosphene threshold was well within the threshold range of controls. These results suggest that acquired synaesthesia is not characterized by atypical visual cortex excitability.

scholarly journals Primary visual cortex is necessary for blindsight-like behavior in neurologically healthy individuals: Review of transcranial magnetic stimulation studies

2021 ◽  
Author(s):  
Henry Railo ◽  
Mikko Hurme
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Visual Perception ◽  
Primary Visual Cortex ◽  
Visual Stimulus ◽  
Magnetic Stimulation ◽  
Neural Mechanisms ◽  
Partial Recovery ◽  
Visually Guided ◽  
Healthy Individuals

The visual pathways that bypass the primary visual cortex (V1) are often assumed to support visually guided behavior in humans in the absence of conscious vision. This conclusion is largely based on findings on patients: V1 lesions cause blindness but sometimes leave some visually guided behaviors intact—this is known as blindsight. With the aim of examining how well the findings on blindsight patients generalize to neurologically healthy individuals, we review studies which have tried to uncover transcranial magnetic stimulation (TMS) induced blindsight. In general, these studies have failed to demonstrate a completely unconscious blindsight-like capacity in neurologically healthy individuals. A possible exception to this is TMS-induced blindsight of stimulus presence or location. Because blindsight in patients is often associated with some form of introspective access to the visual stimulus, and may be associated with neural reorganization, we suggest that rather than revealing a dissociation between neural mechanisms of behavior and conscious seeing, blindsight may reflect preservation or partial recovery of conscious visual perception after the lesion.

Investigation of the primary visual cortex using short-interval paired-pulse transcranial magnetic stimulation (TMS)

2005 ◽  
Vol 382 (3) ◽  
pp. 312-316 ◽  
Author(s):  
Roland Sparing ◽  
Nina Dambeck ◽  
Kathrin Stock ◽  
Ingo G. Meister ◽  
Dorothee Huetter ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Primary Visual Cortex ◽  
Magnetic Stimulation ◽  
Short Interval ◽  
Paired Pulse

Excitability of Visual V1-V2 and Motor Cortices To Single Transcranial Magnetic Stimuli in Migraine: A Reappraisal Using A Figure-Of-Eight Coil

Cephalalgia ◽  
2003 ◽  
Vol 23 (4) ◽  
pp. 264-270 ◽  
Author(s):  
V Bohotin ◽  
A Fumai ◽  
M Vandenheede ◽  
C Bohotin ◽  
J Schoenen
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Healthy Volunteers ◽  
Migraine Attack ◽  
Magnetic Stimulation ◽  
Occipital Cortex ◽  
Motor Threshold ◽  
Phosphene Threshold

We used transcranial magnetic stimulation (TMS) with a figure-of-eight coil to excite motor and visual V1-V2 cortices in patients suffering from migraine without (MO) ( n = 24) or with aura (MA) ( n = 13) and in healthy volunteers (HV) ( n = 33). Patients who had a migraine attack within 3 days before or after the recordings were excluded. All females were recorded at mid-cycle. Single TMS pulses over the occipital cortex elicited phosphenes in 64% of HV, 63% of MO and 69% of MA patients. Compared with HV, the phosphene threshold was significantly increased in MO ( P = 0.001) and in MA ( P = 0.007), but there was no difference between the two groups of migraineurs. The motor threshold tended to be higher in both migraine groups than in HV, but the differences were not significant. In conclusion, this study shows that two-thirds (64.86%) of patients affected by either migraine type present an increased phosphene threshold in the interictal period, which suggests that their visual cortex is hypoexcitable.

Involvement of primary visual cortex in visual mental imagery: A transcranial magnetic stimulation study

1999 ◽  
Vol 25 (1) ◽  
pp. 25-31 ◽  
Author(s):  
Andr� Aleman ◽  
Alfredo A. L. d'Alfonso ◽  
Albert Postma ◽  
Edward H.F. de Haan
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Primary Visual Cortex ◽  
Mental Imagery ◽  
Magnetic Stimulation ◽  
Visual Mental Imagery

scholarly journals Effect of transcranial magnetic stimulation on single‐unit activity in the cat primary visual cortex

2003 ◽  
Vol 553 (2) ◽  
pp. 665-679 ◽  
Author(s):  
Vera Moliadze ◽  
Yongqiang Zhao ◽  
Ulf Eysel ◽  
Klaus Funke
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Primary Visual Cortex ◽  
Unit Activity ◽  
Magnetic Stimulation ◽  
Single Unit ◽  
Single Unit Activity

scholarly journals Perceptual Load Modulates Visual Cortex Excitability to Magnetic Stimulation

