Localisation of “unseen” visual stimuli: Blindsight in normal observers?

2003 ◽  
Vol 62 (3) ◽  
pp. 159-165
Author(s):  
H. Schärli ◽  
P. Brugger ◽  
M. Regard ◽  
C. Mohr ◽  
Th. Landis
Keyword(s):  
Apparent Motion ◽  
Target Stimulus ◽  
Visual Stimuli ◽  
Normal Subjects ◽  
Conscious Awareness ◽  
Computer Screen ◽  
Subjective Confidence ◽  
Localization Performance ◽  
Phenomenal Awareness ◽  
Detection And Localization

We developed two experiments on normal subjects to simulate “blindsight”, i.e., above chance localization performance of visual stimuli without phenomenal awareness. In both experiments, visual targets were presented on a computer screen at one of six possible locations, followed by a metacontrast mask. Subjects (1) indicated whether they had seen the target stimulus or not, and (2) guessed at which location the stimulus had been presented. Fifty percent were blank trials. We found that even when subjects did not acknowledge the presence of a stimulus, they nevertheless guessed its location with above chance accuracy. Apparent motion improved both detection and localization performance. Subjective confidence was related to stimulus presence and localisation performance. Thus, simulated blindsight appeared to be based on residual conscious awareness.

Perceptual characteristics of computerized program visualizations can differentially affect detection and localization performance

2006 ◽  
Author(s):  
Elizabeth T. Davis ◽  
Kenneth Hailston ◽  
Eileen Kraemer ◽  
Ashley Hamilton-Taylor ◽  
Philippa Rhodes ◽  
...  
Keyword(s):  
Affect Detection ◽  
Localization Performance ◽  
Perceptual Characteristics ◽  
Detection And Localization

Abnormal Emotional Responses to Pleasant and Unpleasant Visual Stimuli in First Episode Schizophrenia: f-MRI Investigation

2009 ◽  
Vol 24 (S1) ◽  
pp. 1-1
Author(s):  
M. Casacchia ◽  
M. Mazza ◽  
A. Catalucci ◽  
R. Pollice ◽  
M. Gallucci ◽  
...  
Keyword(s):  
Negative Symptoms ◽  
Psychiatric Service ◽  
Visual Stimuli ◽  
Chronic Schizophrenia ◽  
Normal Subjects ◽  
Blood Oxygenation ◽  
First Episode ◽  
Affective Deficits ◽  
Oxygenation Level ◽  
Mri Study

Aims:Affective deficits (flat affect, a diminished expression of emotion, anhedonia, and lowered ability to experience pleasure) are very common in schizophrenia. In emotion feeling, the crucial role of the insula, rather than of the primary somatosensory cortices, strongly suggests that the neural substrate for emotions is not merely sensorial. It is more likely that the activation of the insula representation of the viscero-motor activity is responsible for feeling of disgust. A recent MRI study demonstrated specific left anterior insular volume reduction in chronic schizophrenia patients: sustainable is the suggestion that emotion of disgust or of taste may be related to the experience of pleasure, which probably is compromise in schizophrenics.We investigated fMRI brain activations in first episode schizophrenic subjects with negative symptoms and in healthy subjects elicited by pleasant and unpleasant visual stimuli.Method:Ten first-episode schizophrenic subjects with normal IQ were recruited from the psychiatric service “SMILE” of San Salvatore Hospital and 10 healthy volunteers matched for age and education were scanned during observation of pleasant and unpleasant visual stimuli. Functional images were acquired with a 1.5T MRI scanner. Blood oxygenation level dependent (BOLD) contrast was obtained using EPI T2* weighted images.Results:The most important result of the study was the demonstration that anterior insula was activated by the exposure to disgusting stimula in normal subjects but not in schizophrenic subjects.Conclusion:This failure of the neural systems used to support emotional attribution is consistent with pervasive problems in experiencing emotions by schizophrenics.

Multimodal Ternus: Visual, Tactile, and Visuo — Tactile Grouping in Apparent Motion

Perception ◽  
10.1068/p5844 ◽  
2007 ◽  
Vol 36 (10) ◽  
pp. 1455-1464 ◽  
Author(s):  
Vanessa Harrar ◽  
Laurence R Harris
Keyword(s):  
Stimulus Onset Asynchrony ◽  
Apparent Motion ◽  
Visual Stimuli ◽  
Stimulus Onset ◽  
Light Touch ◽  
Visual Group ◽  
Motion Stimulus ◽  
Group Motion ◽  
Onset Asynchrony

