Annabel Chen - Academia.edu (original) (raw)

Papers by Annabel Chen

Journal of Personalized Medicine

Background: In transcranial direct current stimulation (tDCS), the injected current becomes distr... more Background: In transcranial direct current stimulation (tDCS), the injected current becomes distributed across the brain areas. The objective is to stimulate the target region of interest (ROI) while minimizing the current in non-target ROIs (the ‘focality’ of tDCS). For this purpose, determining the appropriate current dose for an individual is difficult. Aim: To introduce a dose–target determination index (DTDI) to quantify the focality of tDCS and examine the dose–focality relationship in three different populations. Method: Here, we extended our previous toolbox i-SATA to the MNI reference space. After a tDCS montage is simulated for a current dose, the i-SATA(MNI) computes the average (over voxels) current density for every region in the brain. DTDI is the ratio of the average current density at the target ROI to the ROI with a maximum value (the peak region). Ideally, target ROI should be the peak region, so DTDI shall range from 0 to 1. The higher the value, the better the do...

Aging Neuropsychol Cogn, 1999

... 180 MARC W. HAUT ET AL. ... Visual and verbal variations of self-ordering demonstrated activa... more ... 180 MARC W. HAUT ET AL. ... Visual and verbal variations of self-ordering demonstrated activation in the dorsolateral prefrontal cortex, the inferior parietal cortex, and the anterior cingulate gyrus (Petrides, Alivisatos, Evans, & Meyer, 1993; Petrides, Alivisatos, Meyer, & Evans ...

Novel Trends in Brain Science, 2008

Praxis der Kinderpsychologie und Kinderpsychiatrie

The analysis and intervention of communication is an important focus of autism research. The pres... more The analysis and intervention of communication is an important focus of autism research. The present study is a microanalsis of the communicative behaviour of 10 autistic children with their parents and a therapist. Protests, appropriate initiation and responses of the children were analysed in relation to demands and the specific feedback of the adults. After 20 months of structured therapy changes in the communicative behaviour of the participants were demonstrated. Autistic children showed different communicative pattern with their parents compared to a therapist. The non-verbal group exhibited significantly more protests and decreased responsivity with their parents compared to the therapist. The verbal group interacted with their parents predominantly by echolalia. After 20 months a significant reduction in protests, increased compliance and responsivity were obvious in the non-verbal group. The verbal group showed a reduction in echolalia as well as increased responsive and sp...

Introduction: The PASAT is one of the most widely administered measure of attentional processing ... more Introduction: The PASAT is one of the most widely administered measure of attentional processing for various clinical populations including traumatic brain injury (TBI), multiple sclerosis, systemic lupus erythematosus, and chronic fatigue syndrome. In this test, subjects hear a number-string and add the two most-recently heard numbers. This test has been found to be sensitive to subtle cognitive deficits in mild TBI [1], which has been attributed to its demand on both rapid processing and mental control shifting [2]. There is a growth of research using PASAT in functional neuroimaging studies to examine differences in cortical activations in multiple sclerosis and healthy controls [3-7]. Although areas identified appeared to be related to attention, executive function, and working memory, the specific underlying mechanisms of the cognitive processes involved in PASAT making it a unique task has not been isolated. A PET study [5] administered subcomponents of the PASAT, and found co...

Applied Soft Computing, 2015

ABSTRACT In this study, a dynamic screening strategy is proposed to discriminate subjects with au... more ABSTRACT In this study, a dynamic screening strategy is proposed to discriminate subjects with autistic spectrum disorder (ASD) from healthy controls. The ASD is defined as a neurodevelopmental disorder that disrupts normal patterns of connectivity between the brain regions. Therefore, the potential use of such abnormality for autism screening is investigated. The connectivity patterns are estimated from electroencephalogram (EEG) data collected from 8 brain regions under various mental states. The EEG data of 12 healthy controls and 6 autistic children (age matched in 7-10) were collected during eyes-open and eyes-close resting states as well as when subjects were exposed to affective faces (happy, sad and calm). Subsequently, the subjects were classified as autistic or healthy groups based on their brain connectivity patterns using pattern recognition techniques. Performance of the proposed system in each mental state is separately evaluated. The results present higher recognition rates using functional connectivity features when compared against other existing feature extraction methods.

