83 research outputs found
Electroretinographic investigation of circadian efferent neuromodulation of photoreceptor timing in the lateral eye of Limulus polyphemus
No full textThe sensitivity of the lateral eye of the horseshoe crab Limulus polyphemus increases at night as part of a circadian rhythm mediated by efferent nerves that run from the brain to the eye. These efferents are known to release Octopamine, which implements physiological changes that contribute to this increase. In addition to increasing the amplitude of electroretinograms (ERGs) in the lateral eye, Octopamine has been demonstrated to increase the duration of photoreceptor responses in vitro. The hypothesis underlying the present dissertation predicted that comparable prolongations of photoreceptor responses would be evident in in vivo ERGs. Temporal differences between daytime and nighttime ERGs were evaluated. Nighttime traces were longer in duration, as had been predicted; but, surprisingly, their latencies were accelerated compared to daytime ERGs. The next question was whether a second neurotransmitter contributes to the sensitivity increase at night. The nighttime latency accelerations in nighttime ERGs implicated Substance P as another possible candidate neurotransmitter because a known lateral eye efferent system is immunoreactive for a Substance P-like neuropeptide. Octopamine and Substance P were therefore injected into lateral eyes in vivo. Each mimicked one of the two different aspects of the differences in timing between daytime and nighttime ERGs: Octopamine increased the daytime duration of ERGs and Substance P accelerated response latencies. Finally, an unexpected discovery was also made during these hypothesis-driven experiments: evidence indicated that two separate clocks may control circadian rhythms in the ERG in this animal. One clock has been demonstrated in the brain and is known to affect ERG peak amplitude. But the present results indicate another clock may affect peak latency. This unexpected discovery also indicated that these clocks can become uncoupled, resulting in internal desynchronization. These results then generate a new hypothesis that the second clock controls the circadian signals of the Substance P-like efferent system and that the balance between these two efferent systems regulates lateral eye ERG temporal properties. Although such systems are well known in mammalian systems, no invertebrate system controlling different aspects of the same physiological system seems to have been reported previously
Motor deficits in schizophrenia quantified by nonlinear analysis of postural sway.
No full textMotor dysfunction is a consistently reported but understudied aspect of schizophrenia. Postural sway area was examined in individuals with schizophrenia under four conditions with different amounts of visual and proprioceptive feedback: eyes open or closed and feet together or shoulder width apart. The nonlinear complexity of postural sway was assessed by detrended fluctuation analysis (DFA). The schizophrenia group (n = 27) exhibited greater sway area compared to controls (n = 37). Participants with schizophrenia showed increased sway area following the removal of visual input, while this pattern was absent in controls. Examination of DFA revealed decreased complexity of postural sway and abnormal changes in complexity upon removal of visual input in individuals with schizophrenia. Additionally, less complex postural sway was associated with increased symptom severity in participants with schizophrenia. Given the critical involvement of the cerebellum and related circuits in postural stability and sensorimotor integration, these results are consistent with growing evidence of motor, cerebellar, and sensory integration dysfunction in the disorder, and with theoretical models that implicate cerebellar deficits and more general disconnection of function in schizophrenia
Impaired Sleep Mediates the Relationship Between Interpersonal Trauma and Subtypes of Delusional Ideation
No full textTrauma is a robust risk-factor for delusional ideation. Yet, there is a crucial need to clarify the specificity and processes underlying this relationship. Qualitatively, interpersonal traumas (i.e., trauma caused by another person) appear to have a specific relationship with delusional ideation and furthermore seem most relevant to paranoia, a subtype of delusional ideation, given the commonality of social threat. However, these observations have not been empirically tested and the process by which interpersonal trauma contributes to delusional ideation remains poorly understood. Informed by previous literature, impaired sleep may be a critical mediator, explaining part of the relationship between interpersonal trauma and delusional ideation. Taken together, we hypothesized that interpersonal trauma, but not non-interpersonal trauma, would be positively related to subtypes of delusional ideation, especially paranoia, and that impaired sleep would mediate these relationships. In a large, transdiagnostic community sample (N=478), an exploratory factor analysis of the Peter’s Delusion Inventory identified three subtypes of delusional ideation: magical thinking, grandiosity, and paranoia. Three path models of the above relationships were tested, one for each subtype of delusional ideation. As predicted, paranoia and grandiosity were positively related to interpersonal trauma and unrelated to non-interpersonal trauma. Furthermore, these relationships were significantly mediated by impaired sleep, which appeared strongest for paranoia. In contrast, magical thinking was unrelated to traumatic experiences. These findings support a specific relationship between interpersonal trauma and delusional ideation, with impaired sleep appearing as an important process by which interpersonal trauma contributes to delusional ideation
Motor performance in first-degree relatives of people with schizophrenia
