When transcranial magnetic stimulation (TMS) modulates feature integration

Abstract

How the brain integrates visual information across time into coherent percepts is an open question. Here, we presented two verniers with opposite offset directions one after the other. A vernier consists of two vertical bars that are horizontally offset. When the two verniers are separated by a blank screen (interstimulus interval, ISI), the two verniers are perceived either as two separate entities or as one vernier with the offset moving from one side to the other depending on the ISI. In both cases, their offsets can be reported independently. Transcranial magnet stimulation (TMS) over the occipital cortex does not interfere with the offset discrimination of either vernier. When a grating, instead of the ISI, is presented, the two verniers are not perceived separately anymore, but as 'one' vernier with 'one' fused vernier offset. TMS strongly modulates the percept of the fused vernier offset even though the spatio-temporal position of the verniers is identical in the ISI and grating conditions. We suggest that the grating suppresses the termination signal of the first vernier and the onset signal of the second vernier. As a consequence, perception of the individual verniers is suppressed. Neural representations of the vernier and second vernier inhibit each other, which renders them vulnerable to TMS for at least 300 ms, even though stimulus presentation was only 100 ms. Our data suggest that stimulus features can be flexibly integrated in the occipital cortex, mediated by neural interactions with outlast stimulus presentations by far.

Hard criteria for empirical theories of consciousness

“…A similar finding is that a masked stimulus can be rerendered conscious by a transcranial magnetic stimulation (TMS) pulse (Ro et al, 2003). This unconscious integration period can last for 420 ms as experiments using TMS and feature fusion have shown (Scharnowski et al, 2009;Rüter et al, 2010; see also Pilz et al, 2013). Drissi-Daoudi et al (2019) have also shown mandatory unconscious integration up to 450 ms. Relatedly, Sergent et al (2013) showed that a cue presented after a target stimulus that would otherwise remain unconscious can retrospectively render the stimulus conscious.…”

Paradoxical Evidence Integration in Rapid Decision Processes

“…With an ISI of 20 ms, the two vernier stimuli, presented for 10 ms each, became individually discriminable. Observers could tell whether the first stimulus was offset to the left or to the right by motion cues [41] , [42] . However, for a sequence of ‘A’ immediately followed by ‘B’ with , verniers are not individually visible even though the total duration is 40 ms as in the sequence with the 20 ms ISI.…”

Two primes priming: Does feature integration occur before response activation?

“…Hence, information persistence in a buffer stage might explain why Prime 2 remains dominant even when Prime 1 has a head start long enough to provoke a high rate of response errors under conditions of speeded instead of delayed responding. Such a twostage model was recently proposed for decision making (Rüter, Marcille, Sprekeler, Gerstner, & Herzog, 2012;Rüter, Sprekeler, Gerstner, & Herzog, 2013;Scharnowski, Hermens, Kammer, Ogmen, & Herzog, 2007) and is supported by transcranial magnetic stimulation experiments, which show that vernier fusion takes up to 400 ms (Rüter, Kammer, & Herzog, 2010;Scharnowski et al, 2009).…”