scholarly journals Occipital Petalia and Albinism: A Study of Interhemispheric VEP Asymmetries in Albinism with No Nystagmus

2019 ◽  
Vol 8 (6) ◽  
pp. 802 ◽  
Author(s):  
Alkiviades Liasis ◽  
Sian E. Handley ◽  
Ken K. Nischal
Keyword(s):  
Right Hemisphere ◽  
Normal Subjects ◽  
Visual Pathway ◽  
Field Pattern ◽  
Pattern Reversal ◽  
Full Field ◽  
Pathway Function ◽  
Left And Right ◽  
The Right ◽  
Stimulation Of

The purpose of this study was to assess chiasmal misrouting in a cohort of children with albinism with no nystagmus using hemifield visual evoked potentials (VEP) measures. Methods: Monocular VEPs were recorded and analyzed from three electrodes (O1, Oz, and O2 referred to Fz) from 16 children with albinism without nystagmus. Pattern reversal (full field and hemifield stimulation), full field pattern appearance and flash stimuli were used to evoke VEPs for each eye. Results: The amplitude of the pattern reversal VEPs to stimulation of the hemifield corresponding to the crossing pathways were as expected significantly larger than those to the non-crossing in each eye ((right eye p = 0.000004), (left eye p = 0.001)). Pattern reversal VEPs recorded from the left hemisphere were also larger than those from the right and most evident when comparing the crossing pathways of each eye (p = 0.004). Conclusions: This study has demonstrated electrophysiological differences in visual pathway function of the left and right hemisphere in subjects with albinism like that previously described in controls. Nasal field stimulation activated crossing and non-crossing pathways in patients with albinism and as a result, nasal hemifield VEPs in albinism are less lateralized compared to what is found in normal subjects.

Pattern-reversal visual evoked potentials in patients with hydrocephalus

1985 ◽  
Vol 62 (2) ◽  
pp. 234-237 ◽  
Author(s):  
Shakir M. Alani
Keyword(s):  
Evoked Potentials ◽  
Visual Evoked Potentials ◽  
Right Hemisphere ◽  
Visual Pathway ◽  
Pattern Reversal ◽  
Field Stimulation ◽  
Content Type ◽  
Clinical Methods ◽  
The Right ◽  
Visual Evoked

✓ Pattern-reversal visual evoked potentials (VEP's) in response to whole- and half-field stimulation were studied in 10 patients with hydrocephalus. Abnormalities consistent with optic nerve dysfunction were recorded in four patients. Two patients had response asymmetry to half-field stimulation, which suggested dysfunction of the visual pathway in the right hemisphere. The remaining four patients had normal responses. Measurement of VEP's was repeated after the surgical treatment of hydrocephalus in four patients, and showed marked improvement in two of the three patients with preoperative abnormalities. This study suggests that, in patients with hydrocephalus, VEP's are more sensitive than clinical methods in detecting visual pathway dysfunction and that they can be useful in the follow-up monitoring of surgically treated hydrocephalic patients.

scholarly journals Drawing with the Non-dominant Hand: Implications for the Study of Construction

1998 ◽  
Vol 25 (4) ◽  
pp. 306-309 ◽  
Author(s):  
Sherma Zacharias ◽  
Andrew Kirk
Keyword(s):  
Neurological Disease ◽  
Right Hemisphere ◽  
Normal Subjects ◽  
Elderly Subjects ◽  
Dominant Hand ◽  
Left Hand ◽  
Right Hand ◽  
Left And Right ◽  
The Right ◽  
Right And Left Hand

ABSTRACT:Background:Constructional impairment following left vs. right hemisphere damage has been extensively studied using drawing tasks. A confounding factor in these studies is that right-handed patients with left hemisphere damage (LHD) are often forced by weakness to use their non-dominant (left) hand or hemiparetic dominant hand. Qualitative differences in the drawing characteristics of left and right hand drawings by normal subjects have not previously been characterized. The present study was undertaken to determine the qualitative differences between left and right hand drawings of normal subjects.Methods:Thirty right-handed, elderly subjects without a history of neurological disease were asked to draw, from memory, seven objects using the right and left hand. Half of the subjects were randomly assigned to draw with the left hand first, and half the right hand first. Right and left hand drawings were compared using a standardized scoring system utilized in several previous studies of drawing in focal and diffuse neurological disease. Each drawing was scored on eighteen criteria. Right and left hand drawing scores were then compared using the t-test for paired samples or the Wilcoxon matched-pairs testResults:Drawings made using the left hand were found to be significantly simpler, more tremulous and of poorer overall quality than drawings made by the same subjects using the right hand.Conclusions:The deficits found in left versus right hand drawings of normals are similar to those found in patients with LHD, suggesting that much of the drawing impairment seen following LHD is due to an elementary motor disturbance related to use of the non-dominant hand.

Bihemispheric Language: How the Two Hemispheres Collaborate in the Processing of Language

2004 ◽  
Author(s):  
Norman D. Cook
Keyword(s):  
Language Processing ◽  
Right Hemisphere ◽  
Central Question ◽  
Linguistic Processing ◽  
Figures Of Speech ◽  
Language Functions ◽  
Left And Right ◽  
Level Of Understanding ◽  
The Right

Speech production in most people is strongly lateralized to the left hemisphere (LH), but language understanding is generally a bilateral activity. At every level of linguistic processing that has been investigated experimentally, the right hemisphere (RH) has been found to make characteristic contributions, from the processing of the affective aspects of intonation, through the appreciation of word connotations, the decoding of the meaning of metaphors and figures of speech, to the understanding of the overall coherency of verbal humour, paragraphs and short stories. If both hemispheres are indeed engaged in linguistic decoding and both processes are required to achieve a normal level of understanding, a central question concerns how the separate language functions on the left and right are integrated. This chapter reviews relevant studies on the hemispheric contributions to language processing and the role of interhemispheric communications in cognition.

