ORCID Profile
0000-0002-7204-5684
Current Organisation
Toronto Metropolitan University
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Publisher: Elsevier BV
Date: 08-2011
Publisher: American Psychological Association (APA)
Date: 03-2008
DOI: 10.1037/1040-3590.20.1.76
Abstract: The correlation between a short-form (SF) test and its full-scale (FS) counterpart is a mainstay in the evaluation of SF validity. However, in correcting for overlapping error variance in this measure, investigators have overattenuated the validity coefficient through an intuitive misapplication of P. Levy's (1967) formula. The authors of the present article clarify that such corrections should be based on subtest-level versus FS-level data. Additionally, the authors propose a simple, modified equation incorporating FS-level scores that provides liberal and conservative validity measures for comparison across estimation methods, and they demonstrate its use in both a normative (N = 2,450) and clinical psychiatric (N = 216) s le.
Publisher: American Psychological Association (APA)
Date: 05-2010
DOI: 10.1037/A0018313
Abstract: Enhanced understanding of cognitive deficits, and the neurobiological abnormalities that mediate them, can be achieved through translational research that employs comparable experimental approaches across species. This study employed a multiple-systems framework derived from the rodent literature to investigate visual-spatial memory abilities associated with schizophrenia. Using the bin task, a human analog of rodent maze tasks, everyday objects were hidden in visually identical bins. Following a 1-min filled delay, participants with schizophrenia-spectrum disorders (n = 30) and healthy community controls (n = 30) were asked to identify both the object hidden and bin used on the basis of its spatial location. Three dimensions of visual-spatial memory were contrasted: (a) memory for spatial locations versus memory for objects, (b) allocentric (viewpoint independent) versus egocentric (body-centered) spatial representations, and (c) event (working) memory versus reference memory. Most pronounced was a differential deficit in memory for spatial locations under allocentric (p = .005, d = -0.77) but not egocentric viewing conditions (p = .298, d = -0.28) in the schizophrenia group relative to healthy controls. Similarly, schizophrenia-related spatial memory deficits were pronounced under demands for event memory (p = .004, d = -0.77) but not reference memory (p = .171, d = -0.33). These results support a heuristic of preferential deficits in hippoc al-mediated forms of memory in schizophrenia. Moreover, the task provides a useful paradigm for translational research and the pattern of deficits suggests that persons with schizophrenia may benefit from mnemonic approaches favoring egocentric representations and consistency when interacting with our visual-spatial world.
Publisher: Informa UK Limited
Date: 31-05-2018
DOI: 10.1080/13546805.2018.1479248
Abstract: Introduction Working-memory (WM) is a core cognitive deficit among in iduals with Schizophrenia Spectrum Disorders (SSD). However, the underlying cognitive mechanisms of this deficit are less known. This study applies a modified version of the Corsi Block Test to investigate the role of proactive interference in visuospatial WM (VSWM) impairment in SSD. Methods Healthy and SSD participants completed a modified version of the Corsi Block Test involving both high (typical ascending set size from 4 to 7 items) and low (descending set size from 7 to 4 items) proactive interference conditions. Results The results confirmed that the SSD group performed worse overall relative to a healthy comparison group. More importantly, the SSD group demonstrated greater VSWM scores under low (Descending) versus high (Ascending) proactive interference this pattern is opposite to that of healthy participants. Conclusions This differential pattern of performance supports that proactive interference associated with the traditional administration format contributes to VSWM impairment in SSD. Further research investigating associated neurocognitive mechanisms and the contribution of proactive interference across other domains of cognition in SSD is warranted.
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.PSCYCHRESNS.2017.07.007
Abstract: Different strategies may be spontaneously adopted to solve most navigation tasks. These strategies are associated with dissociable brain systems. Here, we use brain-imaging and cognitive tasks to test the hypothesis that in iduals living with Schizophrenia Spectrum Disorders (SSD) have selective impairment using a hippoc al-dependent spatial navigation strategy. Brain activation and memory performance were examined using functional magnetic resonance imaging (fMRI) during the 4-on-8 virtual maze (4/8VM) task, a human analog of the rodent radial-arm maze that is amenable to both response-based (egocentric or landmark-based) and spatial (allocentric, cognitive mapping) strategies to remember and navigate to target objects. SSD (schizophrenia and schizoaffective disorder) participants who adopted a spatial strategy performed more poorly on the 4/8VM task and had less hippoc al activation than healthy comparison participants using either strategy as well as SSD participants using a response strategy. This study highlights the importance of strategy use in relation to spatial cognitive functioning in SSD. Consistent with a selective-hippoc al dependent deficit in SSD, these results support the further development of protocols to train impaired hippoc al-dependent abilities or harness non-hippoc al dependent intact abilities.
Publisher: American Psychological Association (APA)
Date: 06-2007
DOI: 10.1037/1040-3590.19.2.236
Abstract: An eight-subtest short form (SF8) of the Wechsler Adult Intelligence Scale, Third Edition (WAIS-III), maintaining equal representation of each index factor, was developed for use with psychiatric populations. Data were collected from a mixed inpatient/outpatient s le (99 men and 101 women) referred for neuropsychological assessment. Psychometric analyses revealed an optimal SF8 comprising Vocabulary, Similarities, Arithmetic, Digit Span, Picture Completion, Matrix Reasoning, Digit Symbol Coding, and Symbol Search, scored by linear scaling. Expanding on previous short forms, the current SF8 maximizes the breadth of information and reduces administration time while maintaining the original WAIS-III factor structure.