Administration and policy in mental health, 1997

The authors present a controlled evaluation of a rural adaptation of the assertive community trea... more The authors present a controlled evaluation of a rural adaptation of the assertive community treatment (ACT) model for clients with serious and persistent mental illness (SPMI). Four community mental health settings adopted an ACT model, while a fifth site blended ACT principles with those of the Rhinelander model, another approach to case management for persons with SPMI. A broad array of client and system outcomes were evaluated at 6, 12, and 24 months into the intervention. Twelve-month findings alerted us to potential problems in implementing the treatment model in study year 1; the implementation was qualitatively evaluated and weaknesses were addressed at the beginning of the second treatment year. Small, positive findings at 24 months suggested that the mid-study course correction may have had an impact. We present these findings along with descriptive data on the challenges of implementing complex services models. We give particular attention to describing implementation bar...

2013 7th International Symposium on Medical Information and Communication Technology (ISMICT), 2013

Resting-State Networks (RSNs) shown in functional magnetic resonance imaging (fMRI) have been con... more Resting-State Networks (RSNs) shown in functional magnetic resonance imaging (fMRI) have been consistently and reliably identified. Amongst these, the Default Mode Network (DMN) has been most well researched and shown to have agerelated decrease in functional connectivity and negative consequences for cognition. There are two other distinct RSNs, Salience Network (SN) and Executive Control Network (ECN), shown to co-activate during fMRI tasks. The SN has been suggested to be correlated with cognitive decline in healthy aging, however, the age-related dynamics between these three RSNs are not well understood. The current study examined the DMN, SN and ECN during resting-state fMRI in young and elderly from Japan and Singapore using data-driven independent component analysis (ICA) and functional network connectivity (FNC). We further investigated if the functional connectivity of the DMN and SN varied across tasks of different cognitive demands between young and elderly. Interestingly, the elderly had increased intrinsic activity that deviated from the expected DMN, SN and ECN, and increased functional connectivity within the anterior SN relative to the young during resting-state fMRI. For task fMRI, the elderly showed decreased activation in the primary networks of visual and motor processing, and increased task related activity for higher cognitive processes. However, the DMN and SN for task fMRI revealed consistent increased activity shifted outside the expected regions for the elderly. Difference in functional connectivity between young and elderly was varied across tasks. The elderly had marginally less number of correlated component pairs compared to the young, suggesting a decline in functional network integrity in aging. The current study demonstrated that resting-state data could be combined across two sites using ICA, as well as the use of DMN and SN as reliable networks to examine age-related changes in rest and task fMRI. Understanding the dynamics of these networks in relation to aging will provide potential neuroimaging markers for enhancing cognition, as well as detecting pathological decline.

Schizophrenia Research, 2013

A dysfunction in working memory (WM) is a core cognitive impairment in schizophrenia that involve... more A dysfunction in working memory (WM) is a core cognitive impairment in schizophrenia that involves the cortical-subcortical-cerebellar network. We propose that in addition to other often-referred markers, the signal reduction in the network during verbal working memory (VWM) is a stable and intrinsic indicator of illness. We presented a Sternberg VWM task to 46 patients with schizophrenia and 46 healthy controls matched on performance accuracy during functional magnetic resonance imaging (fMRI). Reduced activation was demonstrated in the thalamus, cerebellar vermis, pons and the triangular part of the inferior frontal gyrus (IFG) in the patient group. We also found a "failure of deactivation" in the default mode network (DMN) in patients as represented by a low versus high load VWM. In addition, a reduced left lateralization in the triangular and opercular parts of the IFG was observed in the patient group replicating previous "failure of lateralization" findings in schizophrenia. A comparison of long (10 to 19 years) and short (3 to 9 years) durations of illness (DoIs) demonstrated that the DoI was only associated with the activation changes in the middle frontal gyrus and lateral temporal cortex but not with the IFG-subcortico-cerebellar regions observed. These alterations were consistent with the cognitive dysmetria described in the cortical-subcortical-cerebellar network in schizophrenia. In conclusion, the combination of reduced activation in the cortical-subcortical-cerebellar network during VWM in particular, reduced deactivation in the DMN and reduced lateralization in the IFG is thought to be stable neuroimaging signatures of schizophrenia.

