Temporal lobe epilepsy does not impair visual perception

Abstract

SUMMARYTemporal lobe epilepsy (TLE) can impair interictal cognitive function. In the perceptual domain, previous psychophysical studies demonstrated specific deficits in auditory and tactile perception in patients with TLE. This study compared performance of 25 TLE subjects and 27 controls on two low-level, visual tasks: luminance discrimination and frequency discrimination. Both tasks were performed under a relatively easy and a relatively difficult condition, by adjusting the stimulus duration. TLE subjects performed as well as controls on both tasks at both stimulus durations. These results imply that interictal occipital lobe function, as reflected in performance on low-level visual tasks, is not impaired in TLE, consistent with functional imaging data. Furthermore, since TLE subjects performed normally while taking therapeutic doses of multiple AEDs, the data suggest that these AEDs do not impair visual perception.

Impaired perceptual networks in temporal lobe epilepsy revealed by resting fMRI

“…In our fMRI study, the patients with mTLE presented increased functional connectivity within the primary visual cortex. Although it is not fully understood currently, our results at least support that the primary visual function in mTLE may not be reduced [23]. Moreover, an early study proposed that the patients with epilepsy may have hyperfunction in visual processing with enhanced prevalence in the epileptic hemisphere [38], although this hypothesis has been little supported by subsequent research (see review, [22]).…”

“…4 Three-dimensional views of the results from group comparisons between the patients with mTLE and the controls, and the negative correlations between the epilepsy duration and mean z values within the RSN4 (green circle), the RSN5 (yellow circle), and the bilateral MT? areas (pink circle) addressed photosensitive epilepsy or occipital lobe epilepsy (see review, [22]), several psychobehavioral studies have found that the primary visual function is not impaired in mTLE [23,45]. Under the luminance and frequent discrimination stimuli, the performance of patients with mTLE did not show a difference from that of controls [23].…”

“…areas (pink circle) addressed photosensitive epilepsy or occipital lobe epilepsy (see review, [22]), several psychobehavioral studies have found that the primary visual function is not impaired in mTLE [23,45]. Under the luminance and frequent discrimination stimuli, the performance of patients with mTLE did not show a difference from that of controls [23]. An ERP study of mTLE has shown that the latency of the P3 in response to the auditory stimulus under attentional condition is delayed, but the response to the visual stimulus is normal compared to controls [45], which has been interpreted to mean that the processings of the visual and auditory information are different in mTLE.…”

“…A series of behavioral and electrophysiological studies by Grant et al and other authors revealed that somatosensory [4,18,22,25] and auditory [16,24] perceptions are impaired. However, a recent physiophysical study by Grant and colleagues [23] found that visual perception is not impaired in mTLE. Consistent with these behavioral findings, brain-imaging evidence has suggested that mTLE is a disorder of neural networks, which may underlie the neurophysiological mechanisms of the widespread functional impairments in mTLE [9,43].…”

Investigations of Brain Network Alterations in Epilepsy Using Functional Magnetic Resonance Imaging

“…The results showed increases in connectivity in TLE in primary visual cortex, coupled with decreases in higher order visual processing regions such as MT+ when compared to controls that decreased with duration of disease. These findings may be consistent with behavioral results that showed no differences between reaction time or accuracy responding to visual stimuli in IGE (Verleger, et al 1997) or TLE (Grant, et al 2008); but deficits in processing of visual stimuli detected by EEG studies of visual evoked potentials (Lucking, et al 1970) and event-related potentials (Verleger, et al 1997). …”