Amanda Bolbecker - Academia.edu (original) (raw)
Papers by Amanda Bolbecker
Postural sway data and R code for the paper named in the title
This represents all the raw data from our paper published in "Schizophrenia Bulletin", ... more This represents all the raw data from our paper published in "Schizophrenia Bulletin", MATLAB code for analysing it, R code for generating the statistics and figures, and a complete manuscript written in RMarkdown which should replicate the published results in the paper using the raw datasheets provided. There are also full supplementary analyses in free statistics programs JASP and JAMOVI.
INTRODUCTION Graph analysis of the resting state fMRI signal can provide a functional connectivit... more INTRODUCTION Graph analysis of the resting state fMRI signal can provide a functional connectivity viewpoint on how the ‘functional network’ as a whole behaves. The data are composed of correlations of time courses between different brain regions. Alterations in the functional network have been found in individuals with brain disorders or neurodegenerative diseases. Head motion and other data acquisition related sources of variability can affect these correlations. Therefore, we attempted to use selected graph analysis measures that are relatively unaffected by noise and variability to compare the nodal centrality of the resting state functional network of schizophrenia subjects (SZ) and normal controls (NC). By applying a support vector machine on the rank of centrality for a certain number of nodes, we were able to distinguish schizophrenia from normal subjects with a high accuracy rate of 77%. METHODS Subjects: 19 SZs (12 male, mean age 33.1 ± 10.9 years) and 29 NCs (13 male, mea...
Schizophrenia bulletin, Jan 25, 2018
Prominent conceptual models characterize schizophrenia as a dysconnectivity syndrome, with recent... more Prominent conceptual models characterize schizophrenia as a dysconnectivity syndrome, with recent research focusing on the contributions of the cerebellum in this framework. The present study examined the role of the cerebellum and its effective connectivity to the cerebrum during sensorimotor synchronization in schizophrenia. Specifically, the role of the cerebellum in temporally coordinating cerebral motor activity was examined through path analysis. Thirty-one individuals diagnosed with schizophrenia and 40 healthy controls completed a finger-tapping fMRI task including tone-paced synchronization and self-paced continuation tapping at a 500 ms intertap interval (ITI). Behavioral data revealed shorter and more variable ITIs during self-paced continuation, greater clock (vs motor) variance, and greater force of tapping in the schizophrenia group. In a whole-brain analysis, groups showed robust activation of the cerebellum during self-paced continuation but not during tone-paced syn...
European Archives of Psychiatry and Clinical Neuroscience
Schizophrenia spectrum disorder (SZ) is associated with deficits in auditory perception as well a... more Schizophrenia spectrum disorder (SZ) is associated with deficits in auditory perception as well as auditory verbal hallucinations (AVH). However, the relationship between auditory feature perception and auditory verbal hallucinations (AVH), one of the most commonly occurring symptoms in psychosis, has not been well characterized. This study evaluated perception of a broad range of auditory features in SZ and determined whether current AVHs relate to auditory feature perception. Auditory perception, including frequency, intensity, duration, pulse-train and temporal order discrimination, as well as an embedded tone task, was assessed in both AVH (n = 20) and non-AVH (n = 24) SZ individuals and in healthy controls (n = 29) with the Test of Basic Auditory Capabilities (TBAC). The Hamilton Program for Schizophrenia Voices Questionnaire (HPSVQ) was used to assess the experience of auditory hallucinations in patients with SZ. Findings suggest that compared to controls, the SZ group had greater deficits on an array of auditory features, with non-AVH SZ individuals showing the most severe degree of abnormality. IQ and measures of cognitive processing were positively associated with performance on the TBAC for all SZ individuals, but not with the HPSVQ scores. These findings indicate that persons with SZ demonstrate impaired auditory perception for a broad range of features. It does not appear that impaired auditory perception is associated with recent auditory verbal hallucinations, but instead associated with the degree of intellectual impairment in SZ.
