Unconscious Priming Requires Early Visual Cortex at Specific Temporal Phases of Processing

2013 ◽  
Vol 25 (9) ◽  
pp. 1493-1503 ◽  
Author(s):  
Marjan Persuh ◽  
Tony Ro
Keyword(s):  
Visual Cortex ◽  
Time Window ◽  
Sufficient Condition ◽  
Conscious Perception ◽  
Feedback Processing ◽  
Temporal Interval ◽  
Temporal Intervals ◽  
Early Visual Cortex

Although examples of unconscious shape priming have been well documented, whether such priming requires early visual cortex (V1/V2) has not been established. In the current study, we used TMS of V1/V2 at varying temporal intervals to suppress the visibility of preceding shape primes while the interval between primes and targets was kept constant. Our results show that, although conscious perception requires V1/V2, unconscious priming can occur without V1/V2 at an intermediate temporal interval but not at early (5–25 msec) or later (65–125 msec) stages of processing. Because the later time window of unconscious priming suppression has been proposed to interfere with feedback processing, our results further suggest that feedback processing is also essential for unconscious priming and may not be a sufficient condition for conscious vision.

Unconscious and Conscious Processing of Color Rely on Activity in Early Visual Cortex: A TMS Study

2012 ◽  
Vol 24 (4) ◽  
pp. 819-829 ◽  
Author(s):  
Henry Railo ◽  
Niina Salminen-Vaparanta ◽  
Linda Henriksson ◽  
Antti Revonsuo ◽  
Mika Koivisto
Keyword(s):  
Visual Cortex ◽  
Time Windows ◽  
Single Pulse ◽  
Stimulus Presentation ◽  
Stimulus Onset ◽  
Forced Choice ◽  
Conscious Perception ◽  
Unconscious Processing ◽  
Early Visual Cortex ◽  
Chromatic Processing

Chromatic information is processed by the visual system both at an unconscious level and at a level that results in conscious perception of color. It remains unclear whether both conscious and unconscious processing of chromatic information depend on activity in the early visual cortex or whether unconscious chromatic processing can also rely on other neural mechanisms. In this study, the contribution of early visual cortex activity to conscious and unconscious chromatic processing was studied using single-pulse TMS in three time windows 40–100 msec after stimulus onset in three conditions: conscious color recognition, forced-choice discrimination of consciously invisible color, and unconscious color priming. We found that conscious perception and both measures of unconscious processing of chromatic information depended on activity in early visual cortex 70–100 msec after stimulus presentation. Unconscious forced-choice discrimination was above chance only when participants reported perceiving some stimulus features (but not color).

scholarly journals Valence-dependent Disruption in Processing of Facial Expressions of Emotion in Early Visual Cortex—A Transcranial Magnetic Stimulation Study

2020 ◽  
Vol 32 (5) ◽  
pp. 906-916 ◽  
Author(s):  
Kun Guo ◽  
Lauren Calver ◽  
Yoshi Soornack ◽  
Patrick Bourke
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Facial Expressions ◽  
Magnetic Stimulation ◽  
Emotional Processing ◽  
Time Window ◽  
Neural Mechanism ◽  
Emotional Valence ◽  
Structure Information ◽  
Early Visual Cortex

Our visual inputs are often entangled with affective meanings in natural vision, implying the existence of extensive interaction between visual and emotional processing. However, little is known about the neural mechanism underlying such interaction. This exploratory transcranial magnetic stimulation (TMS) study examined the possible involvement of the early visual cortex (EVC, Area V1/V2/V3) in perceiving facial expressions of different emotional valences. Across three experiments, single-pulse TMS was delivered at different time windows (50–150 msec) after a brief 10-msec onset of face images, and participants reported the visibility and perceived emotional valence of faces. Interestingly, earlier TMS at ∼90 msec only reduced the face visibility irrespective of displayed expressions, but later TMS at ∼120 msec selectively disrupted the recognition of negative facial expressions, indicating the involvement of EVC in the processing of negative expressions at a later time window, possibly beyond the initial processing of fed-forward facial structure information. The observed TMS effect was further modulated by individuals' anxiety level. TMS at ∼110–120 msec disrupted the recognition of anger significantly more for those scoring relatively low in trait anxiety than the high scorers, suggesting that cognitive bias influences the processing of facial expressions in EVC. Taken together, it seems that EVC is involved in structural encoding of (at least) negative facial emotional valence, such as fear and anger, possibly under modulation from higher cortical areas.

