Relational Memory Is Evident in Eye Movement Behavior despite the Use of Subliminal Testing Methods

While it is generally agreed that perception can occur without awareness, there continues to be debate about the type of representational content that is accessible when awareness is minimized or eliminated. Most investigations that have addressed this issue evaluate access to well-learned representations. Far fewer studies have evaluated whether or not associations encountered just once prior to testing might also be accessed and influence behavior. Here, eye movements were used to examine whether or not memory for studied relationships is evident following the presentation of subliminal cues. Participants (assigned to experimental or control groups) studied scene-face pairs and test trials evaluated implicit and explicit memory for these pairs. Each test trial began with a subliminal scene cue, followed by three visible studied faces. For experimental group participants, one face was the studied associate of the scene (implicit test); for controls none were a match. Subsequently, the Display containing a match was presented to both groups, but now it was preceded by a visible scene cue (explicit test). Eye movements were recorded and recognition Memory responses were made. Participants in the experimental group looked disproportionately at matching faces on implicit test trials and participants from both groups looked disproportionately at matching faces on explicit test trials, even when that face had not been successfully identified as the associate. Critically, implicit memory-based viewing effects seemed not to depend on residual awareness of subliminal scenes cues, as subjective and objective measures indicated that scenes were successfully masked from view. The reported outcomes indicate that memory for studied relationships can be expressed in eye movement behavior without awareness.

Investigating interocclusal perception in tactile teeth sensibility using symmetric and asymmetric analysis

The purpose of this clinical trial was to determine the active tactile sensibility of natural teeth and to obtain a statistical analysis method fitting a psychometric function through the observed data points. On 68 complete dentulous test persons (34 males, 34 females, mean age 45.9 ± 16.1 years), one pair of healthy natural teeth each was tested: n = 24 anterior teeth and n = 44 posterior teeth. The computer-assisted, randomized measurement was done by having the subjects bite on thin copper foils of different thickness (5-200 µm) inserted between the teeth. The threshold of active tactile sensibility was defined by the 50% value of correct answers. Additionally, the gradient of the sensibility curve and the support area (90-10% value) as a description of the shape of the sensibility curve were calculated. For modeling the sensibility curve, symmetric and asymmetric functions were used. The mean sensibility threshold was 14.2 ± 12.1 µm. The older the subject, the higher the tactile threshold (r = 0.42, p = 0.0006). The support area was 41.8 ± 43.3 µm. The higher the 50% threshold, the smaller the gradient of the curve and the larger the support area. The curves showing the active tactile sensibility of natural teeth demonstrate a tendency towards asymmetry, so that the active tactile sensibility of natural teeth can mathematically best be described by using the asymmetric Weibull function.

Slowdown of gist perception in colour diagnostic scenes

Humans perceive the content (gist) of a scene very rapidly within about 40 ms [Castelhano and Henderson, 2008 Journal of Experimental Psychology Human Perception and Performance 43(3) 660-675]. It has also been demonstrated that colours contribute to the perception of the gist of a scene if the colours are diagnostic for the distinction of scenes (Oliva and Schyns, 2000 Cognitive Psychology 41 176-210). We presented 320 coloured photographs of 2 diagnostic (mountains and coasts) and 2 nondiagnostic colour scenes (cities and rooms), 80 per category, in a masking paradigm. The mask consisted of randomly distributed colour patches. SOA was varied between 20 and 80 ms, in steps of 20 ms and subjects had to indicate the gist of the scene (4AFC). A control condition without masking was also included. In line with previous results we have found that the gist of nondiagnostic coloured scenes is extracted within 40 ms. However, if colour comes into play, the extraction of the scene gist is prolonged by about 20 ms. A possible reason for this outcome might be that nondiagnostic colour scenes are identified by their luminance components which are processed faster than the colour information, which in turn mediates the identification of diagnostic colour scenes

Development of a novel fMRI compatible visual perception prototype battery to test older people with and without dementia

Background: Visuoperceptual deficits in dementia are common and can reduce quality of life. Testing of visuoperceptual function is often confounded by impairments in other cognitive domains and motor dysfunction. We aimed to develop, pilot, and test a novel visuocognitive prototype test battery which addressed these issues, suitable for both clinical and functional imaging use. Methods: We recruited 23 participants (14 with dementia, 6 of whom had extrapyramidal motor features, and 9 age-matched controls). The novel Newcastle visual perception prototype battery (NEVIP-B-Prototype) included angle, color, face, motion and form perception tasks, and an adapted response system. It allows for individualized task difficulties. Participants were tested outside and inside the 3T functional magnetic resonance imaging (fMRI) scanner. Functional magnetic resonance imaging data were analyzed using SPM8. Results: All participants successfully completed the task inside and outside the scanner. Functional magnetic resonance imaging analysis showed activation regions corresponding well to the regional specializations of the visual association cortex. In both groups, there was significant activity in the ventral occipital-temporal region in the face and color tasks, whereas the motion task activated the V5 region. In the control group, the angle task activated the occipitoparietal cortex. Patients and controls showed similar levels of activation, except on the angle task for which occipitoparietal activation was lower in patients than controls. Conclusion: Distinct visuoperceptual functions can be tested in patients with dementia and extrapyramidal motor features when tests use individualized thresholds, adapted tasks, and specialized response systems.

Seeing and identifying with a virtual body decreases pain perception

Pain and the conscious mind (or the self) are experienced in our body. Both are intimately linked to the subjective quality of conscious experience. Here, we used virtual reality technology and visuo-tactile conflicts in healthy subjects to test whether experimentally induced changes of bodily self-consciousness (self-location; self-identification) lead to changes in pain perception. We found that visuo-tactile stroking of a virtual body but not of a control object led to increased pressure pain thresholds and self-location. This increase was not modulated by the synchrony of stroking as predicted based on earlier work. This differed for self-identification where we found as predicted that synchrony of stroking increased self-identification with the virtual body (but not a control object), and positively correlated with an increase in pain thresholds. We discuss the functional mechanisms of self-identification, self-location, and the visual perception of human bodies with respect to pain perception.