Right hemisphere speech perception revealed by amobarbital injection and electrical interference

Neurology ◽  
1998 ◽  
Vol 51 (2) ◽  
pp. 458-464 ◽  
Author(s):  
D. Boatman ◽  
J. Hart ◽  
R. P. Lesser ◽  
N. Honeycutt ◽  
N. B. Anderson ◽  
...  
Keyword(s):  
Speech Perception ◽  
Left Hemisphere ◽  
Temporal Lobe ◽  
Right Hemisphere ◽  
Adult Brain ◽  
Left Posterior ◽  
Left And Right ◽  
Sodium Amobarbital ◽  
The Right ◽  
Electrical Interference

Objective: To investigate the right hemispheric speech perception capabilities of an adult right-handed patient with seizures.Methods: Consecutive, unilateral, intracarotid sodium amobarbital injections and left hemispheric electrical interference mapping were used to determine lateralization and localization of speech perception, measured as syllable discrimination.Results: Syllable discrimination remained intact after left and right intracarotid sodium amobarbital injections. Language otherwise strongly lateralized to the left hemisphere. Despite evidence of bilateral speech perception capabilities, electrical interference testing in the left posterior temporal lobe impaired syllable discrimination.Conclusions: The results suggest a functionally symmetric, parallel system in the adult brain with preferential use of left hemispheric pathways for speech perception.

Vocal Reaction Times to Tachistoscopically Presented High- and Low-Frequency Verbs: Some Evidence for Selective Minor Hemisphere Linguistic Analysis

1988 ◽  
Vol 66 (3) ◽  
pp. 803-810 ◽  
Author(s):  
Michael P. Rastatter ◽  
Catherine Loren
Keyword(s):  
Visual Field ◽  
High Frequency ◽  
Right Hemisphere ◽  
Visual Fields ◽  
Reaction Times ◽  
Low Frequency ◽  
Normal Subjects ◽  
Right Visual Field ◽  
Intact Brain ◽  
The Right

The current study investigated the capacity of the right hemisphere to process verbs using a paradigm proven reliable for predicting differential, minor hemisphere lexical analysis in the normal, intact brain. Vocal reaction times of normal subjects were measured to unilaterally presented verbs of high and of low frequency. A significant interaction was noted between the stimulus items and visual fields. Post hoc tests showed that vocal reaction times to verbs of high frequency were significantly faster following right visual-field presentations (right hemisphere). No significant differences in vocal reaction time occurred between the two visual fields for the verbs of low frequency. Also, significant differences were observed between the two types of verbs following left visual-field presentation but not the right. These results were interpreted to suggest that right-hemispheric analysis was restricted to the verbs of high frequency in the presence of a dominant left hemisphere.

scholarly journals Cortical Contrast Processing in Retinitis Pigmentosa: Evidence of PVEPs Spatial Functions

2020 ◽  
Vol 10 (4) ◽  
pp. 1010-1019
Author(s):  
Rafael Mancebo-Azor ◽  
José Antonio Sáez-Moreno ◽  
José Manuel Rodríguez-Ferrer
Keyword(s):  
Retinitis Pigmentosa ◽  
Evoked Potentials ◽  
Visual Evoked Potentials ◽  
Normal Subjects ◽  
Pattern Reversal ◽  
Check Size ◽  
Low Contrast ◽  
Control Subjects ◽  
The Right ◽  
Visual Evoked

Objective: To study the effect of check width size of the stimuli on the amplitude and latency of the P100 component of visual evoked potentials recorded in patients with retinitis pigmentosa (RP). Methods: Pattern reversal visual evoked potentials (PVEPs) were recorded in 16 RP patients and 20 visually normal subjects. Pattern reversal stimuli with five different check widths and 100% of contrast were projected in the right eye of both patients and control subjects. PVEPs induced by stimuli with 78%, 16%, and 6% of contrast were also recorded in 10 of the control subjects. Results: In RP patients, the amplitude of P100 was smaller than controls in all check sized used and the peak P100 amplitude was obtained with a larger check width than in controls. P100 was also delayed in RP patients in all check sizes studied. The P100 amplitude- and latency-check size functions of RP patients were like those found in control subjects with low contrast stimuli of 16% and 6%. Conclusion: The PVEPs spatial functions of RP patients show quantitative and qualitative changes, suggesting disease induced alteration in the neural processing of stimulus contrast.

Hemispheric Asymmetries in a Signal Detection Task

1983 ◽  
Vol 57 (3) ◽  
pp. 923-929 ◽  
Author(s):  
John L. Andreassi ◽  
Charles S. Rebert ◽  
Ferol F. Larsen
Keyword(s):  
Signal Detection ◽  
Right Hemisphere ◽  
Reaction Times ◽  
Vigilance Task ◽  
Verbal Stimulus ◽  
Right Visual Field ◽  
Left And Right ◽  
The Right ◽  
Male Subjects ◽  
Central Fixation

Reaction time and signal detection performance were measured during a 78-min. vigilance task. 12 right-handed male subjects served in two experimental sessions. Subjects focused on a central fixation point and responded to signals presented at unpredictable times in one of three locations: 2.5° to right of central fixation, central, and 2.5° to the left of center. Subjects decided whether to press a response key with either the left or right hand with each presentation. Over-all vigilance performance (signal detections and response time) was similar for left and right visual-field presentations. Evidence from reaction times indicated that responses controlled by the left hemisphere were faster to a verbal stimulus (T) while reactions controlled by the right hemisphere were faster to an apparent non-verbal stimulus, an inverted T.

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