From sensory processes to conscious perception

In recent years, cognitive neuroscientists have began to explore the process of how sensory information gains access to awareness. To further probe this process, event-related functional magnetic resonance imaging (fMRI) was used while testing subjects with a paradigm known as the "attentional blink." In this paradigm, visually presented information sporadically fails to reach awareness. It was found that the magnitude and time course of activation within the anterior cingulate (BA 32), medial prefrontal cortex (BA 9), and frontopolar cortex (BA 10) predicted whether or not information was consciously perceived during the critical period for the attentional blink. These results are discussed in light of a neural framework for conscious processing.     

Visual marking and the perception of salience in visual search

In the present study, the gap paradigm originally developed by Watson and Humphreys (1997) was used to investigate whether the process of visual marking can influence the perceptual salience of a target in visual search. Consistent with previous studies (Watson & Humphreys, 1997), the results showed that search was not affected by the presence of the preceding distractors when the target was relatively low in salience. This finding suggests that visual marking can increase the efficiency of visual search by decreasing the size of the search set. However, more important, the results also showed that search was affected by the presence of the preceding distractors when the target was relatively high in salience. This finding suggests that visual marking may be limited in its ability to increase the perceptual salience of the target. Together, the results of the present study suggest that the effectiveness of visual marking may vary as a function of search context.     

Active inference, sensory attenuation and illusions

Active inference provides a simple and neurobiologically plausible account of how action and perception are coupled in producing (Bayes) optimal behaviour. This can be seen most easily as minimising prediction error: we can either change our predictions to explain sensory input through perception. Alternatively, we can actively change sensory input to fulfil our predictions. In active inference, this action is mediated by classical reflex arcs that minimise proprioceptive prediction error created by descending proprioceptive predictions. However, this creates a conflict between action and perception; in that, self-generated movements require predictions to override the sensory evidence that one is not actually moving. However, ignoring sensory evidence means that externally generated sensations will not be perceived. Conversely, attending to (proprioceptive and somatosensory) sensations enables the detection of externally generated events but precludes generation of actions. This conflict can be resolved by attenuating the precision of sensory evidence during movement or, equivalently, attending away from the consequences of self-made acts. We propose that this Bayes optimal withdrawal of precise sensory evidence during movement is the cause of psychophysical sensory attenuation. Furthermore, it explains the force-matching illusion and reproduces empirical results almost exactly. Finally, if attenuation is removed, the force-matching illusion disappears and false (delusional) inferences about agency emerge. This is important, given the negative correlation between sensory attenuation and delusional beliefs in normal subjects—and the reduction in the magnitude of the illusion in schizophrenia. Active inference therefore links the neuromodulatory optimisation of precision to sensory attenuation and illusory phenomena during the attribution of agency in normal subjects. It also provides a functional account of deficits in syndromes characterised by false inference and impaired movement—like schizophrenia and Parkinsonism—syndromes that implicate abnormal modulatory neurotransmission.     

A common basis for auditory sensory storage in perception and immediate memory

Thirty-two subjects participated in three experiments, one assessing auditory short-term memory for word lists with and without a verbal suffix and two assessing discrimination of synthetic vowels at either short or long interstimulus delays. The purpose was to find out whether the same kind of auditory memory supports both short-term memory and speech discrimination. There was a significant correlation between performance in the suffix and A-X speech-discrimination experiments in those conditions likely to depend partly on echoic memory; however, there was no significant correlation between the tasks in conditions in which echoic memory was presumed to have been removed. The results provide a bridge between perception and memory procedures and support a theoretical model that was made to cover both domains.     

Active artificial echolocation and the nonvisual perception of aperture passability.

The potential of airborne sonar to provide effective information about three-dimensional (3D) spatial layouts was assessed in four companion experiments. Blindfolded participants, never given visual access to the layout of a large room, were asked to use a sonar device whose output they had never previously encountered to judge the passability (by normal walking) of apertures between two aligned wall panels. Estimates were made from fixed and variable locations, approaches to the apertures were made from orthogonal and oblique angles, and the panels were at different distances and orientations. In each experiment, participants gave evidence of an ability to immediately use the information in structured echoes to make these judgments, though aperture location, approach angles, wall alignment and orientation each had significant effects on performance. The data are compared with performance under visual and nonechoic auditory conditions and are discussed with respect to the notions of potential information and effective information during these perceptually guided tasks.     