Schizophrenia Bulletin
Conclusion: The resting-state connectivity within the motor system in schizophrenia differs from ... more Conclusion: The resting-state connectivity within the motor system in schizophrenia differs from controls in thalamocortico and cortico-cerebellar connections. In addition, aberrant functional connectivity in schizophrenia correlates with the extent of motor abnormalities. Thus, altered functional connectivity in the motor system may contribute to the behavioral changes observed in schizophrenia. The different motor signs seem to have distinct associations with functional connectivity in the motor system.
Proceedings of Fechner Day, 2010
Visual attention involves the selective processing of sensory information. Animal model systems l... more Visual attention involves the selective processing of sensory information. Animal model systems long ago demonstrated that such selectivity may be mediated by efferents that proceed from the brain to the eye in order to influence afferent input to the brain. However, such a mechanism seems to be absent from the literature on human visual attention. We here suggest that this omission is the result of an urban legend which holds that there are no retinal efferents in humans. We suggest that this legend exists because mammalian vision in general is degenerate relative to the ancestral vertebrate visual system that is clearly evident in birds. Further, our own work on an ideal animal model system has demonstrated that retinal efferents release neuromodulators that accelerate or delay photoreceptor responses to lights. If the same were true in humans, measurements of retinal response latencies would provide objective quantitative indicators of attention.
Frontiers in psychiatry, 2016
Evidence of cerebellar dysfunction in schizophrenia has mounted over the past several decades, em... more Evidence 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 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 l...
Frontiers in psychiatry, 2015
There is accruing evidence of cerebellar abnormalities in schizophrenia. The theory of cognitive ... more There 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...
Psychiatry Research, 2014
Poster from our presentation at the Federation of European Neuroscience (FENS) Forum in Berlin, G... more Poster from our presentation at the Federation of European Neuroscience (FENS) Forum in Berlin, Germany, 2018, detailing our research showing increased sway in participants with SPD diagnosis.
Schizophrenia research, Jan 20, 2015
A disturbance in the integration of information during mental processing has been implicated in s... more A disturbance in the integration of information during mental processing has been implicated in schizophrenia, possibly due to faulty communication within and between brain regions. Graph theoretic measures allow quantification of functional brain networks. Functional networks are derived from correlations between time courses of brain regions. Group differences between SZ and control groups have been reported for functional network properties, but the potential of such measures to classify individual cases has been little explored. We tested whether the network measure of betweenness centrality could classify persons with schizophrenia and normal controls. Functional networks were constructed for 19 schizophrenic patients and 29 non-psychiatric controls based on resting state functional MRI scans. The betweenness centrality of each node, or fraction of shortest-paths that pass through it, was calculated in order to characterize the centrality of the different regions. The nodes wit...
PLOS ONE, 2015
The Auditory Steady-State Response (ASSR) in the electroencephalogram (EEG) is usually reduced in... more The Auditory Steady-State Response (ASSR) in the electroencephalogram (EEG) is usually reduced in schizophrenia (SZ), particularly to 40 Hz stimulation. The gamma frequency ASSR deficit has been attributed to N-methyl-D-aspartate receptor (NMDAR) hypofunction. We tested whether the NMDAR antagonist, phencyclidine (PCP), produced similar ASSR deficits in rats. EEG was recorded from awake rats via intracranial electrodes overlaying the auditory cortex and at the vertex of the skull. ASSRs to click trains were recorded at 10, 20, 30, 40, 50, and 55 Hz and measured by ASSR Mean Power (MP) and Phase Locking Factor (PLF). In Experiment 1, the effect of different subcutaneous doses of PCP (1.0, 2.5 and 4.0 mg/kg) on the ASSR in 12 rats was assessed. In Experiment 2, ASSRs were compared in PCP treated rats and control rats at baseline, after acute injection (5 mg/kg), following two weeks of subchronic, continuous administration (5 mg/kg/day), and one week after drug cessation. Acute administration of PCP increased PLF and MP at frequencies of stimulation below 50 Hz, and decreased responses at higher frequencies at the auditory cortex site. Acute administration had a less pronounced effect at the vertex site, with a reduction of either PLF or MP observed at frequencies above 20 Hz. Acute effects increased in magnitude with higher doses of PCP. Consistent effects were not observed after subchronic PCP administration. These data indicate that acute administration of PCP, a NMDAR antagonist, produces an increase in ASSR synchrony and power at low frequencies of stimulation and a reduction of high frequency (> 40 Hz) ASSR activity in rats. Subchronic, continuous administration of PCP, on the other hand, has little impact on ASSRs. Thus, while ASSRs are highly sensitive to NMDAR antagonists, their translational utility as a cross-species biomarker for NMDAR hypofunction in SZ and other disorders may be dependent on dose and schedule.