Gestalt rules that describe how visual stimuli are grouped also apply to sounds, but it is unknown if the Gestalt rules also apply to tactile or uniquely multimodal stimuli. To investigate these rules, we used lights, touches, and a combination of lights and touches, arranged in a classic Ternus configuration. Three stimuli (A, B, C) were arranged in a row across three fingers. A and B were presented for 50 ms and, after a delay, B and C were presented for 50 ms. Subjects were asked whether they perceived AB moving to BC (group motion) or A moving to C (element motion). For all three types of stimuli, at short delays, A to C dominated, while at longer delays AB to BC dominated. The critical delay, where perception changed from group to element motion, was significantly different for the visual Ternus (3 lights, 162 ms) and the tactile Ternus (3 touches, 195 ms). The critical delay for the multimodal Ternus (3 light – touch pairs, 161 ms) was not different from the visual or tactile Ternus effects. In a second experiment, subjects were exposed to 2.5 min of visual group motion (stimulus onset asynchrony = 300 ms). The exposure caused a shift in the critical delay of the visual Ternus, a trend in the same direction for the multimodal Ternus, but no shift in the tactile Ternus. These results suggest separate but similar grouping rules for visual, tactile, and multimodal stimuli.

The Tactile Quartet: Comparing Ambiguous Apparent Motion in Tactile and Visual Stimuli

Perception ◽  
2019 ◽  
Vol 49 (1) ◽  
pp. 61-80 ◽  
Author(s):  
Harry H. Haladjian ◽  
Stuart Anstis ◽  
Mark Wexler ◽  
Patrick Cavanagh
Keyword(s):  
Motion Perception ◽  
Apparent Motion ◽  
Index Finger ◽  
Dimensional Space ◽  
Visual Stimuli ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Different Depths ◽  
Three Dimensional Space

In the visual quartet, alternating diagonal pairs of dots produce apparent motion horizontally or vertically, depending on proximity. Here, we studied a tactile quartet where vibrating tactors were attached to the thumbs and index fingers of both hands. Apparent motion was felt either within hands (from index finger to thumb) or between hands. Participants adjusted the distance between their hands to find the point where motion changed directions. Surprisingly, switchovers occurred when between-hand distances were as much as twice that of within-hand distances—a general bias that was also found for tactile judgments of static distances. This expansion of within-hand felt distances was again seen when lights were placed on the hands rather than vibrating tactors. Importantly, switchover points were similar when the hands were placed at different depths, indicating that representations governing tactile motion were in perceptual three-dimensional space, not retinal two-dimensional space. This was true whether the quartets were visual stimuli on the hands or were purely visual on a monitor, suggesting that proximity is generally determined in three-dimensional coordinates for motion perception. Finally, the similarity of visual and tactile results suggests a common computation for apparent motion, albeit with different built-in distance biases for separate modalities.

Audible Performance of Smoke Alarm Sounds

1994 ◽  
Vol 38 (2) ◽  
pp. 147-151 ◽  
Author(s):  
Richard W. Huey ◽  
Dawn S. Buckley ◽  
Neil D. Lerner
Keyword(s):  
Positive Trend ◽  
Smoke Alarm ◽  
Response Data ◽  
Frequency Peak ◽  
Smoke Detectors ◽  
Localization Performance ◽  
Primary Frequency ◽  
Detection And Localization ◽  
Computerized System ◽  
Alarm Sounds

This paper concerns a study aimed at selection of alarm sounds with improved audible performance characteristics for older listeners over current conventional residential smoke detectors. Many current residential smoke detectors possess alarms that have their primary frequency peak in the 4000 Hz region of the audible spectrum. Additionally, many of these alarms are constant instead of providing temporal modulation of the signal. This study analyzed a variety of alternative sounds for selection as a better choice for an “age sensitive” smoke alarm signal. The study presented a battery of candidate sounds to pairs of subjects aged 65 and older with varying levels of hearing impairment (0 to 45 dB) in their own homes to see which sounds performed best in terms of detection, localization, and perceived attention-getting value. Subjects were placed in various location- and masking-based conditions within their homes during listening periods and subjected to sounds played at a constant level. A computerized system collected response data as the battery of stimuli was presented. The data showed a fairly predictable positive trend in detection and localization performance level as the frequency of the stimuli decreased from 4000 Hz to 500 Hz. The data also showed that pulsed signals were more detectable than steady alarms.

scholarly journals A few remarks on "uncrowding" in visual stimuli

2021 ◽  
Author(s):  
Bernt Skottun
Keyword(s):  
Interference Effect ◽  
Target Stimulus ◽  
Visual Stimuli ◽  
Crowding Effect ◽  
Visual Crowding

Visual crowding occurs when a target stimulus is presented along with flanking stimuli. These tend to reduce the visibility of the target. It has been found that adding additional flanking stimuli may reduce the crowding effect. This has been termed "uncrowding". It has previously been demonstrated that interference in the stimuli may have effects similar to visual crowding. Interference takes place in the stimuli and is unrelated to vision. The question is then: Can adding additional flanking stimuli reduce the interference effect of initial flanking stimuli in a manner consistent with uncrowding. The present simple calculations indicate that this is very much a possibility.

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