Object Substitution Masking in Schizophrenia: An Event-Related Potential Analysis

Schizophrenia patients exhibit deficits on visual processing tasks, including visual backward masking, and these impairments are related to deficits in higher-level processes. In the current study we used electroencephalography techniques to examine successive stages and pathways of visual processing in a specialized masking paradigm, four-dot masking, which involves masking by object substitution. Seventy-six schizophrenia patients and 66 healthy controls had event-related potentials (ERPs) recorded during four-dot masking. Target visibility was manipulated by changing stimulus onset asynchrony (SOA) between the target and mask, such that performance decreased with increasing SOA. Three SOAs were used: 0, 50, and 100 ms. The P100 and N100 perceptual ERPs were examined. Additionally, the visual awareness negativity (VAN) to correct vs. incorrect responses, an index of reentrant processing, was examined for SOAs 50 and 100 ms. Results showed that patients performed worse than controls on the behavioral task across all SOAs. The ERP results revealed that patients had significantly smaller P100 and N100 amplitudes, though there was no effect of SOA on either component in either group. In healthy controls, but not patients, N100 amplitude correlated significantly with behavioral performance at SOAs where masking occurred, such that higher accuracy correlated with a larger N100. Healthy controls, but not patients, exhibited a larger VAN to correct vs. incorrect responses. The results indicate that the N100 appears to be related to attentional effort in the task in controls, but not patients. Considering that the VAN is thought to reflect reentrant processing, one interpretation of the findings is that patients’ lack of VAN response and poorer performance may be related to dysfunctional reentrant processing

The role of spatial frequency information for ERP components sensitive to faces and emotional facial expression

To investigate the impact of spatial frequency on emotional facial expression analysis, ERPs were recorded in response to low spatial frequency (LSF), high spatial frequency (HSF), and unfiltered broad spatial frequency (BSF) faces with fearful or neutral expressions, houses, and chairs. In line with previous findings, BSF fearful facial expressions elicited a greater frontal positivity than BSF neutral facial expressions, starting at about 150 ms after stimulus onset. In contrast, this emotional expression effect was absent for HSF and LSF faces. Given that some brain regions involved in emotion processing, such as amygdala and connected structures, are selectively tuned to LSF visual inputs, these data suggest that ERP effects of emotional facial expression do not directly reflect activity in these regions. It is argued that higher order neocortical brain systems are involved in the generation of emotion-specific waveform modulations. The face-sensitive N170 component was neither affected by emotional facial expression nor by spatial frequency information

Cultural Differences in Group Therapy: A Phenomenological Study of the Lived Embodied Experience of the Cultural Bump

Utilizing transcendental phenomenology, this study sought to better understand dance/movement therapists’ experiences of the culture bump phenomenon in the group therapy setting. Culture bumps are defined as moments in which two or more people enter a situation with different culturally-based expectations about customs, behavior, beliefs, communication styles, and other norms (Archer & Nickson, 2012). Data were collected using individual inperson semi-structured interviews with five Chicagoland dance/movement therapists who self identified as having experienced the phenomenon of the culture bump while in the group therapy setting. Data analysis was completed using Moustakas’ (1994) adaptation of the Stevick-Colaizzi-Keen method and resulted in five textural-structural themes that describe the experience of the phenomenon of the culture bump: a) elusory and complex in nature, b) at its essence, about a meeting of differing expectations, c) having a shifting/changing quality to it, d) inextricably tied to the participant’s own cultural context, and e) therapeutically important material. The participants’ experiences indicated culture bumps are a common occurrence in the group dance/movement therapy setting, and both their presence and the processing of them are breeding grounds for necessary conversations about cultural difference. 54 pages - submitted as an article to the American Journal of Dance Therapy in February of 2018 in a format that meets the criteria for that publication, and so is shorter than a standard thesis

CHARACTERIZING HYDROSTRATIGRAPHIC COMMUNICATION OF THE SEMI-CONSOLIDATED SEDIMENT AQUIFERS OF THE FLATHEAD VALLEY IN NORTHWESTERN MONTANA THROUGH HYDROGEOPHYSICAL SURVEYS

