PubMed Health⌕ Search

Biomedical subjects

G G Celesia

Publications and source records attributed to G G Celesia.

At least 19 recordsLinked to original sources
PubMed1992

Spatial frequency evoked visuograms in multiple sclerosis.

We obtained steady-state visual evoked potentials (VEPs) to sinusoidal gratings alternating at 4 Hz with spatial frequencies varying from 0.5 to 8 cpd in 21 normal controls and 21 patients with multiple sclerosis (MS), and analyzed responses by fast Fourier transform. Amplitude- and phase-spatial frequency functions were obtained and referred to as amplitude and phase "visuograms." We observed two types of abnormalities in the phase visuograms of MS patients: (1) abnormal responses at all spatial frequencies tested (37%), and (2) abnormal responses only at selective spatial frequencies (52%). Some patients had phase lag limited to low, middle, or high spatial frequencies. Steady-state and transient VEPs to 2 and 4 cpd showed a similar percent of abnormalities. The use of more than one spatial frequency stimulus increased the diagnostic yield by 17%. Our data confirm that MS may selectively affect specific neuronal channels within the visual pathways.

Adolescent↗
PubMed1992

Event-related potentials.

Event-related potentials (ERPs) are scalp recorded electrophysiological responses that are related to an internal cognitive event. This review summarizes recent findings on the effects of neurologic disease and the origin of ERPs obtained in expectancy, attention, memory, and linguistic tasks. Cognitive ERPs allow the physiologic activity of the brain to be analyzed with exquisite temporal resolution. Our understanding of these potentials is incomplete at present. Advances in cognitive psychology and source localization of these surface potentials, however, may result in an increased understanding of both the organization of cognitive processing in the brain and cognitive deficits that result from neurologic disease.

Arousal↗
PubMed1991

The effects of age on steady-state pattern electroretinograms and visual evoked potentials.

Steady-state pattern-reversal electroretinograms and visual evoked potentials were simultaneously recorded in two groups of young and elderly normal volunteers. The young group consisted of 23 subjects (13 women and 10 men) aged 18 to 28 years, and the elderly group consisted of 24 subjects (11 women and 13 men) aged 58 to 77 years. Stimuli were square-wave gratings ranging in spatial frequency from 0.5 to 6 c/deg and phase reversed at a frequency of 4 Hz. Pattern-reversal electroretinograms and visual evoked potentials consisted of a prominent second and a smaller fourth harmonic response. Spatial frequency-amplitude functions of the pattern-reversal electroretinogram second and fourth harmonics were similar for the young and elderly groups. The mean fourth harmonic phase was significantly shifted in elderly subjects compared with young subjects for all spatial frequencies tested. Spatial frequency tuning was observed for amplitude and phase functions of the visual evoked potential second and fourth harmonic responses for both age groups. Age had a significant effect on phase for spatial frequencies above 1.5 c/deg. Amplitude of the fourth harmonic was significantly lower for the elderly group at 1.5-4 c/deg. Phase was significantly different between groups for spatial frequencies below 3 c/deg. Our results suggest that aging influences both retinal and central visual pathways. Aging differentially affected the visual evoked potential second and fourth harmonic responses, suggesting different neuronal origins for these components.

Adolescent↗
PubMed1991

Cortical blindness and residual vision: is the "second" visual system in humans capable of more than rudimentary visual perception?

We studied 12 patients with static cortical blindness to evaluate residual vision after destruction of area 17 and to assess the visual capacity of the subcortical "second" visual system in humans. In each case, the cause was bilateral infarction of the occipital lobes. Five patients had total blindness, and four had residual rudimentary vision (RRV), characterized by homonymous areas of light perception in the peripheral field and ability to detect moving objects. Only three patients had the ability to read; two of these had spared macular vision, and the other had spared left homonymous hemimaculae and spared temporal crescent. Neuroimaging and visual evoked potentials (VEPs) correlated with the extent of the visual dysfunction. Total destruction of area 17 bilaterally was associated with total permanent visual loss. The larger the amount of spared visual cortex, the better the vision. Positron emission tomography (PET) or single photon emission computed tomography (SPECT) demonstrated retained metabolic activity in islands of preserved area 17 in patients with some residual vision. VEPs were present in totally blind individuals. We conclude that, in humans, useful visual function is preserved only when a critical amount of area 17 is spared. The subcortical second system may participate in the generation of VEPs, but is incapable of conscious visual perception.

