Retinotopy with coordinates of lateral occipital cortex in humans

2004 ◽  
Vol 101 (1) ◽  
pp. 114-118 ◽  
Author(s):  
Takanobu Kaido ◽  
Tohru Hoshida ◽  
Toshiaki Taoka ◽  
Toshisuke Sakaki
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Occipital Lobe ◽  
Occipital Cortex ◽  
Cortical Stimulation ◽  
Content Type ◽  
X Ray ◽  
Lateral Occipital Cortex ◽  
Fine Print ◽  
Stimulation Of

Object. The lateral occipital cortex in humans is known as the “extrastriate visual cortex.” It is, however, an unexplored field of research, and the anatomical nomenclature for its surface has still not been standardized. This study was designed to investigate whether the lateral occipital cortex in humans has retinotopic representation. Methods. Four right-handed patients with a diagnosis of intractable epilepsy from space-occupying lesions in the occipital lobe or epilepsy originating in the occipital lobe received permanently implanted subdural electrodes. Electrical cortical stimulation was applied directly applied to the brain through metal electrodes by using a biphasic stimulator. The location of each electrode was measured on a lateral skull x-ray study. Each patient considered a whiteboard with vertical and horizontal median lines. The patient was asked to look at the midpoint on the whiteboard. If a visual hallucination or illusion occurred, the patient recorded its outline, shape, color, location, and motion on white paper one tenth the size of, and with vertical and horizontal median lines similar to those on, the whiteboard. Polar angles and eccentricities of the midpoints of the phosphenes from the coordinate origin were measured on the paper. On stimulation of the lateral occipital lobe, 44 phosphenes occurred. All phosphenes were circular or dotted, with a diameter of approximately 1 cm, except one that was like a curtain in the peripheral end of the upper and lower visual fields on stimulation of the parietooccipital region. All phosphenes appeared in the visual field contralateral to the cerebral hemisphere stimulated. On stimulation of the lateral occipital lobe, 22 phosphenes moved centrifugally or toward a horizontal line. From three-dimensional scatterplots and contour maps of the polar angles and eccentricities in relation to the x-ray coordinates of the electrodes, one can infer that the lateral occipital cortex in humans has retinotopic representation. Conclusions. The authors found that phosphenes induced by electrical cortical stimulation of the lateral occipital cortex represent retinotopy. From these results one can assert that visual field representation with retinotopic relation exists in the extrastriate visual cortex.

Writing-specific sites in frontal areas: a cortical stimulation study

2004 ◽  
Vol 101 (5) ◽  
pp. 787-798 ◽  
Author(s):  
Vincent Lubrano ◽  
Franck-Emmanuel Roux ◽  
Jean-François Démonet
Keyword(s):  
Brain Tumors ◽  
Individual Variability ◽  
Cortical Stimulation ◽  
Awake Surgery ◽  
Direct Stimulation ◽  
Content Type ◽  
Left Handed ◽  
Language Areas ◽  
Fine Print ◽  
Stimulation Of

Object. The aim of this study was to determine whether cortical areas involved in the writing process are associated with reading or naming areas in patients undergoing surgery for brain tumors in frontal areas. This study was undertaken to spare all language areas found in patients during surgery. Methods. Fourteen patients (eight women and six men [mean age 47 years] of whom 12 were right handed, two left handed, 12 monolingual, and two bilingual) who harbored brain tumors in the left (11 patients) or right (three patients) frontal gyri or in rolandic areas, were tested by direct stimulation by using the awake surgery technique for direct brain mapping. Mapping of the frontal gyri was performed using naming, reading, and writing under dictation tasks in the appropriate language(s). Considerable individual variability in language organization among patients was observed. Interferences in writing were found during direct stimulation in the frontal gyri, in cortical sites common or not common to interferences in naming or reading. In dominant regions, patterns of writing dysfunctions were variable and included writing arrest, illegible script, letter omissions, and paragraphia. These dysfunctions were nonspecific (stimulation-induced eye movements) in nondominant frontal regions and in rolandic gyri (hand contractions). In the same patient, different writing impairments could sometimes be observed during stimulation of different sites. As is the case for naming or reading interference sites, writing interference sites could be extremely localized (1 cm2 in diameter). In this group of patients, writing interference sites found in Broca areas were associated with other sites of language interference, whereas writing-specific interference sites were found twice in the dominant middle frontal gyrus. Conclusions. In this series, we found that writing interference sites could be detected by direct cortical stimulation in dominant inferior and middle frontal gyri regardless of whether they were associated with naming or reading interference sites. Writing disorders elicited by direct stimulation in the frontal lobes are varied and probably depend on the functional status of the stimulated cortical area.