To accurately forecast the cascading effects of increased stress to a hydrologic system, characterization of the continuity and permeability of the primary confining layer (PCL) separating the shallow and deep intermontane alluvial aquifers is required. Geophysical methods provide a faster cost-effective alternative to drilling to acquire additional information on the changes of hydrostratigraphy with depth. Geoelectric resistivity models recovered through inversion of TEM central loop sounding data to delineate changes in geoelectric properties with depth, providing information on the depth, thickness and resistivity of the hydrostratigraphy. Comparison of geoelectric resistivity models with well completion report lithologies yield information about the permeability of the hydrostratigraphy and can infer the potential for occurring hydrostratigraphic communication. The geological history of the Flathead Valley created a complex stratigraphic sequence of glacial sediments comprising the primary confining layer (PCL). Glacial sediments include glaciolacustrine, glaciotectonite tills, subglacial traction tills and melt-out tills. Characterization of the PCL is the primary target for geophysical investigation as a critical element in understanding the hydrostratigraphic communication. The geoelectrical resistivity of glacial sediments is highly variable. Whether the PCL of the Flathead Valley, Montana presents geoelectrical property distinctions that are targetable by electromagnetic surveys is unknown. To assess the targetability of the glacial deposits comprising the PCL, a series of central loop soundings were completed. Geoelectrical models recovered through inversion and compared to well completion report lithology indicate the PCL presents a resistivity target that can be imaged using electromagnetic methods. The PCL appears to be variable throughout the Flathead Valley with predictable geoelectric resistivity ranges

Visual distraction in cytopathology: should we be concerned?

Visual distraction in cytopathology has not been previously investigated as a source of diagnostic error, presumably because the viewing field of a conventional light microscope is considered large enough to minimise interference from peripheral visual stimuli. Virtual microscopy, which involves the examination of digitised images of pathology specimens on computer screens, is beginning to challenge the central role of light microscopy as a diagnostic tool in cytopathology. The relatively narrow visual angle offered by virtual microscopy makes it conceivable that users of these systems are more vulnerable to visual interference. Using a variant of a visual distraction paradigm (the Eriksen flanker task), the aim of the study was to determine whether the accuracy and speed of interpreting cells on a central target screen is affected by images of cells and text displayed on neighbouring monitors under realistic reading room conditions

Blink and shrink: The effect of the attentional blink on spatial processing.

The detection or discrimination of the second of 2 targets in a rapid serial visual presentation (RSVP) task is often temporarily impaired - a phenomenon termed the attentional blink. This study demonstrated that the attentional blink also affects localization performance. Spatial cues pointed out the possible target positions in a subsequent visual search display. When cues were presented inside an attentional blink (as induced by an RSVP task), the observers' capacity to use them was reduced. This effect was not due to attention being highly focused, to general task switching costs, or to complete unawareness of the cues. Instead, the blink induced a systematic localization bias toward the fovea, reflecting what appears to be spatial compression

The influence of spatial pattern on visual short-term memory for contrast

Several psychophysical studies of visual short-term memory (VSTM) have shown high-fidelity storage capacity for many properties of visual stimuli. On judgments of the spatial frequency of gratings, for example, discrimination performance does not decrease significantly, even for memory intervals of up to 30 s. For other properties, such as stimulus orientation and contrast, however, such “perfect storage” behavior is not found, although the reasons for this difference remain unresolved. Here, we report two experiments in which we investigated the nature of the representation of stimulus contrast in VSTM using spatially complex, two-dimensional random-noise stimuli. We addressed whether information about contrast per se is retained during the memory interval by using a test stimulus with the same spatial structure but either the same or the opposite local contrast polarity, with respect to the comparison (i.e., remembered) stimulus. We found that discrimination thresholds got steadily worse with increasing duration of the memory interval. Furthermore, performance was better when the test and comparison stimuli had the same local contrast polarity than when they were contrast-reversed. Finally, when a noise mask was introduced during the memory interval, its disruptive effect was maximal when the spatial configuration of its constituent elements was uncorrelated with those of the comparison and test stimuli. These results suggest that VSTMfor contrast is closely tied to the spatial configuration of stimuli and is not transformed into a more abstract representation