Aged↗
PubMed1979

Somatosensory evoked potentials recorded directly from human thalamus and Sm I cortical area.

Somatosensory evoked potentials (SEPs) to median nerve stimulation were recorded from the nucleus ventralis caudalis. They consisted of monophasic or diphasic potentials with mean onset latency of 13.8 ms. More complex SEPs to median nerve stimulation were obtained from the cortex. The SEPs consisted of two major positive waves, P1 and P2, and were recorded over both the precentral and postcentral gyri, suggesting that somatosensory information converges to the motor cortex, probably to be used for the integration of critical motor activity. In two patients, it was noted that the motor representation of facial movements was larger than the correspondent sensory representation on the postcentral gyrus. This larger motor representation of the face and more specifically of the lips and tongue may be related to human acquisition of mimicry and articulation of language.

Adult↗
PubMed1978

Visual evoked spectrum array and interhemispheric variations.

An EEG spectrum analysis during visual stimulation was computed in 19 normal subjects. Visual stimulation consisted of trains of flashes at frequencies ranging between 2.5 and 20 flashes per second. Recordings were carried out simultaneously from the right and left occipital regions with bipolar and referential montages. Compressed spectral arrays were computed for eight-second epochs at each recording site using a fast Fourier transform. The ratio of the spectral energy from homologus regions of right and left hemispheres at each stimulation frequency was determined. The ratios were graphically displayed in a visual evoked spectrum array (VESA) ratio plot (VESA-GRAM); the mean of the ratio plot was designated the VESA coefficient. The range of variation for these measurements was determined for normal subjects. An application of the technique to patients with hemianopia showed abnormal VESA (characterized by smaller spectral amplitudes over the appropriate hemisphere), abnormal VESA ratio plots, and high VESA coefficients. These preliminary findings suggest that VESA may be a promising method to detect retrochiasmatic visual defects.

Adult↗
PubMed1977

Effects of aging on visual evoked responses.

The effects of aging of visual evoked responses (VER) and critical frequency of photic driving (CFPD) was studied in 74 volunteers aged 18 to 79. The amplitude of VER to pattern reversal stimulation did not vary with sex or age. The latencies of the first major negative and of the first major positive defection of the VER were significantly delayed (P less than .001) with advancing age. This increase of latency probably reflects a slowing of conduction velocity in the optic nerve or optic pathways or both. CFPD, defined as the highest frequency of photic driving response expressed in flashes per second, showed an inverse correlation, decreasing with age in older subjects. Critical frequency of photic driving is the electrophysiological counterpart of critical flicker fusion, which is known to decrease with advancing age. These data support the concept that aging influences the functions of specialized sensory systems.

Adolescent↗
PubMed1977

The effects of epileptogenic activity on auditory evoked potentials in cats.

Epileptogenic foci were produced by application of penicillin to the auditory cortex of cats. A gradual modification of the evoked potentials to clicks and of the recovery cycle to paired clicks was noted following the application of penicillin. With the onset of interictal spikes, responses were initially depressed. The depression gradually changed till every click triggered a reflex epileptogenic spike. Areas surrounding the primary focus and areas at the mirror focus had depressed evoked potentials, while at the primary focus a click elicited reflex spikes. Progressive recruitment of cortical regions farther away from the primary focus was noted with increased epileptogenicity. The recovery cycle was also affected with prolongation of the absolute refractory period. These complex modifications of sensory input were closely related to the intensity of the epileptogenic disturbance, the distance of the area processing the information from the primary epileptogenic focus, and the time of arrival of the signal to be processed in relation to the interictal and ictal discharges.