Saliency affects feedforward more than feedback processing in early visual cortex

2013 ◽  
Vol 51 (8) ◽  
pp. 1497-1503 ◽  
Author(s):  
Tatiana Aloi Emmanouil ◽  
Philip Avigan ◽  
Marjan Persuh ◽  
Tony Ro
Keyword(s):  
Visual Cortex ◽  
Feedback Processing ◽  
Early Visual Cortex

scholarly journals Can processing of face trustworthiness bypass early visual cortex? A transcranial magnetic stimulation masking study

2019 ◽  
Author(s):  
Shanice E. W. Janssens ◽  
Alexander T. Sack ◽  
Sarah Jessen ◽  
Tom A. de Graaf
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Stimulus Onset ◽  
Forced Choice ◽  
Conscious Perception ◽  
Neural Pathways ◽  
Social Species ◽  
Early Visual Cortex ◽  
Human Faces

AbstractAs a highly social species, we constantly evaluate human faces to decide whether we can trust someone. Previous studies suggest that face trustworthiness can be processed unconsciously, but the underlying neural pathways remain unclear. Specifically, the question remains whether processing of face trustworthiness relies on early visual cortex (EVC), required for conscious perception. If processing of trustworthiness can bypass EVC, then disrupting EVC should impair conscious trustworthiness perception while leaving forced-choice trustworthiness judgment intact. We applied double-pulse transcranial magnetic stimulation (TMS) to right EVC, at different stimulus onset asynchronies (SOAs) from presentation of a face in either the left or right hemifield. Faces were slightly rotated clockwise or counterclockwise, and were either trustworthy or untrustworthy. On each trial, participants discriminated 1) trustworthiness, 2) stimulus rotation, and 3) subjective visibility of trustworthiness. At early SOAs and specifically in the left hemifield, orientation processing (captured by the rotation task) was impaired by TMS. Crucially, though TMS also impaired subjective visibility of trustworthiness, no effects on trustworthiness discrimination were obtained. Conscious perception of face trustworthiness (captured by visibility ratings) relies on intact EVC, while forced-choice trustworthiness judgments may not. These results are consistent with the hypothesis that trustworthiness processing can bypass EVC. For basic visual features, extrastriate pathways are well-established; but face trustworthiness depends on a complex configuration of features. Its processing without EVC and outside of awareness is therefore of particular interest, further highlighting its ecological relevance.

scholarly journals Top–Down Modulation of Human Early Visual Cortex after Stimulus Offset Supports Successful Postcued Report

2011 ◽  
Vol 23 (8) ◽  
pp. 1921-1934 ◽  
Author(s):  
Claire Sergent ◽  
Christian C. Ruff ◽  
Antoine Barbot ◽  
Jon Driver ◽  
Geraint Rees
Keyword(s):  
Visual Cortex ◽  
Visual Stimulus ◽  
Sensory Processing ◽  
Time Window ◽  
Critical Time ◽  
Visual Display ◽  
Visual Presentation ◽  
Top Down ◽  
Early Visual Cortex ◽  
Stimulus Offset