Stress and Health, 2013

The association between stress and health has been well researched in the past; however, comparat... more The association between stress and health has been well researched in the past; however, comparatively few mediators have been tested to understand the underlying mechanism. With increasing awareness on mental well-being, this study evaluated the relationship between perceived stress and perceived health and examined mental well-being as a mediator. Two-hundred undergraduates aged 21 to 26 years completed the English Perceived Stress Scale, Health Status Questionnaire and Asian Mental Well-Being Scale that assess perceived stress, perceived health and mental well-being, respectively. Factor analysis and structural equation modelling on the Perceived Stress Scale replicated the reported two-factor structure after excluding an insignificant item. Linear multiple regression analyses indicated that perceived stress was negatively associated with perceived health. Results showed that mental well-being partially mediated the relationship between perceived stress and perceived health, although it is acknowledged that this association could be bidirectional. Findings from the present study suggest that future research could focus on reducing stress and improving mental well-being to alleviate the effect of stress on health.

Psychiatric Rehabilitation Journal, 1998

Neuropsychologia, 2005

Previous investigations have demonstrated that two regions in the right cerebellum, one located s... more Previous investigations have demonstrated that two regions in the right cerebellum, one located superiorly in hemispheral lobule VI/Crus I and another located inferiorly in hemispheral lobule VIIB/VIIIA, are activated during verbal working memory performance. On the basis of functional neuroimaging patterns of activation, as well as known cortico-pontine and ponto-cerebellar projections, the superior region has been hypothesized to contribute to the articulatory control system of working memory whereas the inferior region has been linked to the phonological store. The present study used event-related fMRI and individual estimates of hemodynamic response for both the cerebellum and neocortex to test this model and characterize the task phase specific cerebro-cerebellar activations for a Sternberg verbal working memory task. Results demonstrated that the right superior cerebellum showed the strongest activation during the initial encoding phase of the task, and, consistent with predictions, a similar pattern was observed in left opercular inferior frontal and premotor regions. In contrast, the right inferior cerebellum exhibited the greatest activation during the maintenance phase of the task, and as predicted, corresponded with activation in the left inferior parietal lobule. The significance of the results with respect to cerebro-cerebellar models of verbal working memory and to theoretical accounts of cerebellar involvement in cognition is discussed.

NeuroImage, 2005

Load-dependent and practice-related changes in neocortical and cerebellar structures involved in ... more Load-dependent and practice-related changes in neocortical and cerebellar structures involved in verbal working memory (VWM) were investigated using functional MRI (fMRI) and a two alternative forced choice Sternberg paradigm. Using working memory loads ranging from 2 to 6 letters, regions exhibiting linear and quadratic trends in load-dependent activations were identified. Behaviorally, reaction time measurements revealed significant linear increases with increasing memory load, and significant decreases with increased task practice. Brain activations indicated a preponderance of linear load-dependent responses in both superior (lobule VI/Crus I) and inferior (lobule VIIB/ VIIIA) cerebellar hemispheres, as well as in areas of neocortex including left precentral (BA 6), inferior frontal (BA 47), parahippocampal (BA 35), inferior parietal (BA 40), cingulate (BA 32), and right inferior and middle frontal (BA 46/47) regions. Fewer voxels exhibited quadratic without linear trends with the most prominent of these activations located in left inferior parietal (BA 40), precuneus, and parahippocampal regions. Analysis of load  session interactions revealed that right inferior cerebellar and left inferior parietal activations increased with practice, as did the correlations between activation in each region with reaction time, suggesting that changes in this cerebro-cerebellar network underlie practice-related increases in efficiency of VWM performance. These results replicate and extend our previous findings of fMRI activation in the cerebellum during VWM, and demonstrate predominately linear increases in cerebro-cerebellar activation with increasing memory load as well as changes in network function with increased task proficiency.

