{'fraction_non_alphanumeric': 0.026148969889064975, 'fraction_numerical': 0.001584786053882726, 'mean_word_length': 5.9779005524861875, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Direct electrophysiological metrics of visual surround suppression in humans

Surround suppression is a well known phenomenon whereby the perceived intensity of a stimulus is lowered by the relative intensity of its surroundings. Psychophysical work has demonstrated the influence of a variety of stimulus factors, including similarity of features between the “foreground” (center) and “background” (surround). Such behavioral indices have provided novel insights in clinical studies testing for inhibitory dysfunction, for example in schizophrenia. Surround suppression effects have also been demonstrated in functional imaging work, in which it was established that it is expressed most strongly in primary visual cortex (V1). However, up until now, technical challenges have precluded its direct measurement in noninvasive EEG, which is arguably the most clinically practical recording modality. In this study, we report a novel paradigm that exploits simple signal processing, sensory physiology and psychophysical principles in order to extract a direct index of surround suppression (reduction of “foreground” stimulus response as a function of background contrast) from the primary visual cortex (V1) using non-invasive human electroencephalography (EEG).