2008 ◽  
Vol 100 (1) ◽  
pp. 516-519 ◽  
Author(s):  
Neil Muggleton ◽  
Ruth Lamb ◽  
Vincent Walsh ◽  
Nilli Lavie
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Neural Activity ◽  
Magnetic Stimulation ◽  
Search Task ◽  
Perceptual Load ◽  
Neural Mechanisms ◽  
Task Irrelevant ◽  
Letter Search

Much recent research has shown that the level of perceptual load in a task determines the perception of task-irrelevant stimuli and associated neural activity, but the mediating neural mechanisms remain unclear. Here we show that increasing the level of perceptual load in a static letter search task results in an increase in the intensity of transcranial magnetic stimulation over V5/MT required to elicit the perception of a moving phosphene. These findings suggest that the neural mechanisms mediating the effects of perceptual load involve reduced visual cortex excitability in task-unrelated areas.

scholarly journals Superimposed gratings induce diverse response patterns of gamma oscillations in primary visual cortex

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bin Wang ◽  
Chuanliang Han ◽  
Tian Wang ◽  
Weifeng Dai ◽  
Yang Li ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Field Potential ◽  
Gamma Oscillations ◽  
Neural Mechanisms ◽  
Model Parameters ◽  
Response Patterns ◽  
Region Difference ◽  
High Gamma ◽  
Spiking Activity

AbstractStimulus-dependence of gamma oscillations (GAMMA, 30–90 Hz) has not been fully understood, but it is important for revealing neural mechanisms and functions of GAMMA. Here, we recorded spiking activity (MUA) and the local field potential (LFP), driven by a variety of plaids (generated by two superimposed gratings orthogonal to each other and with different contrast combinations), in the primary visual cortex of anesthetized cats. We found two distinct narrow-band GAMMAs in the LFPs and a variety of response patterns to plaids. Similar to MUA, most response patterns showed that the second grating suppressed GAMMAs driven by the first one. However, there is only a weak site-by-site correlation between cross-orientation interactions in GAMMAs and those in MUAs. We developed a normalization model that could unify the response patterns of both GAMMAs and MUAs. Interestingly, compared with MUAs, the GAMMAs demonstrated a wider range of model parameters and more diverse response patterns to plaids. Further analysis revealed that normalization parameters for high GAMMA, but not those for low GAMMA, were significantly correlated with the discrepancy of spatial frequency between stimulus and sites’ preferences. Consistent with these findings, normalization parameters and diversity of high GAMMA exhibited a clear transition trend and region difference between area 17 to 18. Our results show that GAMMAs are also regulated in the form of normalization, but that the neural mechanisms for these normalizations might differ from those of spiking activity. Normalizations in different brain signals could be due to interactions of excitation and inhibitions at multiple stages in the visual system.

scholarly journals Top-down control of visual cortex by the frontal eye fields through oscillatory realignment

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Domenica Veniero ◽  
Joachim Gross ◽  
Stephanie Morand ◽  
Felix Duecker ◽  
Alexander T. Sack ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Visual Perception ◽  
Magnetic Stimulation ◽  
Single Pulse ◽  
Frontal Eye Fields ◽  
Phase Reset ◽  
Top Down ◽  
Visual Areas ◽  
Beta Frequency

AbstractVoluntary allocation of visual attention is controlled by top-down signals generated within the Frontal Eye Fields (FEFs) that can change the excitability of lower-level visual areas. However, the mechanism through which this control is achieved remains elusive. Here, we emulated the generation of an attentional signal using single-pulse transcranial magnetic stimulation to activate the FEFs and tracked its consequences over the visual cortex. First, we documented changes to brain oscillations using electroencephalography and found evidence for a phase reset over occipital sites at beta frequency. We then probed for perceptual consequences of this top-down triggered phase reset and assessed its anatomical specificity. We show that FEF activation leads to cyclic modulation of visual perception and extrastriate but not primary visual cortex excitability, again at beta frequency. We conclude that top-down signals originating in FEF causally shape visual cortex activity and perception through mechanisms of oscillatory realignment.

Timing of activity in early visual cortex as revealed by transcranial magnetic stimulation

Neuroreport ◽  
1999 ◽  
Vol 10 (12) ◽  
pp. 2631-2634 ◽  
Author(s):  
Erik Corthout ◽  
Bob Uttl ◽  
Vincent Walsh ◽  
Mark Hallett ◽  
Alan Cowey
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Early Visual Cortex
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