Becoming Conscious of That Which We Are Apparently Ignoring: How the Detection of Acoustic Change Can Result in a Forced Intrusion Into Consciousness.

• Main Author: Tavakoli, Paniz
• Other Authors: Campbell, Kenneth B.
• Language: en
• Published: Université d'Ottawa / University of Ottawa 2017
• Subjects: Consciousness; Attention Capture; Event-Related Potentials
• Online Access: http://hdl.handle.net/10393/36601; http://dx.doi.org/10.20381/ruor-20881

We live in a busy and complex world, so the ability to focus our attention on relevant information at the expense of the irrelevant is essential in allowing us to avoid distraction. However, it is also important that our attention be captured by external stimuli that, although irrelevant to the task at hand, may nevertheless provide information about important changes to our immediate environment. This capture/orienting of attention is an involuntary, fundamental, and biological mechanism necessary for survival. The present thesis employed event-related potentials (ERPs), the minute responses of the brains electrical activity, to examine how changes in the acoustic environment can lead to the capture of attention. Study 1 examined an ERP component, the P3a, which is associated with the processes that lead to the forced capture of attention by external stimuli. This intrusion into consciousness can be studied using an auditory sequence, the oddball paradigm, which consists of a frequently occurring and homogenous ‘standard’ stimulus. At times, a feature of the standard is changed to form a rarely occurring ‘deviant’. If the extent of change between standard and deviant is large enough, processes associated with attention capture may be activated. Study 1 of this thesis employed a more time-efficient multi-feature optimal paradigm, which allows for the presentation of numerous deviants in one auditory sequence. The standard stimulus was a pure tone. Four of the six deviants were created by changing a single feature of the standard (frequency, duration, increase and decrease in intensity), while the remaining two deviants varied on more than one feature from the standard (environmental sounds, white noise). Results revealed that only the environmental sounds (i.e. animal sounds, human voices, musical instruments) and white noise bursts, elicited the P3a, while the other four deviants did not. Studies 2 and 3 determined whether the attention capture processes associated with the P3a could be observed during the sleep onset and sleep periods, where awareness of the external environment is diminished. For sleep to be of benefit it needs to remain as undisturbed as possible, without constant awakenings by irrelevant external input, however, the sleeping organism must still have the ability to become conscious of possibly relevant input that requires immediate action. In Study 2, a P3a was elicited again following only the environmental sound and white noise deviants across wakefulness and the sleep onset period. Surprisingly, during definitive sleep, the environmental sounds continued to elicit a P3a suggesting that attention capture processes may still remain active during sleep. Nonetheless, only the first 30 minutes of sleep were examined. Study 3 was then conducted to examine the P3a across the entire night. Results revealed that the environmental sounds did, in fact, elicited a P3a during both NREM and REM sleep. The present thesis demonstrates that attention capture mechanisms, observed during wakefulness, are also active during sleep onset and sleep when awareness of the external environment is diminished. This is especially critical because the sleeping organism may be vulnerable to external danger, requiring the immediate ability to orient attention to incoming information, leading to awaking and conscious awareness.