Functional evaluation using magnetic resonance imaging of the visual cortex in patients with retrochiasmatic lesions

1998 ◽  
Vol 89 (5) ◽  
pp. 780-790 ◽  
Author(s):  
Spyros S. Kollias ◽  
Klara Landau ◽  
Nadia Khan ◽  
Xavier Golay ◽  
Rene Bernays ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Magnetic Resonance ◽  
Visual Field ◽  
Motion Artifacts ◽  
Anatomical Location ◽  
Functional Evaluation ◽  
Essential Information ◽  
Content Type ◽  
Human Visual Cortex ◽  
Fine Print

Object. The goal of this study was to evaluate the clinical potential of combining functional magnetic resonance (fMR) imaging with conventional morphological MR imaging and to assess its usefulness for objective evaluation of visual function as part of treatment planning in patients harboring space-occupying lesions involving the posterior afferent visual system. Methods. It was hypothesized that regional activation of the visual cortex during visual stimulation would show an asymmetric response consistent with the well-known retinotopical organization of the human visual cortex. To test this hypothesis, the pattern of regional cortical activity detected by fMR imaging during binocular repetitive photic stimulation (10 Hz) was compared with the findings of conventional visual field testing. Functional mapping of the visual cortex was performed using a noninvasive blood oxygen level—dependent MR technique in 10 patients with intraaxial and two with extraaxial lesions. Experiments involving two of the patients were unsuccessful because of motion artifacts. In all the remaining patients functional activity was demonstrated in the primary visual area that corresponded to the anatomical location of the calcarine cortex. In nine patients, the identified patterns of activation in the visual cortex were consistent with the visual field deficits (seven homonymous hemianopsias, one homonymous central scotoma, and one inferior quadrantanopsia) and with the traditional teaching of retinotopical representation. Discordance between fMR imaging and perimetric findings was observed in one case. Conclusions. These results demonstrate that fMR imaging can be performed routinely and successfully in patients with visual abnormalities as part of a conventional neuroradiological evaluation. The technique provides essential information about the function—structure relationship specific to an individual patient and holds promise not only for diagnosis and therapy planning, but also for understanding the topography and functional specialization of the human visual cortex.

Phosphene perceptions and safety of chronic visual cortex stimulation in a blind subject

2020 ◽  
Vol 132 (6) ◽  
pp. 2000-2007 ◽  
Author(s):  
Soroush Niketeghad ◽  
Abirami Muralidharan ◽  
Uday Patel ◽  
Jessy D. Dorn ◽  
Laura Bonelli ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Adverse Events ◽  
Clinical Intervention ◽  
Occipital Cortex ◽  
Neuronal Population ◽  
Serious Adverse Events ◽  
Stimulation Parameters ◽  
The Right ◽  
Visual Cortical ◽  
Stimulation Of

