Adaptation to moving tactile stimuli and its effects on perceived speed and direction

Like other senses, tactile perception is subject to adaptation effects in which systematic changes in the pattern of sensory input lead to predictable changes in perception. In this thesis, aftereffects of adaptation to tactile motion are used to reveal the processes that give rise to tactile motion perception from the relevant sensory inputs. The first aftereffect is the tactile speed aftereffect (tSAE), in which the speed of motion appears slower following exposure to a moving surface. Perceived speed of a test surface was reduced by about 30% regardless of the direction of the adapting stimulus, indicating that the tSAE is not direction sensitive. Additionally, higher adapting speeds produced a stronger tSAE, and this dependence on adapting speed could not be attributed to differences in temporal frequency or spatial period that accompanied the different adapting speeds. The second motion aftereffect that was investigated is the dynamic tactile motion aftereffect (tMAE), in which a direction-neutral test stimulus appears to move in the opposite direction to previously felt adapting motion. The strength of the tMAE depended on the speed of the adapting motion, with higher speeds producing a stronger aftereffect. Both the tSAE and the tMAE showed evidence of an intensive speed code in their underlying neural populations, with faster adapting speeds resulting in stronger aftereffects. In neither case was any evidence of speed tuning found, that is, neither aftereffect was strongest with a match between the speeds of the adapting and test stimuli. This is compatible with the response properties of motion sensitive neurons in the primary somatosensory cortex. Despite these shared features, speed and direction are unlikely to be jointly coded in the same neurons because the lack of direction sensitivity of the tSAE requires neural adaptation effects to be uniform across neurons preferring all directions, whereas the tMAE requires direction selective adaptation

Adaptation to moving tactile stimuli and its effects on perceived speed and direction

Like other senses, tactile perception is subject to adaptation effects in which systematic changes in the pattern of sensory input lead to predictable changes in perception. In this thesis, aftereffects of adaptation to tactile motion are used to reveal the processes that give rise to tactile motion perception from the relevant sensory inputs. The first aftereffect is the tactile speed aftereffect (tSAE), in which the speed of motion appears slower following exposure to a moving surface. Perceived speed of a test surface was reduced by about 30% regardless of the direction of the adapting stimulus, indicating that the tSAE is not direction sensitive. Additionally, higher adapting speeds produced a stronger tSAE, and this dependence on adapting speed could not be attributed to differences in temporal frequency or spatial period that accompanied the different adapting speeds. The second motion aftereffect that was investigated is the dynamic tactile motion aftereffect (tMAE), in which a direction-neutral test stimulus appears to move in the opposite direction to previously felt adapting motion. The strength of the tMAE depended on the speed of the adapting motion, with higher speeds producing a stronger aftereffect. Both the tSAE and the tMAE showed evidence of an intensive speed code in their underlying neural populations, with faster adapting speeds resulting in stronger aftereffects. In neither case was any evidence of speed tuning found, that is, neither aftereffect was strongest with a match between the speeds of the adapting and test stimuli. This is compatible with the response properties of motion sensitive neurons in the primary somatosensory cortex. Despite these shared features, speed and direction are unlikely to be jointly coded in the same neurons because the lack of direction sensitivity of the tSAE requires neural adaptation effects to be uniform across neurons preferring all directions, whereas the tMAE requires direction selective adaptation

Can a witness report hearsay evidence unintentionally? The effects of discussion on eyewitness memory

When eyewitnesses are exposed to misinformation about an event from a co-witness, they often incorporate this misinformation in their recall of the event. The current research aimed to investigate whether this memory conformity phenomenon is due to change in the witness's memory for the event, or to social pressures to conform to the co-witness's account. Participants were shown a crime video and then asked to discuss the video in groups, with some receiving misinformation about the event from their discussion partners. After a one week delay some participants were warned about possible misinformation before all participants provided their own account of the event. In Study 1, participants made remember/know judgments about the items recalled, and in Study 2 they indicated the source of their memories. Co-witness information was incorporated into participants' testimonies, and this effect was not reduced by warnings or source monitoring instructions, suggesting memory change may have occurred. However, there was some indication that remember/know judgments may help distinguish between "real" memories and co-witness information

Fact Sheet: Conference works: getting the most out of conferences

Conferences provide the opportunity to keep up with new developments, present ideas, meet people who inspire you to think or work differently, foster communication and form new relationships (Collins, 2000). In this fact sheet, we outline ways you can enhance the experience of attending conferences. These suggestions have been collected from conference evaluations, discussions with delegates at a number of conferences, and personal experiences

Co-registration of optoacoustic tomography and magnetic resonance imaging data from murine tumour models.