Publisher: CMA Joule Inc.
Date: 2010
DOI: 10.1503/JPN.080039
Publisher: Elsevier BV
Date: 10-2020
Publisher: Informa UK Limited
Date: 15-05-2023
Publisher: Elsevier BV
Date: 12-2014
DOI: 10.1016/J.BANDC.2014.10.009
Abstract: Previous studies from the human, rodent, and computational research have identified the hippoc us as a core structure mediating pattern separation. However, these investigations have generally focused on the role of distinct subregions of the hippoc us. Less well-understood is how the human hippoc us interacts with other brain regions to support pattern separation. The purpose of this study was to identify the functional networks connected to the hippoc us during delayed matching-to-s le pattern separation tasks promoting either spatial or temporal interference. Results revealed that the hippoc us was functionally connected to two distinct networks. The first network was characterized by correlated activation with the hippoc us primarily in bilateral temporal regions. This network was differentially related to spatial and temporal conditions, suggesting hippoc al connectivity to this network is modulated by interference type. A secondary network was characterized by correlations between the left hippoc us and several other sparsely distributed brain regions, including bilateral cerebellum and frontal and temporal cortices. This network was not modulated by interference type, suggesting that it may be a domain-general pattern separation network. We suggest that the hippoc us may play a role in integrating information from these networks to support performance on pattern separation tasks.
Publisher: Elsevier BV
Date: 07-2005
DOI: 10.1016/J.SCHRES.2005.01.009
Abstract: Clinicians frequently use a crossover approach in switching antipsychotics, although historically there has been a lack of data addressing the question of switch strategies. To establish if there is now empiric evidence that may guide clinicians in this regard, a MEDLINE search to April 2004 was carried out to identify published, randomized and controlled trials that have addressed this topic. A total of 404 articles were identified in the search, which resulted in the identification of four reports meeting the criteria. The four studies evaluated switching strategies to one of three atypical antipsychotics: aripiprazole, olanzapine (two reports), and ziprasidone. The switching process itself could be sub ided as follows: discontinuation (abrupt vs. gradual) and, replacement (abrupt vs. gradual). Meta-analyses confirmed a lack of difference in outcome, regardless of approach. While a crossover approach does not appear to increase adverse events, the available empiric evidence does not support its clinical superiority on various outcome measures. The existing data therefore argue against the position that a crossover approach in switching antipsychotics represents a 'safer' means of preventing clinical deterioration during the switch.
Publisher: Wiley
Date: 25-10-2013
DOI: 10.1002/HIPO.22189
Abstract: Spatial memory is impaired among persons with schizophrenia (SCZ). However, different strategies may be used to solve most spatial memory and navigation tasks. This study investigated the hypothesis that participants with schizophrenia-spectrum disorders (SSD) would demonstrate differential impairment during acquisition and retrieval of target locations when using a hippoc al-dependent spatial strategy, but not a response strategy, which is more associated with caudate function. Healthy control (CON) and SSD participants were tested using the 4-on-8 virtual maze (4/8VM), a virtual navigation task designed to differentiate between participants' use of spatial and response strategies. Consistent with our predictions, SSD participants demonstrated a differential deficit such that those who navigated using a spatial strategy made more errors and took longer to locate targets. In contrast, SSD participants who spontaneously used a response strategy performed as well as CON participants. The differential pattern of spatial-memory impairment in SSD provides only indirect support for underlying hippoc al dysfunction. These findings emphasize the importance of considering in idual strategies when investigating SSD-related memory and navigation performance. Future cognitive intervention protocols may harness SSD participants' intact ability to navigate using a response strategy and/or train the deficient ability to navigate using a spatial strategy to improve navigation and memory abilities in participants with SSD.
Publisher: Elsevier BV
Date: 08-2019
DOI: 10.1016/J.PSYCHRES.2019.05.032
Abstract: Spatial memory is core to wayfinding and everyday memory. Interestingly, in iduals with schizophrenia using spatial navigation strategies (cognitive mapping) are impaired, whereas those using response-based (e.g., single-landmark) strategies show relatively intact memory performance. We observed abnormal brain communication in schizophrenia participants who used a spatial strategy during a virtual-reality navigation task, particularly between temporal and frontal brain regions. In contrast, schizophrenia participants using a response strategy recruited similar brain systems to healthy participants, but to a greater extent to support memory performance. These findings highlight that strategy use is an important consideration for understanding memory systems and navigation in schizophrenia.
Publisher: Informa UK Limited
Date: 12-2013
DOI: 10.1080/13803395.2013.857389
Abstract: This study builds upon our previous work indicating that impaired hippoc al-dependent forms of memory are core to schizophrenia. Using a virtual-reality courtyard task, we presented participants with schizophrenia spectrum disorders (SSD n = 20) and a healthy community comparison group (n = 20) with objects to remember within a town square, followed by a recognition test of the location of objects from either the same viewpoint or a shifted viewpoint relative to initial presentation. The SSD group demonstrated a relative deficit under shifted- compared to same-view conditions. These findings provide further support for deficient hippoc al-dependent cognition in SSD.
No related grants have been discovered for Todd Girard.