Stimulation of primary visual cortices has the potential to restore some degree of vision to blind individuals. Developing safe and reliable visual cortical prostheses requires assessment of the long-term stability, feasibility, and safety of generating stimulation-evoked perceptions.A NeuroPace responsive neurostimulation system was implanted in a blind individual with an 8-year history of bare light perception, and stimulation-evoked phosphenes were evaluated over 19 months (41 test sessions). Electrical stimulation was delivered via two four-contact subdural electrode strips implanted over the right medial occipital cortex. Current and charge thresholds for eliciting visual perception (phosphenes) were measured, as were the shape, size, location, and intensity of the phosphenes. Adverse events were also assessed.Stimulation of all contacts resulted in phosphene perception. Phosphenes appeared completely or partially in the left hemifield. Stimulation of the electrodes below the calcarine sulcus elicited phosphenes in the superior hemifield and vice versa. Changing the stimulation parameters of frequency, pulse width, and burst duration affected current thresholds for eliciting phosphenes, and increasing the amplitude or frequency of stimulation resulted in brighter perceptions. While stimulation thresholds decreased between an average of 5% and 12% after 19 months, spatial mapping of phosphenes remained consistent over time. Although no serious adverse events were observed, the subject experienced mild headaches and dizziness in three instances, symptoms that did not persist for more than a few hours and for which no clinical intervention was required.Using an off-the-shelf neurostimulator, the authors were able to reliably generate phosphenes in different areas of the visual field over 19 months with no serious adverse events, providing preliminary proof of feasibility and safety to proceed with visual epicortical prosthetic clinical trials. Moreover, they systematically explored the relationship between stimulation parameters and phosphene thresholds and discovered the direct relation of perception thresholds based on primary visual cortex (V1) neuronal population excitation thresholds.

The mechanism and effect of chronic electrical stimulation of the globus pallidus for treatment of Parkinson disease

2004 ◽  
Vol 100 (6) ◽  
pp. 997-1001 ◽  
Author(s):  
Mitsuhiro Ogura ◽  
Naoyuki Nakao ◽  
Ekini Nakai ◽  
Yuji Uematsu ◽  
Toru Itakura
Keyword(s):  
Electrical Stimulation ◽  
Parkinson Disease ◽  
Globus Pallidus ◽  
Rating Scale ◽  
Underlying Mechanism ◽  
Clinical Effects ◽  
Content Type ◽  
Chronic Electrical Stimulation ◽  
Fine Print ◽  
Stimulation Of

Object. Although chronic electrical stimulation of the globus pallidus (GP) has been shown to ameliorate motor disabilities in Parkinson disease (PD), the underlying mechanism remains to be clarified. In this study the authors explored the mechanism for the effects of deep brain stimulation of the GP by investigating the changes in neurotransmitter levels in the cerebrospinal fluid (CSF) during the stimulation. Methods. Thirty patients received chronic electrical stimulation of the GP internus (GPi). Clinical effects were assessed using the Unified PD Rating Scale (UPDRS) and the Hoehn and Yahr Staging Scale at 1 week before surgery and at 6 and 12 months after surgery. One day after surgery, CSF samples were collected through a ventricular tube before and 1 hour after GPi stimulation. The concentration of neurotransmitters such as γ-aminobutyric acid (GABA), noradrenaline, dopamine, and homovanillic acid (HVA) in the CSF was measured using high-performance liquid chromatography. The treatment was effective for tremors, rigidity, and drug-induced dyskinesia. The concentration of GABA in the CSF increased significantly during stimulation, although there were no significant changes in the level of noradrenaline, dopamine, and HVA. A comparison between an increased rate of GABA concentration and a lower UPDRS score 6 months postimplantation revealed that the increase in the GABA level correlated with the stimulation-induced clinical effects. Conclusions. Stimulation of the GPi substantially benefits patients with PD. The underlying mechanism of the treatment may involve activation of GABAergic afferents in the GP.

Effect of stimulation of the medullary reticular formation on cerebral vasomotor tonus and intracranial pressure

1987 ◽  
Vol 66 (4) ◽  
pp. 548-554 ◽  
Author(s):  
Seigo Nagao ◽  
Tsukasa Nishiura ◽  
Hideyuki Kuyama ◽  
Masakazu Suga ◽  
Takenobu Murota
Keyword(s):  
Intracranial Pressure ◽  
Reticular Formation ◽  
Cerebral Blood Volume ◽  
Systemic Arterial Pressure ◽  
Brain Swelling ◽  
Dorsomedial Nucleus ◽  
Medullary Reticular Formation ◽  
Content Type ◽  
Fine Print ◽  
Stimulation Of

