Thesis (M. Soc. Sc.)--University of Hong Kong, 2006.

Primary sensory cortex has long been believed to play a straightforward role in the initial processing of sensory information. Yet, the superficial layers of cortex overall are sparsely active, even during strong sensory stimulation; moreover, cortical activity is influenced by other modalities, task context, reward, and behavioral state. The experiments described in this thesis demonstrate that reinforcement learning dramatically alters representations among longitudinally imaged neurons in superficial layers of mouse primary somatosensory cortex. Cells were confirmed to be sparsely active in naïve animals; however, learning an object detection task recruited previously unresponsive neurons, enlarging the neuronal population sensitive to tactile stimuli. In contrast, cortical responses habituated, decreasing upon repeated exposure to unrewarded stimuli. In addition, after conditioning, the cell population as well as individual neurons better encoded the rewarded stimuli, as well as behavioral choice. Furthermore, in well-trained mice, the neuronal population encoded of the passage of time. We further found evidence that the temporal information was contained in sequences of cell activity, meaning that different cells in the population activated at different moments within the trial. This kind of time-keeping was not observed in naïve animals, nor did it arise after repeated stimulus exposure. Finally, unexpected deviations in trial timing elicited even stronger responses than touch did. In conclusion, the superficial layers of sensory cortex exhibit a high degree of learning-dependent plasticity and are strongly modulated by non-sensory but behaviorally-relevant features, such as timing and surprise.

Neocortical sensory areas have associated primary and secondary thalamic nuclei. While primary nuclei transmit sensory information to cortex, secondary nuclei remain poorly understood. I recorded juxtasomally from the secondary somatosensory (POm) and visual (LP) nuclei of awake mice. POm activity correlated with whisking, but not precise whisker kinematics. This movement modulation was not a result of sensory reafference, nor was it due to input from motor or somatosensory cortex, nor the superior colliculus. Whisking and pupil dilation were strongly correlated, reflecting arousal. Indeed LP, which is not part of the whisker system, tracked whisking equally well, indicating that POm activity does not encode whisker movement per se. The semblance of movement-related activity is likely instead a global effect of arousal on both nuclei. I then investigated how POm and LP may support feature-based attention. I trained head-fixed mice to attend to one sensory modality while ignoring a second modality. I used multielectrode arrays to record simultaneously from both regions. In mice trained to respond to tactile stimuli and ignore visual stimuli, POm was robustly activated by touch and largely unresponsive to visual stimuli. The reverse pattern was observed when mice were trained to respond to visual stimuli and ignore touch, with POm now more robustly activated during visual trials. This POm activity was not explained by differences in movements (i.e., whisking, licking) resulting from the two tasks. LP exhibited similar phenomena. I conclude that behavioral training reshapes activity in secondary thalamic nuclei. Secondary nuclei may respond to behaviorally relevant, reward-predicting stimuli regardless of stimulus modality.

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Vibrotactile sensitivity is measured using a "dry" procedure as opposed to a "wet" procedure previously used. Thresholds are determined using 40 Hz and 160 Hz stimuli across seven temperatures ranging from 20°C to 44°C. Twelve male subjects participated in each of four sessions, producing a high degree of reliability. Results indicate that vibrotactile sensitivity increases with temperatures above 32°C and decreases at temperatures below 32°C; thresholds represent similar functions for both high and low frequency vibrotactile receptor populations. Concerns with previous studies are discussed. Implications are made with regard to future work in the area regarding skin pigmentation and subject age. / Master of Science

The present study examined whether previously reported effects of altered prenatal sensory experience on the subsequent acceleration of intersensory functions are mediated by mechanisms sensitive to the overall amount of stimulation. Results reveal that chicks exposed to augmented amounts of prenatal visual stimulation show interference in subsequent species-typical perceptual development. Specifically, chicks continued to respond to maternal auditory cues into later stages of postnatal development and failed to respond to maternal visual cues at the age when normally reared chicks to exhibit this species-specific ability. Embryos in this study also failed to demonstrate early auditory learning of an individual maternal call, a behavior reliably seen in unmanipulated embryos. These findings suggest that substantially increased amounts of visual stimulation appear to prevent the emergence of species-typical patterns of intersensory functioning and lend support to the notion that stimulation that falls within some optimal range seems to maintain or facilitate normal patterns of perceptual functioning, while stimulation beyond the range of the species norm appears to result in intersensory interference. / Master of Science