NeuroImage, 2009

S70 Schedule of Poster Presentations 160 F-PM Local gyrification index analysis further character... more S70 Schedule of Poster Presentations 160 F-PM Local gyrification index analysis further characterizes significant midline and fronto-parietal brain anomalies in children with chromosome 22q11.2 deletion,

NeuroImage, 2005

Converging evidence has implicated the cerebellum in verbal working memory. The current fMRI stud... more Converging evidence has implicated the cerebellum in verbal working memory. The current fMRI study sought to further characterize cerebrocerebellar participation in this cognitive process by revealing regions of activation common to a verbal working task and an articulatory control task, as well as regions that are uniquely activated by working memory. Consistent with our model's predictions, loaddependent activations were observed in Broca's area (BA 44/6) and the superior cerebellar hemisphere (VI/CrusI) for both working memory and motoric rehearsal. In contrast, activations unique to verbal working memory were found in the inferior parietal lobule (BA 40) and the right inferior cerebellum hemisphere (VIIB). These findings provide evidence for two cerebrocerebellar networks for verbal working memory: a frontal/superior cerebellar articulatory control system and a parietal/inferior cerebellar phonological storage system.

NeuroImage, 2003

Although there is clear evidence of alcoholism-related damage to the frontal lobes and cerebellum... more Although there is clear evidence of alcoholism-related damage to the frontal lobes and cerebellum from neuroimaging, neuropathological, and neuropsychological studies, the functional role of the cerebellum and cerebrocerebellar circuits related to verbal working memory deficits of alcoholics have not been well studied. Alcoholic and nonalcoholic subjects performed a Sternberg verbal working memory task while receiving an fMRI scan in a 3T magnet. This task has been found in previous studies to reliably activate the articulatory control and phonological storage components of the phonological loop (left frontal, left temporal/parietal structures, right superior cerebellar regions) in young healthy controls. We hypothesized that the alcoholics would show a different pattern of activation from the controls, based on the regions of interest (ROIs) identified from a previous study of healthy subjects. Behavioral results showed the alcoholics to be performing at a comparable level to the matched controls in terms of accuracy and median reaction time, with no statistically significant differences. However, analysis of the functional data revealed that the alcoholics exhibited greater activation in the left frontal (BA44/45) and right superior cerebellum (HVI) regions relative to the matched controls. These findings suggest that brain activation in left frontal and right cerebellar regions that support the articulatory control system of verbal working memory may require a compensatory increase in alcoholics in order to maintain the same level of performance as controls.

Journal of Personalized Medicine

Background: In transcranial direct current stimulation (tDCS), the injected current becomes distr... more Background: In transcranial direct current stimulation (tDCS), the injected current becomes distributed across the brain areas. The objective is to stimulate the target region of interest (ROI) while minimizing the current in non-target ROIs (the ‘focality’ of tDCS). For this purpose, determining the appropriate current dose for an individual is difficult. Aim: To introduce a dose–target determination index (DTDI) to quantify the focality of tDCS and examine the dose–focality relationship in three different populations. Method: Here, we extended our previous toolbox i-SATA to the MNI reference space. After a tDCS montage is simulated for a current dose, the i-SATA(MNI) computes the average (over voxels) current density for every region in the brain. DTDI is the ratio of the average current density at the target ROI to the ROI with a maximum value (the peak region). Ideally, target ROI should be the peak region, so DTDI shall range from 0 to 1. The higher the value, the better the do...

Aging Neuropsychol Cogn, 1999

... 180 MARC W. HAUT ET AL. ... Visual and verbal variations of self-ordering demonstrated activa... more ... 180 MARC W. HAUT ET AL. ... Visual and verbal variations of self-ordering demonstrated activation in the dorsolateral prefrontal cortex, the inferior parietal cortex, and the anterior cingulate gyrus (Petrides, Alivisatos, Evans, & Meyer, 1993; Petrides, Alivisatos, Meyer, & Evans ...

Novel Trends in Brain Science, 2008

Praxis der Kinderpsychologie und Kinderpsychiatrie

The analysis and intervention of communication is an important focus of autism research. The pres... more The analysis and intervention of communication is an important focus of autism research. The present study is a microanalsis of the communicative behaviour of 10 autistic children with their parents and a therapist. Protests, appropriate initiation and responses of the children were analysed in relation to demands and the specific feedback of the adults. After 20 months of structured therapy changes in the communicative behaviour of the participants were demonstrated. Autistic children showed different communicative pattern with their parents compared to a therapist. The non-verbal group exhibited significantly more protests and decreased responsivity with their parents compared to the therapist. The verbal group interacted with their parents predominantly by echolalia. After 20 months a significant reduction in protests, increased compliance and responsivity were obvious in the non-verbal group. The verbal group showed a reduction in echolalia as well as increased responsive and sp...