✓ The authors report the results of a study to evaluate the effect of stimulation of the medullary reticular formation on cerebral vasomotor tonus and intracranial pressure (ICP) after the hypothalamic dorsomedial nucleus and midbrain reticular formation were destroyed. Systemic arterial pressure (BP), ICP, and local cerebral blood volume (CBV) were continuously recorded in 32 cats. To assess the changes in the cerebral vasomotor tonus, the vasomotor index defined by the increase in ICP per unit change in BP was calculated. In 29 of the 32 animals, BP, ICP, and CBV increased simultaneously immediately after stimulation. The increase in ICP was not secondary to the increase in BP, because the vasomotor index during stimulation was significantly higher than the vasomotor index after administration of angiotensin II. The vasomotor index was high during stimulation of the area around the nucleus reticularis parvocellularis. In animals with the spinal cord transected at the C-2 vertebral level, ICP increased without a change in BP. These findings indicate that the areas stimulated in the medullary reticular formation play an important role in decreasing cerebral vasomotor tonus. This effect was not influenced by bilateral superior cervical ganglionectomy, indicating that there is an intrinsic neural pathway that regulates cerebral vasomotor tonus directly. In three animals, marked biphasic or progressive increases in ICP up to 100 mm Hg were evoked by stimulation. The reduction of cerebral vasomotor tonus and concomitant vasopressor response induced by stimulation of the medullary reticular formation may be one of the causes of acute brain swelling.

Transcorneal stimulation of trigeminal nerve afferents to increase cerebral blood flow in rats with cerebral vasospasm: a noninvasive method to activate the trigeminovascular reflex

2002 ◽  
Vol 97 (5) ◽  
pp. 1179-1183 ◽  
Author(s):  
Basar Atalay ◽  
Hayrunnisa Bolay ◽  
Turgay Dalkara ◽  
Figen Soylemezoglu ◽  
Kamil Oge ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cerebral Vasospasm ◽  
Trigeminal Nerve ◽  
Nerve Endings ◽  
Noninvasive Method ◽  
Direct Stimulation ◽  
Content Type ◽  
Fine Print ◽  
Stimulation Of

Object. The goal of this study was to investigate whether stimulation of trigeminal afferents in the cornea could enhance cerebral blood flow (CBF) in rats after they have been subjected to experimental subarachnoid hemorrhage (SAH). Cerebral vasospasm following SAH may compromise CBF and increase the risks of morbidity and mortality. Currently, there is no effective treatment for SAH-induced vasospasm. Direct stimulation of the trigeminal nerve has been shown to dilate constricted cerebral arteries after SAH; however, a noninvasive method to activate this nerve would be preferable for human applications. The authors hypothesized that stimulation of free nerve endings of trigeminal sensory fibers in the face might be as effective as direct stimulation of the trigeminal nerve. Methods. Autologous blood obtained from the tail artery was injected into the cisterna magna of 10 rats. Forty-eight and 96 hours later (five rats each) trigeminal afferents were stimulated selectively by applying transcorneal biphasic pulses (1 msec, 3 mA, and 30 Hz), and CBF enhancements were detected using laser Doppler flowmetry in the territory of the middle cerebral artery. Stimulation-induced changes in cerebrovascular parameters were compared with similar parameters in sham-operated controls (six rats). Development of vasospasm was histologically verified in every rat with SAH. Corneal stimulation caused an increase in CBF and blood pressure and a net decrease in cerebrovascular resistance. There were no significant differences between groups for these changes. Conclusions. Data from the present study demonstrate that transcorneal stimulation of trigeminal nerve endings induces vasodilation and a robust increase in CBF. The vasodilatory response of cerebral vessels to trigeminal activation is retained after SAH-induced vasospasm.