No full textThis dataset was collected as part of Honours student Louisa Quiddington's thesis in 2020. It is comprised of questionnaire screening data from a Qualtrics online survey combined with online behavioural data collected via Inquisit (Millisecond, 2019), as well as code written in R Statistical Software to combine and analyse the data. The questionnaire data concerns whether the participant has a family member with schizophrenia, as well as some basic demographic data and a modified version of the Family Interview for Genetic Studies (FIGS; Gershon et al., 1988; Maxwell, 1992). The behavioural data is from a finger tapping task (FTT) where the participants were required to tap the space bar as quickly as possible for 5 blocks of 10 seconds each. Data for the task includes scores for the dominant and non-dominant hand for: the mean number of taps, the mean and median reaction time between taps, the standard deviation of the reaction time, the coefficient of variation for these statistics, and the box-cox transformations of this. It also includes the values for slope - testing whether participants responded more slowly across blocks or across trials within a block. The variable "Group" explains whether the person was a first-degree relative or a control, or was unsure. IP address and location were recorded but have been redacted from the data for privacy reasons. The data are in .sav format for SPSS but are also available in .csv format and can be read into R via the code provided, or into the free software jamovi
Data_Sheet_1_Emotion regulation and delusion-proneness relate to empathetic tendencies in a transdiagnostic sample.docx
No full textEmpathetic tendencies (i.e., perspective taking and empathic concern) are a key factor in interpersonal relationships, which may be impacted by emotion regulation (i.e., reappraisal and suppression) and mental health symptoms, such as psychotic-like experiences. However, it is unclear if certain psychotic-like experiences, such as delusion-proneness, are still associated with reduced empathetic tendencies after accounting for emotion regulation style and dimensions of psychopathology that are often comorbid. In the current study, linear models tested these associations in a transdiagnostic community sample (N = 128), using the Interpersonal Reactivity Index (IRI), Emotion Regulation Questionnaire, and the Peter’s Delusion Inventory. Results indicated that perspective taking was positively associated with reappraisal and negatively associated with delusion-proneness, after controlling for age, sex, race, intelligence, and symptoms of anxiety and depression. A significant change in R2 supported the addition of delusion-proneness in this model. Specificity analyses demonstrated perspective taking was also negatively associated with suppression, but this relationship did not remain after accounting for the effects of reappraisal and delusion-proneness. Additional specificity analyses found no association between empathic concern and reappraisal or delusion-proneness but replicated previous findings that empathic concern was negatively associated with suppression. Taken together, delusion-proneness accounts for unique variance in perspective taking, which can inform future experimental research and may have important implications for psychosocial interventions.</p
New insights into the nature of cerebellar-dependent eyeblink conditioning deficits in schizophrenia: A hierarchical linear modeling approach
No full textEvidence of cerebellar dysfunction in schizophrenia has mounted over the past several decades, emerging from neuroimaging, neuropathological, and behavioral studies. Consistent with these findings, cerebellar-dependent delay eyeblink conditioning (dEBC) deficits have been identified in schizophrenia. While repeated measures analysis of variance (ANOVA) is traditionally used to analyze dEBC data, hierarchical linear modeling (HLM) more reliably describes change over time by accounting for the dependence in repeated measures data. This analysis approach is well suited to dEBC data analysis because it has less restrictive assumptions and allows unequal variances. The current study examined dEBC measured with electromyography in a single-cue tone paradigm in an age-matched sample of schizophrenia participants and healthy controls (N=56 per group) using HLM. Subjects participated in 90 trials (10 blocks) of dEBC, during which a 400 ms tone co-terminated with a 50 ms air puff delivered to the left eye. Each block also contained 1 tone-alone trial. The resulting block averages of dEBC data were fitted to a 3-parameter logistic model in HLM, revealing significant differences between schizophrenia and control groups on asymptote and inflection point, but not slope. These findings suggest that while the learning rate is not significantly different compared to controls, associative learning begins to level off later and a lower ultimate level of associative learning is achieved in schizophrenia. Given the large sample size in the present study, HLM may provide a more nuanced and definitive analysis of differences between schizophrenia and controls on dEBC
Eyeblink Conditioning in Schizophrenia: A Critical Review
No full textThere is accruing evidence of cerebellar abnormalities in schizophrenia. The theory of cognitive dysmetria considers cerebellar dysfunction a key component of schizophrenia. Delay eyeblink conditioning (EBC), a cerebellar-dependent translational probe, is a behavioral index of cerebellar integrity. The circuitry underlying EBC has been well characterized by non-human animal research, revealing the cerebellum as the essential circuitry for the associative learning instantiated by this task. However, there have been persistent inconsistencies in EBC findings in schizophrenia. This article thoroughly reviews published studies investigating EBC in schizophrenia, with an emphasis on possible effects of antipsychotic medication and stimulus and analysis parameters on reports of EBC performance in schizophrenia. Results indicate a consistent finding of impaired EBC performance in schizophrenia, as measured by decreased rates of conditioning, and that medication or study design confounds do not account for this impairment. Results are discussed within the context of theoretical and neurochemical models of schizophrenia
Postural Sway in First-Degree Relatives of Individuals with Schizophrenia: Data and Code
No full textPostural sway data and R code for the paper named in the titl
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