Introduction: The PASAT is one of the most widely administered measure of attentional processing ... more Introduction: The PASAT is one of the most widely administered measure of attentional processing for various clinical populations including traumatic brain injury (TBI), multiple sclerosis, systemic lupus erythematosus, and chronic fatigue syndrome. In this test, subjects hear a number-string and add the two most-recently heard numbers. This test has been found to be sensitive to subtle cognitive deficits in mild TBI [1], which has been attributed to its demand on both rapid processing and mental control shifting [2]. There is a growth of research using PASAT in functional neuroimaging studies to examine differences in cortical activations in multiple sclerosis and healthy controls [3-7]. Although areas identified appeared to be related to attention, executive function, and working memory, the specific underlying mechanisms of the cognitive processes involved in PASAT making it a unique task has not been isolated. A PET study [5] administered subcomponents of the PASAT, and found co...

Applied Soft Computing, 2015

ABSTRACT In this study, a dynamic screening strategy is proposed to discriminate subjects with au... more ABSTRACT In this study, a dynamic screening strategy is proposed to discriminate subjects with autistic spectrum disorder (ASD) from healthy controls. The ASD is defined as a neurodevelopmental disorder that disrupts normal patterns of connectivity between the brain regions. Therefore, the potential use of such abnormality for autism screening is investigated. The connectivity patterns are estimated from electroencephalogram (EEG) data collected from 8 brain regions under various mental states. The EEG data of 12 healthy controls and 6 autistic children (age matched in 7-10) were collected during eyes-open and eyes-close resting states as well as when subjects were exposed to affective faces (happy, sad and calm). Subsequently, the subjects were classified as autistic or healthy groups based on their brain connectivity patterns using pattern recognition techniques. Performance of the proposed system in each mental state is separately evaluated. The results present higher recognition rates using functional connectivity features when compared against other existing feature extraction methods.

Administration and policy in mental health, 1997

The authors present a controlled evaluation of a rural adaptation of the assertive community trea... more The authors present a controlled evaluation of a rural adaptation of the assertive community treatment (ACT) model for clients with serious and persistent mental illness (SPMI). Four community mental health settings adopted an ACT model, while a fifth site blended ACT principles with those of the Rhinelander model, another approach to case management for persons with SPMI. A broad array of client and system outcomes were evaluated at 6, 12, and 24 months into the intervention. Twelve-month findings alerted us to potential problems in implementing the treatment model in study year 1; the implementation was qualitatively evaluated and weaknesses were addressed at the beginning of the second treatment year. Small, positive findings at 24 months suggested that the mid-study course correction may have had an impact. We present these findings along with descriptive data on the challenges of implementing complex services models. We give particular attention to describing implementation bar...

2013 7th International Symposium on Medical Information and Communication Technology (ISMICT), 2013

Resting-State Networks (RSNs) shown in functional magnetic resonance imaging (fMRI) have been con... more Resting-State Networks (RSNs) shown in functional magnetic resonance imaging (fMRI) have been consistently and reliably identified. Amongst these, the Default Mode Network (DMN) has been most well researched and shown to have agerelated decrease in functional connectivity and negative consequences for cognition. There are two other distinct RSNs, Salience Network (SN) and Executive Control Network (ECN), shown to co-activate during fMRI tasks. The SN has been suggested to be correlated with cognitive decline in healthy aging, however, the age-related dynamics between these three RSNs are not well understood. The current study examined the DMN, SN and ECN during resting-state fMRI in young and elderly from Japan and Singapore using data-driven independent component analysis (ICA) and functional network connectivity (FNC). We further investigated if the functional connectivity of the DMN and SN varied across tasks of different cognitive demands between young and elderly. Interestingly, the elderly had increased intrinsic activity that deviated from the expected DMN, SN and ECN, and increased functional connectivity within the anterior SN relative to the young during resting-state fMRI. For task fMRI, the elderly showed decreased activation in the primary networks of visual and motor processing, and increased task related activity for higher cognitive processes. However, the DMN and SN for task fMRI revealed consistent increased activity shifted outside the expected regions for the elderly. Difference in functional connectivity between young and elderly was varied across tasks. The elderly had marginally less number of correlated component pairs compared to the young, suggesting a decline in functional network integrity in aging. The current study demonstrated that resting-state data could be combined across two sites using ICA, as well as the use of DMN and SN as reliable networks to examine age-related changes in rest and task fMRI. Understanding the dynamics of these networks in relation to aging will provide potential neuroimaging markers for enhancing cognition, as well as detecting pathological decline.

