Facilitatory Effects of Intermittent Photic Stimulation on Visual Cortical Kindling

Abstract

There are few reports on kindling preparation by daily electrical stimulation to the primary visual cortex. In our previous studies on cats, it was demonstrated that repeated stimulation to the primary visual cortex brought a similar progress in seizure development as in amygdaloid kindling, although it took more trials. In this study, we examined the effects of intermittent photic stimulation (IPS) (2.5 Hz) on the visual cortical kindling preparation to clarify more underlying mechanisms of photosensitivity. Under IPS, afterdischarges synchronizing to IPS were seen and a duration of afterdischarge was extremely prolonged, even in the early stage of the kindling process. The threshold of stimulus intensity inducing afterdischarge was significantly reduced and the generalized convulsive seizure was obtained with fewer times of stimulation, as compared to visual cortical kindling without IPS. In visual cortical kindling myoclonic responses were sometimes caused by IPS for a few minutes immediately after cessation of the electrically induced generalized seizure. Such phenomena were never seen in amygdaloid kindling. These results indicate that IPS facilitates a seizure development in all stages of visual cortical kindling.

Differential Conditioning of Environmental Cues With Amygdala Kindling

“…Despite numerous methodological differences the present results parallel those reported by Baba (1982). In both studies, pairing of visual stimuli with the kindling stimulus decreased the number of stimulations needed to elicit a generalized seizure.…”

“…However, comparison of the present effect of training condition on kindled AD durations with those of Baba (1982) is complicated by the differences in experimental designs. Baba (1982) reported longer AD durations for the group that had the IPS paired with visual cortex kindling as compared with the control group. In the present study, shorter AD durations were found in the discrimination groups.…”

“…In both studies, pairing of visual stimuli with the kindling stimulus decreased the number of stimulations needed to elicit a generalized seizure. However, comparison of the present effect of training condition on kindled AD durations with those of Baba (1982) is complicated by the differences in experimental designs. Baba (1982) reported longer AD durations for the group that had the IPS paired with visual cortex kindling as compared with the control group.…”

“…Wyler and Heavner (1979) found that when a neutral stimulus was paired with the electrical stimulation used for kindling, the stimulus significantly retarded the rate of kindling. In direct contrast, Baba (1982) found that intermittent photic stimulation (IPS) facilitated the development of (visual cortical) kindling. Concurrently, IPS also reduced afterdischarge (AD) thresholds.…”

In vivo models of cortical acquired epilepsy

“…Neocortical kindling is characterized by a higher threshold to elicit acute seizures, an unstable seizure development, and for its difficulty to induce a generalized convulsive seizure state (Majkowski et al, 1981; Okamoto, 1982). However, neocortical kindling has been described in the visual (Baba, 1982; Ono et al, 1981; Wada et al, 1989), somatosensory (Majkowski et al, 1981), motor (Fukushima et al, 1987), auditory (Valentine et al, 2004), and associative cortices of the cat (Nita et al, 2008a; Nita et al, 2008b). Kindling was also demonstrated in different species including frogs, mice, gerbils, rats, rabbits, cats, dogs, rhesus monkeys, and baboons (reviewed in (McNamara et al, 1980)).…”