Psychiatry Research, 2014
Data suggests that emotion reactivity as measured by the affect-modulated startle paradigm in tho... more Data suggests that emotion reactivity as measured by the affect-modulated startle paradigm in those with schizophrenia (SZ) may be similar to healthy controls (HC). However, normative classification of the stimuli may not accurately reflect emotional experience, especially for those with SZ. To examine this possibility, the present study measured the affect-modulated startle response with images classified according to both normative and subjective ratings. Seventeen HC and 17 SZ completed an image viewing task during which startle probes were presented, followed by subjective valence and arousal ratings. Both groups exhibited inhibited startle responses to positive images, intermediate startle amplitudes to neutral images, and potentiated startle amplitudes to negative images. SZ rated the positive images as less positive than HC. When images were reclassified based on subjective valence ratings, both groups' startle magnitudes increased in response to subjectively rated positive images and decreased to subjectively rated neutral images. The number of trials classified into each valence condition suggested a tendency for SZ to classify neutral images as negative more often than HC. Overall, these findings suggest that affective stimuli modulate the startle response in HC and SZ in similar ways, but subjective emotional experience may differ in those with schizophrenia.
Postural sway data and R code for the paper named in the title
This represents all the raw data from our paper published in "Schizophrenia Bulletin", ... more This represents all the raw data from our paper published in "Schizophrenia Bulletin", MATLAB code for analysing it, R code for generating the statistics and figures, and a complete manuscript written in RMarkdown which should replicate the published results in the paper using the raw datasheets provided. There are also full supplementary analyses in free statistics programs JASP and JAMOVI.
INTRODUCTION Graph analysis of the resting state fMRI signal can provide a functional connectivit... more INTRODUCTION Graph analysis of the resting state fMRI signal can provide a functional connectivity viewpoint on how the ‘functional network’ as a whole behaves. The data are composed of correlations of time courses between different brain regions. Alterations in the functional network have been found in individuals with brain disorders or neurodegenerative diseases. Head motion and other data acquisition related sources of variability can affect these correlations. Therefore, we attempted to use selected graph analysis measures that are relatively unaffected by noise and variability to compare the nodal centrality of the resting state functional network of schizophrenia subjects (SZ) and normal controls (NC). By applying a support vector machine on the rank of centrality for a certain number of nodes, we were able to distinguish schizophrenia from normal subjects with a high accuracy rate of 77%. METHODS Subjects: 19 SZs (12 male, mean age 33.1 ± 10.9 years) and 29 NCs (13 male, mea...
Schizophrenia bulletin, Jan 25, 2018
Prominent conceptual models characterize schizophrenia as a dysconnectivity syndrome, with recent... more Prominent conceptual models characterize schizophrenia as a dysconnectivity syndrome, with recent research focusing on the contributions of the cerebellum in this framework. The present study examined the role of the cerebellum and its effective connectivity to the cerebrum during sensorimotor synchronization in schizophrenia. Specifically, the role of the cerebellum in temporally coordinating cerebral motor activity was examined through path analysis. Thirty-one individuals diagnosed with schizophrenia and 40 healthy controls completed a finger-tapping fMRI task including tone-paced synchronization and self-paced continuation tapping at a 500 ms intertap interval (ITI). Behavioral data revealed shorter and more variable ITIs during self-paced continuation, greater clock (vs motor) variance, and greater force of tapping in the schizophrenia group. In a whole-brain analysis, groups showed robust activation of the cerebellum during self-paced continuation but not during tone-paced syn...
