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Biomedical subjects

M J Soso

Publications and source records attributed to M J Soso.

12 recordsLinked to original sources
PubMed1992

Visual angle of the mind's eye before and after unilateral occipital lobectomy.

Do mental images occur in a spatially mapped (i.e., analog, or array-format) representational medium? Kosslyn's (1978) method was used to measure the visual angle of "the mind's eye" to estimate the extent of the imagery medium before and after unilateral occipital lobectomy. It was found that the overall size of the largest possible image was reduced following the surgery. In addition, only the horizontal extent, and not the vertical extent, of the imagery medium was reduced. Finally, it was determined that the S understood the tasks, was not aware of our predictions, and was unaffected by a strong demand characteristic in a different imagery task. These results are consistent with the hypothesis that imagery occurs in a spatially mapped representational medium dependent on occipital cortex.

Adult↗
PubMed1992

Relationship between prolonged and self-limited photoparoxysmal responses and seizure incidence: study and review.

Photoparoxysmal responses (PPRs) are generalized epileptiform abnormalities occurring during photic stimulation. Prolonged PPRs, which outlast the stimulus, can be distinguished from self-limited PPRs, which cease spontaneously or when the flashes stop. Reilly and Peters (1973) found a higher incidence of seizures in patients with prolonged, rather than self-limited, PPRs. More recently, Jayakar and Chiappa (1990) reported a similar seizure incidence in the prolonged and self-limited groups. In order to assess these discordant results, we reviewed EEG records performed in our laboratory from 1983 to 1988. Sixty-eight EEGs had PPRs (19 prolonged and 49 self-limited). Patients with PPRs had a significantly higher incidence of seizures than controls (total patients versus controls, p less than 0.001; prolonged subgroup compared to controls, p less than 0.001; self-limited subgroup versus controls, p less than 0.01). Comparing PPR groups, we found that a prolonged PPR was associated with a higher incidence of seizures than a self-limited response (p less than 0.05); however, patients with a prolonged PPR more often had other epileptiform abnormalities than the self-limited group (p less than 0.001). There was no difference in seizure incidence between the PPR groups when comparing patients whose EEGs also contained other epileptiform abnormalities. Meta-analysis suggests apparent differences among the three studies are superficial.

Adolescent↗
PubMed1989

Migraine and stripe-induced visual discomfort.

We investigated stripe-induced visual discomfort and its relation to migraine. Some people find viewing striped patterns aversive. Prior work has suggested that migraineurs, in particular, are bothered by stripes. Subjects were selected by opportunity sampling. They were shown striped patterns and asked questions about their general health and their headache history, if any. Of the 102 subjects, 38 were diagnosed as having migraine headaches, 22 had nonmigraine headaches, and 42 were considered to be nonheadache subjects; 82% of those with migraines were stripe sensitive while only 6.2% without migraines were stripe sensitive. We conclude that stripe aversiveness is related to migraine headaches and can assist differentiation of migraine and nonmigraine headaches.

Adult↗
PubMed1984

Palatal myoclonus. Reflex activation of contractions.

We report two unusual features of a 37-year-old man with palatal myoclonus. Although the rhythmic palatal contractions of this disorder are usually incessant, he was able to voluntarily suppress them for minutes. During periods of suppression, specific voluntary actions using the left side of his body, but not the right, reliably elicited single contractions. Various stimuli to the left side of his body, but not the right, also produced single contractions. Stimulation of trigeminal nerve branches evoked palatal electromyographic discharge after 55 ms. Microsurgical vascular decompression of posterior fossa neural structures led to improvement of several of the patient's symptoms and signs.

Adult↗
PubMed1980

Case report: responses to stripe width changes and to complex gratings of a patient with pattern-sensitive epilepsy.

A pattern-sensitive subject's ability to see faint gratings of several different stripe widths (spatial frequencies) was essentially normal, with the greatest sensitivity occurring for gratings with 2 cycles of light and dark stripes per degree of visual arc (c/deg). Epileptiform discharges, however, occurred maximally at a narrower stripe width, 5 c/deg. The 50% bandwidth of the epileptic response was approximately one octave, which is similar to postulated 'spatial frequency channels' in the visual system. Hypothesized inhibitory interactions between the 5 c/deg grating and a 15 c/deg grating were not observed.

Adult↗
PubMed1980

Pattern-sensitive epilepsy. I: A demonstration of a spatial frequency selective epileptic response to gratings.

Rare individuals suffer epileptic seizures when they view certain images, particularly stripes. Contrast-threshold functions (the ability to see faint stripes of various widths) were determined for two pattern-sensitive brothers, and the epileptogenicity of various patterns was assessed for one of them. Sine wave grating contrast-detection thresholds for the two subjects were essentially normal, with lowest thresholds at approximately 2 cycles/degree (c/deg). Epileptiform discharges occurred maximally at 5 c/deg with a 1-octave 50% bandwidth. Pattern epileptogenicity was increased by the addition of a third harmonic sine wave grating to its fundamental, but was unaffected by the phase relation of the two gratings. The frequency selectivity of epileptic responsiveness was quantitatively similar to a "spatial frequency channel." Inhibitory interaction were not present. The findings suggest relations between the phenomena of pattern-sensitive epilepsy and hypothesized spatial frequency channels which merit further exploration.

Adolescent↗
PubMed1980

Pattern-sensitive epilepsy. II: Effects of pattern orientation and hemifield stimulation.

The majority of pattern-sensitive epileptics described in the literature have responded mainly to veritical or near-vertical gratings. In this study, orientation selectivity was reexamined in two patients and the effects of hemifield stimulation are also reported. Prior studies of our subjects by Chatrian et al. (1970) revealed that Case 1 was sensitive to all orientations and that Case 2 was responsive to vertical or near-vertical gratings only. Upon reexamination, Case 1 was distinctly less sensitive to oblique orientations and Case 2 was slightly responsive to horizontal gratings. At the time of testing, Case 1 was clinically improved and Case 2 was acutely worse compared to their conditions during the 1970 studies. With low-contrast gratings, Case 1 responded only to vertical orientations. However, when presented with a checkerboard pattern, he responded only when the edges were diagonal and not when they were vertical and horizontal. Upper hemifield gratings were epileptogenic, whereas lower hemifield presentations were almost ineffective. Lateral hemifield presentation produced discharges mainly in the contralateral hemisphere. The results suggest that orientation selectivity is not a fixed property of the pattern-sensitive condition. Instead, it is apparently influenced by clinical status and pattern properties. The checkerboard results suggest that the epileptogenic feature of the pattern is its Fourier fundamental component rather than individual lines and edges. The hemifield results may indicate a functional difference between the upper and lower visual fields.

Adolescent↗
PubMed1978

Grating contrast detection perimetry in a patient with occipital lobe epilepsy.

A new perimetry technique is based upon detection of faint gratings. This method permits assessment of visual field abnormalities that are not detectable by Goldmann perimetry or tangent screen examination. These abnormalities occurred in a 57-year-old man with a seizure disorder of left occipital origin. The technique may have advantages over conventional field study methods for the early detection of geniculocalcarine pathology.

Adult↗