Modulations of sensory processing in early visual areas are thought to play an important role in conscious perception. To date, most empirical studies focused on effects occurring before or during visual presentation. By contrast, several emerging theories postulate that sensory processing and conscious visual perception may also crucially depend on late top–down influences, potentially arising after a visual display. To provide a direct test of this, we performed an fMRI study using a postcued report procedure. The ability to report a target at a specific spatial location in a visual display can be enhanced behaviorally by symbolic auditory postcues presented shortly after that display. Here we showed that such auditory postcues can enhance target-specific signals in early human visual cortex (V1 and V2). For postcues presented 200 msec after stimulus termination, this target-specific enhancement in visual cortex was specifically associated with correct conscious report. The strength of this modulation predicted individual levels of performance in behavior. By contrast, although later postcues presented 1000 msec after stimulus termination had some impact on activity in early visual cortex, this modulation no longer related to conscious report. These results demonstrate that within a critical time window of a few hundred milliseconds after a visual stimulus has disappeared, successful conscious report of that stimulus still relates to the strength of top–down modulation in early visual cortex. We suggest that, within this critical time window, sensory representation of a visual stimulus is still under construction and so can still be flexibly influenced by top–down modulatory processes.

Alpha Oscillations and Feedback Processing in Visual Cortex for Conscious Perception

2019 ◽  
Vol 31 (7) ◽  
pp. 948-960 ◽  
Author(s):  
Tony Ro
Keyword(s):  
Visual Cortex ◽  
Visual Information ◽  
Conscious Perception ◽  
Evoked Responses ◽  
Feedback Processing ◽  
Visual Suppression ◽  
Alpha Oscillations ◽  
Visual Evoked Responses ◽  
Alpha Oscillation ◽  
Visual Evoked

Variability in perception between individuals may be a consequence of different inherent neural processing speeds. To assess whether alpha oscillations systematically reflect a feedback pacing mechanism for cortical processing during visual perception, comparisons were made between alpha oscillations, visual suppression from TMS, visual evoked responses, and metacontrast masking. Peak alpha oscillation frequencies, measured through scalp EEG recordings, significantly correlated with the optimum latencies for visual suppression from TMS of early visual cortex. Individuals with shorter alpha periods (i.e., higher peak alpha frequencies) processed visual information faster than those with longer alpha periods (i.e., lower peak alpha frequencies). Moreover, peak alpha oscillation periods and optimum TMS visual suppression latencies predicted the latencies of late but not early visual evoked responses. Together, these findings demonstrate an important role of alpha oscillatory and late feedback activity in visual cortex for conscious perception. They also show that the timing for visual awareness varies across individuals, depending on the pace of one's endogenous oscillatory cycling frequency.

scholarly journals No overlap between unconscious and imagined representations

2021 ◽  
Author(s):  
Nadine Dijkstra
Keyword(s):  
Visual Cortex ◽  
Long Range ◽  
Visual Representations ◽  
Occipital Cortex ◽  
Conscious Perception ◽  
Neural Processing ◽  
Feedback Processing ◽  
Unconscious Processing ◽  
Neural Representations ◽  
Lateral Occipital Cortex

Visual representations can be generated via feedforward or feedback processes. The extent to which these processes result in overlapping representations remains unclear. Previous work has shown that imagined stimuli elicit similar representations as perceived stimuli throughout the visual cortex. However, while representations during imagery are indeed only caused by feedback processing, neural processing during perception is an interplay of both feedforward and feedback processing. This means that any overlap could be due to overlap in feedback processes. In the current study we aimed to investigate this issue by characterizing the overlap between feedforward- and feedback-initiated category-representations during imagery, conscious perception and unconscious processing using fMRI. While all three conditions elicited stimulus representations in left lateral occipital cortex (LOC), significant similarities were only observed between imagery and conscious perception in this area. Furthermore, PPI-analyses revealed stronger connectivity between frontal areas and left LOC during conscious perception and imagery compared to unconscious processing. Together, these findings can be explained by the idea that long-range feedback modifies visual representations, thereby reducing neural overlap between purely feedforward and feedback-initiated stimulus representations measured by fMRI. Neural representations caused by feedback, either stimulus-driven (perception) or internally-driven (imagery), are however relatively similar.

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