Bilateral stimulation of the subthalamic nucleus in patients with Parkinson disease: a study of efficacy and safety

2002 ◽  
Vol 96 (4) ◽  
pp. 666-672 ◽  
Author(s):  
Tanya Simuni ◽  
Jurg L. Jaggi ◽  
Heather Mulholland ◽  
Howard I. Hurtig ◽  
Amy Colcher ◽  
...  
Keyword(s):  
Deep Brain Stimulation ◽  
Parkinson Disease ◽  
Subthalamic Nucleus ◽  
Brain Stimulation ◽  
Bilateral Stimulation ◽  
Content Type ◽  
Preoperative Status ◽  
Fine Print ◽  
Deep Brain ◽  
Stimulation Of

Object. Palliative neurosurgery has reemerged as a valid therapy for patients with advanced Parkinson disease (PD) that is complicated by severe motor fluctuations. Despite great enthusiasm for long-term deep brain stimulation (DBS) of the subthalamic nucleus (STN), existing reports on this treatment are limited. The present study was designed to investigate the safety and efficacy of bilateral stimulation of the STN for the treatment of PD. Methods. In 12 patients with severe PD, electrodes were stereotactically implanted into the STN with the assistance of electrophysiological conformation of the target location. All patients were evaluated preoperatively during both medication-off and -on conditions, as well as postoperatively at 3, 6, and 12 months during medication-on and -off states and stimulation-on and -off conditions. Tests included assessments based on the Unified Parkinson's Disease Rating Scale (UPDRS) and timed motor tests. The stimulation effect was significant in patients who were in the medication-off state, resulting in a 47% improvement in the UPDRS Part III (Motor Examination) score at 12 months, compared with preoperative status. The benefit was stable for the duration of the follow-up period. Stimulation produced no additional benefit during the medication-on state, however, when compared with patient preoperative status. Significant improvements were made in reducing dyskinesias, fluctuations, and duration of off periods. Conclusions. This study demonstrates that DBS of the STN is an effective treatment for patients with advanced, medication-refractory PD. Deep brain stimulation of the STN produced robust improvements in motor performance in these severely disabled patients while they were in the medication-off state. Serious adverse events were common in this cohort; however, only two patients suffered permanent sequelae.

Anterior sacral meningocele contiguous with a pelvic hamartoma

1984 ◽  
Vol 61 (1) ◽  
pp. 188-190 ◽  
Author(s):  
Eugene Leibowitz ◽  
William Barton ◽  
Parvis Sadighi ◽  
Jeffrey S. Ross
Keyword(s):  
Computerized Tomography ◽  
Content Type ◽  
Transabdominal Approach ◽  
X Ray ◽  
Anterior Sacral Meningocele ◽  
Fine Print

✓ A patient with an anterior sacral meningocele combined with a hamartoma was diagnosed with x-ray films, myelography, and computerized tomography. She was successfully operated on by a transabdominal approach.

Equal Degrees of Object Selectivity for Upper and Lower Visual Field Stimuli

2010 ◽  
Vol 104 (4) ◽  
pp. 2075-2081 ◽  
Author(s):  
Lars Strother ◽  
Adrian Aldcroft ◽  
Cheryl Lavell ◽  
Tutis Vilis
Keyword(s):  
Visual Field ◽  
Occipital Cortex ◽  
Recognition System ◽  
Blood Oxygen Level Dependent ◽  
Lower Visual Field ◽  
Blood Oxygen Level ◽  
Visual Areas ◽  
Bold Responses ◽  
Cortical Regions ◽  
Lateral Occipital Cortex

Functional MRI (fMRI) studies of the human object recognition system commonly identify object-selective cortical regions by comparing blood oxygen level–dependent (BOLD) responses to objects versus those to scrambled objects. Object selectivity distinguishes human lateral occipital cortex (LO) from earlier visual areas. Recent studies suggest that, in addition to being object selective, LO is retinotopically organized; LO represents both object and location information. Although LO responses to objects have been shown to depend on location, it is not known whether responses to scrambled objects vary similarly. This is important because it would suggest that the degree of object selectivity in LO does not vary with retinal stimulus position. We used a conventional functional localizer to identify human visual area LO by comparing BOLD responses to objects versus scrambled objects presented to either the upper (UVF) or lower (LVF) visual field. In agreement with recent findings, we found evidence of position-dependent responses to objects. However, we observed the same degree of position dependence for scrambled objects and thus object selectivity did not differ for UVF and LVF stimuli. We conclude that, in terms of BOLD response, LO discriminates objects from non-objects equally well in either visual field location, despite stronger responses to objects in the LVF.

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