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Abstract
We measured the effects of epilepsy on visual contrast sensitivity to linear and vertical sine-wave gratings. Sixteen female adults, aged 21 to 50 years, comprised the sample in this study, including eight adults with generalized tonic-clonic seizure-type epilepsy and eight age-matched controls without epilepsy. Contrast threshold was measured using a temporal two-alternative forced-choice binocular psychophysical method at a distance of 150 cm from the stimuli, with a mean luminance of 40.1 cd/m2. A one-way analysis of variance (ANOVA) applied to the linear contrast threshold showed significant differences between groups (F[3,188] = 14.829; p < .05). Adults with epilepsy had higher contrast thresholds (1.45, 1.04, and 1.18 times for frequencies of 0.25, 2.0, and 8.0 cycles per degree of visual angle, respectively). The Tukey Honestly Significant Difference post hoc test showed significant differences (p < .05) for all of the tested spatial frequencies. The largest difference between groups was in the lowest spatial frequency. Therefore, epilepsy may cause more damage to the neural pathways that process low spatial frequencies. However, epilepsy probably alters both the magnocellular visual pathway, which processes low spatial frequencies, and the parvocellular visual pathway, which processes high spatial frequencies. The experimental group had lower visual contrast sensitivity to all tested spatial frequencies.
Highlights
Epilepsy is a chronic neurological disorder, but no consensus has been reached about its accurate definition (Guerreiro & Guerreiro, 1996)
Partial seizures begin with an electrical discharge in one limited area of the brain, whereas general seizures begin with widespread electrical discharge that involves both sides of the brain at once
The aim of this research was to verify whether epilepsy alters the response of the visual system or basic sensory mechanisms related to the processing of luminance contrast in sine-wave gratings of 0.25, 2.0, and 8.0 cpd
Summary
Epilepsy is a chronic neurological disorder, but no consensus has been reached about its accurate definition (Guerreiro & Guerreiro, 1996). It is characterized by recurrent and uncontrollable seizures that occur as a result of excessive electrical discharges in a group of brain cells. This sudden and usually brief alteration in brain activity is reversible, and different parts of the brain can elicit such discharges (Fonseca & Tedrus, 2004; Kaplan & Sandock, 1997; Lorenzato, Cavalli, & Duarte, 2002). During tonic-clonic seizures, the patient initially presents a loss of conscience and falls, exhibiting rigidity shortly thereafter, and the extremities of the body begin to shake and contract (Guerreiro & Guerreiro, 1996)
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