European Archives of Psychiatry and Clinical Neuroscience
Schizophrenia spectrum disorder (SZ) is associated with deficits in auditory perception as well a... more Schizophrenia spectrum disorder (SZ) is associated with deficits in auditory perception as well as auditory verbal hallucinations (AVH). However, the relationship between auditory feature perception and auditory verbal hallucinations (AVH), one of the most commonly occurring symptoms in psychosis, has not been well characterized. This study evaluated perception of a broad range of auditory features in SZ and determined whether current AVHs relate to auditory feature perception. Auditory perception, including frequency, intensity, duration, pulse-train and temporal order discrimination, as well as an embedded tone task, was assessed in both AVH (n = 20) and non-AVH (n = 24) SZ individuals and in healthy controls (n = 29) with the Test of Basic Auditory Capabilities (TBAC). The Hamilton Program for Schizophrenia Voices Questionnaire (HPSVQ) was used to assess the experience of auditory hallucinations in patients with SZ. Findings suggest that compared to controls, the SZ group had greater deficits on an array of auditory features, with non-AVH SZ individuals showing the most severe degree of abnormality. IQ and measures of cognitive processing were positively associated with performance on the TBAC for all SZ individuals, but not with the HPSVQ scores. These findings indicate that persons with SZ demonstrate impaired auditory perception for a broad range of features. It does not appear that impaired auditory perception is associated with recent auditory verbal hallucinations, but instead associated with the degree of intellectual impairment in SZ.
Schizophrenia Bulletin
Conclusion: The resting-state connectivity within the motor system in schizophrenia differs from ... more Conclusion: The resting-state connectivity within the motor system in schizophrenia differs from controls in thalamocortico and cortico-cerebellar connections. In addition, aberrant functional connectivity in schizophrenia correlates with the extent of motor abnormalities. Thus, altered functional connectivity in the motor system may contribute to the behavioral changes observed in schizophrenia. The different motor signs seem to have distinct associations with functional connectivity in the motor system.
Proceedings of Fechner Day, 2010
Visual attention involves the selective processing of sensory information. Animal model systems l... more Visual attention involves the selective processing of sensory information. Animal model systems long ago demonstrated that such selectivity may be mediated by efferents that proceed from the brain to the eye in order to influence afferent input to the brain. However, such a mechanism seems to be absent from the literature on human visual attention. We here suggest that this omission is the result of an urban legend which holds that there are no retinal efferents in humans. We suggest that this legend exists because mammalian vision in general is degenerate relative to the ancestral vertebrate visual system that is clearly evident in birds. Further, our own work on an ideal animal model system has demonstrated that retinal efferents release neuromodulators that accelerate or delay photoreceptor responses to lights. If the same were true in humans, measurements of retinal response latencies would provide objective quantitative indicators of attention.
Frontiers in psychiatry, 2016
Evidence of cerebellar dysfunction in schizophrenia has mounted over the past several decades, em... more Evidence 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 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 l...
Frontiers in psychiatry, 2015
There is accruing evidence of cerebellar abnormalities in schizophrenia. The theory of cognitive ... more There 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...
Psychiatry Research, 2014
Poster from our presentation at the Federation of European Neuroscience (FENS) Forum in Berlin, G... more Poster from our presentation at the Federation of European Neuroscience (FENS) Forum in Berlin, Germany, 2018, detailing our research showing increased sway in participants with SPD diagnosis.
