Lorazepam Strongly Prolongs Visual Information Processing

Abstract

Lorazepam is a drug that has been widely used for over 30 years. Whereas its therapeutic and amnestic effects are fairly well known, the visuo-perceptual impairments induced by this drug have been studied to a much lesser degree and only little is known about the influence of lorazepam on the time course of visual information processing. To gain a better insight specifically on these temporal characteristics, we used the recently discovered backward masking technique, 'shine-through', in which a vernier target precedes a grating. We tested subjects, treated with lorazepam, diazepam, or a placebo, with masking gratings of various spatial layouts. Our experiments reveal surprising results. First, for the unmasked vernier target, lorazepam induced a strong deterioration of performance compared to both diazepam and placebo. Performance deteriorated even more significantly if a masking grating was presented following the vernier. We observed that vernier discrimination could be completely abolished even if the grating appeared 400 ms after the vernier presentation. Such long time intervals are beyond usual visual masking effects. When performing the task under placebo, the participants perceived the vernier target and the masking grating as two independent time events rather than as a single event. It appears that lorazepam prolongs dramatically the processing of visual targets. The masking effects revealed here are specific to the type of grating and are much stronger under lorazepam than under diazepam.

GABAA Agonist Reduces Visual Awareness: A Masking–EEG Experiment

“…Behavioral effects of LZP on visual processing have been observed previously (Lorenceau, Giersch, & Seriés, 2005;Giersch & Herzog, 2004; Beckers, Wagemans, Boucart, & Figure 7. Ratings of sedation per drug over time in hours (2 hr, begin of task; 3 hr, end of task; 3.5 hr, end of session) as assessed with visual analogue scales.…”

Subjective Duration as a Signature of Coding Efficiency: Emerging Links Among Stimulus Repetition, Predictive Coding, and Cortical GABA Levels

“…Specifically, the magnitude of the hemodynamic response of the fMRI-BOLD signal in the visual cortex was reduced in individuals with larger GABA levels in this region, possibly through an effect on local circulation or glutamate levels (Muthukumaraswamy et al, 2009). Pharmacological studies complement this finding by showing that GABA agonists reduce perceptual awareness (van Loon et al, 2012) and visual discrimination (Giersch & Herzog, 2004), and attenuate the neurophysiological response to visual oddball stimuli (P3 event-related brain potential component; Watson et al, 2009). Further studies showed that GABA agonists also impair temporal discrimination of auditory intervals (Rammsayer, 1992(Rammsayer, , 1999.…”

Some facilitatory effects of lorazepam on dynamic visual binding

“…In particular, lorazepam, but not diazepam, has been shown to specifically facilitate the detection of a discontinuity between collinear contours (Beckers et al, 2001;Giersch, 1999Giersch, , 2001) resulting in the impaired integration of local visual information into global configurations (Giersch et al, 1997;Giersch & Lorenceau, 1999). Diazepam and lorazepam have also been shown to differ with respects to the identification of fragmented pictures Vidailhet et al, 1994;Wagemans et al, 1998), perceptual priming effects Vidailhet et al, 1994;Sellal et al, 1992), the detection of discontinuities in lines (Beckers et al, 2001), and in their effects on masking and vernier offset detection (Giersch & Herzog, 2004). The reason why both drugs differ in these effects has still to be determined.…”