Tony Ro

While interest in synesthesia among cognitive scientists has been steadily increasing in recent years, one question remains relatively unexplored: what is the relationship between synesthesia and consciousness? In this chapter, we consider some central aspects of this relationship and focus our discussion on two main questions. First, we explore the question of whether synesthesia can occur unconsciously. We identify some complications that arise in interpreting some of the relevant empirical results, and then endorse an affirmative answer to this question based on the limited findings available. Second, we look at four major theories of consciousness and evaluate their predictions regarding the neural correlates of consciousness using synesthesia as a test case. We highlight the ways in which findings concerning the neural correlates of synesthetic experience would seem to offer support for or against these major theories.

Crowdsourcing has been shown to be a powerful method for solving a variety of problems. In this paper, we introduce an approach for allowing a crowd to help navigate a visually impaired user to their destination in real-time. Furthermore, we experiment with several approaches in aggregating and feeding back crowd data to determine the optimal method. Our approach streams live video from the visually impaired user's mobile device to a crowd of sighted volunteers. Each crowd member is able to provide their opinion on how the user should proceed and our algorithm aggregates this into a single opinion that is sent as feedback to the user. In this paper, we first present the design and implementation of our crowd sourced navigation system, including webapp design and two aggregation algorithms: averaging and league leader approaches. A virtualized user (avatar) is also developed for more controlled and repeatable testing of aggregation approaches with multiple crowd sourced volunteers. We also tested two navigation modes: a real-user controlled avatar, and a program controlled avatar. Experimental results are provided with the two aggregation methods and the two navigation modes. Our results show that we do not have significant difference between the aggregation methods and the program controlled avatar performed better than a real-user controlled avatar.

Synesthesia is a fairly common condition in which individuals experience atypical responses (such as color experiences) in association with certain types of stimuli (such as non-colored letters). Although synesthesia has been described for centuries, only very recently has there been an explosive growth of systematic scientific examinations of this condition. In this article, we review and critically evaluate current methods for both assessing synesthesia and examining its psychological basis, including the "test-retest" procedure, online battery assessments, and behavioral experiments. We highlight the limitations of these methods for understanding the nature of this complex condition and propose potential solutions to address some of these limitations. We also provide a set of characteristics that aid in distinguishing synesthesia from other closely related psychological phenomena.

Hearing and feeling both rely upon the transduction of physical events into frequency-based neural codes, suggesting that the auditory system may be intimately related to the somatosensory system. Here, we provide evidence that the neural substrates for audition and somatosensation are anatomically linked. Using diffusion tensor imaging with both deterministic and probabilistic tractography to measure white matter connectivity, we show that there are extensive ipsilateral connections between the primary auditory cortex and the primary and secondary somatosensory regions in the human cerebral cortex. We further show that these cross-modal connections are exaggerated between the auditory and secondary somatosensory cortex in the lesioned hemisphere of a patient (SR) with acquired auditory-tactile synesthesia, in whom sounds alone produce bodily sensations. These results provide an anatomical basis for multisensory interactions between audition and somatosensation and suggest that cross-talk between these regions may explain why some sounds, such as nails screeching down a chalkboard or an audible mosquito, can induce feelings of touch, especially on the contralesional body surface of patient SR.

Alpha oscillations are ubiquitous in the brain, but their role in cortical processing remains a matter of debate. Recently, evidence has begun to accumulate in support of a role for alpha oscillations in attention selection and control. Here we first review evidence that 8–12 Hz oscillations in the brain have a general inhibitory role in cognitive processing, with an emphasis on their role in visual processing. Then, we summarize the evidence in support of our recent proposal that alpha represents a pulsed-inhibition of ongoing neural activity. The phase of the ongoing electroencephalography can influence evoked activity and subsequent processing, and we propose that alpha exerts its inhibitory role through alternating microstates of inhibition and excitation. Finally, we discuss evidence that this pulsed-inhibition can be entrained to rhythmic stimuli in the environment, such that preferential processing occurs for stimuli at predictable moments. The entrainment of preferential phase may provide a mechanism for temporal attention in the brain. This pulsed inhibitory account of alpha has important implications for many common cognitive phenomena, such as the attentional blink, and seems to indicate that our visual experience may at least some times be coming through in waves.

Several studies have demonstrated that faces are processed differently from other types of objects, implicating a special role that faces have within the human visual system. However, other studies have suggested that faces may be special only in that they constitute a highly familiar category of visual objects with which most humans have expertise. In this study, we tested a group of expert musicians with a musical instrument classification task during which irrelevant images of musical instruments were presented as visual distractors under varying conditions of perceptual load. Unlike nonmusicians (who had been tested in Lavie, Ro, & Russell, 2003, using the same paradigm as in the present study), the musicians processed these irrelevant images of musical instruments even under conditions of high perceptual load. These results suggest that musical instruments are processed automatically and without capacity limits in subjects with musical expertise and implicate a specialized processing mechanism for objects of high familiarity.

Certain sounds, such as fingernails screeching down a chalkboard, have a strong association with somatosensory percepts. In order to assess the influences of audition on somatosensory perception, three experiments measured how task-irrelevant auditory stimuli alter detection rates for near-threshold somatosensory stimuli. In Experiment 1, we showed that a simultaneous auditory stimulus increases sensitivity, but not response biases, to the detection of an electrical cutaneous stimulus delivered to the hand. Experiment 2 demonstrated that this enhancement of somatosensory perception is spatially specific—only monaural sounds on the same side increased detection. Experiment 3 revealed that the effects of audition on touch are also frequency dependent—only sounds with the same frequency as the vibrotactile frequency enhanced tactile detection. These results indicate that auditory information influences touch perception in highly systematic ways and suggest that similar coding mechanisms may underlie the processing of information from these different sensory modalities.