Person perception informs understanding of cognition during visual search

Does person perception—the impressions we form from watching others—hold clues to the mental states of people engaged in cognitive tasks? We investigated this with a two-phase method: In Phase 1, participants searched on a computer screen (Experiment 1) or in an office (Experiment 2); in Phase 2, other participants rated the searchers’ video-recorded behavior. The results showed that blind raters are sensitive to individual differences in search proficiency and search strategy, as well as to environmental factors affecting search difficulty. Also, different behaviors were linked to search success in each setting: Eye movement frequency predicted successful search on a computer screen; head movement frequency predicted search success in an office. In both settings, an active search strategy and positive emotional expressions were linked to search success. These data indicate that person perception informs cognition beyond the scope of performance measures, offering the potential for new measurements of cognition that are both rich and unobtrusive.     

Independent effects of emotion and attention on sensory and affective pain perception

The present study investigated whether attention and emotion independently influence sensory and affective pain ratings. Fifty-four (27 female) participants rated sensory and affective pain in response to painful mechanic pressure stimulation while exposed to positive, neutral and negative slides from the International Affective Picture System. In doing so, participants were assigned to one of three groups, which focused attention either on the pictures or on the sensory or on the affective aspects of the pressure stimulation. Consistent with the motivational priming hypothesis, sensory and affective pain ratings were generally lower during exposure to positive compared to negative and neutral slides. In line with our assumptions, attention modulated sensory pain ratings with lowest ratings in the picture focusing group and highest in the affective pain focusing group. No attention effect for affective pain ratings and no interactions between emotional and attentional effects on pain perception were found.     

Visual memory and visual perception: when memory improves visual search

This study examined the relationship between memory and perception in order to identify the influence of a memory dimension in perceptual processing. Our aim was to determine whether the variation of typical size between items (i.e., the size in real life) affects visual search. In two experiments, the congruency between typical size difference and perceptual size difference was manipulated in a visual search task. We observed that congruency between the typical and perceptual size differences decreased reaction times in the visual search (Exp. 1), and noncongruency between these two differences increased reaction times in the visual search (Exp. 2). We argue that these results highlight that memory and perception share some resources and reveal the intervention of typical size difference on the computation of the perceptual size difference.     

The interaction between sensory and tonic factors in the perception of the vertical in pigeons

In two separate experiments, 21 pigeons were given 10 days of training to peck a key on which a white vertical line was exposed. Next, the birds were given generalization tests along the angularity dimension with the floor tilted 24° to the right or to the left. Reliable asymmetrical gradients were obtained with enhanced responding to the side toward which the floor was tilted. This posturally induced distortion in the visual perception of the vertical indicates that sensory-tonic interactions typically observed in humans have a parallel in this lower species.     

Learning by selection: visual search and object perception in young infants

The authors examined how visual selection mechanisms may relate to developing cognitive functions in infancy. Twenty-two 3-month-old infants were tested in 2 tasks on the same day: perceptual completion and visual search. In the perceptual completion task, infants were habituated to a partly occluded moving rod and subsequently presented with unoccluded broken and complete rod test stimuli. In the visual search task, infants viewed displays in which single targets of varying levels of salience were cast among homogeneous static vertical distractors. Infants whose posthabituation preference indicated unity perception in the completion task provided evidence of a functional visual selective attention mechanism in the search task. The authors discuss the implications of the efficiency of attentional mechanisms for information processing and learning.     

Linguistic asymmetry,egocentric anchoring,and sensory modality as factors for the observed association between time and space perception

Temporal and spatial representations have been consistently shown to be inextricably intertwined. However, the exact nature of time–space mapping remains unknown. On the one hand, the conceptual metaphor theory postulates unilateral, asymmetric mapping of time onto space, that is, time is perceived in spatial terms but the perception of space is relatively independent of time. On the other hand, a theory of magnitude assumes bilateral and symmetric interactions between temporal and spatial perceptions. In the present paper, we argue that the concepts of linguistic asymmetry, egocentric anchoring, and sensory modality provide potential explanations for why evidences favoring both asymmetry and symmetry have been obtained. We first examine the asymmetry model and suggest that language plays a critical role in it. Next, we discuss the symmetry model in relation to egocentric anchoring and sensory modality. We conclude that since these three factors may jointly account for some conflicting past results regarding the strength and directionality of time–space mapping, they should be taken into serious consideration in future test designs.