Schizophrenia research, Jan 20, 2015
A disturbance in the integration of information during mental processing has been implicated in s... more A disturbance in the integration of information during mental processing has been implicated in schizophrenia, possibly due to faulty communication within and between brain regions. Graph theoretic measures allow quantification of functional brain networks. Functional networks are derived from correlations between time courses of brain regions. Group differences between SZ and control groups have been reported for functional network properties, but the potential of such measures to classify individual cases has been little explored. We tested whether the network measure of betweenness centrality could classify persons with schizophrenia and normal controls. Functional networks were constructed for 19 schizophrenic patients and 29 non-psychiatric controls based on resting state functional MRI scans. The betweenness centrality of each node, or fraction of shortest-paths that pass through it, was calculated in order to characterize the centrality of the different regions. The nodes wit...
PLOS ONE, 2015
The Auditory Steady-State Response (ASSR) in the electroencephalogram (EEG) is usually reduced in... more The Auditory Steady-State Response (ASSR) in the electroencephalogram (EEG) is usually reduced in schizophrenia (SZ), particularly to 40 Hz stimulation. The gamma frequency ASSR deficit has been attributed to N-methyl-D-aspartate receptor (NMDAR) hypofunction. We tested whether the NMDAR antagonist, phencyclidine (PCP), produced similar ASSR deficits in rats. EEG was recorded from awake rats via intracranial electrodes overlaying the auditory cortex and at the vertex of the skull. ASSRs to click trains were recorded at 10, 20, 30, 40, 50, and 55 Hz and measured by ASSR Mean Power (MP) and Phase Locking Factor (PLF). In Experiment 1, the effect of different subcutaneous doses of PCP (1.0, 2.5 and 4.0 mg/kg) on the ASSR in 12 rats was assessed. In Experiment 2, ASSRs were compared in PCP treated rats and control rats at baseline, after acute injection (5 mg/kg), following two weeks of subchronic, continuous administration (5 mg/kg/day), and one week after drug cessation. Acute administration of PCP increased PLF and MP at frequencies of stimulation below 50 Hz, and decreased responses at higher frequencies at the auditory cortex site. Acute administration had a less pronounced effect at the vertex site, with a reduction of either PLF or MP observed at frequencies above 20 Hz. Acute effects increased in magnitude with higher doses of PCP. Consistent effects were not observed after subchronic PCP administration. These data indicate that acute administration of PCP, a NMDAR antagonist, produces an increase in ASSR synchrony and power at low frequencies of stimulation and a reduction of high frequency (> 40 Hz) ASSR activity in rats. Subchronic, continuous administration of PCP, on the other hand, has little impact on ASSRs. Thus, while ASSRs are highly sensitive to NMDAR antagonists, their translational utility as a cross-species biomarker for NMDAR hypofunction in SZ and other disorders may be dependent on dose and schedule.
Psychiatry Research, 2014
Data suggests that emotion reactivity as measured by the affect-modulated startle paradigm in tho... more Data suggests that emotion reactivity as measured by the affect-modulated startle paradigm in those with schizophrenia (SZ) may be similar to healthy controls (HC). However, normative classification of the stimuli may not accurately reflect emotional experience, especially for those with SZ. To examine this possibility, the present study measured the affect-modulated startle response with images classified according to both normative and subjective ratings. Seventeen HC and 17 SZ completed an image viewing task during which startle probes were presented, followed by subjective valence and arousal ratings. Both groups exhibited inhibited startle responses to positive images, intermediate startle amplitudes to neutral images, and potentiated startle amplitudes to negative images. SZ rated the positive images as less positive than HC. When images were reclassified based on subjective valence ratings, both groups' startle magnitudes increased in response to subjectively rated positive images and decreased to subjectively rated neutral images. The number of trials classified into each valence condition suggested a tendency for SZ to classify neutral images as negative more often than HC. Overall, these findings suggest that affective stimuli modulate the startle response in HC and SZ in similar ways, but subjective emotional experience may differ in those with schizophrenia.