As optoacoustic tomography (OT) emerges as a mainstream pre-clinical imaging modality, understanding the relationship between optoacoustic and other imaging biomarkers in the context of the underlying tissue biology becomes vitally important. Complementary insight into tumour vasculature and hypoxia can be gained using OT alongside magnetic resonance imaging (MRI)-based techniques. To evaluate the relationship between these metrics and the relative performance of the two modalities in assessment of tumour physiology, co-registration of their output imaging data is required. Unfortunately, this poses a significant challenge due to differences in animal positioning during imaging. Here, we present an integrated framework for registration of OT and MR image data in mice. Our framework combines a novel MR animal holder, to improve animal positioning during imaging, and a landmark-based software co-registration algorithm. We demonstrate that our protocol significantly improves registration of both body and tumour contours between these modalities, enabling more precise multi-modal tumour characterisation

Developing a Data Compilation for the Marin Autism Collaborative

There is a documented need for better services for those with autism spectrum disorders. Various barriers, such as availability and accessibility of services and financial barriers, prevent those who need services from obtaining them. According to the literature, using data, particularly population level data, leads to improved services. Understanding the effectiveness and ineffectiveness of services helps healthcare providers identify areas for improvement and/or capitalize on past successful methods. The purpose of this project was to provide a data compilation containing autism statistics including but not limited to prevalence, trend data, service use, and needs for the Marin Autism Collaborative (MAC). The compilation is meant to aid the various organizations that comprise MAC in improving existing supports for the autism community to better meet this population’s needs. The presented data compilation follows the trend in datadriven service development, while taking an occupational justice perspective on the various trends in autism data at the county, state, and national levels. In addition, it highlights the gaps in current autism statistics. A survey including a Likert scale and open-ended questions was sent to MAC agencies to evaluate the data compilation, the results of which were overall positive

Investigating teeth eruption and eating quality

In Australia, a sheep ceases to be a lamb as soon as the eruption of its first permanent incisor teeth is evident. As part of a wider program to investigate a number of aspects of sheep meat eating quality, a project was undertaken to determine whether lamb eating quality would be compromised if sheep with partially erupted teeth continued to be classified as lamb. Overall, the results indicated that meat from young sheep with partially erupted teeth was unlikely to be inferior in eating quality than the meat currently classified as lamb

Tactile motion adaptation reduces perceived speed but shows no evidence of direction sensitivity

Introduction: While the directionality of tactile motion processing has been studied extensively, tactile speed processing and its relationship to direction is little-researched and poorly understood. We investigated this relationship in humans using the ‘tactile speed aftereffect’ (tSAE), in which the speed of motion appears slower following prolonged exposure to a moving surface. Method: We used psychophysical methods to test whether the tSAE is direction sensitive. After adapting to a ridged moving surface with one hand, participants compared the speed of test stimuli on the adapted and unadapted hands. We varied the direction of the adapting stimulus relative to the test stimulus. Results: Perceived speed of the surface moving at 81 mms−1 was reduced by about 30% regardless of the direction of the adapting stimulus (when adapted in the same direction, Mean reduction = 23 mms−1, SD = 11; with opposite direction, Mean reduction = 26 mms−1, SD = 9). In addition to a large reduction in perceived speed due to adaptation, we also report that this effect is not direction sensitive. Conclusions: Tactile motion is susceptible to speed adaptation. This result complements previous reports of reliable direction aftereffects when using a dynamic test stimulus as together they describe how perception of a moving stimulus in touch depends on the immediate history of stimulation. Given that the tSAE is not direction sensitive, we argue that peripheral adaptation does not explain it, because primary afferents are direction sensitive with friction-creating stimuli like ours (thus motion in their preferred direction should result in greater adaptation, and if perceived speed were critically dependent on these afferents’ response intensity, the tSAE should be direction sensitive). The adaptation that reduces perceived speed therefore seems to be of central origin

Low-power transcutaneous current stimulator for wearable applications

BACKGROUND: Peripheral neuropathic desensitization associated with aging, diabetes, alcoholism and HIV/AIDS, affects tens of millions of people worldwide, and there is little or no treatment available to improve sensory function. Recent studies that apply imperceptible continuous vibration or electrical stimulation have shown promise in improving sensitivity in both diseased and healthy participants. This class of interventions only has an effect during application, necessitating the design of a wearable device for everyday use. We present a circuit that allows for a low-power, low-cost and small form factor implementation of a current stimulator for the continuous application of subthreshold currents. RESULTS: This circuit acts as a voltage-to-current converter and has been tested to drive + 1 to - 1 mA into a 60 k[Formula: see text] load from DC to 1 kHz. Driving a 60 k[Formula: see text] load with a 2 mA peak-to-peak 1 kHz sinusoid, the circuit draws less than 21 mA from a 9 V source. The minimum operating current of the circuit is less than 12 mA. Voltage compliance is ± 60 V with just 1.02 mA drawn by the high voltage current drive circuitry. The circuit was implemented as a compact 46 mm × 21 mm two-layer PCB highlighting its potential for use in a body-worn device. CONCLUSIONS: No design to the best of our knowledge presents comparably low quiescent power with such high voltage compliance. This makes the design uniquely appropriate for low-power transcutaneous current stimulation in wearable applications. Further development of driving and instrumentation circuitry is recommended