Schizophrenia Research, 2013

A dysfunction in working memory (WM) is a core cognitive impairment in schizophrenia that involve... more A dysfunction in working memory (WM) is a core cognitive impairment in schizophrenia that involves the cortical-subcortical-cerebellar network. We propose that in addition to other often-referred markers, the signal reduction in the network during verbal working memory (VWM) is a stable and intrinsic indicator of illness. We presented a Sternberg VWM task to 46 patients with schizophrenia and 46 healthy controls matched on performance accuracy during functional magnetic resonance imaging (fMRI). Reduced activation was demonstrated in the thalamus, cerebellar vermis, pons and the triangular part of the inferior frontal gyrus (IFG) in the patient group. We also found a "failure of deactivation" in the default mode network (DMN) in patients as represented by a low versus high load VWM. In addition, a reduced left lateralization in the triangular and opercular parts of the IFG was observed in the patient group replicating previous "failure of lateralization" findings in schizophrenia. A comparison of long (10 to 19 years) and short (3 to 9 years) durations of illness (DoIs) demonstrated that the DoI was only associated with the activation changes in the middle frontal gyrus and lateral temporal cortex but not with the IFG-subcortico-cerebellar regions observed. These alterations were consistent with the cognitive dysmetria described in the cortical-subcortical-cerebellar network in schizophrenia. In conclusion, the combination of reduced activation in the cortical-subcortical-cerebellar network during VWM in particular, reduced deactivation in the DMN and reduced lateralization in the IFG is thought to be stable neuroimaging signatures of schizophrenia.

Stress and Health, 2013

The association between stress and health has been well researched in the past; however, comparat... more The association between stress and health has been well researched in the past; however, comparatively few mediators have been tested to understand the underlying mechanism. With increasing awareness on mental well-being, this study evaluated the relationship between perceived stress and perceived health and examined mental well-being as a mediator. Two-hundred undergraduates aged 21 to 26 years completed the English Perceived Stress Scale, Health Status Questionnaire and Asian Mental Well-Being Scale that assess perceived stress, perceived health and mental well-being, respectively. Factor analysis and structural equation modelling on the Perceived Stress Scale replicated the reported two-factor structure after excluding an insignificant item. Linear multiple regression analyses indicated that perceived stress was negatively associated with perceived health. Results showed that mental well-being partially mediated the relationship between perceived stress and perceived health, although it is acknowledged that this association could be bidirectional. Findings from the present study suggest that future research could focus on reducing stress and improving mental well-being to alleviate the effect of stress on health.

Psychiatric Rehabilitation Journal, 1998

Neuropsychologia, 2005

Previous investigations have demonstrated that two regions in the right cerebellum, one located s... more Previous investigations have demonstrated that two regions in the right cerebellum, one located superiorly in hemispheral lobule VI/Crus I and another located inferiorly in hemispheral lobule VIIB/VIIIA, are activated during verbal working memory performance. On the basis of functional neuroimaging patterns of activation, as well as known cortico-pontine and ponto-cerebellar projections, the superior region has been hypothesized to contribute to the articulatory control system of working memory whereas the inferior region has been linked to the phonological store. The present study used event-related fMRI and individual estimates of hemodynamic response for both the cerebellum and neocortex to test this model and characterize the task phase specific cerebro-cerebellar activations for a Sternberg verbal working memory task. Results demonstrated that the right superior cerebellum showed the strongest activation during the initial encoding phase of the task, and, consistent with predictions, a similar pattern was observed in left opercular inferior frontal and premotor regions. In contrast, the right inferior cerebellum exhibited the greatest activation during the maintenance phase of the task, and as predicted, corresponded with activation in the left inferior parietal lobule. The significance of the results with respect to cerebro-cerebellar models of verbal working memory and to theoretical accounts of cerebellar involvement in cognition is discussed.