Animals↗
PubMed1977

Effect of thalamotomy and levodopa therapy on the speech of Parkinson patients.

The speech of three groups of Parkinson patients--nonsurgical, postunilateral and postbilateral thalamotomy--was evaluated. Dysarthria, bulbar motility and pyramidal tract indexes were determined for each patient. There was a statistically significant greater impairment in dysarthria and pyramidal tract indexes of patients with thalamotomy. L-Dopa and carbidopa therapy failed to significantly improve speech in any group.

Aged↗
PubMed1977

Visual electroencephalographic computer analysis (VECA). A new electrophysiologic test for the diagnosis of optic nerve lesions.

The function of optic pathways was studied by visual electroencephalographic computer analysis (VECA). Pattern and flash stimuli were used. The VECA profile was abnormal in two types of lesions: pathology involving the eye, and pathology involving the optic nerve. When ocular pathology is excluded, an abnormal profile indicates optic nerve dysfunction. Of the multiple sclerosis patients tested, 77 percent had an abnormal VECA profile. The test was always abnormal in patients with optic neuritis. Delayed visual evoked responses occurred in 18 of 29 multiple sclerosis patients judged to be clinically without visual deficits. VECA is reliable and sensitive for detecting clinical and subclinical optic nerve pathology.

Adult↗
PubMed1976

Thrombocytopenia associated with long-term levodopa therapy.

A 63-year-old man had severe thrombocytopenia after long-term levodopa therapy. Serologic studies and clinical features indicate that the thrombocytopenia was due to an autoimmune process, presumably similar to that induced by the chemically similar drug methyldopa. Direct allergy to levodopa was ruled out by controlled challenge of the patient receiving levodopa. Combined levodopa-prednisone therapy was then instituted, with good clinical response and no recurrence of thrombocytopenia.

Administration, Oral↗
PubMed1976

Modern concepts of status epilepticus.

Among 60 cases of status epilepticus, there were 45 cases of convulsive status and 15 cases of nonconvulsive or confusional status. In 37 cases, status was due to an identifiable cause. The most frequent etiologic factors were vascular (nine cases), traumatic (seven cases), and metabolic (five cases). Four patients with metabolic encephalopathy had focal status. While the possibility of expanding lesions should be investigated in every case of convulsive status, a complete metabolic screening is also necessary. Non-convulsive status was represented by two cases of psychomotor status and 13 cases of absence status. Clinically, these cases were characterized by various impairments of intellectual functioning and confusion. Diagnosis was determined by characteristic changes in the electroencephalogram. Aggressive treatment is indicated by one or more of the major anticonvulsants, supplemented by adequate oxygenation and maintenance of biochemical homeostasis.

Adolescent↗
PubMed1976

Organization of auditory cortical areas in man.

Average responses to clicks were recorded from the exposed human cortex of 19 adult patients during operation for the treatment of intracranial diseases. Auditory evoked responses were obtained from two areas. Short latency potentials were recorded on the superior surface of the temporal lobe corresponding to the transverse temporal gyri. These responses consisted of two positive waves P1 and P2 separated by a negative wave N1. P1 had a mean latency of 14-7+/-1-5 ms, N1 a mean latency of 19-1+/-2-6 ms and P2 a mean latency of 32-2+/-4-1 ms. Responses to stimulation of the contralateral ear were of higher amplitude than responses to stimulation of the ipsilateral ear. Responses of smaller amplitude and longer latency were obtained from the superior temporal gyrus and the upper lip of the sylvian fissure. These responses had a mean peak latency for P1 of 40-2+/-2-6 ms, for N1 of 62-5+/-12-5 ms and for P2 of 97-7+/-17-2 ms. It is concluded that the cortical auditory region of man may be subdivided in two major areas: an area on the supratemporal plane representing the primary auditory area or A1 and a region surrounding A1 which perhaps comprises two areas, one on the superior temporal gyrus and one on the upper bank of the sylvian fissure including frontal and parietal operculi.

Adult↗