Yes / Amidst strong competition and lack of resources and functional superiority, ethical brands may seek an experiential approach to marketing online. A between-subjects online experiment (N=308) shows that ethically congruent visual and auditory cues, and a tactile priming statement, positively influence consumers' willingness to pay (WTP) for an ethical brand online. Altruistic and Biospheric value-orientation (ALTBIO) and Need for Touch (NfT) were considered as moderators to account for specific segments. For consumers with high ALTBIO, the effects of visual and auditory cues are mediated by Consumer Perceived Brand Ethicality (CPBE). Tactile priming has a significant effect only for consumers with high NfT. However, the interaction between the three cues has a positive effect on WTP irrespective of CPBE, ALTBIO, and NfT. Findings illustrate multisensory marketing's efficacy in fostering sensible consumption (considerate of natural and societal environments and their inhabitants) online for the mass-market and specific segments by creating an experiential customer judgement-context.

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Action has many influences on how and what we perceive. One robust example of the relationship between action and subsequent perception, which has recently received great attention in the cognitive sciences, is the “intentional binding” effect: When people estimate the timing of their actions and those actions’ effects, they judge the actions and effects as having occurred closer together in time than two events that do not involve voluntary action (Haggard, Clark, & Kalogeras, 2002). This dissertation examines the possible mechanisms and consequences of the intentional binding effect. First, in Chapter 1, I discuss previous literature on the relationships between experiences of time, action, and causality. Impressions of time and causality are psychologically related: The perceived timing of events impacts, and is impacted by, perceived causality. Similarly, one’s experience of causing and controlling events with voluntary action, sometimes called the sense of agency, shapes and is shaped by how those events’ timing is perceived—as shown by the intentional binding effect. In Chapter 2 I present a series of experiments investigating a hypothesized mechanism underlying the intentional binding effect: Actions may lead to a slowing of subjective time, which would explain the intentional binding effect by postulating a shorter experienced duration between action and effect. This hypothesis predicts that, following action, durations separating any two stimuli would appear subjectively shorter. We tested this hypothesis in the context of visual motion illusions: Two visual stimuli are presented in short succession and if the duration between the stimuli (inter-stimulus interval; ISI) is short, participants tend to perceive motion such that the first stimulus appears to move to the position of the second stimulus. If actions shorten subjective durations, even in visual perception, people should observe motion at longer ISIs when the stimuli follow voluntary action because the two stimuli would be separated by less subjective time. Three experiments confirmed this prediction. An additional experiment showed that verbal estimates of the ISI are also shorter following action. A control experiment suggested that a shift in the ability to prepare for the stimuli, afforded by the participant initiating the stimuli, is an unlikely alternative explanation of the observed results. In Chapter 3 I further investigate whether temporal contiguity of actions and their effects, which is known to impact intentional binding, affects perceptions of visual motion illusions. Two experiments showed that temporal contiguity modulates perceptions of illusory motion in a manner similar to contiguity’s effect on intentional binding. Together, these results show that actions impact perception of visual motion illusions and suggest that general slowing of subjective time is a plausible mechanism underlying the intentional binding effect.

Previous research suggests that larger context effects are observed when participants are required to search a scene in order to find the to-be-remembered stimuli. Similarly, animal research on brain oscillations has shown theta wave activation when animals are searching their environment. These theta wave oscillations are positively correlated with learning. However, theta activation can also occur in response to sensory stimulation, for example, auditory stimulation with binaural beats or visual stimulation with a checkerboard pattern reversal. The results of several studies suggest that while a visual search task seems to reliably improve free recall performance, the effects of passive sensory stimulation on memory are less consistent. Implications and suggestions for future research are discussed.