NeuroImage, 2005

Load-dependent and practice-related changes in neocortical and cerebellar structures involved in ... more Load-dependent and practice-related changes in neocortical and cerebellar structures involved in verbal working memory (VWM) were investigated using functional MRI (fMRI) and a two alternative forced choice Sternberg paradigm. Using working memory loads ranging from 2 to 6 letters, regions exhibiting linear and quadratic trends in load-dependent activations were identified. Behaviorally, reaction time measurements revealed significant linear increases with increasing memory load, and significant decreases with increased task practice. Brain activations indicated a preponderance of linear load-dependent responses in both superior (lobule VI/Crus I) and inferior (lobule VIIB/ VIIIA) cerebellar hemispheres, as well as in areas of neocortex including left precentral (BA 6), inferior frontal (BA 47), parahippocampal (BA 35), inferior parietal (BA 40), cingulate (BA 32), and right inferior and middle frontal (BA 46/47) regions. Fewer voxels exhibited quadratic without linear trends with the most prominent of these activations located in left inferior parietal (BA 40), precuneus, and parahippocampal regions. Analysis of load  session interactions revealed that right inferior cerebellar and left inferior parietal activations increased with practice, as did the correlations between activation in each region with reaction time, suggesting that changes in this cerebro-cerebellar network underlie practice-related increases in efficiency of VWM performance. These results replicate and extend our previous findings of fMRI activation in the cerebellum during VWM, and demonstrate predominately linear increases in cerebro-cerebellar activation with increasing memory load as well as changes in network function with increased task proficiency.

NeuroImage, 2009

S70 Schedule of Poster Presentations 160 F-PM Local gyrification index analysis further character... more S70 Schedule of Poster Presentations 160 F-PM Local gyrification index analysis further characterizes significant midline and fronto-parietal brain anomalies in children with chromosome 22q11.2 deletion,

NeuroImage, 2005

Converging evidence has implicated the cerebellum in verbal working memory. The current fMRI stud... more Converging evidence has implicated the cerebellum in verbal working memory. The current fMRI study sought to further characterize cerebrocerebellar participation in this cognitive process by revealing regions of activation common to a verbal working task and an articulatory control task, as well as regions that are uniquely activated by working memory. Consistent with our model's predictions, loaddependent activations were observed in Broca's area (BA 44/6) and the superior cerebellar hemisphere (VI/CrusI) for both working memory and motoric rehearsal. In contrast, activations unique to verbal working memory were found in the inferior parietal lobule (BA 40) and the right inferior cerebellum hemisphere (VIIB). These findings provide evidence for two cerebrocerebellar networks for verbal working memory: a frontal/superior cerebellar articulatory control system and a parietal/inferior cerebellar phonological storage system.

NeuroImage, 2003

Although there is clear evidence of alcoholism-related damage to the frontal lobes and cerebellum... more Although there is clear evidence of alcoholism-related damage to the frontal lobes and cerebellum from neuroimaging, neuropathological, and neuropsychological studies, the functional role of the cerebellum and cerebrocerebellar circuits related to verbal working memory deficits of alcoholics have not been well studied. Alcoholic and nonalcoholic subjects performed a Sternberg verbal working memory task while receiving an fMRI scan in a 3T magnet. This task has been found in previous studies to reliably activate the articulatory control and phonological storage components of the phonological loop (left frontal, left temporal/parietal structures, right superior cerebellar regions) in young healthy controls. We hypothesized that the alcoholics would show a different pattern of activation from the controls, based on the regions of interest (ROIs) identified from a previous study of healthy subjects. Behavioral results showed the alcoholics to be performing at a comparable level to the matched controls in terms of accuracy and median reaction time, with no statistically significant differences. However, analysis of the functional data revealed that the alcoholics exhibited greater activation in the left frontal (BA44/45) and right superior cerebellum (HVI) regions relative to the matched controls. These findings suggest that brain activation in left frontal and right cerebellar regions that support the articulatory control system of verbal working memory may require a compensatory increase in alcoholics in order to maintain the same level of performance as controls.